Stateless NAT is useful in controlled environments where restrictions are
placed on through traffic such that we don't need connection tracking to
correctly NAT protocol-specific data.
In particular, this is of interest when the number of flows or the number
of addresses being NATed is large, or if connection tracking information
has to be replicated and where it is not practical to do so.
Previously we had stateless NAT functionality which was integrated into
the IPv4 routing subsystem. This was a great solution as long as the NAT
worked on a subnet to subnet basis such that the number of NAT rules was
relatively small. The reason is that for SNAT the routing based system
had to perform a linear scan through the rules.
If the number of rules is large then major renovations would have take
place in the routing subsystem to make this practical.
For the time being, the least intrusive way of achieving this is to use
the u32 classifier written by Alexey Kuznetsov along with the actions
infrastructure implemented by Jamal Hadi Salim.
The following patch is an attempt at this problem by creating a new nat
action that can be invoked from u32 hash tables which would allow large
number of stateless NAT rules that can be used/updated in constant time.
The actual NAT code is mostly based on the previous stateless NAT code
written by Alexey. In future we might be able to utilise the protocol
NAT code from netfilter to improve support for other protocols.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This was simply making templates of functions and mostly causing a lot
of code duplication in the classifier action modules.
We solve this more cleanly by having a common "struct tcf_common" that
hash worker functions contained once in act_api.c can work with.
Callers work with real action objects that have the common struct
plus their module specific struct members. You go from a common
object to the higher level one using a "to_foo()" macro which makes
use of container_of() to do the dirty work.
This also kills off act_generic.h which was only used by act_simple.c
and keeping it around was more work than the it's value.
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch moves {ip,ip6,arp}t_entry_{match,target} definitions to
x_tables.h. This move simplifies code and future compatibility fixes.
Signed-off-by: Dmitry Mishin <dim@openvz.org>
Acked-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
And provide an example simply action in order to
demonstrate usage.
Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
