[tproxy] Need your input regarding some issue with tproxy (may not be related to tproxy)

[Pranav Desai]

On Wed, Oct 15, 2008 at 5:29 PM, Pranav Desai <pranavadesai at gmail.com> wrote:
> Hello,
>
> We have a http proxy server which is in full transparent mode using
> tproxy 2.0.6 + kernel 2.6.20.15.
>
> The iptables rule to redirect port 80 traffic from clients is:
>
>  574K   34M REDIRECT   tcp  --  *      *       0.0.0.0/0
> 0.0.0.0/0           tcp dpts:80:82 redir ports 8001
>
> 8001 is our proxy port. We use tproxy to send connections to web
> servers using the clients IP. Using setsockopt(TPROXY_ASSIGN) ...
>
> The server is at around 240req/s. Most of the time its working fine
> i.e. I see a lot of traffic on port 80 going out using the clients IP,
> but I see quite a few pkts going out using src port 8001 (trace
> below). The rate is not as high port 80 traffic, but still high enough
> to be a concern.
>
> The interesting thing is I don't see any pkts destined to port 8001. I
> have been monitoring this server for an entire day. Hence, I am
> guessing that at times for some reason tproxy is not able to assign
> the foreign address and just uses the local address:port ...
>
> Any ideas or suggestions on how I should go about debugging this. Or
> whether I should be looking somewhere other than the tproxy module.
>
> Its a production server, so I can't get the client side traces, but I
> can get more info from the server. Let me know if you need any other
> information.
>
> I would really appreciate any help I can get.
>
> Thanks
> -- Pranav
>


The 10.10.224.6 is the server IP running tproxy.
The 10.1.x.x addresses are the client address.

So the return traffic or the response seems to be having the problem
where sometimes the src is 10.10.224.6:8001 instead of the origin
server IP:PORT.


> Here is a small part of the trace using (tcpdump -vvv -nn -i bond1 port 8001)
> ===========================================================
> 03:15:19.915737 IP (tos 0x0, ttl  64, id 28888, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.1.8.4849: F [tcp sum ok]
> 4133498992:4133498992(0) ack 3495097709 win 7290
> 03:15:22.180160 IP (tos 0x0, ttl  64, id 12306, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.1.8.4826: F [tcp sum ok]
> 4117981558:4117981558(0) ack 2998309917 win 9310
> 03:15:24.578292 IP (tos 0x0, ttl  64, id 65515, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.2.47.1106: F [tcp sum ok]
> 4086941566:4086941566(0) ack 3480965117 win 6432
> 03:15:25.064570 IP (tos 0x0, ttl  64, id 38848, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.3.131.1044: F [tcp sum
> ok] 4055165713:4055165713(0) ack 3713243767 win 9648
> 03:15:27.232857 IP (tos 0x0, ttl  64, id 17142, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.1.8.4888: F [tcp sum ok]
> 4134874226:4134874226(0) ack 2610855931 win 7380
> 03:15:30.079850 IP (tos 0x0, ttl  64, id 13364, offset 0, flags [DF],
> proto 6, length: 1185) 10.10.224.6.8001 > 10.1.4.49.46316: P
> 22595600:22596733(1133) ack 805897755 win 1746 <nop,nop,timestamp
> 24258316 3379834444>
> 03:15:31.089784 IP (tos 0x0, ttl  64, id 37000, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.3.131.1045: F [tcp sum
> ok] 4053960032:4053960032(0) ack 1538769655 win 6432
> 03:15:36.686007 IP (tos 0x0, ttl  64, id 3070, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.1.8.4824: F [tcp sum ok]
> 4120796002:4120796002(0) ack 2440799003 win 10992
> 03:15:37.229926 IP (tos 0x0, ttl  64, id 60997, offset 0, flags [DF],
> proto 6, length: 52) 10.10.224.6.8001 > 10.1.1.86.2288: F [tcp sum ok]
> 4164262937:4164262937(0) ack 3891303954 win 7497 <nop,nop,timestamp
> 24260104 27180085>
> 03:15:37.802145 IP (tos 0x0, ttl  64, id 60433, offset 0, flags [DF],
> proto 6, length: 40) 10.10.224.6.8001 > 10.1.1.8.4816: F [tcp sum ok]
> 4105151875:4105151875(0) ack 189658004 win 6432
>