[PATCH v2 00/12] RFC: ICMP reworks preliminary to flow table integration

[PATCH v2 00/12] RFC: ICMP reworks preliminary to flow table integration

[David Gibson]

As with TCP, it turns out that there are a bunch of clean ups and
reworks to the ICMP code which will make integration with the flow
table easier, even before introducing a non-trivial version of the
flow table itself.

Based on the flow based dispatch/allocation, and bind/addressing
cleanup series.

Changes since v1:
 * Rebased on newer version of flow dispatch & allocation series
 * Added 12/12 splitting out close and new sequence functions

David Gibson (12):
  checksum: Don't use linux/icmp.h when netinet/ip_icmp.h will do
  icmp: Don't set "port" on destination sockaddr for ping sockets
  icmp: Remove redundant initialisation of sendto() address
  icmp: Don't attempt to handle "wrong direction" ping socket traffic
  icmp: Don't attempt to match host IDs to guest IDs
  icmp: Use -1 to represent "missing" sockets
  icmp: Simplify socket expiry scanning
  icmp: Share more between IPv4 and IPv6 paths in icmp_tap_handler()
  icmp: Consolidate icmp_sock_handler() with icmpv6_sock_handler()
  icmp: Warn on receive errors from ping sockets
  icmp: Validate packets received on ping sockets
  icmp: Dedicated functions for starting and closing ping sequences

 checksum.c |   2 +-
 icmp.c     | 326 ++++++++++++++++++++++++++---------------------------
 icmp.h     |   5 +-
 passt.c    |   4 +-
 4 files changed, 164 insertions(+), 173 deletions(-)

-- 
2.43.0

[PATCH v2 01/12] checksum: Don't use linux/icmp.h when netinet/ip_icmp.h will do

[David Gibson]

In most places where we need to get ICMP definitions, we get them from
<netinet/ip_icmp.h>.  However in checksum.c we instead include
<linux/icmp.h>.  Change it to use <netinet/ip_icmp.h> for consistency.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 checksum.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/checksum.c b/checksum.c
index 03b8a7c..f21c9b7 100644
--- a/checksum.c
+++ b/checksum.c
@@ -49,11 +49,11 @@
 #include <arpa/inet.h>
 #include <netinet/ip.h>
 #include <netinet/tcp.h>
+#include <netinet/ip_icmp.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include <linux/udp.h>
-#include <linux/icmp.h>
 #include <linux/icmpv6.h>
 
 /* Checksums are optional for UDP over IPv4, so we usually just set
-- 
@@ -49,11 +49,11 @@
 #include <arpa/inet.h>
 #include <netinet/ip.h>
 #include <netinet/tcp.h>
+#include <netinet/ip_icmp.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include <linux/udp.h>
-#include <linux/icmp.h>
 #include <linux/icmpv6.h>
 
 /* Checksums are optional for UDP over IPv4, so we usually just set
-- 
2.43.0

[PATCH v2 02/12] icmp: Don't set "port" on destination sockaddr for ping sockets

[David Gibson]

We set the port to the ICMP id on the sendto() address when using ICMP
ping sockets.  However, this has no effect: the ICMP id the kernel
uses is determined only by the "port" on the socket's *bound* address
(which is constructed inside sock_l4(), using the id we also pass to
it).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/icmp.c b/icmp.c
index 325dfb0..d3e5bc6 100644
--- a/icmp.c
+++ b/icmp.c
@@ -182,8 +182,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY)
 			return 1;
 
-		sa.sin_port = ih->un.echo.id;
-
 		iref.id = id = ntohs(ih->un.echo.id);
 
 		if ((s = icmp_id_map[V4][id].sock) <= 0) {
@@ -229,8 +227,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
 			return 1;
 
-		sa.sin6_port = ih->icmp6_identifier;
-
 		iref.id = id = ntohs(ih->icmp6_identifier);
 		if ((s = icmp_id_map[V6][id].sock) <= 0) {
 			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
-- 
@@ -182,8 +182,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY)
 			return 1;
 
-		sa.sin_port = ih->un.echo.id;
-
 		iref.id = id = ntohs(ih->un.echo.id);
 
 		if ((s = icmp_id_map[V4][id].sock) <= 0) {
@@ -229,8 +227,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
 			return 1;
 
-		sa.sin6_port = ih->icmp6_identifier;
-
 		iref.id = id = ntohs(ih->icmp6_identifier);
 		if ((s = icmp_id_map[V6][id].sock) <= 0) {
 			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
-- 
2.43.0

[PATCH v2 03/12] icmp: Remove redundant initialisation of sendto() address

[David Gibson]

We initialise the address portion of the sockaddr for sendto() to the
unspecified address, but then always overwrite it with the actual
destination address before we call the sendto().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/icmp.c b/icmp.c
index d3e5bc6..c745b7b 100644
--- a/icmp.c
+++ b/icmp.c
@@ -169,7 +169,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 	if (af == AF_INET) {
 		struct sockaddr_in sa = {
 			.sin_family = AF_INET,
-			.sin_addr = IN4ADDR_ANY_INIT,
 		};
 		union icmp_epoll_ref iref;
 		struct icmphdr *ih;
@@ -213,7 +212,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 	} else if (af == AF_INET6) {
 		struct sockaddr_in6 sa = {
 			.sin6_family = AF_INET6,
-			.sin6_addr = IN6ADDR_ANY_INIT,
 			.sin6_scope_id = c->ifi6,
 		};
 		union icmp_epoll_ref iref;
-- 
@@ -169,7 +169,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 	if (af == AF_INET) {
 		struct sockaddr_in sa = {
 			.sin_family = AF_INET,
-			.sin_addr = IN4ADDR_ANY_INIT,
 		};
 		union icmp_epoll_ref iref;
 		struct icmphdr *ih;
@@ -213,7 +212,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 	} else if (af == AF_INET6) {
 		struct sockaddr_in6 sa = {
 			.sin6_family = AF_INET6,
-			.sin6_addr = IN6ADDR_ANY_INIT,
 			.sin6_scope_id = c->ifi6,
 		};
 		union icmp_epoll_ref iref;
-- 
2.43.0

[PATCH v2 04/12] icmp: Don't attempt to handle "wrong direction" ping socket traffic

[David Gibson]

Linux ICMP "ping" sockets are very specific in what they do.  They let
userspace send ping requests (ICMP_ECHO or ICMP6_ECHO_REQUEST), and receive
matching replies (ICMP_ECHOREPLY or ICMP6_ECHO_REPLY).  They don't let you
intercept or handle incoming ping requests.

In the case of passt/pasta that means we can process echo requests from tap
and forward them to a ping socket, then take the replies from the ping
socket and forward them to tap.  We can't do the reverse: take echo
requests from the host and somehow forward them to the guest. There's
really no way for something outside to initiate a ping to a passt/pasta
connected guest and if there was we'd need an entirely different mechanism
to handle it.

However, we have some logic to deal with packets going in that reverse
direction.  Remove it, since it can't ever be used that way.  While we're
there use defines for the ICMPv6 types, instead of open coded type values.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/icmp.c b/icmp.c
index c745b7b..1f41440 100644
--- a/icmp.c
+++ b/icmp.c
@@ -93,8 +93,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
 		icmp_id_map[V4][id].seq = seq;
 	}
 
-	debug("ICMP: echo %s to tap, ID: %i, seq: %i",
-	      (ih->type == ICMP_ECHO) ? "request" : "reply", id, seq);
+	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
 
 	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
 }
@@ -138,8 +137,7 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
 		icmp_id_map[V6][id].seq = seq;
 	}
 
-	debug("ICMPv6: echo %s to tap, ID: %i, seq: %i",
-	      (ih->icmp6_type == 128) ? "request" : "reply", id, seq);
+	debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq);
 
 	tap_icmp6_send(c, &sr.sin6_addr,
 		       tap_ip6_daddr(c, &sr.sin6_addr), buf, n);
@@ -178,7 +176,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (!ih)
 			return 1;
 
-		if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY)
+		if (ih->type != ICMP_ECHO)
 			return 1;
 
 		iref.id = id = ntohs(ih->un.echo.id);
@@ -205,8 +203,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 			debug("ICMP: failed to relay request to socket");
 		} else {
-			debug("ICMP: echo %s to socket, ID: %i, seq: %i",
-			      (ih->type == ICMP_ECHO) ? "request" : "reply",
+			debug("ICMP: echo request to socket, ID: %i, seq: %i",
 			      id, ntohs(ih->un.echo.sequence));
 		}
 	} else if (af == AF_INET6) {
@@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (!ih)
 			return 1;
 
-		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
+		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
 			return 1;
 
 		iref.id = id = ntohs(ih->icmp6_identifier);
@@ -249,8 +246,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
 			debug("ICMPv6: failed to relay request to socket");
 		} else {
-			debug("ICMPv6: echo %s to socket, ID: %i, seq: %i",
-			      (ih->icmp6_type == 128) ? "request" : "reply",
+			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
 			      id, ntohs(ih->icmp6_sequence));
 		}
 	}
-- 
@@ -93,8 +93,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
 		icmp_id_map[V4][id].seq = seq;
 	}
 
-	debug("ICMP: echo %s to tap, ID: %i, seq: %i",
-	      (ih->type == ICMP_ECHO) ? "request" : "reply", id, seq);
+	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
 
 	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
 }
@@ -138,8 +137,7 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
 		icmp_id_map[V6][id].seq = seq;
 	}
 
-	debug("ICMPv6: echo %s to tap, ID: %i, seq: %i",
-	      (ih->icmp6_type == 128) ? "request" : "reply", id, seq);
+	debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq);
 
 	tap_icmp6_send(c, &sr.sin6_addr,
 		       tap_ip6_daddr(c, &sr.sin6_addr), buf, n);
@@ -178,7 +176,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (!ih)
 			return 1;
 
-		if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY)
+		if (ih->type != ICMP_ECHO)
 			return 1;
 
 		iref.id = id = ntohs(ih->un.echo.id);
@@ -205,8 +203,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 			debug("ICMP: failed to relay request to socket");
 		} else {
-			debug("ICMP: echo %s to socket, ID: %i, seq: %i",
-			      (ih->type == ICMP_ECHO) ? "request" : "reply",
+			debug("ICMP: echo request to socket, ID: %i, seq: %i",
 			      id, ntohs(ih->un.echo.sequence));
 		}
 	} else if (af == AF_INET6) {
@@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (!ih)
 			return 1;
 
-		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
+		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
 			return 1;
 
 		iref.id = id = ntohs(ih->icmp6_identifier);
@@ -249,8 +246,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
 			debug("ICMPv6: failed to relay request to socket");
 		} else {
-			debug("ICMPv6: echo %s to socket, ID: %i, seq: %i",
-			      (ih->icmp6_type == 128) ? "request" : "reply",
+			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
 			      id, ntohs(ih->icmp6_sequence));
 		}
 	}
-- 
2.43.0

[PATCH v2 05/12] icmp: Don't attempt to match host IDs to guest IDs

[David Gibson]

When forwarding pings from tap, currently we create a ping socket with
a socket address whose port is set to the ID of the ping received from the
guest.  This causes the socket to send pings with the same ID on the host.
Although this seems look a good idea for maximum transparency, it's
probably unwise.

First, it's fallible - the bind() could fail, and we already have fallback
logic which will overwrite the packets with the expected guest id if the
id we get on replies doesn't already match.  We might as well do that
unconditionally.

But more importantly, we don't know what else on the host might be using
ping sockets, so we could end up with an ID that's the same as an existing
socket.  You'd expect that to fail the bind() with EADDRINUSE, which would
be fine: we'd fall back to rewriting the reply ids.  However it appears the
kernel (v6.6.3 at least), does *not* fail the bind() and instead it's
"last socket wins" in terms of who gets the replies.  So we could
accidentally intercept ping replies for something else on the host.

