[PATCH v2 7/8] tcp: make tcp_rst_no_conn() respond with correct mac address

[Jon Maloy <jmaloy@redhat.com>]

tcp_rst_no_conn() needs to identify and specify which source mac
address to use when sending an RST to the guest. This is because
it doesn't have access to any flow structure where this address
could be fetched.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 tcp.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/tcp.c b/tcp.c
index 1a32424..b49f603 100644
--- a/tcp.c
+++ b/tcp.c
@@ -309,6 +309,7 @@
 #include "tcp_internal.h"
 #include "tcp_buf.h"
 #include "tcp_vu.h"
+#include "netlink.h"
 
 #ifndef __USE_MISC
 /* From Linux UAPI, missing in netinet/tcp.h provided by musl */
@@ -1888,6 +1889,9 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
 			    const struct tcphdr *th, size_t l4len)
 {
 	struct iov_tail payload = IOV_TAIL(NULL, 0, 0);
+	unsigned char src_mac[ETH_ALEN];
+	union inany_addr translated;
+	union inany_addr dst;
 	struct tcphdr *rsth;
 	char buf[USHRT_MAX];
 	uint32_t psum = 0;
@@ -1897,8 +1901,15 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
 	if (th->rst)
 		return;
 
+	/* If remote host on local network - respond with its mac address */
+	memcpy(src_mac, c->our_tap_mac, ETH_ALEN);
+	inany_from_af(&dst, af, daddr);
+	nat_outbound(c, &dst, &translated);
+	if (!memcmp(&dst, &translated, sizeof(dst)))
+		nl_mac_get(nl_sock, &dst, src_mac);
+
 	if (af == AF_INET) {
-		struct iphdr *ip4h = tap_push_l2h(c, buf, NULL, ETH_P_IP);
+		struct iphdr *ip4h = tap_push_l2h(c, buf, src_mac, ETH_P_IP);
 		const struct in_addr *rst_src = daddr;
 		const struct in_addr *rst_dst = saddr;
 
@@ -1908,7 +1919,7 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
 					      *rst_src, *rst_dst);
 
 	} else {
-		struct ipv6hdr *ip6h = tap_push_l2h(c, buf, NULL, ETH_P_IPV6);
+		struct ipv6hdr *ip6h = tap_push_l2h(c, buf, src_mac, ETH_P_IPV6);
 		const struct in6_addr *rst_src = daddr;
 		const struct in6_addr *rst_dst = saddr;
 
-- 
@@ -309,6 +309,7 @@
 #include "tcp_internal.h"
 #include "tcp_buf.h"
 #include "tcp_vu.h"
+#include "netlink.h"
 
 #ifndef __USE_MISC
 /* From Linux UAPI, missing in netinet/tcp.h provided by musl */
@@ -1888,6 +1889,9 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
 			    const struct tcphdr *th, size_t l4len)
 {
 	struct iov_tail payload = IOV_TAIL(NULL, 0, 0);
+	unsigned char src_mac[ETH_ALEN];
+	union inany_addr translated;
+	union inany_addr dst;
 	struct tcphdr *rsth;
 	char buf[USHRT_MAX];
 	uint32_t psum = 0;
@@ -1897,8 +1901,15 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
 	if (th->rst)
 		return;
 
+	/* If remote host on local network - respond with its mac address */
+	memcpy(src_mac, c->our_tap_mac, ETH_ALEN);
+	inany_from_af(&dst, af, daddr);
+	nat_outbound(c, &dst, &translated);
+	if (!memcmp(&dst, &translated, sizeof(dst)))
+		nl_mac_get(nl_sock, &dst, src_mac);
+
 	if (af == AF_INET) {
-		struct iphdr *ip4h = tap_push_l2h(c, buf, NULL, ETH_P_IP);
+		struct iphdr *ip4h = tap_push_l2h(c, buf, src_mac, ETH_P_IP);
 		const struct in_addr *rst_src = daddr;
 		const struct in_addr *rst_dst = saddr;
 
@@ -1908,7 +1919,7 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
 					      *rst_src, *rst_dst);
 
 	} else {
-		struct ipv6hdr *ip6h = tap_push_l2h(c, buf, NULL, ETH_P_IPV6);
+		struct ipv6hdr *ip6h = tap_push_l2h(c, buf, src_mac, ETH_P_IPV6);
 		const struct in6_addr *rst_src = daddr;
 		const struct in6_addr *rst_dst = saddr;
 
-- 
2.48.1