[Bridge] [PATCH net v2] net: bridge: Fix ethernet header pointer before check skb forwardable

Toshiaki Makita makita.toshiaki at lab.ntt.co.jp
Tue Jan 15 07:49:56 UTC 2019

On 2019/01/15 12:12, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian at huawei.com>
> The skb header should be set to ethernet header before using
> is_skb_forwardable. Because the ethernet header length has been
> considered in is_skb_forwardable(including dev->hard_header_len
> length).
> To reproduce the issue:
> 1, add 2 ports on linux bridge br using following commands:
> $ brctl addbr br
> $ brctl addif br eth0
> $ brctl addif br eth1
> 2, the mtu of eth0 and eth1 is 1500
> 3, send a 1504 packet from eth0 to eth1
> So the expect result is packet larger than 1500 cannot pass through
> eth0 and eth1. But currently, the packet passes through success, it
> means eth1's mtu limit donen't take effect.

I agree with the change but this test does not look appropriate.
In the first place is_skb_forwardable() accepts 4 bytes extra size (for
VLAN header). Doesn't your test case fail even after the change?

Toshiaki Makita

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