So, instead of using bind() to set the id, just let the kernel pick one
and expect to translate the replies back.  Although theoretically this
makes the passt/pasta link a bit less "transparent", essentially nothing
cares about specific ping IDs, much like TCP source ports, which we also
don't preserve.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/icmp.c b/icmp.c
index 1f41440..7a505b4 100644
--- a/icmp.c
+++ b/icmp.c
@@ -80,11 +80,12 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
 	if (n < 0)
 		return;
 
-	id = ntohs(ih->un.echo.id);
 	seq = ntohs(ih->un.echo.sequence);
 
-	if (id != ref.icmp.id)
-		ih->un.echo.id = htons(ref.icmp.id);
+	/* Adjust the packet to have the ID the guest was using, rather than the
+	 * host chosen value */
+	id = ref.icmp.id;
+	ih->un.echo.id = htons(id);
 
 	if (c->mode == MODE_PASTA) {
 		if (icmp_id_map[V4][id].seq == seq)
@@ -119,15 +120,12 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
 	if (n < 0)
 		return;
 
-	id = ntohs(ih->icmp6_identifier);
 	seq = ntohs(ih->icmp6_sequence);
 
-	/* If bind() fails e.g. because of a broken SELinux policy,
-	 * this might happen. Fix up the identifier to match the sent
-	 * one.
-	 */
-	if (id != ref.icmp.id)
-		ih->icmp6_identifier = htons(ref.icmp.id);
+	/* Adjust the packet to have the ID the guest was using, rather than the
+	 * host chosen value */
+	id = ref.icmp.id;
+	ih->icmp6_identifier = htons(id);
 
 	/* In PASTA mode, we'll get any reply we send, discard them. */
 	if (c->mode == MODE_PASTA) {
@@ -183,7 +181,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 
 		if ((s = icmp_id_map[V4][id].sock) <= 0) {
 			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
-				    c->ip4.ifname_out, id, iref.u32);
+				    c->ip4.ifname_out, 0, iref.u32);
 			if (s < 0)
 				goto fail_sock;
 			if (s > FD_REF_MAX) {
@@ -226,7 +224,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if ((s = icmp_id_map[V6][id].sock) <= 0) {
 			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
 				    &c->ip6.addr_out,
-				    c->ip6.ifname_out, id, iref.u32);
+				    c->ip6.ifname_out, 0, iref.u32);
 			if (s < 0)
 				goto fail_sock;
 			if (s > FD_REF_MAX) {
-- 
@@ -80,11 +80,12 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
 	if (n < 0)
 		return;
 
-	id = ntohs(ih->un.echo.id);
 	seq = ntohs(ih->un.echo.sequence);
 
-	if (id != ref.icmp.id)
-		ih->un.echo.id = htons(ref.icmp.id);
+	/* Adjust the packet to have the ID the guest was using, rather than the
+	 * host chosen value */
+	id = ref.icmp.id;
+	ih->un.echo.id = htons(id);
 
 	if (c->mode == MODE_PASTA) {
 		if (icmp_id_map[V4][id].seq == seq)
@@ -119,15 +120,12 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
 	if (n < 0)
 		return;
 
-	id = ntohs(ih->icmp6_identifier);
 	seq = ntohs(ih->icmp6_sequence);
 
-	/* If bind() fails e.g. because of a broken SELinux policy,
-	 * this might happen. Fix up the identifier to match the sent
-	 * one.
-	 */
-	if (id != ref.icmp.id)
-		ih->icmp6_identifier = htons(ref.icmp.id);
+	/* Adjust the packet to have the ID the guest was using, rather than the
+	 * host chosen value */
+	id = ref.icmp.id;
+	ih->icmp6_identifier = htons(id);
 
 	/* In PASTA mode, we'll get any reply we send, discard them. */
 	if (c->mode == MODE_PASTA) {
@@ -183,7 +181,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 
 		if ((s = icmp_id_map[V4][id].sock) <= 0) {
 			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
-				    c->ip4.ifname_out, id, iref.u32);
+				    c->ip4.ifname_out, 0, iref.u32);
 			if (s < 0)
 				goto fail_sock;
 			if (s > FD_REF_MAX) {
@@ -226,7 +224,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if ((s = icmp_id_map[V6][id].sock) <= 0) {
 			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
 				    &c->ip6.addr_out,
-				    c->ip6.ifname_out, id, iref.u32);
+				    c->ip6.ifname_out, 0, iref.u32);
 			if (s < 0)
 				goto fail_sock;
 			if (s > FD_REF_MAX) {
-- 
2.43.0

[PATCH v2 06/12] icmp: Use -1 to represent "missing" sockets

[David Gibson]

icmp_id_map[] contains, amongst other things, fds for "ping" sockets
associated with various ICMP echo ids.  However, we only lazily open()
those sockets, so many will be missing.  We currently represent that with
a 0, which isn't great, since that's technically a valid fd.  Use -1
instead.  This does require initializing the fields in icmp_id_map[] but
we already have an obvious place to do that.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/icmp.c b/icmp.c
index 7a505b4..dd98c7f 100644
--- a/icmp.c
+++ b/icmp.c
@@ -179,7 +179,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 
 		iref.id = id = ntohs(ih->un.echo.id);
 
-		if ((s = icmp_id_map[V4][id].sock) <= 0) {
+		if ((s = icmp_id_map[V4][id].sock) < 0) {
 			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
 				    c->ip4.ifname_out, 0, iref.u32);
 			if (s < 0)
@@ -221,7 +221,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			return 1;
 
 		iref.id = id = ntohs(ih->icmp6_identifier);
-		if ((s = icmp_id_map[V6][id].sock) <= 0) {
+		if ((s = icmp_id_map[V6][id].sock) < 0) {
 			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
 				    &c->ip6.addr_out,
 				    c->ip6.ifname_out, 0, iref.u32);
@@ -277,7 +277,7 @@ static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
 
 	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
 	close(id_map->sock);
-	id_map->sock = 0;
+	id_map->sock = -1;
 	id_map->seq = -1;
 }
 
@@ -315,6 +315,8 @@ void icmp_init(void)
 {
 	unsigned i;
 
-	for (i = 0; i < ICMP_NUM_IDS; i++)
+	for (i = 0; i < ICMP_NUM_IDS; i++) {
 		icmp_id_map[V4][i].seq = icmp_id_map[V6][i].seq = -1;
+		icmp_id_map[V4][i].sock = icmp_id_map[V6][i].sock = -1;
+	}
 }
-- 
@@ -179,7 +179,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 
 		iref.id = id = ntohs(ih->un.echo.id);
 
-		if ((s = icmp_id_map[V4][id].sock) <= 0) {
+		if ((s = icmp_id_map[V4][id].sock) < 0) {
 			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
 				    c->ip4.ifname_out, 0, iref.u32);
 			if (s < 0)
@@ -221,7 +221,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			return 1;
 
 		iref.id = id = ntohs(ih->icmp6_identifier);
-		if ((s = icmp_id_map[V6][id].sock) <= 0) {
+		if ((s = icmp_id_map[V6][id].sock) < 0) {
 			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
 				    &c->ip6.addr_out,
 				    c->ip6.ifname_out, 0, iref.u32);
@@ -277,7 +277,7 @@ static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
 
 	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
 	close(id_map->sock);
-	id_map->sock = 0;
+	id_map->sock = -1;
 	id_map->seq = -1;
 }
 
@@ -315,6 +315,8 @@ void icmp_init(void)
 {
 	unsigned i;
 
-	for (i = 0; i < ICMP_NUM_IDS; i++)
+	for (i = 0; i < ICMP_NUM_IDS; i++) {
 		icmp_id_map[V4][i].seq = icmp_id_map[V6][i].seq = -1;
+		icmp_id_map[V4][i].sock = icmp_id_map[V6][i].sock = -1;
+	}
 }
-- 
2.43.0

[PATCH v2 07/12] icmp: Simplify socket expiry scanning

[David Gibson]

Currently we use icmp_act[] to scan for ICMP ids which might have an open
socket which could time out.  However icmp_act[] contains no information
that's not already in icmp_id_map[] - it's just an "index" which allows
scanning for relevant entries with less cache footprint.

We only scan for ICMP socket expiry every 1s, though, so it's not clear
that cache footprint really matters.  Furthermore, there's no strong reason
we need to scan even that often - the timeout is fairly arbitrary and
approximate.

So, eliminate icmp_act[] in favour of directly scanning icmp_id_map[] and
compensate for the cache impact by reducing the scan frequency to once
every 10s.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 34 ++++++----------------------------
 icmp.h |  2 +-
 2 files changed, 7 insertions(+), 29 deletions(-)

diff --git a/icmp.c b/icmp.c
index dd98c7f..02739b9 100644
--- a/icmp.c
+++ b/icmp.c
@@ -56,9 +56,6 @@ struct icmp_id_sock {
 /* Indexed by ICMP echo identifier */
 static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
 
-/* Bitmaps, activity monitoring needed for identifier */
-static uint8_t icmp_act[IP_VERSIONS][DIV_ROUND_UP(ICMP_NUM_IDS, 8)];
-
 /**
  * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
  * @c:		Execution context
@@ -194,7 +191,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			debug("ICMP: new socket %i for echo ID %i", s, id);
 		}
 		icmp_id_map[V4][id].ts = now->tv_sec;
-		bitmap_set(icmp_act[V4], id);
 
 		sa.sin_addr = *(struct in_addr *)daddr;
 		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
@@ -237,7 +233,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			debug("ICMPv6: new socket %i for echo ID %i", s, id);
 		}
 		icmp_id_map[V6][id].ts = now->tv_sec;
-		bitmap_set(icmp_act[V6], id);
 
 		sa.sin6_addr = *(struct in6_addr *)daddr;
 		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
@@ -261,20 +256,15 @@ fail_sock:
 /**
  * icmp_timer_one() - Handler for timed events related to a given identifier
  * @c:		Execution context
- * @v6:		Set for IPv6 echo identifier bindings
- * @id:		Echo identifier, host order
+ * @id_map:	id socket information to check timers for
  * @now:	Current timestamp
  */
-static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
+static void icmp_timer_one(const struct ctx *c, struct icmp_id_sock *id_map,
 			   const struct timespec *now)
 {
-	struct icmp_id_sock *id_map = &icmp_id_map[v6 ? V6 : V4][id];
-
-	if (now->tv_sec - id_map->ts <= ICMP_ECHO_TIMEOUT)
+	if (id_map->sock < 0 || now->tv_sec - id_map->ts <= ICMP_ECHO_TIMEOUT)
 		return;
 
-	bitmap_clear(icmp_act[v6 ? V6 : V4], id);
-
 	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
 	close(id_map->sock);
 	id_map->sock = -1;
@@ -288,23 +278,11 @@ static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
  */
 void icmp_timer(const struct ctx *c, const struct timespec *now)
 {
-	long *word, tmp;
 	unsigned int i;
-	int n, v6 = 0;
-
-v6:
-	word = (long *)icmp_act[v6 ? V6 : V4];
-	for (i = 0; i < ARRAY_SIZE(icmp_act); i += sizeof(long), word++) {
-		tmp = *word;
-		while ((n = ffsl(tmp))) {
-			tmp &= ~(1UL << (n - 1));
-			icmp_timer_one(c, v6, i * 8 + n - 1, now);
-		}
-	}
 
-	if (!v6) {
-		v6 = 1;
-		goto v6;
+	for (i = 0; i < ICMP_NUM_IDS; i++) {
+		icmp_timer_one(c, &icmp_id_map[V4][i], now);
+		icmp_timer_one(c, &icmp_id_map[V6][i], now);
 	}
 }
 
diff --git a/icmp.h b/icmp.h
index 1a08594..4096c65 100644
--- a/icmp.h
+++ b/icmp.h
@@ -6,7 +6,7 @@
 #ifndef ICMP_H
 #define ICMP_H
 
-#define ICMP_TIMER_INTERVAL		1000 /* ms */
+#define ICMP_TIMER_INTERVAL		10000 /* ms */
 
 struct ctx;
 
-- 
@@ -6,7 +6,7 @@
 #ifndef ICMP_H
 #define ICMP_H
 
-#define ICMP_TIMER_INTERVAL		1000 /* ms */
+#define ICMP_TIMER_INTERVAL		10000 /* ms */
 
 struct ctx;
 
-- 
2.43.0

[PATCH v2 08/12] icmp: Share more between IPv4 and IPv6 paths in icmp_tap_handler()

[David Gibson]

Currently icmp_tap_handler() consists of two almost disjoint paths for the
IPv4 and IPv6 cases.  The only thing they share is an error message.
We can use some intermediate variables to refactor this to share some more
code between those paths.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 140 ++++++++++++++++++++++++++++-----------------------------
 1 file changed, 69 insertions(+), 71 deletions(-)

diff --git a/icmp.c b/icmp.c
index 02739b9..f6c744a 100644
--- a/icmp.c
+++ b/icmp.c
@@ -154,102 +154,100 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		     const void *saddr, const void *daddr,
 		     const struct pool *p, const struct timespec *now)
 {
+	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
+	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
+	union {
+		struct sockaddr sa;
+		struct sockaddr_in sa4;
+		struct sockaddr_in6 sa6;
+	} sa = { .sa.sa_family = af };
+	const socklen_t sl = af == AF_INET ? sizeof(sa.sa4) : sizeof(sa.sa6);
+	struct icmp_id_sock *id_map;
+	uint16_t id, seq;
 	size_t plen;
+	void *pkt;
+	int s;
 
