From: Shmulik Ladkani <shmulik@xxxxxxxxxxxxxxxx> [ Upstream commit d2f0c961148f65bc73eda72b9fa3a4e80973cb49 ] Previously, during fragmentation after forwarding, skb->skb_iif isn't preserved, i.e. 'ip_copy_metadata' does not copy skb_iif from given 'from' skb. As a result, ip_do_fragment's creates fragments with zero skb_iif, leading to inconsistent behavior. Assume for example an eBPF program attached at tc egress (post forwarding) that examines __sk_buff->ingress_ifindex: - the correct iif is observed if forwarding path does not involve fragmentation/refragmentation - a bogus iif is observed if forwarding path involves fragmentation/refragmentatiom Fix, by preserving skb_iif during 'ip_copy_metadata'. Signed-off-by: Shmulik Ladkani <shmulik.ladkani@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/ip_output.c | 1 + 1 file changed, 1 insertion(+) --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -454,6 +454,7 @@ static void ip_copy_metadata(struct sk_b to->pkt_type = from->pkt_type; to->priority = from->priority; to->protocol = from->protocol; + to->skb_iif = from->skb_iif; skb_dst_drop(to); skb_dst_copy(to, from); to->dev = from->dev;
