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authorLinus Torvalds <torvalds@linux-foundation.org>2008-10-11 09:33:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-11 09:33:18 -0700
commit4dd9ec4946b4651a295d3bc8df9c15ac692a8f4e (patch)
treeafb300c752de7175bb2df4722d5c857e070c75d9 /Documentation/networking/tproxy.txt
parent86ed5a93b8b56e4e0877b914af0e10883a196384 (diff)
parent6861ff35ec5b60fafaf8651754c9a75142bfa9a4 (diff)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6: (1075 commits) myri10ge: update driver version number to 1.4.3-1.369 r8169: add shutdown handler r8169: preliminary 8168d support r8169: support additional 8168cp chipset r8169: change default behavior for mildly identified 8168c chipsets r8169: add a new 8168cp flavor r8169: add a new 8168c flavor (bis) r8169: add a new 8168c flavor r8169: sync existing 8168 device hardware start sequences with vendor driver r8169: 8168b Tx performance tweak r8169: make room for more specific 8168 hardware start procedure r8169: shuffle some registers handling around (8168 operation only) r8169: new phy init parameters for the 8168b r8169: update phy init parameters r8169: wake up the PHY of the 8168 af_key: fix SADB_X_SPDDELETE response ath9k: Fix return code when ath9k_hw_setpower() fails on reset ath9k: remove nasty FAIL macro from ath9k_hw_reset() gre: minor cleanups in netlink interface gre: fix copy and paste error ...
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+Transparent proxy support
+=========================
+
+This feature adds Linux 2.2-like transparent proxy support to current kernels.
+To use it, enable NETFILTER_TPROXY, the socket match and the TPROXY target in
+your kernel config. You will need policy routing too, so be sure to enable that
+as well.
+
+
+1. Making non-local sockets work
+================================
+
+The idea is that you identify packets with destination address matching a local
+socket on your box, set the packet mark to a certain value, and then match on that
+value using policy routing to have those packets delivered locally:
+
+# iptables -t mangle -N DIVERT
+# iptables -t mangle -A PREROUTING -p tcp -m socket -j DIVERT
+# iptables -t mangle -A DIVERT -j MARK --set-mark 1
+# iptables -t mangle -A DIVERT -j ACCEPT
+
+# ip rule add fwmark 1 lookup 100
+# ip route add local 0.0.0.0/0 dev lo table 100
+
+Because of certain restrictions in the IPv4 routing output code you'll have to
+modify your application to allow it to send datagrams _from_ non-local IP
+addresses. All you have to do is enable the (SOL_IP, IP_TRANSPARENT) socket
+option before calling bind:
+
+fd = socket(AF_INET, SOCK_STREAM, 0);
+/* - 8< -*/
+int value = 1;
+setsockopt(fd, SOL_IP, IP_TRANSPARENT, &value, sizeof(value));
+/* - 8< -*/
+name.sin_family = AF_INET;
+name.sin_port = htons(0xCAFE);
+name.sin_addr.s_addr = htonl(0xDEADBEEF);
+bind(fd, &name, sizeof(name));
+
+A trivial patch for netcat is available here:
+http://people.netfilter.org/hidden/tproxy/netcat-ip_transparent-support.patch
+
+
+2. Redirecting traffic
+======================
+
+Transparent proxying often involves "intercepting" traffic on a router. This is
+usually done with the iptables REDIRECT target; however, there are serious
+limitations of that method. One of the major issues is that it actually
+modifies the packets to change the destination address -- which might not be
+acceptable in certain situations. (Think of proxying UDP for example: you won't
+be able to find out the original destination address. Even in case of TCP
+getting the original destination address is racy.)
+
+The 'TPROXY' target provides similar functionality without relying on NAT. Simply
+add rules like this to the iptables ruleset above:
+
+# iptables -t mangle -A PREROUTING -p tcp --dport 80 -j TPROXY \
+ --tproxy-mark 0x1/0x1 --on-port 50080
+
+Note that for this to work you'll have to modify the proxy to enable (SOL_IP,
+IP_TRANSPARENT) for the listening socket.
+
+
+3. Iptables extensions
+======================
+
+To use tproxy you'll need to have the 'socket' and 'TPROXY' modules
+compiled for iptables. A patched version of iptables is available
+here: http://git.balabit.hu/?p=bazsi/iptables-tproxy.git
+
+
+4. Application support
+======================
+
+4.1. Squid
+----------
+
+Squid 3.HEAD has support built-in. To use it, pass
+'--enable-linux-netfilter' to configure and set the 'tproxy' option on
+the HTTP listener you redirect traffic to with the TPROXY iptables
+target.
+
+For more information please consult the following page on the Squid
+wiki: http://wiki.squid-cache.org/Features/Tproxy4