 	(void)saddr;
 	(void)pif;
 
+	pkt = packet_get(p, 0, 0, 0, &plen);
+	if (!pkt)
+		return 1;
+
 	if (af == AF_INET) {
-		struct sockaddr_in sa = {
-			.sin_family = AF_INET,
-		};
-		union icmp_epoll_ref iref;
-		struct icmphdr *ih;
-		int id, s;
-
-		ih = packet_get(p, 0, 0, sizeof(*ih), &plen);
-		if (!ih)
+		struct icmphdr *ih = (struct icmphdr *)pkt;
+
+		if (plen < sizeof(*ih))
 			return 1;
 
 		if (ih->type != ICMP_ECHO)
 			return 1;
 
-		iref.id = id = ntohs(ih->un.echo.id);
+		id = ntohs(ih->un.echo.id);
+		id_map = &icmp_id_map[V4][id];
+		seq = ntohs(ih->un.echo.sequence);
+		sa.sa4.sin_addr = *(struct in_addr *)daddr;
+	} else if (af == AF_INET6) {
+		struct icmp6hdr *ih = (struct icmp6hdr *)pkt;
 
-		if ((s = icmp_id_map[V4][id].sock) < 0) {
-			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
-				    c->ip4.ifname_out, 0, iref.u32);
-			if (s < 0)
-				goto fail_sock;
-			if (s > FD_REF_MAX) {
-				close(s);
-				return 1;
-			}
+		if (plen < sizeof(*ih))
+			return 1;
 
-			icmp_id_map[V4][id].sock = s;
+		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
+			return 1;
 
-			debug("ICMP: new socket %i for echo ID %i", s, id);
-		}
-		icmp_id_map[V4][id].ts = now->tv_sec;
+		id = ntohs(ih->icmp6_identifier);
+		id_map = &icmp_id_map[V6][id];
+		seq = ntohs(ih->icmp6_sequence);
+		sa.sa6.sin6_addr = *(struct in6_addr *)daddr;
+		sa.sa6.sin6_scope_id = c->ifi6;
+	} else {
+		ASSERT(0);
+	}
+
+	if ((s = id_map->sock) < 0) {
+		union icmp_epoll_ref iref = { .id = id };
+		const void *bind_addr;
+		const char *bind_if;
 
-		sa.sin_addr = *(struct in_addr *)daddr;
-		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
-			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
-			debug("ICMP: failed to relay request to socket");
+		if (af == AF_INET) {
+			bind_addr = &c->ip4.addr_out;
+			bind_if = c->ip4.ifname_out;
 		} else {
-			debug("ICMP: echo request to socket, ID: %i, seq: %i",
-			      id, ntohs(ih->un.echo.sequence));
+			bind_addr = &c->ip6.addr_out;
+			bind_if = c->ip6.ifname_out;
 		}
-	} else if (af == AF_INET6) {
-		struct sockaddr_in6 sa = {
-			.sin6_family = AF_INET6,
-			.sin6_scope_id = c->ifi6,
-		};
-		union icmp_epoll_ref iref;
-		struct icmp6hdr *ih;
-		int id, s;
-
-		ih = packet_get(p, 0, 0, sizeof(struct icmp6hdr), &plen);
-		if (!ih)
-			return 1;
 
-		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
-			return 1;
+		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
 
-		iref.id = id = ntohs(ih->icmp6_identifier);
-		if ((s = icmp_id_map[V6][id].sock) < 0) {
-			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
-				    &c->ip6.addr_out,
-				    c->ip6.ifname_out, 0, iref.u32);
-			if (s < 0)
-				goto fail_sock;
-			if (s > FD_REF_MAX) {
-				close(s);
-				return 1;
-			}
-
-			icmp_id_map[V6][id].sock = s;
-
-			debug("ICMPv6: new socket %i for echo ID %i", s, id);
+		if (s < 0) {
+			warn("Cannot open \"ping\" socket. You might need to:");
+			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
+			warn("...echo requests/replies will fail.");
+			return 1;
 		}
-		icmp_id_map[V6][id].ts = now->tv_sec;
 
-		sa.sin6_addr = *(struct in6_addr *)daddr;
-		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
-			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
-			debug("ICMPv6: failed to relay request to socket");
-		} else {
-			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
-			      id, ntohs(ih->icmp6_sequence));
+		if (s > FD_REF_MAX) {
+			close(s);
+			return 1;
 		}
+
+		id_map->sock = s;
+
+		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
 	}
 
-	return 1;
+	id_map->ts = now->tv_sec;
+
+	if (sendto(s, pkt, plen, MSG_NOSIGNAL, &sa.sa, sl) < 0) {
+		debug("%s: failed to relay request to socket: %s",
+		      pname, strerror(errno));
+	} else {
+		debug("%s: echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
+		      pname, id, seq);
+	}
 
-fail_sock:
-	warn("Cannot open \"ping\" socket. You might need to:");
-	warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
-	warn("...echo requests/replies will fail.");
 	return 1;
 }
 
-- 
@@ -154,102 +154,100 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		     const void *saddr, const void *daddr,
 		     const struct pool *p, const struct timespec *now)
 {
+	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
+	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
+	union {
+		struct sockaddr sa;
+		struct sockaddr_in sa4;
+		struct sockaddr_in6 sa6;
+	} sa = { .sa.sa_family = af };
+	const socklen_t sl = af == AF_INET ? sizeof(sa.sa4) : sizeof(sa.sa6);
+	struct icmp_id_sock *id_map;
+	uint16_t id, seq;
 	size_t plen;
+	void *pkt;
+	int s;
 
 	(void)saddr;
 	(void)pif;
 
+	pkt = packet_get(p, 0, 0, 0, &plen);
+	if (!pkt)
+		return 1;
+
 	if (af == AF_INET) {
-		struct sockaddr_in sa = {
-			.sin_family = AF_INET,
-		};
-		union icmp_epoll_ref iref;
-		struct icmphdr *ih;
-		int id, s;
-
-		ih = packet_get(p, 0, 0, sizeof(*ih), &plen);
-		if (!ih)
+		struct icmphdr *ih = (struct icmphdr *)pkt;
+
+		if (plen < sizeof(*ih))
 			return 1;
 
 		if (ih->type != ICMP_ECHO)
 			return 1;
 
-		iref.id = id = ntohs(ih->un.echo.id);
+		id = ntohs(ih->un.echo.id);
+		id_map = &icmp_id_map[V4][id];
+		seq = ntohs(ih->un.echo.sequence);
+		sa.sa4.sin_addr = *(struct in_addr *)daddr;
+	} else if (af == AF_INET6) {
+		struct icmp6hdr *ih = (struct icmp6hdr *)pkt;
 
-		if ((s = icmp_id_map[V4][id].sock) < 0) {
-			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
-				    c->ip4.ifname_out, 0, iref.u32);
-			if (s < 0)
-				goto fail_sock;
-			if (s > FD_REF_MAX) {
-				close(s);
-				return 1;
-			}
+		if (plen < sizeof(*ih))
+			return 1;
 
-			icmp_id_map[V4][id].sock = s;
+		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
+			return 1;
 
-			debug("ICMP: new socket %i for echo ID %i", s, id);
-		}
-		icmp_id_map[V4][id].ts = now->tv_sec;
+		id = ntohs(ih->icmp6_identifier);
+		id_map = &icmp_id_map[V6][id];
+		seq = ntohs(ih->icmp6_sequence);
+		sa.sa6.sin6_addr = *(struct in6_addr *)daddr;
+		sa.sa6.sin6_scope_id = c->ifi6;
+	} else {
+		ASSERT(0);
+	}
+
+	if ((s = id_map->sock) < 0) {
+		union icmp_epoll_ref iref = { .id = id };
+		const void *bind_addr;
+		const char *bind_if;
 
-		sa.sin_addr = *(struct in_addr *)daddr;
-		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
-			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
-			debug("ICMP: failed to relay request to socket");
+		if (af == AF_INET) {
+			bind_addr = &c->ip4.addr_out;
+			bind_if = c->ip4.ifname_out;
 		} else {
-			debug("ICMP: echo request to socket, ID: %i, seq: %i",
-			      id, ntohs(ih->un.echo.sequence));
+			bind_addr = &c->ip6.addr_out;
+			bind_if = c->ip6.ifname_out;
 		}
-	} else if (af == AF_INET6) {
-		struct sockaddr_in6 sa = {
-			.sin6_family = AF_INET6,
-			.sin6_scope_id = c->ifi6,
-		};
-		union icmp_epoll_ref iref;
-		struct icmp6hdr *ih;
-		int id, s;
-
-		ih = packet_get(p, 0, 0, sizeof(struct icmp6hdr), &plen);
-		if (!ih)
-			return 1;
 
-		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
-			return 1;
+		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
 
-		iref.id = id = ntohs(ih->icmp6_identifier);
-		if ((s = icmp_id_map[V6][id].sock) < 0) {
-			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
-				    &c->ip6.addr_out,
-				    c->ip6.ifname_out, 0, iref.u32);
-			if (s < 0)
-				goto fail_sock;
-			if (s > FD_REF_MAX) {
-				close(s);
-				return 1;
-			}
-
-			icmp_id_map[V6][id].sock = s;
-
-			debug("ICMPv6: new socket %i for echo ID %i", s, id);
+		if (s < 0) {
+			warn("Cannot open \"ping\" socket. You might need to:");
+			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
+			warn("...echo requests/replies will fail.");
+			return 1;
 		}
-		icmp_id_map[V6][id].ts = now->tv_sec;
 
-		sa.sin6_addr = *(struct in6_addr *)daddr;
-		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
-			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
-			debug("ICMPv6: failed to relay request to socket");
-		} else {
-			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
-			      id, ntohs(ih->icmp6_sequence));
+		if (s > FD_REF_MAX) {
+			close(s);
+			return 1;
 		}
+
+		id_map->sock = s;
+
+		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
 	}
 
-	return 1;
+	id_map->ts = now->tv_sec;
+
+	if (sendto(s, pkt, plen, MSG_NOSIGNAL, &sa.sa, sl) < 0) {
+		debug("%s: failed to relay request to socket: %s",
+		      pname, strerror(errno));
+	} else {
+		debug("%s: echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
+		      pname, id, seq);
+	}
 
-fail_sock:
-	warn("Cannot open \"ping\" socket. You might need to:");
-	warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
-	warn("...echo requests/replies will fail.");
 	return 1;
 }
 
-- 
2.43.0

[PATCH v2 09/12] icmp: Consolidate icmp_sock_handler() with icmpv6_sock_handler()

[David Gibson]

Currently we have separate handlers for ICMP and ICMPv6 ping replies.
Although there are a number of points of difference, with some creative
refactoring we can combine these together sensibly.  Although it doesn't
save a vast amount of code, it does make it clearer that we're performing
basically the same steps for each case.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c  | 90 ++++++++++++++++++++++-----------------------------------
 icmp.h  |  3 +-
 passt.c |  4 +--
 3 files changed, 37 insertions(+), 60 deletions(-)

diff --git a/icmp.c b/icmp.c
index f6c744a..b26c61f 100644
--- a/icmp.c
+++ b/icmp.c
@@ -57,85 +57,63 @@ struct icmp_id_sock {
 static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
 
 /**
- * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
+ * icmp_sock_handler() - Handle new data from ICMP or ICMPv6 socket
  * @c:		Execution context
+ * @af:		Address family (AF_INET or AF_INET6)
  * @ref:	epoll reference
  */
-void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
+void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 {
+	struct icmp_id_sock *const id_map = af == AF_INET
+		? &icmp_id_map[V4][ref.icmp.id] : &icmp_id_map[V6][ref.icmp.id];
+	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
 	char buf[USHRT_MAX];
-	struct icmphdr *ih = (struct icmphdr *)buf;
-	struct sockaddr_in sr;
+	union {
+		struct sockaddr sa;
+		struct sockaddr_in sa4;
+		struct sockaddr_in6 sa6;
+	} sr;
 	socklen_t sl = sizeof(sr);
-	uint16_t seq, id;
+	uint16_t seq;
 	ssize_t n;
 
 	if (c->no_icmp)
 		return;
 
-	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
+	n = recvfrom(ref.fd, buf, sizeof(buf), 0, &sr.sa, &sl);
 	if (n < 0)
 		return;
 
-	seq = ntohs(ih->un.echo.sequence);
-
-	/* Adjust the packet to have the ID the guest was using, rather than the
-	 * host chosen value */
-	id = ref.icmp.id;
-	ih->un.echo.id = htons(id);
+	if (af == AF_INET) {
+		struct icmphdr *ih4 = (struct icmphdr *)buf;
 
