Hi Dave,
This is the sixth round of transparent proxying patches recently
discussed on the Netfilter Workshop. Since the last incarnation [1]
we've added support for related ICMP packets in the socket
match. Should apply cleanly on top of net-next-2.6. Could you please
apply patches 1-11 (those touching core networking parts) and I'll ask
Patrick McHardy to take care of patches 12-16 (the Netfilter parts).
The aim of the patchset is to make non-locally bound sockets work both
for receiving and sending. The target is IPv4 TCP/UDP at the moment.
Speaking of the patches, there are two big parts:
* Output path (patches 1-7): these modifications make it possible to
send IPv4 datagrams with non-local source IP address by:
- Introducing a new flowi flag (FLOWI_FLAG_ANYSRC) which disables
source address checking in ip_route_output_slow(). This is
also necessary for some of the tricks LVS does. [2]
- Adding the IP_TRANSPARENT socket option (setting this requires
CAP_NET_ADMIN to prevent source address spoofing).
- Gluing these together across the TCP/UDP code.
* Input path (patches 8-15): these changes add redirection support
for TCP along with an iptables target implementing NAT-less traffic
interception, and an iptables match to make ahead-of-time socket
lookups on PREROUTING. These combined with a set of iptables rules
and policy routing make non-locally bound sockets work.
- IPv4 TCP and UDP input path is modified to use this stored socket
reference if it's present.
- Netfilter IPv4 defragmentation is split into a separate
module. (This could make sense independently of tproxy and
conntrack, for example to have a stateless firewall which still
does fragment reassembly.)
- The 'socket' iptables match does a socket lookup on the
destination address and matches if a socket was found.
- The 'TPROXY' iptables target provides a way to intercept traffic
without NAT -- it does an ahead-of-time socket lookup on the
configured address and caches the socket reference in the skb.
The last patch adds a short intro on how to use it. A trivial patch
for netcat demonstrating the necessary modifications for proxies is
available separately at [3]. Squid has support for it in the 3.HEAD
(3.1) branch.
References:
[1] http://lwn.net/Articles/254527/
[2] http://marc.info/?l=linux-netdev&m=118065358510836&;...
[3] http://people.netfilter.org/hidden/tproxy/netcat-ip_trans...
--
KOVACS Krisztian
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
