[PATCH net-next 10/11] netfilter: nft_fwd_netdev: check ttl/hl before forwarding

Florian Westphal
2026-04-10T11:24:40Z

Drop packets if their ttl/hl is too small for forwarding.

Fixes: d32de98ea70f ("netfilter: nft_fwd_netdev: allow to forward packets via neighbour layer")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
net/netfilter/nft_fwd_netdev.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/net/netfilter/nft_fwd_netdev.c b/net/netfilter/nft_fwd_netdev.c
index ad48dcd45abe..4bce36c3a6a0 100644
--- a/net/netfilter/nft_fwd_netdev.c
+++ b/net/netfilter/nft_fwd_netdev.c
@@ -116,6 +116,11 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,
goto out;
}
iph = ip_hdr(skb);
+ if (iph->ttl <= 1) {
+ verdict = NF_DROP;
+ goto out;
+ }
+
ip_decrease_ttl(iph);
neigh_table = NEIGH_ARP_TABLE;
break;
@@ -132,6 +137,11 @@ static void nft_fwd_neigh_eval(const struct nft_expr *expr,
goto out;
}
ip6h = ipv6_hdr(skb);
+ if (ip6h->hop_limit <= 1) {
+ verdict = NF_DROP;
+ goto out;
+ }
+
ip6h->hop_limit--;
neigh_table = NEIGH_ND_TABLE;
break;
--
2.52.0