-	if (c->mode == MODE_PASTA) {
-		if (icmp_id_map[V4][id].seq == seq)
-			return;
+		/* Adjust packet back to guest-side ID */
+		ih4->un.echo.id = htons(ref.icmp.id);
+		seq = ntohs(ih4->un.echo.sequence);
+	} else if (af == AF_INET6) {
+		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;
 
-		icmp_id_map[V4][id].seq = seq;
+		/* Adjust packet back to guest-side ID */
+		ih6->icmp6_identifier = htons(ref.icmp.id);
+		seq = ntohs(ih6->icmp6_sequence);
+	} else {
+		ASSERT(0);
 	}
 
-	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
-
-	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
-}
-
-/**
- * icmpv6_sock_handler() - Handle new data from ICMPv6 socket
- * @c:		Execution context
- * @ref:	epoll reference
- */
-void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
-{
-	char buf[USHRT_MAX];
-	struct icmp6hdr *ih = (struct icmp6hdr *)buf;
-	struct sockaddr_in6 sr;
-	socklen_t sl = sizeof(sr);
-	uint16_t seq, id;
-	ssize_t n;
-
-	if (c->no_icmp)
-		return;
-
-	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
-	if (n < 0)
-		return;
-
-	seq = ntohs(ih->icmp6_sequence);
-
-	/* Adjust the packet to have the ID the guest was using, rather than the
-	 * host chosen value */
-	id = ref.icmp.id;
-	ih->icmp6_identifier = htons(id);
-
-	/* In PASTA mode, we'll get any reply we send, discard them. */
 	if (c->mode == MODE_PASTA) {
-		if (icmp_id_map[V6][id].seq == seq)
+		if (id_map->seq == seq)
 			return;
 
-		icmp_id_map[V6][id].seq = seq;
+		id_map->seq = seq;
 	}
 
-	debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq);
-
-	tap_icmp6_send(c, &sr.sin6_addr,
-		       tap_ip6_daddr(c, &sr.sin6_addr), buf, n);
+	debug("%s: echo reply to tap, ID: %"PRIu16", seq: %"PRIu16, pname,
+	      ref.icmp.id, seq);
+	if (af == AF_INET)
+		tap_icmp4_send(c, sr.sa4.sin_addr, tap_ip4_daddr(c), buf, n);
+	else if (af == AF_INET6)
+		tap_icmp6_send(c, &sr.sa6.sin6_addr,
+			       tap_ip6_daddr(c, &sr.sa6.sin6_addr), buf, n);
 }
 
 /**
diff --git a/icmp.h b/icmp.h
index 4096c65..0083597 100644
--- a/icmp.h
+++ b/icmp.h
@@ -10,8 +10,7 @@
 
 struct ctx;
 
-void icmp_sock_handler(const struct ctx *c, union epoll_ref ref);
-void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref);
+void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref);
 int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		     const void *saddr, const void *daddr,
 		     const struct pool *p, const struct timespec *now);
diff --git a/passt.c b/passt.c
index d315438..44d3a0b 100644
--- a/passt.c
+++ b/passt.c
@@ -392,10 +392,10 @@ loop:
 			udp_sock_handler(&c, ref, eventmask, &now);
 			break;
 		case EPOLL_TYPE_ICMP:
-			icmp_sock_handler(&c, ref);
+			icmp_sock_handler(&c, AF_INET, ref);
 			break;
 		case EPOLL_TYPE_ICMPV6:
-			icmpv6_sock_handler(&c, ref);
+			icmp_sock_handler(&c, AF_INET6, ref);
 			break;
 		default:
 			/* Can't happen */
-- 
@@ -392,10 +392,10 @@ loop:
 			udp_sock_handler(&c, ref, eventmask, &now);
 			break;
 		case EPOLL_TYPE_ICMP:
-			icmp_sock_handler(&c, ref);
+			icmp_sock_handler(&c, AF_INET, ref);
 			break;
 		case EPOLL_TYPE_ICMPV6:
-			icmpv6_sock_handler(&c, ref);
+			icmp_sock_handler(&c, AF_INET6, ref);
 			break;
 		default:
 			/* Can't happen */
-- 
2.43.0

[PATCH v2 10/12] icmp: Warn on receive errors from ping sockets

[David Gibson]

Currently we silently ignore an errors receiving a packet from a ping
socket.  We don't expect that to happen, so it's probably worth reporting
if it does.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/icmp.c b/icmp.c
index b26c61f..7e698f3 100644
--- a/icmp.c
+++ b/icmp.c
@@ -81,8 +81,11 @@ void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 		return;
 
 	n = recvfrom(ref.fd, buf, sizeof(buf), 0, &sr.sa, &sl);
-	if (n < 0)
+	if (n < 0) {
+		warn("%s: recvfrom() error on ping socket: %s",
+		     pname, strerror(errno));
 		return;
+	}
 
 	if (af == AF_INET) {
 		struct icmphdr *ih4 = (struct icmphdr *)buf;
-- 
@@ -81,8 +81,11 @@ void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 		return;
 
 	n = recvfrom(ref.fd, buf, sizeof(buf), 0, &sr.sa, &sl);
-	if (n < 0)
+	if (n < 0) {
+		warn("%s: recvfrom() error on ping socket: %s",
+		     pname, strerror(errno));
 		return;
+	}
 
 	if (af == AF_INET) {
 		struct icmphdr *ih4 = (struct icmphdr *)buf;
-- 
2.43.0

[PATCH v2 11/12] icmp: Validate packets received on ping sockets

[David Gibson]

We access fields of packets received from ping sockets assuming they're
echo replies, without actually checking that.  Of course, we don't expect
anything else from the kernel, but it's probably best to verify.

While we're at it, also check for short packets, or a receive address of
the wrong family.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/icmp.c b/icmp.c
index 7e698f3..129a7f1 100644
--- a/icmp.c
+++ b/icmp.c
@@ -86,16 +86,25 @@ void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 		     pname, strerror(errno));
 		return;
 	}
+	if (sr.sa.sa_family != af)
+		goto unexpected;
 
 	if (af == AF_INET) {
 		struct icmphdr *ih4 = (struct icmphdr *)buf;
 
+		if ((size_t)n < sizeof(*ih4) || ih4->type != ICMP_ECHOREPLY)
+			goto unexpected;
+
 		/* Adjust packet back to guest-side ID */
 		ih4->un.echo.id = htons(ref.icmp.id);
 		seq = ntohs(ih4->un.echo.sequence);
 	} else if (af == AF_INET6) {
 		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;
 
+		if ((size_t)n < sizeof(*ih6) ||
+		    ih6->icmp6_type != ICMPV6_ECHO_REPLY)
+			goto unexpected;
+
 		/* Adjust packet back to guest-side ID */
 		ih6->icmp6_identifier = htons(ref.icmp.id);
 		seq = ntohs(ih6->icmp6_sequence);
@@ -117,6 +126,10 @@ void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 	else if (af == AF_INET6)
 		tap_icmp6_send(c, &sr.sa6.sin6_addr,
 			       tap_ip6_daddr(c, &sr.sa6.sin6_addr), buf, n);
+	return;
+
+unexpected:
+	warn("%s: Unexpected packet on ping socket", pname);
 }
 
 /**
-- 
@@ -86,16 +86,25 @@ void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 		     pname, strerror(errno));
 		return;
 	}
+	if (sr.sa.sa_family != af)
+		goto unexpected;
 
 	if (af == AF_INET) {
 		struct icmphdr *ih4 = (struct icmphdr *)buf;
 
+		if ((size_t)n < sizeof(*ih4) || ih4->type != ICMP_ECHOREPLY)
+			goto unexpected;
+
 		/* Adjust packet back to guest-side ID */
 		ih4->un.echo.id = htons(ref.icmp.id);
 		seq = ntohs(ih4->un.echo.sequence);
 	} else if (af == AF_INET6) {
 		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;
 
+		if ((size_t)n < sizeof(*ih6) ||
+		    ih6->icmp6_type != ICMPV6_ECHO_REPLY)
+			goto unexpected;
+
 		/* Adjust packet back to guest-side ID */
 		ih6->icmp6_identifier = htons(ref.icmp.id);
 		seq = ntohs(ih6->icmp6_sequence);
@@ -117,6 +126,10 @@ void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
 	else if (af == AF_INET6)
 		tap_icmp6_send(c, &sr.sa6.sin6_addr,
 			       tap_ip6_daddr(c, &sr.sa6.sin6_addr), buf, n);
+	return;
+
+unexpected:
+	warn("%s: Unexpected packet on ping socket", pname);
 }
 
 /**
-- 
2.43.0

[PATCH v2 12/12] icmp: Dedicated functions for starting and closing ping sequences

[David Gibson]

ICMP sockets are cleaned up on a timeout implemented in icmp_timer_one(),
and the logic to do that cleanup is open coded in that function.  Similarly
new sockets are opened when we discover we don't have an existing one in
icmp_tap_handler(), and again the logic is open-coded.

That's not the worst thing, but it's a bit cleaner to have dedicated
functions for the creation and destruction of ping sockets.  This will also
make things a bit easier for future changes we have in mind.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c | 102 +++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 67 insertions(+), 35 deletions(-)

diff --git a/icmp.c b/icmp.c
index 129a7f1..d669351 100644
--- a/icmp.c
+++ b/icmp.c
@@ -132,6 +132,70 @@ unexpected:
 	warn("%s: Unexpected packet on ping socket", pname);
 }
 
+/**
+ * icmp_ping_close() - Close out and cleanup a ping sequence
+ * @c:		Execution context
+ * @id_map:	id map entry of the sequence to close
+ */
+static void icmp_ping_close(const struct ctx *c, struct icmp_id_sock *id_map)
+{
+	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
+	close(id_map->sock);
+	id_map->sock = -1;
+	id_map->seq = -1;
+}
+
+/**
+ * icmp_ping_new() - Prepare a new ping socket for a new id
+ * @c:		Execution context
+ * @id_map:	id map entry of the sequence to open
+ * @af:		Address family, AF_INET or AF_INET6
+ * @id:		ICMP id for the new sequence
+ *
+ * Return: Newly opened ping socket fd, or -1 on failure
+ */
+static int icmp_ping_new(const struct ctx *c, struct icmp_id_sock *id_map,
+			 int af, uint16_t id)
+{
+	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
+	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
+	union icmp_epoll_ref iref = { .id = id };
+	const void *bind_addr;
+	const char *bind_if;
+	int s;
+
+	if (af == AF_INET) {
+		bind_addr = &c->ip4.addr_out;
+		bind_if = c->ip4.ifname_out;
+	} else {
+		bind_addr = &c->ip6.addr_out;
+		bind_if = c->ip6.ifname_out;
+	}
+
+	s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
+
+	if (s < 0) {
+		warn("Cannot open \"ping\" socket. You might need to:");
+		warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
+		warn("...echo requests/replies will fail.");
+		goto cancel;
+	}
+
+	if (s > FD_REF_MAX)
+		goto cancel;
+
+	id_map->sock = s;
+
+	debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
+
+	return s;
+
+cancel:
+	if (s >= 0)
+		close(s);
+	return -1;
+}
+
 /**
  * icmp_tap_handler() - Handle packets from tap
  * @c:		Execution context
@@ -148,7 +212,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		     const void *saddr, const void *daddr,
 		     const struct pool *p, const struct timespec *now)
 {
-	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
 	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
 	union {
 		struct sockaddr sa;
@@ -200,37 +263,9 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		ASSERT(0);
 	}
 
-	if ((s = id_map->sock) < 0) {
-		union icmp_epoll_ref iref = { .id = id };
-		const void *bind_addr;
-		const char *bind_if;
-
-		if (af == AF_INET) {
-			bind_addr = &c->ip4.addr_out;
-			bind_if = c->ip4.ifname_out;
-		} else {
-			bind_addr = &c->ip6.addr_out;
-			bind_if = c->ip6.ifname_out;
-		}
-
-		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
-
-		if (s < 0) {
-			warn("Cannot open \"ping\" socket. You might need to:");
-			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
-			warn("...echo requests/replies will fail.");
-			return 1;
-		}
-
-		if (s > FD_REF_MAX) {
-			close(s);
+	if ((s = id_map->sock) < 0)
+		if ((s = icmp_ping_new(c, id_map, af, id)) < 0)
 			return 1;
-		}
-
-		id_map->sock = s;
-
-		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
-	}
 
 	id_map->ts = now->tv_sec;
 
@@ -257,10 +292,7 @@ static void icmp_timer_one(const struct ctx *c, struct icmp_id_sock *id_map,
 	if (id_map->sock < 0 || now->tv_sec - id_map->ts <= ICMP_ECHO_TIMEOUT)
 		return;
 
