[PATCH net-next v4 1/2] icmp: fix ICMP error source address when xfrm policy matches

[Antony Antony]

When an IPsec gateway generates an ICMP error (e.g., Destination Host
Unreachable), the source address incorrectly shows the unreachable
destination instead of the gateway's address. IPv6 behaves correctly.

Before fix:
  ping 10.1.6.3
  From 10.1.6.3 icmp_seq=1 Destination Host Unreachable
  (wrong - 10.1.6.3 is the unreachable host)

After fix:
  ping 10.1.6.3
  From 10.1.5.2 icmp_seq=1 Destination Host Unreachable
  (correct - 10.1.5.2 is the gateway)

The fix removes the memcpy that overwrote fl4 with fl4_dec after
xfrm_lookup(). A follow-up commit adds a selftest.

Fixes: 415b3334a21a ("icmp: Fix regression in nexthop resolution during replies.")
Cc: stable+noautosel@xxxxxxxxxx # Avoid false positives in tests
Signed-off-by: Antony Antony <antony.antony@xxxxxxxxxxx>
Acked-by: Tobias Brunner <tobias@xxxxxxxxxxxxxx>
---
 net/ipv4/icmp.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 19c9c838967f..4bd421208ce0 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -569,7 +569,6 @@ static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
 	rt2 = dst_rtable(dst2);
 	if (!IS_ERR(dst2)) {
 		dst_release(&rt->dst);
-		memcpy(fl4, &fl4_dec, sizeof(*fl4));
 		rt = rt2;
 	} else if (PTR_ERR(dst2) == -EPERM) {
 		if (rt)
--
2.39.5