linux-kernel - Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge

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Date:	Fri, 25 May 2007 19:49:25 +0200
From:	Adam Osuchowski <adwol@...k.pl>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	bridge@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge

Stephen Hemminger wrote:
> It would be better to account for the tag in the length check.
> Something like
> 	if (skb->protocol == htons(ETH_P_IP) &&
> 	    skb->len > skb->dev->mtu - (IS_VLAN_IP(skb) ? VLAN_HLEN : 0) &&
> 	    !skb_is_gso(skb))
> 		return ip_fragment ...

It isn't good solution because one of IS_VLAN_IP() necessary condition is

    skb->protocol == htons(ETH_P_8021Q)

which is, of course, mutually exclusive with

    skb->protocol == htons(ETH_P_IP)

from br_nf_dev_queue_xmit(). IMHO, one should check length of ETH_P_IP
and ETH_P_8021Q frames separately:

    if (((skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu) ||
        (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN)) &&
	!skb_is_gso(skb))
	    return ip_fragment ...
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