* [PATCH v7] udp: support traceroute in direction tap-socket
@ 2025-04-05 19:21 Jon Maloy
2025-04-07 4:55 ` David Gibson
0 siblings, 1 reply; 2+ messages in thread
From: Jon Maloy @ 2025-04-05 19:21 UTC (permalink / raw)
To: sbrivio, dgibson, jmaloy, passt-dev
Now that ICMP pass-through from socket-to-tap is in place, it is
easy to support UDP based traceroute functionality in direction
tap-to-socket.
We fix that in this commit.
Link: https://bugs.passt.top/show_bug.cgi?id=64
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
v2: - Using ancillary data instead of setsockopt to transfer outgoing
TTL.
- Support IPv6
v3: - Storing ttl per packet instead of per flow. This may not be
elegant, but much less intrusive than changing the flow
criteria. This eliminates the need for the extra, flow-changing
patch we introduced in v2.
v4: - Going back to something similar to the original solution, but
storing current ttl in struct udp_flow, plus ensuring that all
packets in a struct tap4_l4_t/tap6_l4_t instance have the same
ttl. After input from David Gibson.
v5: - Some minor fixes after feedback from Stefano Brivio.
v6: - Ensured that socket TTL is initialized at flow creation.
- Ensured that setting of hop limit on IPv6 socket works.
v7: - Setting of IPv6 hop_limit fails sometimes unless it is 4 bytes.
---
tap.c | 17 +++++++++++++----
udp.c | 22 +++++++++++++++++++++-
udp.h | 3 ++-
udp_flow.c | 1 +
udp_flow.h | 4 +++-
5 files changed, 40 insertions(+), 7 deletions(-)
diff --git a/tap.c b/tap.c
index 3a6fcbe..d630f6d 100644
--- a/tap.c
+++ b/tap.c
@@ -559,6 +559,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
* struct l4_seq4_t - Message sequence for one protocol handler call, IPv4
* @msgs: Count of messages in sequence
* @protocol: Protocol number
+ * @ttl: Time to live
* @source: Source port
* @dest: Destination port
* @saddr: Source address
@@ -567,6 +568,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
*/
static struct tap4_l4_t {
uint8_t protocol;
+ uint8_t ttl;
uint16_t source;
uint16_t dest;
@@ -586,6 +588,7 @@ static struct tap4_l4_t {
* @dest: Destination port
* @saddr: Source address
* @daddr: Destination address
+ * @hop_limit: Hop limit
* @msg: Array of messages that can be handled in a single call
*/
static struct tap6_l4_t {
@@ -598,6 +601,8 @@ static struct tap6_l4_t {
struct in6_addr saddr;
struct in6_addr daddr;
+ uint8_t hop_limit;
+
struct pool_l4_t p;
} tap6_l4[TAP_SEQS /* Arbitrary: TAP_MSGS in theory, so limit in users */];
@@ -786,7 +791,8 @@ resume:
#define L4_MATCH(iph, uh, seq) \
((seq)->protocol == (iph)->protocol && \
(seq)->source == (uh)->source && (seq)->dest == (uh)->dest && \
- (seq)->saddr.s_addr == (iph)->saddr && (seq)->daddr.s_addr == (iph)->daddr)
+ (seq)->saddr.s_addr == (iph)->saddr && \
+ (seq)->daddr.s_addr == (iph)->daddr && (seq)->ttl == (iph)->ttl)
#define L4_SET(iph, uh, seq) \
do { \
@@ -795,6 +801,7 @@ resume:
(seq)->dest = (uh)->dest; \
(seq)->saddr.s_addr = (iph)->saddr; \
(seq)->daddr.s_addr = (iph)->daddr; \
+ (seq)->ttl = (iph)->ttl; \
} while (0)
if (seq && L4_MATCH(iph, uh, seq) && seq->p.count < UIO_MAXIOV)
