🔗 Configuring Transparent Interception with Fedora Core Linux and WCCPv2

• by Reuben Farrelly

🔗 Outline

This configuration for a Fedora Core Linux 2.6.18 box running Squid and receiving WCCPv2 traffic through ip_gre. It is expected that another device will perform the WCCPv2 routing and forward it to this box for processing.

🔗 Fedora Core WCCPv2 configuration

The GRE packets are sourced from one of the IPs on the router - I’m guessing its the "Router Identifier". This may not be the local ethernet IP (so in this case it isn’t 192.168.1.1.)

🔗 /etc/sysctl.conf

# Controls IP packet forwarding
net.ipv4.ip_forward = 1
# Controls source route verification
net.ipv4.conf.default.rp_filter = 0
# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

🔗 /etc/sysconfig/network-scripts/ifcfg-gre0

DEVICE=gre0
BOOTPROTO=static
IPADDR=172.16.1.6
NETMASK=255.255.255.252
ONBOOT=yes
IPV6INIT=no

By configuring the interface like this, it automatically comes up at boot, and the module is loaded automatically. I can additionally ifup or ifdown the interface at will. This is the standard Fedora way of configuring a GRE interface.

🔗 Fedora Core Intercept configuration

Then you need to redirect the packets coming in the gre0 interface to the Squid application.

🔗 /etc/sysconfig/iptables

-A PREROUTING -s 192.168.0.0/255.255.255.0 -d ! 192.168.0.0/255.255.255.0 -i gre0 -p tcp -m tcp --dport 80 -j DNAT --to-destination $SQUIDIP:3127

🔗 Squid Configuration File

http_port 3127 transparent
wccp2_router $ROUTERIP
# GRE forwarding
wccp2_forwarding_method gre
# GRE return method
wccp2_return_method gre
wccp2_service standard 0

🔗 What does it all look like?

my operating system runs a GRE tunnel which looks like this:

[root@tornado squid]# ifconfig gre0
gre0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
 inet addr:172.16.1.6 Mask:255.255.255.252
 UP RUNNING NOARP MTU:1476 Metric:1
 RX packets:449 errors:0 dropped:0 overruns:0 frame:0
 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:0
 RX bytes:20917 (20.4 KiB) TX bytes:0 (0.0 b)

my router sees the cache engine, and tells me how much traffic it has switched through to the cache:

router#show ip wccp web-cache
Global WCCP information:
 Router information:
 Router Identifier: 172.16.1.5
 Protocol Version: 2.0
 Service Identifier: web-cache
 Number of Service Group Clients: 1
 Number of Service Group Routers: 1
 Total Packets s/w Redirected: 1809
 Process: 203
 Fast: 1606
 CEF: 0
 Redirect access-list: -none-
 Total Packets Denied Redirect: 0
 Total Packets Unassigned: 0
 Group access-list: -none-
 Total Messages Denied to Group: 0
 Total Authentication failures: 0
 Total Bypassed Packets Received: 0
router#
router#show ip wccp web-cache detail
WCCP Client information:
 WCCP Client ID: 192.168.0.5
 Protocol Version: 2.0
 State: Usable
 Initial Hash Info: 00000000000000000000000000000000
 00000000000000000000000000000000
 Assigned Hash Info: FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
 Hash Allotment: 256 (100.00%)
 Packets s/w Redirected: 449
 Connect Time: 13:51:42
 Bypassed Packets
 Process: 0
 Fast: 0
 CEF: 0
router#

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or guarantee of suitability. If you have any further questions about
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