netdev - RE: [PATCH] tcp: md5: fix md5 RST when both sides have listener

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Date:	Wed, 1 Feb 2012 03:11:17 -0500
From:	Shawn Lu <shawn.lu@...csson.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"xiaoclu@...il.com" <xiaoclu@...il.com>
Subject: RE: [PATCH] tcp: md5: fix md5 RST when both sides have listener

Why? Do you mean packet is droped by netfilter before getting to tcp and No RST is generated. 

-----Original Message-----
From: Eric Dumazet [mailto:eric.dumazet@...il.com] 
Sent: Tuesday, January 31, 2012 11:54 PM
To: Shawn Lu
Cc: davem@...emloft.net; netdev@...r.kernel.org; xiaoclu@...il.com
Subject: RE: [PATCH] tcp: md5: fix md5 RST when both sides have listener

Le mercredi 01 février 2012 à 02:48 -0500, Shawn Lu a écrit :
> Hi, Eric:
> 
> How about change the title and log to following:
> 
>   tcp: md5: RST: getting md5 key from listener
> 
>     TCP RST mechanism is broken in TCP md5(RFC2385). When
>     connection is gone, md5 key is lost, sending RST
>     without md5 hash is deem to ignored by peer. This can
>     be a problem since RST help protocal like bgp to fast
>     recove from peer crash.
> 
>     In most case, users of tcp md5, such as bgp and ldp,
>     have listener on both side to accept connection from peer.
>     md5 keys for peers are saved in listening socket.
> 
>     There are two cases in finding md5 key when connection is
>     lost:
>     1.Passive receive RST: The message is send to well known port,
>     tcp will associate packet with listener. md5 key can be gotten
>     from listener.
> 
>     2.Active receive RST (no sock): The message is send to ative
>     side, there is no socket associated with message. In this case,
>     finding listener from source port, then find md5 key from
>     listener.
> 
>     we are not loosing sercuriy here:
>     packet is checked with md5 hash. No RST is generated
>     if md5 hash doesn't match or no md5 key can be found.
> 
> Note:
> Will send out a new version that is on top of your new patch
> -- "tcp: md5: protects md5sig_info with RCU"
> 

Seems good to me !

By the way, is the patch going to work if netfilter conntrack is enabled ?



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