From 3365afd3abda5f6a54f4a822dad5c9314e94c3fc Mon Sep 17 00:00:00 2001 From: Petr Machata Date: Tue, 17 Jun 2025 00:44:15 +0200 Subject: [PATCH] net: ipv6: ip6mr: Fix in/out netdev to pass to the FORWARD chain The netfilter hook is invoked with skb->dev for input netdevice, and vif_dev for output netdevice. However at the point of invocation, skb->dev is already set to vif_dev, and MR-forwarded packets are reported with in=out: # ip6tables -A FORWARD -j LOG --log-prefix '[forw]' # cd tools/testing/selftests/net/forwarding # ./router_multicast.sh # dmesg | fgrep '[forw]' [ 1670.248245] [forw]IN=v5 OUT=v5 [...] For reference, IPv4 MR code shows in and out as appropriate. Fix by caching skb->dev and using the updated value for output netdev. Fixes: 7bc570c8b4f7 ("[IPV6] MROUTE: Support multicast forwarding.") Signed-off-by: Petr Machata Reviewed-by: Ido Schimmel Reviewed-by: Nikolay Aleksandrov Link: https://patch.msgid.link/3141ae8386fbe13fef4b793faa75e6bae58d798a.1750113335.git.petrm@nvidia.com Signed-off-by: Jakub Kicinski --- net/ipv6/ip6mr.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c index 9db31e5b998c1..426859cd34092 100644 --- a/net/ipv6/ip6mr.c +++ b/net/ipv6/ip6mr.c @@ -2039,6 +2039,7 @@ static int ip6mr_forward2(struct net *net, struct mr_table *mrt, struct sk_buff *skb, int vifi) { struct vif_device *vif = &mrt->vif_table[vifi]; + struct net_device *indev = skb->dev; struct net_device *vif_dev; struct ipv6hdr *ipv6h; struct dst_entry *dst; @@ -2101,7 +2102,7 @@ static int ip6mr_forward2(struct net *net, struct mr_table *mrt, IP6CB(skb)->flags |= IP6SKB_FORWARDED; return NF_HOOK(NFPROTO_IPV6, NF_INET_FORWARD, - net, NULL, skb, skb->dev, vif_dev, + net, NULL, skb, indev, skb->dev, ip6mr_forward2_finish); out_free: -- 2.47.2