-	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
-	close(id_map->sock);
-	id_map->sock = -1;
-	id_map->seq = -1;
+	icmp_ping_close(c, id_map);
 }
 
 /**
-- 
@@ -132,6 +132,70 @@ unexpected:
 	warn("%s: Unexpected packet on ping socket", pname);
 }
 
+/**
+ * icmp_ping_close() - Close out and cleanup a ping sequence
+ * @c:		Execution context
+ * @id_map:	id map entry of the sequence to close
+ */
+static void icmp_ping_close(const struct ctx *c, struct icmp_id_sock *id_map)
+{
+	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
+	close(id_map->sock);
+	id_map->sock = -1;
+	id_map->seq = -1;
+}
+
+/**
+ * icmp_ping_new() - Prepare a new ping socket for a new id
+ * @c:		Execution context
+ * @id_map:	id map entry of the sequence to open
+ * @af:		Address family, AF_INET or AF_INET6
+ * @id:		ICMP id for the new sequence
+ *
+ * Return: Newly opened ping socket fd, or -1 on failure
+ */
+static int icmp_ping_new(const struct ctx *c, struct icmp_id_sock *id_map,
+			 int af, uint16_t id)
+{
+	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
+	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
+	union icmp_epoll_ref iref = { .id = id };
+	const void *bind_addr;
+	const char *bind_if;
+	int s;
+
+	if (af == AF_INET) {
+		bind_addr = &c->ip4.addr_out;
+		bind_if = c->ip4.ifname_out;
+	} else {
+		bind_addr = &c->ip6.addr_out;
+		bind_if = c->ip6.ifname_out;
+	}
+
+	s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
+
+	if (s < 0) {
+		warn("Cannot open \"ping\" socket. You might need to:");
+		warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
+		warn("...echo requests/replies will fail.");
+		goto cancel;
+	}
+
+	if (s > FD_REF_MAX)
+		goto cancel;
+
+	id_map->sock = s;
+
+	debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
+
+	return s;
+
+cancel:
+	if (s >= 0)
+		close(s);
+	return -1;
+}
+
 /**
  * icmp_tap_handler() - Handle packets from tap
  * @c:		Execution context
@@ -148,7 +212,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		     const void *saddr, const void *daddr,
 		     const struct pool *p, const struct timespec *now)
 {
-	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
 	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
 	union {
 		struct sockaddr sa;
@@ -200,37 +263,9 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		ASSERT(0);
 	}
 
-	if ((s = id_map->sock) < 0) {
-		union icmp_epoll_ref iref = { .id = id };
-		const void *bind_addr;
-		const char *bind_if;
-
-		if (af == AF_INET) {
-			bind_addr = &c->ip4.addr_out;
-			bind_if = c->ip4.ifname_out;
-		} else {
-			bind_addr = &c->ip6.addr_out;
-			bind_if = c->ip6.ifname_out;
-		}
-
-		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
-
-		if (s < 0) {
-			warn("Cannot open \"ping\" socket. You might need to:");
-			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
-			warn("...echo requests/replies will fail.");
-			return 1;
-		}
-
-		if (s > FD_REF_MAX) {
-			close(s);
+	if ((s = id_map->sock) < 0)
+		if ((s = icmp_ping_new(c, id_map, af, id)) < 0)
 			return 1;
-		}
-
-		id_map->sock = s;
-
-		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
-	}
 
 	id_map->ts = now->tv_sec;
 
@@ -257,10 +292,7 @@ static void icmp_timer_one(const struct ctx *c, struct icmp_id_sock *id_map,
 	if (id_map->sock < 0 || now->tv_sec - id_map->ts <= ICMP_ECHO_TIMEOUT)
 		return;
 
-	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
-	close(id_map->sock);
-	id_map->sock = -1;
-	id_map->seq = -1;
+	icmp_ping_close(c, id_map);
 }
 
 /**
-- 
2.43.0

Re: [PATCH v2 04/12] icmp: Don't attempt to handle "wrong direction" ping socket traffic

[Stefano Brivio]

On Thu, 21 Dec 2023 17:53:19 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Linux ICMP "ping" sockets are very specific in what they do.  They let
> userspace send ping requests (ICMP_ECHO or ICMP6_ECHO_REQUEST), and receive
> matching replies (ICMP_ECHOREPLY or ICMP6_ECHO_REPLY).  They don't let you
> intercept or handle incoming ping requests.

Right... I don't know exactly what I was trying to do with this, back
then. By the way this is the main reason why it took me a while to
review this series... did I really write all those checks without a
purpose? :) Well, it looks like it.

Anyway, if you look at ping_err() in net/ipv4/ping.c, you'll see that
among the messages which can be sent back as error (they're received on
the socket causing the error -- same as ICMP messages you get on a UDP
socket for port unreachable), ICMP_ECHO is allowed (see
ping_supported()).

I think I just used that ping_supported() function to find out which
messages we could get on the socket. But we're not going to get those
anyway.

By the way, ICMP{,V6}_EXT_ECHO{,_REQUEST} support (RFC 8335, PROBE
messages) was added a while ago (kernel commit 08baf54f01f5 "net: add
support for sending RFC 8335 PROBE messages")... we should add that at
some point, it's kind of trivial.

> In the case of passt/pasta that means we can process echo requests from tap
> and forward them to a ping socket, then take the replies from the ping
> socket and forward them to tap.  We can't do the reverse: take echo
> requests from the host and somehow forward them to the guest. There's
> really no way for something outside to initiate a ping to a passt/pasta
> connected guest and if there was we'd need an entirely different mechanism
> to handle it.
> 
> However, we have some logic to deal with packets going in that reverse
> direction.  Remove it, since it can't ever be used that way.  While we're
> there use defines for the ICMPv6 types, instead of open coded type values.

I guess this last sentence only applied to a previous version of your
patch. It doesn't matter so much, but it would be nice to drop if you
re-spin.

> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index c745b7b..1f41440 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -93,8 +93,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
>  		icmp_id_map[V4][id].seq = seq;
>  	}
>  
> -	debug("ICMP: echo %s to tap, ID: %i, seq: %i",
> -	      (ih->type == ICMP_ECHO) ? "request" : "reply", id, seq);
> +	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
>  
>  	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
>  }
> @@ -138,8 +137,7 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
>  		icmp_id_map[V6][id].seq = seq;
>  	}
>  
> -	debug("ICMPv6: echo %s to tap, ID: %i, seq: %i",
> -	      (ih->icmp6_type == 128) ? "request" : "reply", id, seq);
> +	debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq);
>  
>  	tap_icmp6_send(c, &sr.sin6_addr,
>  		       tap_ip6_daddr(c, &sr.sin6_addr), buf, n);
> @@ -178,7 +176,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  		if (!ih)
>  			return 1;
>  
> -		if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY)
> +		if (ih->type != ICMP_ECHO)
>  			return 1;
>  
>  		iref.id = id = ntohs(ih->un.echo.id);
> @@ -205,8 +203,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
>  			debug("ICMP: failed to relay request to socket");
>  		} else {
> -			debug("ICMP: echo %s to socket, ID: %i, seq: %i",
> -			      (ih->type == ICMP_ECHO) ? "request" : "reply",
> +			debug("ICMP: echo request to socket, ID: %i, seq: %i",
>  			      id, ntohs(ih->un.echo.sequence));
>  		}
>  	} else if (af == AF_INET6) {
> @@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  		if (!ih)
>  			return 1;
>  
> -		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
> +		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
>  			return 1;
>  
>  		iref.id = id = ntohs(ih->icmp6_identifier);
> @@ -249,8 +246,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
>  			debug("ICMPv6: failed to relay request to socket");
>  		} else {
> -			debug("ICMPv6: echo %s to socket, ID: %i, seq: %i",
> -			      (ih->icmp6_type == 128) ? "request" : "reply",
> +			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
>  			      id, ntohs(ih->icmp6_sequence));
>  		}
>  	}

Re: [PATCH v2 06/12] icmp: Use -1 to represent "missing" sockets

[Stefano Brivio]

On Thu, 21 Dec 2023 17:53:21 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> icmp_id_map[] contains, amongst other things, fds for "ping" sockets
> associated with various ICMP echo ids.  However, we only lazily open()
> those sockets, so many will be missing.  We currently represent that with
> a 0, which isn't great, since that's technically a valid fd.  Use -1
> instead.  This does require initializing the fields in icmp_id_map[] but
> we already have an obvious place to do that.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index 7a505b4..dd98c7f 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -179,7 +179,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  
>  		iref.id = id = ntohs(ih->un.echo.id);
>  
> -		if ((s = icmp_id_map[V4][id].sock) <= 0) {
> +		if ((s = icmp_id_map[V4][id].sock) < 0) {
>  			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
>  				    c->ip4.ifname_out, 0, iref.u32);
>  			if (s < 0)
> @@ -221,7 +221,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  			return 1;
>  
>  		iref.id = id = ntohs(ih->icmp6_identifier);
> -		if ((s = icmp_id_map[V6][id].sock) <= 0) {
> +		if ((s = icmp_id_map[V6][id].sock) < 0) {
>  			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
>  				    &c->ip6.addr_out,
>  				    c->ip6.ifname_out, 0, iref.u32);
> @@ -277,7 +277,7 @@ static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
>  
>  	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
>  	close(id_map->sock);
> -	id_map->sock = 0;
> +	id_map->sock = -1;
>  	id_map->seq = -1;
>  }
>  
> @@ -315,6 +315,8 @@ void icmp_init(void)
>  {
>  	unsigned i;
>  
> -	for (i = 0; i < ICMP_NUM_IDS; i++)
> +	for (i = 0; i < ICMP_NUM_IDS; i++) {
>  		icmp_id_map[V4][i].seq = icmp_id_map[V6][i].seq = -1;
> +		icmp_id_map[V4][i].sock = icmp_id_map[V6][i].sock = -1;
> +	}

Another (well, kind of existing) use case for a 0xff-initialising
helper.

-- 
Stefano

Re: [PATCH v2 07/12] icmp: Simplify socket expiry scanning

[Stefano Brivio]

On Thu, 21 Dec 2023 17:53:22 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Currently we use icmp_act[] to scan for ICMP ids which might have an open
> socket which could time out.  However icmp_act[] contains no information
> that's not already in icmp_id_map[] - it's just an "index" which allows
> scanning for relevant entries with less cache footprint.
> 
> We only scan for ICMP socket expiry every 1s, though, so it's not clear
> that cache footprint really matters.  Furthermore, there's no strong reason
> we need to scan even that often - the timeout is fairly arbitrary and
> approximate.
> 
> So, eliminate icmp_act[] in favour of directly scanning icmp_id_map[] and
> compensate for the cache impact by reducing the scan frequency to once
> every 10s.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c | 34 ++++++----------------------------
>  icmp.h |  2 +-
>  2 files changed, 7 insertions(+), 29 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index dd98c7f..02739b9 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -56,9 +56,6 @@ struct icmp_id_sock {
>  /* Indexed by ICMP echo identifier */
>  static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
>  
> -/* Bitmaps, activity monitoring needed for identifier */
> -static uint8_t icmp_act[IP_VERSIONS][DIV_ROUND_UP(ICMP_NUM_IDS, 8)];
> -
>  /**
>   * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
>   * @c:		Execution context
> @@ -194,7 +191,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  			debug("ICMP: new socket %i for echo ID %i", s, id);
>  		}
>  		icmp_id_map[V4][id].ts = now->tv_sec;
> -		bitmap_set(icmp_act[V4], id);
>  
>  		sa.sin_addr = *(struct in_addr *)daddr;
>  		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> @@ -237,7 +233,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  			debug("ICMPv6: new socket %i for echo ID %i", s, id);
>  		}
>  		icmp_id_map[V6][id].ts = now->tv_sec;
> -		bitmap_set(icmp_act[V6], id);
>  
>  		sa.sin6_addr = *(struct in6_addr *)daddr;
>  		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> @@ -261,20 +256,15 @@ fail_sock:
>  /**
>   * icmp_timer_one() - Handler for timed events related to a given identifier
>   * @c:		Execution context
> - * @v6:		Set for IPv6 echo identifier bindings
> - * @id:		Echo identifier, host order
> + * @id_map:	id socket information to check timers for

It took me a few readings to understand this... what about:

 * @id_sock:	Socket number and activity timestamp

?

