| Message ID | 20170309220340.12713-1-fw@strlen.de |
|---|---|
| State | Superseded |
| Headers | show |
Florian Westphal <fw@strlen.de> wrote: > 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@strlen.de> > --- > No Fixes tag, seems this problem has always existed. > 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. > > without this patch, ping/ping6 only works for sizes <= 1500 > and > 9000. grrr. it breaks the normal path... > diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c > index 95087e6e8258..81889afee212 100644 > --- a/net/bridge/br_netfilter_hooks.c > +++ b/net/bridge/br_netfilter_hooks.c > @@ -721,18 +721,19 @@ 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 = nf_bridge->frag_max_size; This can be 0, I'll send a v2. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 95087e6e8258..81889afee212 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -721,18 +721,19 @@ 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 = nf_bridge->frag_max_size; + if (mtu > skb->dev->mtu) + mtu = skb->dev->mtu; - 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. */
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@strlen.de> --- No Fixes tag, seems this problem has always existed. 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. without this patch, ping/ping6 only works for sizes <= 1500 and > 9000. net/bridge/br_netfilter_hooks.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)