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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070525085947.12841835@freepuppy>
Date:	Fri, 25 May 2007 08:59:47 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Adam Osuchowski <adwol@...k.pl>
Cc:	bridge@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN
 frames on bridge

On Fri, 25 May 2007 10:17:50 +0200
Adam Osuchowski <adwol@...k.pl> wrote:

> There is a problem with fragmented IP packet sent within 802.1Q tagged
> ethernet frame through bridge. Problem exists when conntrack is enabled
> (i.e. nf_conntrack_ipv4 module is loaded). Then, such packets are not
> fragmented again (after prior reassembling on bridge device) during
> passing it to bridge enslaved NIC. It cause MTU exceeding and as a result
> dropping packet.
> 
> Problem exists from kernel version 2.6.17 to 2.6.21.3 inclusive.
> 
> Below, there is a patch to fix it.
> 
> Regards.
> 
> 
> --- linux-2.6.21.3.orig/net/bridge/br_netfilter.c	2007-05-25 09:56:15.000000000 +0200
> +++ linux-2.6.21.3/net/bridge/br_netfilter.c	2007-05-25 10:11:42.000000000 +0200
> @@ -731,7 +731,7 @@
>  
>  static int br_nf_dev_queue_xmit(struct sk_buff *skb)
>  {
> -	if (skb->protocol == htons(ETH_P_IP) &&
> +	if ((skb->protocol == htons(ETH_P_IP) || IS_VLAN_IP(skb)) &&
>  	    skb->len > skb->dev->mtu &&
>  	    !skb_is_gso(skb))
>  		return ip_fragment(skb, br_dev_queue_push_xmit);

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 ...


-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/