@@ -843,7 +850,7 @@ append:
for (k = 0; k < p->count; )
k += udp_tap_handler(c, PIF_TAP, AF_INET,
&seq->saddr, &seq->daddr,
- p, k, now);
+ seq->ttl, p, k, now);
}
}
@@ -966,7 +973,8 @@ resume:
(seq)->dest == (uh)->dest && \
(seq)->flow_lbl == ip6_get_flow_lbl(ip6h) && \
IN6_ARE_ADDR_EQUAL(&(seq)->saddr, saddr) && \
- IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr))
+ IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr) && \
+ (seq)->hop_limit == (ip6h)->hop_limit)
#define L4_SET(ip6h, proto, uh, seq) \
do { \
@@ -976,6 +984,7 @@ resume:
(seq)->flow_lbl = ip6_get_flow_lbl(ip6h); \
(seq)->saddr = *saddr; \
(seq)->daddr = *daddr; \
+ (seq)->hop_limit = (ip6h)->hop_limit; \
} while (0)
if (seq && L4_MATCH(ip6h, proto, uh, seq) &&
@@ -1026,7 +1035,7 @@ append:
for (k = 0; k < p->count; )
k += udp_tap_handler(c, PIF_TAP, AF_INET6,
&seq->saddr, &seq->daddr,
- p, k, now);
+ seq->hop_limit, p, k, now);
}
}
diff --git a/udp.c b/udp.c
index b275db3..3600336 100644
--- a/udp.c
+++ b/udp.c
@@ -818,6 +818,7 @@ fail:
* @af: Address family, AF_INET or AF_INET6
* @saddr: Source address
* @daddr: Destination address
+ * @ttl: TTL or hop limit for packets to be sent in this call
* @p: Pool of UDP packets, with UDP headers
* @idx: Index of first packet to process
* @now: Current timestamp
@@ -828,7 +829,8 @@ fail:
*/
int udp_tap_handler(const struct ctx *c, uint8_t pif,
sa_family_t af, const void *saddr, const void *daddr,
- const struct pool *p, int idx, const struct timespec *now)
+ uint8_t ttl, const struct pool *p, int idx,
+ const struct timespec *now)
{
const struct flowside *toside;
struct mmsghdr mm[UIO_MAXIOV];
@@ -907,6 +909,24 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif,
mm[i].msg_hdr.msg_controllen = 0;
mm[i].msg_hdr.msg_flags = 0;
+ if (ttl != uflow->ttl[tosidx.sidei]) {
+ uflow->ttl[tosidx.sidei] = ttl;
+ if (af == AF_INET) {
+ if (setsockopt(s, IPPROTO_IP, IP_TTL,
+ &ttl, sizeof(ttl)) < 0)
+ flow_perror(uflow,
+ "setsockopt IP_TTL");
+ } else {
+ /* IPv6 hop_limit cannot be only 1 byte */
+ int hop_limit = ttl;
+
+ if (setsockopt(s, SOL_IPV6, IPV6_UNICAST_HOPS,
+ &hop_limit, sizeof(hop_limit)) < 0)
+ flow_perror(uflow,
+ "setsockopt IPV6_UNICAST_HOPS");
+ }
+ }
+
count++;
}
diff --git a/udp.h b/udp.h
index 8fc4283..8f8531a 100644
--- a/udp.h
+++ b/udp.h
@@ -15,7 +15,8 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref,
uint32_t events, const struct timespec *now);
int udp_tap_handler(const struct ctx *c, uint8_t pif,
sa_family_t af, const void *saddr, const void *daddr,
- const struct pool *p, int idx, const struct timespec *now);
+ uint8_t ttl, const struct pool *p, int idx,
+ const struct timespec *now);
int udp_sock_init(const struct ctx *c, int ns, const union inany_addr *addr,
const char *ifname, in_port_t port);
int udp_init(struct ctx *c);
diff --git a/udp_flow.c b/udp_flow.c
index af15d7f..d84d170 100644
--- a/udp_flow.c
+++ b/udp_flow.c
@@ -136,6 +136,7 @@ static flow_sidx_t udp_flow_new(const struct ctx *c, union flow *flow,
uflow = FLOW_SET_TYPE(flow, FLOW_UDP, udp);
uflow->ts = now->tv_sec;
uflow->s[INISIDE] = uflow->s[TGTSIDE] = -1;
