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: Florian Westphal <fw@xxxxxxxxx>
---
changes since v1:
only use nonzero frag_max_size, else non-fragmented packets won't
be forwarded anymore.
tested in kvm with both ipv4 and ipv6 and following setup:
client (mtu 1500) --- bridge(mtu 9k) --- client (mtu 1500)
bridge (incl. all ports) have 9k mtu.
I tested ping & ping6 with sizes of 64, 8000, 32000.
Without patch, 8000-sized packets are dropped on the bridge.
diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
index 95087e6e8258..3c5185021c1c 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -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) {
nf_bridge_info_free(skb);
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.
*/
--
2.10.2
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