[PATCH v6 8/8] icmp: let icmp use mac address from flowside structure

[Jon Maloy <jmaloy@redhat.com>]

Even ICMP needs to be updated to use the external MAC address instead
of just the own tap address when applicable. We do that here.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---
v3: - Adapted to the move of external MAC address from struct flowside
      to struct flow_common
v4: - Adapted to name changes in previous commits in this series
v5: - Added conditional lookup in ARP/NDP if the flow's tap_omac is
      undefined
v6: - Looking up MAC of ICMP generating node in udp_send_tap_icmp4/6()
      when available, instead trusting the contents of flow->tap_omac.
---
 icmp.c |  8 ++++++--
 ndp.c  |  2 +-
 tap.c  | 10 ++++++----
 tap.h  |  4 ++--
 udp.c  | 12 ++++++++++--
 5 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/icmp.c b/icmp.c
index 6dffafb..1d99632 100644
--- a/icmp.c
+++ b/icmp.c
@@ -125,17 +125,21 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
 	flow_dbg(pingf, "echo reply to tap, ID: %"PRIu16", seq: %"PRIu16,
 		 ini->eport, seq);
 
+	/* Try to find true MAC address in ARP/NDP table if needed */
+	if (MAC_IS_ZERO(pingf->f.tap_omac))
+		fwd_neigh_mac_get(c, &ini->oaddr, pingf->f.tap_omac);
+
 	if (pingf->f.type == FLOW_PING4) {
 		const struct in_addr *saddr = inany_v4(&ini->oaddr);
 		const struct in_addr *daddr = inany_v4(&ini->eaddr);
 
 		ASSERT(saddr && daddr); /* Must have IPv4 addresses */
-		tap_icmp4_send(c, *saddr, *daddr, buf, n);
+		tap_icmp4_send(c, *saddr, *daddr, buf, pingf->f.tap_omac, n);
 	} else if (pingf->f.type == FLOW_PING6) {
 		const struct in6_addr *saddr = &ini->oaddr.a6;
 		const struct in6_addr *daddr = &ini->eaddr.a6;
 
-		tap_icmp6_send(c, saddr, daddr, buf, n);
+		tap_icmp6_send(c, saddr, daddr, buf, pingf->f.tap_omac, n);
 	}
 	return;
 
diff --git a/ndp.c b/ndp.c
index 944371c..1e9d0f4 100644
--- a/ndp.c
+++ b/ndp.c
@@ -184,7 +184,7 @@ static void ndp_send(const struct ctx *c, const struct in6_addr *dst,
 {
 	const struct in6_addr *src = &c->ip6.our_tap_ll;
 
-	tap_icmp6_send(c, src, dst, buf, l4len);
+	tap_icmp6_send(c, src, dst, buf, c->our_tap_mac, l4len);
 }
 
 /**
diff --git a/tap.c b/tap.c
index a390be8..8b10e14 100644
--- a/tap.c
+++ b/tap.c
@@ -277,13 +277,14 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
  * @src:	IPv4 source address
  * @dst:	IPv4 destination address
  * @in:		ICMP packet, including ICMP header
+ * @src_mac:	MAC address to be used as source for message
  * @l4len:	ICMP packet length, including ICMP header
  */
 void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
-		    const void *in, size_t l4len)
+		    const void *in, const void *src_mac, size_t l4len)
 {
 	char buf[USHRT_MAX];
-	struct iphdr *ip4h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IP);
+	struct iphdr *ip4h = tap_push_l2h(c, buf, src_mac, ETH_P_IP);
 	struct icmphdr *icmp4h = tap_push_ip4h(ip4h, src, dst,
 					       l4len, IPPROTO_ICMP);
 
@@ -384,14 +385,15 @@ void tap_udp6_send(const struct ctx *c,
  * @src:	IPv6 source address
  * @dst:	IPv6 destination address
  * @in:		ICMP packet, including ICMP header
+ * @src_mac:	MAC address to be used as source for message
  * @l4len:	ICMP packet length, including ICMP header
  */
 void tap_icmp6_send(const struct ctx *c,
 		    const struct in6_addr *src, const struct in6_addr *dst,
-		    const void *in, size_t l4len)
+		    const void *in, const void *src_mac, size_t l4len)
 {
 	char buf[USHRT_MAX];
-	struct ipv6hdr *ip6h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IPV6);
+	struct ipv6hdr *ip6h = tap_push_l2h(c, buf, src_mac, ETH_P_IPV6);
 	struct icmp6hdr *icmp6h = tap_push_ip6h(ip6h, src, dst, l4len,
 						IPPROTO_ICMPV6, 0);
 