+ uflow->ttl[INISIDE] = uflow->ttl[TGTSIDE] = 0;
flow_foreach_sidei(sidei) {
if (pif_is_socket(uflow->f.pif[sidei]))
diff --git a/udp_flow.h b/udp_flow.h
index d518737..90d3b29 100644
--- a/udp_flow.h
+++ b/udp_flow.h
@@ -8,13 +8,14 @@
#define UDP_FLOW_H
/**
- * struct udp - Descriptor for a flow of UDP packets
+ * struct udp_flow - Descriptor for a flow of UDP packets
* @f: Generic flow information
* @closed: Flow is already closed
* @flush0: @s[0] may have datagrams queued for other flows
* @flush1: @s[1] may have datagrams queued for other flows
* @ts: Activity timestamp
* @s: Socket fd (or -1) for each side of the flow
+ * @ttl: TTL or hop_limit for both sides
*/
struct udp_flow {
/* Must be first element */
@@ -24,6 +25,7 @@ struct udp_flow {
bool flush0, flush1 :1;
time_t ts;
int s[SIDES];
+ uint8_t ttl[SIDES];
};
struct udp_flow *udp_at_sidx(flow_sidx_t sidx);
--
@@ -8,13 +8,14 @@
#define UDP_FLOW_H
/**
- * struct udp - Descriptor for a flow of UDP packets
+ * struct udp_flow - Descriptor for a flow of UDP packets
* @f: Generic flow information
* @closed: Flow is already closed
* @flush0: @s[0] may have datagrams queued for other flows
* @flush1: @s[1] may have datagrams queued for other flows
* @ts: Activity timestamp
* @s: Socket fd (or -1) for each side of the flow
+ * @ttl: TTL or hop_limit for both sides
*/
struct udp_flow {
/* Must be first element */
@@ -24,6 +25,7 @@ struct udp_flow {
bool flush0, flush1 :1;
time_t ts;
int s[SIDES];
+ uint8_t ttl[SIDES];
};
struct udp_flow *udp_at_sidx(flow_sidx_t sidx);
--
2.48.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v7] udp: support traceroute in direction tap-socket
2025-04-05 19:21 [PATCH v7] udp: support traceroute in direction tap-socket Jon Maloy
@ 2025-04-07 4:55 ` David Gibson
0 siblings, 0 replies; 2+ messages in thread
From: David Gibson @ 2025-04-07 4:55 UTC (permalink / raw)
To: Jon Maloy; +Cc: sbrivio, dgibson, passt-dev
[-- Attachment #1: Type: text/plain, Size: 8420 bytes --]
On Sat, Apr 05, 2025 at 03:21:26PM -0400, Jon Maloy wrote:
> Now that ICMP pass-through from socket-to-tap is in place, it is
> easy to support UDP based traceroute functionality in direction
> tap-to-socket.
>
> We fix that in this commit.
>
> Link: https://bugs.passt.top/show_bug.cgi?id=64
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> ---
> v2: - Using ancillary data instead of setsockopt to transfer outgoing
> TTL.
> - Support IPv6
> v3: - Storing ttl per packet instead of per flow. This may not be
> elegant, but much less intrusive than changing the flow
> criteria. This eliminates the need for the extra, flow-changing
> patch we introduced in v2.
> v4: - Going back to something similar to the original solution, but
> storing current ttl in struct udp_flow, plus ensuring that all
> packets in a struct tap4_l4_t/tap6_l4_t instance have the same
> ttl. After input from David Gibson.
> v5: - Some minor fixes after feedback from Stefano Brivio.
> v6: - Ensured that socket TTL is initialized at flow creation.
> - Ensured that setting of hop limit on IPv6 socket works.
> v7: - Setting of IPv6 hop_limit fails sometimes unless it is 4 bytes.
