mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-29 23:53:55 +08:00
d2f26037a3
Add basic usage instructions to Documentation/networking. Signed-off-by: KOVACS Krisztian <hidden@sch.bme.hu> Signed-off-by: Patrick McHardy <kaber@trash.net>
86 lines
3.0 KiB
Plaintext
86 lines
3.0 KiB
Plaintext
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
|