diff --git a/tap.h b/tap.h
index 02f7761..1864173 100644
--- a/tap.h
+++ b/tap.h
@@ -91,7 +91,7 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
 		   struct in_addr dst, in_port_t dport,
 		   const void *in, size_t dlen);
 void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
-		    const void *in, size_t l4len);
+		    const void *in, const void *src_mac, size_t l4len);
 const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
 				     const struct in6_addr *src);
 void *tap_push_ip6h(struct ipv6hdr *ip6h,
@@ -103,7 +103,7 @@ void tap_udp6_send(const struct ctx *c,
 		   uint32_t flow, void *in, size_t dlen);
 void tap_icmp6_send(const struct ctx *c,
 		    const struct in6_addr *src, const struct in6_addr *dst,
-		    const void *in, size_t l4len);
+		    const void *in, const void *src_mac, size_t l4len);
 void tap_send_single(const struct ctx *c, const void *data, size_t l2len);
 size_t tap_send_frames(const struct ctx *c, const struct iovec *iov,
 		       size_t bufs_per_frame, size_t nframes);
diff --git a/udp.c b/udp.c
index eb57f05..ff15e37 100644
--- a/udp.c
+++ b/udp.c
@@ -400,6 +400,8 @@ static void udp_send_tap_icmp4(const struct ctx *c,
 	struct in_addr eaddr = toside->eaddr.v4mapped.a4;
 	in_port_t eport = toside->eport;
 	in_port_t oport = toside->oport;
+	union inany_addr saddr_any;
+	uint8_t tap_omac[ETH_ALEN];
 	struct {
 		struct icmphdr icmp4h;
 		struct iphdr ip4h;
@@ -421,7 +423,10 @@ static void udp_send_tap_icmp4(const struct ctx *c,
 	tap_push_uh4(&msg.uh, eaddr, eport, oaddr, oport, in, dlen);
 	memcpy(&msg.data, in, dlen);
 
-	tap_icmp4_send(c, saddr, eaddr, &msg, msglen);
+	/* Try to obtain the MAC address of the generating node */
+	saddr_any = inany_from_v4(saddr);
+	fwd_neigh_mac_get(c, &saddr_any, tap_omac);
+	tap_icmp4_send(c, saddr, eaddr, &msg, tap_omac, msglen);
 }
 
 
@@ -445,6 +450,7 @@ static void udp_send_tap_icmp6(const struct ctx *c,
 	const struct in6_addr *eaddr = &toside->eaddr.a6;
 	in_port_t eport = toside->eport;
 	in_port_t oport = toside->oport;
+	uint8_t tap_omac[ETH_ALEN];
 	struct {
 		struct icmp6_hdr icmp6h;
 		struct ipv6hdr ip6h;
@@ -466,7 +472,9 @@ static void udp_send_tap_icmp6(const struct ctx *c,
 	tap_push_uh6(&msg.uh, eaddr, eport, oaddr, oport, in, dlen);
 	memcpy(&msg.data, in, dlen);
 
-	tap_icmp6_send(c, saddr, eaddr, &msg, msglen);
+	/* Try to obtain the MAC address of the generating node */
+	fwd_neigh_mac_get(c, (union inany_addr *) saddr, tap_omac);
+	tap_icmp6_send(c, saddr, eaddr, &msg, tap_omac, msglen);
 }
 
 /**
-- 
@@ -400,6 +400,8 @@ static void udp_send_tap_icmp4(const struct ctx *c,
 	struct in_addr eaddr = toside->eaddr.v4mapped.a4;
 	in_port_t eport = toside->eport;
 	in_port_t oport = toside->oport;
+	union inany_addr saddr_any;
+	uint8_t tap_omac[ETH_ALEN];
 	struct {
 		struct icmphdr icmp4h;
 		struct iphdr ip4h;
@@ -421,7 +423,10 @@ static void udp_send_tap_icmp4(const struct ctx *c,
 	tap_push_uh4(&msg.uh, eaddr, eport, oaddr, oport, in, dlen);
 	memcpy(&msg.data, in, dlen);
 
-	tap_icmp4_send(c, saddr, eaddr, &msg, msglen);
+	/* Try to obtain the MAC address of the generating node */
+	saddr_any = inany_from_v4(saddr);
+	fwd_neigh_mac_get(c, &saddr_any, tap_omac);
+	tap_icmp4_send(c, saddr, eaddr, &msg, tap_omac, msglen);
 }
 
 
@@ -445,6 +450,7 @@ static void udp_send_tap_icmp6(const struct ctx *c,
 	const struct in6_addr *eaddr = &toside->eaddr.a6;
 	in_port_t eport = toside->eport;
 	in_port_t oport = toside->oport;
+	uint8_t tap_omac[ETH_ALEN];
 	struct {
 		struct icmp6_hdr icmp6h;
 		struct ipv6hdr ip6h;
@@ -466,7 +472,9 @@ static void udp_send_tap_icmp6(const struct ctx *c,
 	tap_push_uh6(&msg.uh, eaddr, eport, oaddr, oport, in, dlen);
 	memcpy(&msg.data, in, dlen);
 
-	tap_icmp6_send(c, saddr, eaddr, &msg, msglen);
+	/* Try to obtain the MAC address of the generating node */
+	fwd_neigh_mac_get(c, (union inany_addr *) saddr, tap_omac);
+	tap_icmp6_send(c, saddr, eaddr, &msg, tap_omac, msglen);
 }
 
 /**
-- 
2.50.1