Commit 4ca60d08 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: bridge: honor frag_max_size when refragmenting

consider a bridge with mtu 9000, but end host sending smaller
packets to another host with mtu < 9000.

In this case, after reassembly, bridge+defrag would refragment,
and then attempt to send the reassembled packet as long as it
was below 9k.

Instead we have to cap by the largest fragment size seen.

Signed-off-by: default avatarFlorian Westphal <>
Signed-off-by: default avatarPablo Neira Ayuso <>
parent 10596608
......@@ -721,18 +721,20 @@ static unsigned int nf_bridge_mtu_reduction(const struct sk_buff *skb)
static int br_nf_dev_queue_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
struct nf_bridge_info *nf_bridge;
unsigned int mtu_reserved;
struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
unsigned int mtu, mtu_reserved;
mtu_reserved = nf_bridge_mtu_reduction(skb);
mtu = skb->dev->mtu;
if (nf_bridge->frag_max_size && nf_bridge->frag_max_size < mtu)
mtu = nf_bridge->frag_max_size;
if (skb_is_gso(skb) || skb->len + mtu_reserved <= skb->dev->mtu) {
if (skb_is_gso(skb) || skb->len + mtu_reserved <= mtu) {
return br_dev_queue_push_xmit(net, sk, skb);
nf_bridge = nf_bridge_info_get(skb);
/* This is wrong! We should preserve the original fragment
* boundaries by preserving frag_list rather than refragmenting.
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