From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: [PATCH nf] netfilter: bridge: honor frag_max_size when refragmenting Date: Thu, 9 Mar 2017 23:03:40 +0100 Message-ID: <20170309220340.12713-1-fw@strlen.de> Cc: Florian Westphal To: Return-path: Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:44508 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751300AbdCIWDY (ORCPT ); Thu, 9 Mar 2017 17:03:24 -0500 Sender: netfilter-devel-owner@vger.kernel.org List-ID: 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 --- 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(-) 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. */ -- 2.10.2