-- 
Stefano

Re: [PATCH v2 08/12] icmp: Share more between IPv4 and IPv6 paths in icmp_tap_handler()

[Stefano Brivio]

On Thu, 21 Dec 2023 17:53:23 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Currently icmp_tap_handler() consists of two almost disjoint paths for the
> IPv4 and IPv6 cases.  The only thing they share is an error message.
> We can use some intermediate variables to refactor this to share some more
> code between those paths.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c | 140 ++++++++++++++++++++++++++++-----------------------------
>  1 file changed, 69 insertions(+), 71 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index 02739b9..f6c744a 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -154,102 +154,100 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  		     const void *saddr, const void *daddr,
>  		     const struct pool *p, const struct timespec *now)
>  {
> +	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
> +	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
> +	union {
> +		struct sockaddr sa;
> +		struct sockaddr_in sa4;
> +		struct sockaddr_in6 sa6;
> +	} sa = { .sa.sa_family = af };
> +	const socklen_t sl = af == AF_INET ? sizeof(sa.sa4) : sizeof(sa.sa6);
> +	struct icmp_id_sock *id_map;
> +	uint16_t id, seq;
>  	size_t plen;
> +	void *pkt;
> +	int s;
>  
>  	(void)saddr;
>  	(void)pif;
>  
> +	pkt = packet_get(p, 0, 0, 0, &plen);
> +	if (!pkt)
> +		return 1;
> +
>  	if (af == AF_INET) {
> -		struct sockaddr_in sa = {
> -			.sin_family = AF_INET,
> -		};
> -		union icmp_epoll_ref iref;
> -		struct icmphdr *ih;
> -		int id, s;
> -
> -		ih = packet_get(p, 0, 0, sizeof(*ih), &plen);
> -		if (!ih)
> +		struct icmphdr *ih = (struct icmphdr *)pkt;
> +
> +		if (plen < sizeof(*ih))
>  			return 1;

This is obviously the same as the existing check. On the other hand,
I've been trying to use packet_get() to validate any packet read length
we need.

Here, the first call sets plen, but the only purpose is to get the
length of the message we need to relay. Given that we need at least
sizeof(*ih) here, I would prefer keep the explicit packet_get()
validation.

Same for the IPv6 path below.

>  
>  		if (ih->type != ICMP_ECHO)
>  			return 1;
>  
> -		iref.id = id = ntohs(ih->un.echo.id);
> +		id = ntohs(ih->un.echo.id);
> +		id_map = &icmp_id_map[V4][id];
> +		seq = ntohs(ih->un.echo.sequence);
> +		sa.sa4.sin_addr = *(struct in_addr *)daddr;
> +	} else if (af == AF_INET6) {
> +		struct icmp6hdr *ih = (struct icmp6hdr *)pkt;
>  
> -		if ((s = icmp_id_map[V4][id].sock) < 0) {
> -			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
> -				    c->ip4.ifname_out, 0, iref.u32);
> -			if (s < 0)
> -				goto fail_sock;
> -			if (s > FD_REF_MAX) {
> -				close(s);
> -				return 1;
> -			}
> +		if (plen < sizeof(*ih))
> +			return 1;
>  
> -			icmp_id_map[V4][id].sock = s;
> +		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
> +			return 1;
>  
> -			debug("ICMP: new socket %i for echo ID %i", s, id);
> -		}
> -		icmp_id_map[V4][id].ts = now->tv_sec;
> +		id = ntohs(ih->icmp6_identifier);
> +		id_map = &icmp_id_map[V6][id];
> +		seq = ntohs(ih->icmp6_sequence);
> +		sa.sa6.sin6_addr = *(struct in6_addr *)daddr;
> +		sa.sa6.sin6_scope_id = c->ifi6;
> +	} else {
> +		ASSERT(0);
> +	}
> +
> +	if ((s = id_map->sock) < 0) {
> +		union icmp_epoll_ref iref = { .id = id };
> +		const void *bind_addr;
> +		const char *bind_if;
>  
> -		sa.sin_addr = *(struct in_addr *)daddr;
> -		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> -			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
> -			debug("ICMP: failed to relay request to socket");
> +		if (af == AF_INET) {
> +			bind_addr = &c->ip4.addr_out;
> +			bind_if = c->ip4.ifname_out;
>  		} else {
> -			debug("ICMP: echo request to socket, ID: %i, seq: %i",
> -			      id, ntohs(ih->un.echo.sequence));
> +			bind_addr = &c->ip6.addr_out;
> +			bind_if = c->ip6.ifname_out;
>  		}
> -	} else if (af == AF_INET6) {
> -		struct sockaddr_in6 sa = {
> -			.sin6_family = AF_INET6,
> -			.sin6_scope_id = c->ifi6,
> -		};
> -		union icmp_epoll_ref iref;
> -		struct icmp6hdr *ih;
> -		int id, s;
> -
> -		ih = packet_get(p, 0, 0, sizeof(struct icmp6hdr), &plen);
> -		if (!ih)
> -			return 1;
>  
> -		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
> -			return 1;
> +		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
>  
> -		iref.id = id = ntohs(ih->icmp6_identifier);
> -		if ((s = icmp_id_map[V6][id].sock) < 0) {
> -			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
> -				    &c->ip6.addr_out,
> -				    c->ip6.ifname_out, 0, iref.u32);
> -			if (s < 0)
> -				goto fail_sock;
> -			if (s > FD_REF_MAX) {
> -				close(s);
> -				return 1;
> -			}
> -
> -			icmp_id_map[V6][id].sock = s;
> -
> -			debug("ICMPv6: new socket %i for echo ID %i", s, id);
> +		if (s < 0) {
> +			warn("Cannot open \"ping\" socket. You might need to:");
> +			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
> +			warn("...echo requests/replies will fail.");
> +			return 1;
>  		}
> -		icmp_id_map[V6][id].ts = now->tv_sec;
>  
> -		sa.sin6_addr = *(struct in6_addr *)daddr;
> -		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> -			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
> -			debug("ICMPv6: failed to relay request to socket");
> -		} else {
> -			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
> -			      id, ntohs(ih->icmp6_sequence));
> +		if (s > FD_REF_MAX) {
> +			close(s);
> +			return 1;
>  		}
> +
> +		id_map->sock = s;
> +
> +		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
>  	}
>  
> -	return 1;
> +	id_map->ts = now->tv_sec;
> +
> +	if (sendto(s, pkt, plen, MSG_NOSIGNAL, &sa.sa, sl) < 0) {
> +		debug("%s: failed to relay request to socket: %s",
> +		      pname, strerror(errno));
> +	} else {
> +		debug("%s: echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
> +		      pname, id, seq);
> +	}
>  
> -fail_sock:
> -	warn("Cannot open \"ping\" socket. You might need to:");
> -	warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
> -	warn("...echo requests/replies will fail.");
>  	return 1;
>  }
>  

-- 
Stefano

Re: [PATCH v2 09/12] icmp: Consolidate icmp_sock_handler() with icmpv6_sock_handler()

[Stefano Brivio]

On Thu, 21 Dec 2023 17:53:24 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Currently we have separate handlers for ICMP and ICMPv6 ping replies.
> Although there are a number of points of difference, with some creative
> refactoring we can combine these together sensibly.  Although it doesn't
> save a vast amount of code, it does make it clearer that we're performing
> basically the same steps for each case.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c  | 90 ++++++++++++++++++++++-----------------------------------
>  icmp.h  |  3 +-
>  passt.c |  4 +--
>  3 files changed, 37 insertions(+), 60 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index f6c744a..b26c61f 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -57,85 +57,63 @@ struct icmp_id_sock {
>  static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
>  
>  /**
> - * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
> + * icmp_sock_handler() - Handle new data from ICMP or ICMPv6 socket
>   * @c:		Execution context
> + * @af:		Address family (AF_INET or AF_INET6)
>   * @ref:	epoll reference
>   */
> -void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
> +void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
>  {
> +	struct icmp_id_sock *const id_map = af == AF_INET
> +		? &icmp_id_map[V4][ref.icmp.id] : &icmp_id_map[V6][ref.icmp.id];
> +	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
>  	char buf[USHRT_MAX];
> -	struct icmphdr *ih = (struct icmphdr *)buf;
> -	struct sockaddr_in sr;
> +	union {
> +		struct sockaddr sa;
> +		struct sockaddr_in sa4;
> +		struct sockaddr_in6 sa6;
> +	} sr;
>  	socklen_t sl = sizeof(sr);
> -	uint16_t seq, id;
> +	uint16_t seq;
>  	ssize_t n;
>  
>  	if (c->no_icmp)
>  		return;
>  
> -	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
> +	n = recvfrom(ref.fd, buf, sizeof(buf), 0, &sr.sa, &sl);
>  	if (n < 0)
>  		return;
>  
> -	seq = ntohs(ih->un.echo.sequence);
> -
> -	/* Adjust the packet to have the ID the guest was using, rather than the
> -	 * host chosen value */
> -	id = ref.icmp.id;
> -	ih->un.echo.id = htons(id);
> +	if (af == AF_INET) {
> +		struct icmphdr *ih4 = (struct icmphdr *)buf;
>  
> -	if (c->mode == MODE_PASTA) {
> -		if (icmp_id_map[V4][id].seq == seq)
> -			return;
> +		/* Adjust packet back to guest-side ID */
> +		ih4->un.echo.id = htons(ref.icmp.id);
> +		seq = ntohs(ih4->un.echo.sequence);
> +	} else if (af == AF_INET6) {
> +		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;
>  
> -		icmp_id_map[V4][id].seq = seq;
> +		/* Adjust packet back to guest-side ID */
> +		ih6->icmp6_identifier = htons(ref.icmp.id);
> +		seq = ntohs(ih6->icmp6_sequence);
> +	} else {
> +		ASSERT(0);
>  	}
>  
> -	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
> -
> -	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
> -}
> -
> -/**
> - * icmpv6_sock_handler() - Handle new data from ICMPv6 socket
> - * @c:		Execution context
> - * @ref:	epoll reference
> - */
> -void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
> -{
> -	char buf[USHRT_MAX];
> -	struct icmp6hdr *ih = (struct icmp6hdr *)buf;
> -	struct sockaddr_in6 sr;
> -	socklen_t sl = sizeof(sr);
> -	uint16_t seq, id;
> -	ssize_t n;
> -
> -	if (c->no_icmp)
> -		return;
> -
> -	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
> -	if (n < 0)
> -		return;
> -
> -	seq = ntohs(ih->icmp6_sequence);
> -
> -	/* Adjust the packet to have the ID the guest was using, rather than the
> -	 * host chosen value */
> -	id = ref.icmp.id;
> -	ih->icmp6_identifier = htons(id);
> -
> -	/* In PASTA mode, we'll get any reply we send, discard them. */
>  	if (c->mode == MODE_PASTA) {

The comment here should be kept -- the kernel behaviour was rather
surprising to me, and I would have otherwise no idea why we return
early here.

-- 
Stefano

Re: [PATCH v2 12/12] icmp: Dedicated functions for starting and closing ping sequences

[Stefano Brivio]

On Thu, 21 Dec 2023 17:53:27 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> ICMP sockets are cleaned up on a timeout implemented in icmp_timer_one(),
> and the logic to do that cleanup is open coded in that function.  Similarly
> new sockets are opened when we discover we don't have an existing one in
> icmp_tap_handler(), and again the logic is open-coded.
> 
> That's not the worst thing, but it's a bit cleaner to have dedicated
> functions for the creation and destruction of ping sockets.  This will also
> make things a bit easier for future changes we have in mind.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c | 102 +++++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 67 insertions(+), 35 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index 129a7f1..d669351 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -132,6 +132,70 @@ unexpected:
>  	warn("%s: Unexpected packet on ping socket", pname);
>  }
>  
> +/**
> + * icmp_ping_close() - Close out and cleanup a ping sequence

s/cleanup/clean up/ (verb)

The commit title and this comment (referring to a sequence) are a bit
misleading... this pretty much closes the socket, and as far as I can
see setting the sequence to -1 doesn't actually have an effect (despite
the fact it's a good practice).

If you mean "sequence" not as "sequence number" but rather as a
"sequence of pings", then I think we should rename one of the two...
either 'seqnum' for the sequence number, or maybe s/sequence/socket/g
here.

