netdev - Re: [PATCH] tproxy: nf_tproxy_assign

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Date:	Sat, 10 Jul 2010 00:18:28 -0300
From:	Felipe W Damasio <felipewd@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>,
	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tproxy: nf_tproxy_assign_sock() can handle tw sockets

Hi Mr. Dumazet,

2010/7/9 Eric Dumazet <eric.dumazet@...il.com>:
> Reviewing tproxy stuff I spotted a problem in nf_tproxy_assign_sock()
> but I could not see how it could explain your crash.
>
> We can read uninitialized memory and trigger a fault in
> nf_tproxy_assign_sock(), not later in tcp_recvmsg()...
>
> David, Patrick, what do you think ?

But do you think that the bug that squid triggered was caused by the
TProxy code?

Or is related to the network-stack in some other point.

I don't know if this helps, but I'm using ebtables to remove the
packets from the bridge, and iptables to redirect the traffic to
squid.

ebtables rules are:

-p IPv4 -i eth0 --ip-proto tcp --ip-dport 80 -j redirect  --redirect-target DROP
-p IPv4 -i eth1 --ip-proto tcp --ip-sport 80 -j redirect  --redirect-target DROP


iptables -t mangle -L -n is:

iptables -t mangle -L -n
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination
DIVERT     tcp  --  0.0.0.0/0            0.0.0.0/0           socket
extrachain  tcp  --  0.0.0.0/0            0.0.0.0/0           tcp
dpt:80 ctstate NEW
TPROXY     tcp  --  0.0.0.0/0           !201.40.162.5        tcp
dpt:80 connmark match 0x0 TPROXY redirect 127.0.0.1:3127 mark 0x1/0x1
TPROXY     tcp  --  0.0.0.0/0           !201.40.162.5        tcp
dpt:80 connmark match 0x1 TPROXY redirect 127.0.0.1:3128 mark 0x1/0x1
TPROXY     tcp  --  0.0.0.0/0           !201.40.162.5        tcp
dpt:80 connmark match 0x2 TPROXY redirect 127.0.0.1:3129 mark 0x1/0x1

Chain DIVERT (1 references)
target     prot opt source               destination
MARK       all  --  0.0.0.0/0            0.0.0.0/0           MARK xset
0x1/0xffffffff
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0

Chain extrachain (1 references)
target     prot opt source               destination
CONNMARK   all  --  0.0.0.0/0            0.0.0.0/0           statistic
mode nth every 35 CONNMARK and 0x0
CONNMARK   all  --  0.0.0.0/0            0.0.0.0/0           statistic
mode nth every 35 packet 1 CONNMARK xset 0x1/0xffffffff
CONNMARK   all  --  0.0.0.0/0            0.0.0.0/0           statistic
mode nth every 35 packet 2 CONNMARK xset 0x2/0xffffffff

Don't know if the code on these can be traced back to tcp_recvmsg()
accessing some wrong memory address...

Cheers,

Felipe Damasio
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