> ---
> tap.c | 17 +++++++++++++----
> udp.c | 22 +++++++++++++++++++++-
> udp.h | 3 ++-
> udp_flow.c | 1 +
> udp_flow.h | 4 +++-
> 5 files changed, 40 insertions(+), 7 deletions(-)
>
> diff --git a/tap.c b/tap.c
> index 3a6fcbe..d630f6d 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -559,6 +559,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
> * struct l4_seq4_t - Message sequence for one protocol handler call, IPv4
> * @msgs: Count of messages in sequence
> * @protocol: Protocol number
> + * @ttl: Time to live
> * @source: Source port
> * @dest: Destination port
> * @saddr: Source address
> @@ -567,6 +568,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
> */
> static struct tap4_l4_t {
> uint8_t protocol;
> + uint8_t ttl;
>
> uint16_t source;
> uint16_t dest;
> @@ -586,6 +588,7 @@ static struct tap4_l4_t {
> * @dest: Destination port
> * @saddr: Source address
> * @daddr: Destination address
> + * @hop_limit: Hop limit
> * @msg: Array of messages that can be handled in a single call
> */
> static struct tap6_l4_t {
> @@ -598,6 +601,8 @@ static struct tap6_l4_t {
> struct in6_addr saddr;
> struct in6_addr daddr;
>
> + uint8_t hop_limit;
> +
> struct pool_l4_t p;
> } tap6_l4[TAP_SEQS /* Arbitrary: TAP_MSGS in theory, so limit in users */];
>
> @@ -786,7 +791,8 @@ resume:
> #define L4_MATCH(iph, uh, seq) \
> ((seq)->protocol == (iph)->protocol && \
> (seq)->source == (uh)->source && (seq)->dest == (uh)->dest && \
> - (seq)->saddr.s_addr == (iph)->saddr && (seq)->daddr.s_addr == (iph)->daddr)
> + (seq)->saddr.s_addr == (iph)->saddr && \
> + (seq)->daddr.s_addr == (iph)->daddr && (seq)->ttl == (iph)->ttl)
>
> #define L4_SET(iph, uh, seq) \
> do { \
> @@ -795,6 +801,7 @@ resume:
> (seq)->dest = (uh)->dest; \
> (seq)->saddr.s_addr = (iph)->saddr; \
> (seq)->daddr.s_addr = (iph)->daddr; \
> + (seq)->ttl = (iph)->ttl; \
> } while (0)
>
> if (seq && L4_MATCH(iph, uh, seq) && seq->p.count < UIO_MAXIOV)
> @@ -843,7 +850,7 @@ append:
> for (k = 0; k < p->count; )
> k += udp_tap_handler(c, PIF_TAP, AF_INET,
> &seq->saddr, &seq->daddr,
> - p, k, now);
> + seq->ttl, p, k, now);
> }
> }
>
> @@ -966,7 +973,8 @@ resume:
> (seq)->dest == (uh)->dest && \
> (seq)->flow_lbl == ip6_get_flow_lbl(ip6h) && \
> IN6_ARE_ADDR_EQUAL(&(seq)->saddr, saddr) && \
> - IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr))
> + IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr) && \
> + (seq)->hop_limit == (ip6h)->hop_limit)
>
> #define L4_SET(ip6h, proto, uh, seq) \
> do { \
> @@ -976,6 +984,7 @@ resume:
> (seq)->flow_lbl = ip6_get_flow_lbl(ip6h); \
> (seq)->saddr = *saddr; \
> (seq)->daddr = *daddr; \
> + (seq)->hop_limit = (ip6h)->hop_limit; \
> } while (0)
>
> if (seq && L4_MATCH(ip6h, proto, uh, seq) &&
> @@ -1026,7 +1035,7 @@ append:
> for (k = 0; k < p->count; )
> k += udp_tap_handler(c, PIF_TAP, AF_INET6,
> &seq->saddr, &seq->daddr,
> - p, k, now);
> + seq->hop_limit, p, k, now);
> }
> }
>
> diff --git a/udp.c b/udp.c
> index b275db3..3600336 100644
> --- a/udp.c
> +++ b/udp.c
> @@ -818,6 +818,7 @@ fail:
> * @af: Address family, AF_INET or AF_INET6
> * @saddr: Source address
> * @daddr: Destination address
> + * @ttl: TTL or hop limit for packets to be sent in this call