> + * @c:		Execution context
> + * @id_map:	id map entry of the sequence to close
> + */
> +static void icmp_ping_close(const struct ctx *c, struct icmp_id_sock *id_map)
> +{
> +	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
> +	close(id_map->sock);
> +	id_map->sock = -1;
> +	id_map->seq = -1;
> +}
> +
> +/**
> + * icmp_ping_new() - Prepare a new ping socket for a new id
> + * @c:		Execution context
> + * @id_map:	id map entry of the sequence to open
> + * @af:		Address family, AF_INET or AF_INET6
> + * @id:		ICMP id for the new sequence
> + *
> + * Return: Newly opened ping socket fd, or -1 on failure
> + */
> +static int icmp_ping_new(const struct ctx *c, struct icmp_id_sock *id_map,
> +			 int af, uint16_t id)
> +{
> +	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
> +	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
> +	union icmp_epoll_ref iref = { .id = id };
> +	const void *bind_addr;
> +	const char *bind_if;
> +	int s;
> +
> +	if (af == AF_INET) {
> +		bind_addr = &c->ip4.addr_out;
> +		bind_if = c->ip4.ifname_out;
> +	} else {
> +		bind_addr = &c->ip6.addr_out;
> +		bind_if = c->ip6.ifname_out;
> +	}
> +
> +	s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
> +
> +	if (s < 0) {
> +		warn("Cannot open \"ping\" socket. You might need to:");
> +		warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
> +		warn("...echo requests/replies will fail.");
> +		goto cancel;
> +	}
> +
> +	if (s > FD_REF_MAX)
> +		goto cancel;
> +
> +	id_map->sock = s;
> +
> +	debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
> +
> +	return s;
> +
> +cancel:
> +	if (s >= 0)
> +		close(s);
> +	return -1;
> +}
> +
>  /**
>   * icmp_tap_handler() - Handle packets from tap
>   * @c:		Execution context
> @@ -148,7 +212,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  		     const void *saddr, const void *daddr,
>  		     const struct pool *p, const struct timespec *now)
>  {
> -	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
>  	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
>  	union {
>  		struct sockaddr sa;
> @@ -200,37 +263,9 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  		ASSERT(0);
>  	}
>  
> -	if ((s = id_map->sock) < 0) {
> -		union icmp_epoll_ref iref = { .id = id };
> -		const void *bind_addr;
> -		const char *bind_if;
> -
> -		if (af == AF_INET) {
> -			bind_addr = &c->ip4.addr_out;
> -			bind_if = c->ip4.ifname_out;
> -		} else {
> -			bind_addr = &c->ip6.addr_out;
> -			bind_if = c->ip6.ifname_out;
> -		}
> -
> -		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
> -
> -		if (s < 0) {
> -			warn("Cannot open \"ping\" socket. You might need to:");
> -			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
> -			warn("...echo requests/replies will fail.");
> -			return 1;
> -		}
> -
> -		if (s > FD_REF_MAX) {
> -			close(s);
> +	if ((s = id_map->sock) < 0)
> +		if ((s = icmp_ping_new(c, id_map, af, id)) < 0)
>  			return 1;
> -		}
> -
> -		id_map->sock = s;
> -
> -		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
> -	}
>  
>  	id_map->ts = now->tv_sec;
>  
> @@ -257,10 +292,7 @@ static void icmp_timer_one(const struct ctx *c, struct icmp_id_sock *id_map,
>  	if (id_map->sock < 0 || now->tv_sec - id_map->ts <= ICMP_ECHO_TIMEOUT)
>  		return;
>  
> -	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
> -	close(id_map->sock);
> -	id_map->sock = -1;
> -	id_map->seq = -1;
> +	icmp_ping_close(c, id_map);
>  }
>  
>  /**

-- 
Stefano

Re: [PATCH v2 04/12] icmp: Don't attempt to handle "wrong direction" ping socket traffic

[David Gibson]

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On Sat, Jan 06, 2024 at 04:59:11PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:19 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Linux ICMP "ping" sockets are very specific in what they do.  They let
> > userspace send ping requests (ICMP_ECHO or ICMP6_ECHO_REQUEST), and receive
> > matching replies (ICMP_ECHOREPLY or ICMP6_ECHO_REPLY).  They don't let you
> > intercept or handle incoming ping requests.
> 
> Right... I don't know exactly what I was trying to do with this, back
> then. By the way this is the main reason why it took me a while to
> review this series... did I really write all those checks without a
> purpose? :) Well, it looks like it.
> 
> Anyway, if you look at ping_err() in net/ipv4/ping.c, you'll see that
> among the messages which can be sent back as error (they're received on
> the socket causing the error -- same as ICMP messages you get on a UDP
> socket for port unreachable), ICMP_ECHO is allowed (see
> ping_supported()).
> 
> I think I just used that ping_supported() function to find out which
> messages we could get on the socket. But we're not going to get those
> anyway.

Right.

> By the way, ICMP{,V6}_EXT_ECHO{,_REQUEST} support (RFC 8335, PROBE
> messages) was added a while ago (kernel commit 08baf54f01f5 "net: add
> support for sending RFC 8335 PROBE messages")... we should add that at
> some point, it's kind of trivial.

Indeed.  Want to make a BZ for it so we don't forget?

> > In the case of passt/pasta that means we can process echo requests from tap
> > and forward them to a ping socket, then take the replies from the ping
> > socket and forward them to tap.  We can't do the reverse: take echo
> > requests from the host and somehow forward them to the guest. There's
> > really no way for something outside to initiate a ping to a passt/pasta
> > connected guest and if there was we'd need an entirely different mechanism
> > to handle it.
> > 
> > However, we have some logic to deal with packets going in that reverse
> > direction.  Remove it, since it can't ever be used that way.  While we're
> > there use defines for the ICMPv6 types, instead of open coded type values.
> 
> I guess this last sentence only applied to a previous version of your
> patch. It doesn't matter so much, but it would be nice to drop if you
> re-spin.

Uh... no.. that change is right:

[snip]
> > @@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  		if (!ih)
> >  			return 1;
> >  
> > -		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
> > +		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)

here.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2 06/12] icmp: Use -1 to represent "missing" sockets

[David Gibson]

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On Sat, Jan 06, 2024 at 04:59:32PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:21 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > icmp_id_map[] contains, amongst other things, fds for "ping" sockets
> > associated with various ICMP echo ids.  However, we only lazily open()
> > those sockets, so many will be missing.  We currently represent that with
> > a 0, which isn't great, since that's technically a valid fd.  Use -1
> > instead.  This does require initializing the fields in icmp_id_map[] but
> > we already have an obvious place to do that.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index 7a505b4..dd98c7f 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -179,7 +179,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  
> >  		iref.id = id = ntohs(ih->un.echo.id);
> >  
> > -		if ((s = icmp_id_map[V4][id].sock) <= 0) {
> > +		if ((s = icmp_id_map[V4][id].sock) < 0) {
> >  			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
> >  				    c->ip4.ifname_out, 0, iref.u32);
> >  			if (s < 0)
> > @@ -221,7 +221,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  			return 1;
> >  
> >  		iref.id = id = ntohs(ih->icmp6_identifier);
> > -		if ((s = icmp_id_map[V6][id].sock) <= 0) {
> > +		if ((s = icmp_id_map[V6][id].sock) < 0) {
> >  			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
> >  				    &c->ip6.addr_out,
> >  				    c->ip6.ifname_out, 0, iref.u32);
> > @@ -277,7 +277,7 @@ static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
> >  
> >  	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
> >  	close(id_map->sock);
> > -	id_map->sock = 0;
> > +	id_map->sock = -1;
> >  	id_map->seq = -1;
> >  }
> >  
> > @@ -315,6 +315,8 @@ void icmp_init(void)
> >  {
> >  	unsigned i;
> >  
> > -	for (i = 0; i < ICMP_NUM_IDS; i++)
> > +	for (i = 0; i < ICMP_NUM_IDS; i++) {
> >  		icmp_id_map[V4][i].seq = icmp_id_map[V6][i].seq = -1;
> > +		icmp_id_map[V4][i].sock = icmp_id_map[V6][i].sock = -1;
> > +	}
> 
> Another (well, kind of existing) use case for a 0xff-initialising
> helper.

Hm.. it's still not every field, so only sorta.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2 07/12] icmp: Simplify socket expiry scanning

[David Gibson]

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On Sat, Jan 06, 2024 at 04:59:53PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:22 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Currently we use icmp_act[] to scan for ICMP ids which might have an open
> > socket which could time out.  However icmp_act[] contains no information
> > that's not already in icmp_id_map[] - it's just an "index" which allows
> > scanning for relevant entries with less cache footprint.
> > 
> > We only scan for ICMP socket expiry every 1s, though, so it's not clear
> > that cache footprint really matters.  Furthermore, there's no strong reason
> > we need to scan even that often - the timeout is fairly arbitrary and
> > approximate.
> > 
> > So, eliminate icmp_act[] in favour of directly scanning icmp_id_map[] and
> > compensate for the cache impact by reducing the scan frequency to once
> > every 10s.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c | 34 ++++++----------------------------
> >  icmp.h |  2 +-
> >  2 files changed, 7 insertions(+), 29 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index dd98c7f..02739b9 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -56,9 +56,6 @@ struct icmp_id_sock {
> >  /* Indexed by ICMP echo identifier */
> >  static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
> >  
> > -/* Bitmaps, activity monitoring needed for identifier */
> > -static uint8_t icmp_act[IP_VERSIONS][DIV_ROUND_UP(ICMP_NUM_IDS, 8)];
> > -
> >  /**
> >   * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
> >   * @c:		Execution context
> > @@ -194,7 +191,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  			debug("ICMP: new socket %i for echo ID %i", s, id);
> >  		}
> >  		icmp_id_map[V4][id].ts = now->tv_sec;
> > -		bitmap_set(icmp_act[V4], id);
> >  
> >  		sa.sin_addr = *(struct in_addr *)daddr;
> >  		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> > @@ -237,7 +233,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  			debug("ICMPv6: new socket %i for echo ID %i", s, id);
> >  		}
> >  		icmp_id_map[V6][id].ts = now->tv_sec;
> > -		bitmap_set(icmp_act[V6], id);
> >  
> >  		sa.sin6_addr = *(struct in6_addr *)daddr;
> >  		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> > @@ -261,20 +256,15 @@ fail_sock:
> >  /**
> >   * icmp_timer_one() - Handler for timed events related to a given identifier
> >   * @c:		Execution context
> > - * @v6:		Set for IPv6 echo identifier bindings
> > - * @id:		Echo identifier, host order
> > + * @id_map:	id socket information to check timers for
> 
> It took me a few readings to understand this... what about:
> 
>  * @id_sock:	Socket number and activity timestamp
> 
> ?

Works for me.  Updated.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2 09/12] icmp: Consolidate icmp_sock_handler() with icmpv6_sock_handler()

[David Gibson]

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On Sat, Jan 06, 2024 at 05:00:44PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:24 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Currently we have separate handlers for ICMP and ICMPv6 ping replies.
> > Although there are a number of points of difference, with some creative
> > refactoring we can combine these together sensibly.  Although it doesn't
> > save a vast amount of code, it does make it clearer that we're performing
> > basically the same steps for each case.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c  | 90 ++++++++++++++++++++++-----------------------------------
> >  icmp.h  |  3 +-
> >  passt.c |  4 +--
> >  3 files changed, 37 insertions(+), 60 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index f6c744a..b26c61f 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -57,85 +57,63 @@ struct icmp_id_sock {
> >  static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
> >  
> >  /**
> > - * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
> > + * icmp_sock_handler() - Handle new data from ICMP or ICMPv6 socket
> >   * @c:		Execution context
> > + * @af:		Address family (AF_INET or AF_INET6)
> >   * @ref:	epoll reference
> >   */
> > -void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
> > +void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
> >  {
> > +	struct icmp_id_sock *const id_map = af == AF_INET
> > +		? &icmp_id_map[V4][ref.icmp.id] : &icmp_id_map[V6][ref.icmp.id];
> > +	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
> >  	char buf[USHRT_MAX];
> > -	struct icmphdr *ih = (struct icmphdr *)buf;
> > -	struct sockaddr_in sr;
> > +	union {
> > +		struct sockaddr sa;
> > +		struct sockaddr_in sa4;
> > +		struct sockaddr_in6 sa6;
> > +	} sr;
> >  	socklen_t sl = sizeof(sr);
> > -	uint16_t seq, id;
> > +	uint16_t seq;
> >  	ssize_t n;
> >  
> >  	if (c->no_icmp)
> >  		return;
> >  
> > -	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
> > +	n = recvfrom(ref.fd, buf, sizeof(buf), 0, &sr.sa, &sl);
> >  	if (n < 0)
> >  		return;
> >  
> > -	seq = ntohs(ih->un.echo.sequence);
> > -
> > -	/* Adjust the packet to have the ID the guest was using, rather than the
> > -	 * host chosen value */
> > -	id = ref.icmp.id;
> > -	ih->un.echo.id = htons(id);
> > +	if (af == AF_INET) {
> > +		struct icmphdr *ih4 = (struct icmphdr *)buf;
> >  
> > -	if (c->mode == MODE_PASTA) {
> > -		if (icmp_id_map[V4][id].seq == seq)
> > -			return;
> > +		/* Adjust packet back to guest-side ID */
> > +		ih4->un.echo.id = htons(ref.icmp.id);
> > +		seq = ntohs(ih4->un.echo.sequence);
> > +	} else if (af == AF_INET6) {
> > +		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;
> >  
> > -		icmp_id_map[V4][id].seq = seq;
> > +		/* Adjust packet back to guest-side ID */
> > +		ih6->icmp6_identifier = htons(ref.icmp.id);
> > +		seq = ntohs(ih6->icmp6_sequence);
> > +	} else {
> > +		ASSERT(0);
> >  	}
> >  
> > -	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
> > -
> > -	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
> > -}
> > -
> > -/**
> > - * icmpv6_sock_handler() - Handle new data from ICMPv6 socket
> > - * @c:		Execution context
> > - * @ref:	epoll reference
> > - */
> > -void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
> > -{
> > -	char buf[USHRT_MAX];
> > -	struct icmp6hdr *ih = (struct icmp6hdr *)buf;
> > -	struct sockaddr_in6 sr;
> > -	socklen_t sl = sizeof(sr);
> > -	uint16_t seq, id;
> > -	ssize_t n;
> > -
> > -	if (c->no_icmp)
> > -		return;
> > -
> > -	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
> > -	if (n < 0)
> > -		return;
> > -
> > -	seq = ntohs(ih->icmp6_sequence);
> > -
> > -	/* Adjust the packet to have the ID the guest was using, rather than the
> > -	 * host chosen value */
> > -	id = ref.icmp.id;
> > -	ih->icmp6_identifier = htons(id);
> > -
> > -	/* In PASTA mode, we'll get any reply we send, discard them. */
> >  	if (c->mode == MODE_PASTA) {
> 
> The comment here should be kept -- the kernel behaviour was rather
> surprising to me, and I would have otherwise no idea why we return
> early here.

