I have determined what is happening but am not sure what to do to fix the problem. I ran tcpdump on my client and it sent 3 SYN requests. I saw 378 SYN requests come in my GRE interface and saw 375 SYN requests go out my ETH interface with a source IP of the client address. Since the source address is not the Squid machine, WCCP is sending them back to me again. Is Linux forwarding these packets acting as a router or does Squid use the client IP address in its request to contact the real web server? Thanks, Kevin -----Original Message----- From: Van Der Hart, Kevin [mailto:kvanderhart@xxxxxxxxxxxxxx] Sent: Monday, June 11, 2007 10:09 AM To: Henrik Nordstrom Cc: squid-users@xxxxxxxxxxxxxxx Subject: RE: Red Hat 5 - Squid 2.6 Stable 13 WCCP V2 and GRE >lör 2007-06-09 klockan 08:28 -0500 skrev Van Der Hart, Kevin: >> I am trying to get a transparent proxy working via WCCP V2 and am having >> an issue. I am running Red Hat 5 fully updated. IP Forwarding is >> enabled, RP_FILTER is disabled, the firewall is disabled. The kernel on >> Red Hat 5 is 2.6.18 which is supposed to have the patched version of >> ip_gre. >It should.. >> My iptable entry is built to port map traffic on port 80 to 3128 >> and I have tested that it is working. The gre tunnel is online and I can >> see traffic coming through the tunnel to port 80. The SYN packet comes >> in but no SYN ACK ever leaves. >Have you disabled rp_filter on the GRE interface? And is your iptables >rule for intercepting port 80 active on the GRE interface? # cat /proc/sys/net/ipv4/conf/gre1/rp_filter 0 # iptables -t nat -L PREROUTING Chain PREROUTING (policy ACCEPT) target prot opt source destination REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 3128 I have also tried removing the iptable entry and running Squid on port 80 and had the same results. >Note: The SYN ACK should leave via the Ethernet, not the GRE. The GRE is just for Router->Proxy traffic. I have been running tcpdump on both the GRE and ETH interfaces and do not see the SYN ACK on either. >> I placed a laptop on the same subnet as >> the Linux machine and pointed my default route to the Linux machine. The >> transparent proxying worked properly,I could surf the Internet, and I >> saw the requests in my access.log file so I am confident that Squid is >> configured properly for transparency. >It is. >Regards >Henrik Any other ideas that I should try? Thanks for the response. Kevin