> * @p: Pool of UDP packets, with UDP headers
> * @idx: Index of first packet to process
> * @now: Current timestamp
> @@ -828,7 +829,8 @@ fail:
> */
> int udp_tap_handler(const struct ctx *c, uint8_t pif,
> sa_family_t af, const void *saddr, const void *daddr,
> - const struct pool *p, int idx, const struct timespec *now)
> + uint8_t ttl, const struct pool *p, int idx,
> + const struct timespec *now)
> {
> const struct flowside *toside;
> struct mmsghdr mm[UIO_MAXIOV];
> @@ -907,6 +909,24 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif,
> mm[i].msg_hdr.msg_controllen = 0;
> mm[i].msg_hdr.msg_flags = 0;
>
> + if (ttl != uflow->ttl[tosidx.sidei]) {
> + uflow->ttl[tosidx.sidei] = ttl;
> + if (af == AF_INET) {
> + if (setsockopt(s, IPPROTO_IP, IP_TTL,
> + &ttl, sizeof(ttl)) < 0)
> + flow_perror(uflow,
> + "setsockopt IP_TTL");
> + } else {
> + /* IPv6 hop_limit cannot be only 1 byte */
> + int hop_limit = ttl;
> +
> + if (setsockopt(s, SOL_IPV6, IPV6_UNICAST_HOPS,
> + &hop_limit, sizeof(hop_limit)) < 0)
> + flow_perror(uflow,
> + "setsockopt IPV6_UNICAST_HOPS");
> + }
> + }
> +
> count++;
> }
>
> diff --git a/udp.h b/udp.h
> index 8fc4283..8f8531a 100644
> --- a/udp.h
> +++ b/udp.h
> @@ -15,7 +15,8 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref,
> uint32_t events, const struct timespec *now);
> int udp_tap_handler(const struct ctx *c, uint8_t pif,
> sa_family_t af, const void *saddr, const void *daddr,
> - const struct pool *p, int idx, const struct timespec *now);
> + uint8_t ttl, const struct pool *p, int idx,
> + const struct timespec *now);
> int udp_sock_init(const struct ctx *c, int ns, const union inany_addr *addr,
> const char *ifname, in_port_t port);
> int udp_init(struct ctx *c);
> diff --git a/udp_flow.c b/udp_flow.c
> index af15d7f..d84d170 100644
> --- a/udp_flow.c
> +++ b/udp_flow.c
> @@ -136,6 +136,7 @@ static flow_sidx_t udp_flow_new(const struct ctx *c, union flow *flow,
> uflow = FLOW_SET_TYPE(flow, FLOW_UDP, udp);
> uflow->ts = now->tv_sec;
> uflow->s[INISIDE] = uflow->s[TGTSIDE] = -1;
> + uflow->ttl[INISIDE] = uflow->ttl[TGTSIDE] = 0;
>
> flow_foreach_sidei(sidei) {
> if (pif_is_socket(uflow->f.pif[sidei]))
> diff --git a/udp_flow.h b/udp_flow.h
> index d518737..90d3b29 100644
> --- a/udp_flow.h
> +++ b/udp_flow.h
> @@ -8,13 +8,14 @@
> #define UDP_FLOW_H
>
> /**
> - * struct udp - Descriptor for a flow of UDP packets
> + * struct udp_flow - Descriptor for a flow of UDP packets
> * @f: Generic flow information
> * @closed: Flow is already closed
> * @flush0: @s[0] may have datagrams queued for other flows
> * @flush1: @s[1] may have datagrams queued for other flows
> * @ts: Activity timestamp
> * @s: Socket fd (or -1) for each side of the flow
> + * @ttl: TTL or hop_limit for both sides
> */
> struct udp_flow {
> /* Must be first element */
> @@ -24,6 +25,7 @@ struct udp_flow {
> bool flush0, flush1 :1;
> time_t ts;
> int s[SIDES];
> + uint8_t ttl[SIDES];
> };
>
> struct udp_flow *udp_at_sidx(flow_sidx_t sidx);
--
David Gibson (he or they) | 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
[-- Attachment #2: signature.asc --]
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