Good point, comment restored.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2 12/12] icmp: Dedicated functions for starting and closing ping sequences

[David Gibson]

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On Sat, Jan 06, 2024 at 05:01:04PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:27 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > ICMP sockets are cleaned up on a timeout implemented in icmp_timer_one(),
> > and the logic to do that cleanup is open coded in that function.  Similarly
> > new sockets are opened when we discover we don't have an existing one in
> > icmp_tap_handler(), and again the logic is open-coded.
> > 
> > That's not the worst thing, but it's a bit cleaner to have dedicated
> > functions for the creation and destruction of ping sockets.  This will also
> > make things a bit easier for future changes we have in mind.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c | 102 +++++++++++++++++++++++++++++++++++++--------------------
> >  1 file changed, 67 insertions(+), 35 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index 129a7f1..d669351 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -132,6 +132,70 @@ unexpected:
> >  	warn("%s: Unexpected packet on ping socket", pname);
> >  }
> >  
> > +/**
> > + * icmp_ping_close() - Close out and cleanup a ping sequence
> 
> s/cleanup/clean up/ (verb)

Done.

> The commit title and this comment (referring to a sequence) are a bit
> misleading... this pretty much closes the socket, and as far as I can
> see setting the sequence to -1 doesn't actually have an effect (despite
> the fact it's a good practice).
> 
> If you mean "sequence" not as "sequence number" but rather as a
> "sequence of pings", then I think we should rename one of the two...
> either 'seqnum' for the sequence number, or maybe s/sequence/socket/g
> here.

Right, I was basically meaning "flow", but avoiding it because this is
not (yet) linked to the flow table.  I've gone with
s/sequence/socket/g, more or less, and I think that works out.

> 
> > + * @c:		Execution context
> > + * @id_map:	id map entry of the sequence to close
> > + */
> > +static void icmp_ping_close(const struct ctx *c, struct icmp_id_sock *id_map)
> > +{
> > +	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
> > +	close(id_map->sock);
> > +	id_map->sock = -1;
> > +	id_map->seq = -1;
> > +}
> > +
> > +/**
> > + * icmp_ping_new() - Prepare a new ping socket for a new id
> > + * @c:		Execution context
> > + * @id_map:	id map entry of the sequence to open
> > + * @af:		Address family, AF_INET or AF_INET6
> > + * @id:		ICMP id for the new sequence
> > + *
> > + * Return: Newly opened ping socket fd, or -1 on failure
> > + */
> > +static int icmp_ping_new(const struct ctx *c, struct icmp_id_sock *id_map,
> > +			 int af, uint16_t id)
> > +{
> > +	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
> > +	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
> > +	union icmp_epoll_ref iref = { .id = id };
> > +	const void *bind_addr;
> > +	const char *bind_if;
> > +	int s;
> > +
> > +	if (af == AF_INET) {
> > +		bind_addr = &c->ip4.addr_out;
> > +		bind_if = c->ip4.ifname_out;
> > +	} else {
> > +		bind_addr = &c->ip6.addr_out;
> > +		bind_if = c->ip6.ifname_out;
> > +	}
> > +
> > +	s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
> > +
> > +	if (s < 0) {
> > +		warn("Cannot open \"ping\" socket. You might need to:");
> > +		warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
> > +		warn("...echo requests/replies will fail.");
> > +		goto cancel;
> > +	}
> > +
> > +	if (s > FD_REF_MAX)
> > +		goto cancel;
> > +
> > +	id_map->sock = s;
> > +
> > +	debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
> > +
> > +	return s;
> > +
> > +cancel:
> > +	if (s >= 0)
> > +		close(s);
> > +	return -1;
> > +}
> > +
> >  /**
> >   * icmp_tap_handler() - Handle packets from tap
> >   * @c:		Execution context
> > @@ -148,7 +212,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  		     const void *saddr, const void *daddr,
> >  		     const struct pool *p, const struct timespec *now)
> >  {
> > -	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
> >  	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
> >  	union {
> >  		struct sockaddr sa;
> > @@ -200,37 +263,9 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  		ASSERT(0);
> >  	}
> >  
> > -	if ((s = id_map->sock) < 0) {
> > -		union icmp_epoll_ref iref = { .id = id };
> > -		const void *bind_addr;
> > -		const char *bind_if;
> > -
> > -		if (af == AF_INET) {
> > -			bind_addr = &c->ip4.addr_out;
> > -			bind_if = c->ip4.ifname_out;
> > -		} else {
> > -			bind_addr = &c->ip6.addr_out;
> > -			bind_if = c->ip6.ifname_out;
> > -		}
> > -
> > -		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);
> > -
> > -		if (s < 0) {
> > -			warn("Cannot open \"ping\" socket. You might need to:");
> > -			warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
> > -			warn("...echo requests/replies will fail.");
> > -			return 1;
> > -		}
> > -
> > -		if (s > FD_REF_MAX) {
> > -			close(s);
> > +	if ((s = id_map->sock) < 0)
> > +		if ((s = icmp_ping_new(c, id_map, af, id)) < 0)
> >  			return 1;
> > -		}
> > -
> > -		id_map->sock = s;
> > -
> > -		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
> > -	}
> >  
> >  	id_map->ts = now->tv_sec;
> >  
> > @@ -257,10 +292,7 @@ static void icmp_timer_one(const struct ctx *c, struct icmp_id_sock *id_map,
> >  	if (id_map->sock < 0 || now->tv_sec - id_map->ts <= ICMP_ECHO_TIMEOUT)
> >  		return;
> >  
> > -	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
> > -	close(id_map->sock);
> > -	id_map->sock = -1;
> > -	id_map->seq = -1;
> > +	icmp_ping_close(c, id_map);
> >  }
> >  
> >  /**
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2 08/12] icmp: Share more between IPv4 and IPv6 paths in icmp_tap_handler()

[David Gibson]

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On Sat, Jan 06, 2024 at 05:00:21PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:23 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Currently icmp_tap_handler() consists of two almost disjoint paths for the
> > IPv4 and IPv6 cases.  The only thing they share is an error message.
> > We can use some intermediate variables to refactor this to share some more
> > code between those paths.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c | 140 ++++++++++++++++++++++++++++-----------------------------
> >  1 file changed, 69 insertions(+), 71 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index 02739b9..f6c744a 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -154,102 +154,100 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  		     const void *saddr, const void *daddr,
> >  		     const struct pool *p, const struct timespec *now)
> >  {
> > +	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
> > +	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
> > +	union {
> > +		struct sockaddr sa;
> > +		struct sockaddr_in sa4;
> > +		struct sockaddr_in6 sa6;
> > +	} sa = { .sa.sa_family = af };
> > +	const socklen_t sl = af == AF_INET ? sizeof(sa.sa4) : sizeof(sa.sa6);
> > +	struct icmp_id_sock *id_map;
> > +	uint16_t id, seq;
> >  	size_t plen;
> > +	void *pkt;
> > +	int s;
> >  
> >  	(void)saddr;
> >  	(void)pif;
> >  
> > +	pkt = packet_get(p, 0, 0, 0, &plen);
> > +	if (!pkt)
> > +		return 1;
> > +
> >  	if (af == AF_INET) {
> > -		struct sockaddr_in sa = {
> > -			.sin_family = AF_INET,
> > -		};
> > -		union icmp_epoll_ref iref;
> > -		struct icmphdr *ih;
> > -		int id, s;
> > -
> > -		ih = packet_get(p, 0, 0, sizeof(*ih), &plen);
> > -		if (!ih)
> > +		struct icmphdr *ih = (struct icmphdr *)pkt;
> > +
> > +		if (plen < sizeof(*ih))
> >  			return 1;
> 
> This is obviously the same as the existing check. On the other hand,
> I've been trying to use packet_get() to validate any packet read length
> we need.
> 
> Here, the first call sets plen, but the only purpose is to get the
> length of the message we need to relay. Given that we need at least
> sizeof(*ih) here, I would prefer keep the explicit packet_get()
> validation.
> 
> Same for the IPv6 path below.

Ok, fair enough.  Updated.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2 04/12] icmp: Don't attempt to handle "wrong direction" ping socket traffic

[Stefano Brivio]

On Sun, 7 Jan 2024 11:37:46 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Sat, Jan 06, 2024 at 04:59:11PM +0100, Stefano Brivio wrote:
> > On Thu, 21 Dec 2023 17:53:19 +1100
> > David Gibson <david@gibson.dropbear.id.au> wrote:
> >   
> > > Linux ICMP "ping" sockets are very specific in what they do.  They let
> > > userspace send ping requests (ICMP_ECHO or ICMP6_ECHO_REQUEST), and receive
> > > matching replies (ICMP_ECHOREPLY or ICMP6_ECHO_REPLY).  They don't let you
> > > intercept or handle incoming ping requests.  
> > 
> > Right... I don't know exactly what I was trying to do with this, back
> > then. By the way this is the main reason why it took me a while to
> > review this series... did I really write all those checks without a
> > purpose? :) Well, it looks like it.
> > 
> > Anyway, if you look at ping_err() in net/ipv4/ping.c, you'll see that
> > among the messages which can be sent back as error (they're received on
> > the socket causing the error -- same as ICMP messages you get on a UDP
> > socket for port unreachable), ICMP_ECHO is allowed (see
> > ping_supported()).
> > 
> > I think I just used that ping_supported() function to find out which
> > messages we could get on the socket. But we're not going to get those
> > anyway.  
> 
> Right.
> 
> > By the way, ICMP{,V6}_EXT_ECHO{,_REQUEST} support (RFC 8335, PROBE
> > messages) was added a while ago (kernel commit 08baf54f01f5 "net: add
> > support for sending RFC 8335 PROBE messages")... we should add that at
> > some point, it's kind of trivial.  
> 
> Indeed.  Want to make a BZ for it so we don't forget?

Done, it's https://bugs.passt.top/show_bug.cgi?id=78.

> > > In the case of passt/pasta that means we can process echo requests from tap
> > > and forward them to a ping socket, then take the replies from the ping
> > > socket and forward them to tap.  We can't do the reverse: take echo
> > > requests from the host and somehow forward them to the guest. There's
> > > really no way for something outside to initiate a ping to a passt/pasta
> > > connected guest and if there was we'd need an entirely different mechanism
> > > to handle it.
> > > 
> > > However, we have some logic to deal with packets going in that reverse
> > > direction.  Remove it, since it can't ever be used that way.  While we're
> > > there use defines for the ICMPv6 types, instead of open coded type values.  
> > 
> > I guess this last sentence only applied to a previous version of your
> > patch. It doesn't matter so much, but it would be nice to drop if you
> > re-spin.  
> 
> Uh... no.. that change is right:
> 
> [snip]
> > > @@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> > >  		if (!ih)
> > >  			return 1;
> > >  
> > > -		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
> > > +		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)  
> 
> here.

Ah, sorry, I missed this one.

-- 
Stefano