[PATCH/RFC 00/13] Transparent proxying patches, take two

[KOVACS Krisztian <hidden@balabit.hu>]

  Hi,

These patches are my second try at providing Linux 2.2-like transparent
proxying support for Linux 2.6.

Major changes since the first version:

- iptable_tproxy now does IPv4 fragment reassembly (necessary for
  processing TCP/UDP header)

- The removal of the source address check in ip_route_output() was
  incorrect.  Instead, I've implemented a separate setsockopt-settable
  per-socket flag (setting it requires CAP_NET_ADMIN) to selectively
  loosen that check in ip_route_output().

Besides these, I've tried to fix all the problems raised on netdev@ in
January.

Unfortunately the newly introduced IP_TRANSPARENT socket option leads to
a quite intrusive set of patches touching core IPv4 routing and TCP
code, however this was necessary as DaveM rejected our idea of using
IP_FREEBIND instead (and he's right, of course, as it would have caused
ABI breakage.) The current approach works by adding a new bit to the
flag field in "struct flowi".

Furthermore, I haven't removed the IPv4 routing local diversion code
(caching socket lookups in the skb) yet. Patrick recommended throwing it
out altogether and use mark-based policy routing instead, but I still
think that would be harming usability as the user would need to
harmonize the configuration in order to have two completely independent
subsystems interoperate.

-- 
 Regards,
  Krisztian Kovacs