From: Florian Westphal <fw@strlen.de>
To: Rundong Ge <rdong.ge@gmail.com>
Cc: davem@davemloft.net, kuznet@ms2.inr.ac.ru,
yoshfuji@linux-ipv6.org, netdev@vger.kernel.org,
pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de,
roopa@cumulusnetworks.com, netfilter-devel@vger.kernel.org,
coreteam@netfilter.org, bridge@lists.linux-foundation.org,
nikolay@cumulusnetworks.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bridge:fragmented packets dropped by bridge
Date: Tue, 30 Jul 2019 14:35:42 +0200 [thread overview]
Message-ID: <20190730123542.zrsrfvcy7t2n3d4g@breakpoint.cc> (raw)
In-Reply-To: <20190730122534.30687-1-rdong.ge@gmail.com>
Rundong Ge <rdong.ge@gmail.com> wrote:
> Given following setup:
> -modprobe br_netfilter
> -echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables
> -brctl addbr br0
> -brctl addif br0 enp2s0
> -brctl addif br0 enp3s0
> -brctl addif br0 enp6s0
> -ifconfig enp2s0 mtu 1300
> -ifconfig enp3s0 mtu 1500
> -ifconfig enp6s0 mtu 1500
> -ifconfig br0 up
>
> multi-port
> mtu1500 - mtu1500|bridge|1500 - mtu1500
> A | B
> mtu1300
How can a bridge forward a frame from A/B to mtu1300?
> With netfilter defragmentation/conntrack enabled, fragmented
> packets from A will be defragmented in prerouting, and refragmented
> at postrouting.
Yes, but I don't see how that relates to the problem at hand.
> But in this scenario the bridge found the frag_max_size(1500) is
> larger than the dst mtu stored in the fake_rtable whitch is
> always equal to the bridge's mtu 1300, then packets will be dopped.
What happens without netfilter or non-fragmented packets?
> This modifies ip_skb_dst_mtu to use the out dev's mtu instead
> of bridge's mtu in bridge refragment.
It seems quite a hack? The above setup should use a router, not a bridge.
next prev parent reply other threads:[~2019-07-30 12:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 12:25 [PATCH] bridge:fragmented packets dropped by bridge Rundong Ge
2019-07-30 12:35 ` Florian Westphal [this message]
2019-07-30 13:50 ` Rundong Ge
2019-08-26 7:59 ` Jan Engelhardt
2019-08-28 9:21 ` Rundong Ge
2019-07-30 12:41 ` Nikolay Aleksandrov
2019-07-30 13:58 ` Rundong Ge
2019-08-26 2:45 ` Rundong Ge
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