src: add nat support for the inet family

consider a simple ip6 nat table:

table ip6 nat { chain output {
  type nat hook output priority 0; policy accept;
  dnat to dead:2::99
}

Now consider same ruleset, but using 'table inet nat':
nft now lacks context to determine address family to parse 'to $address'.

This adds code to make the following work:

table inet nat { [ .. ]
  # detect af from network protocol context:
  ip6 daddr dead::2::1 dnat to dead:2::99

  # use new dnat ip6 keyword:
  dnat ip6 to dead:2::99
  }

On list side, the keyword is only shown in the inet family, else the
short version (dnat to ...) is used as the family is redundant when the
table already mandates the ip protocol version supported.

Address mismatches such as

table ip6 { ..
	dnat ip to 1.2.3.4

are detected/handled during the evaluation phase.

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/tests/py/inet/snat.t.payload b/tests/py/inet/snat.t.payload
new file mode 100644
index 00000000..00bb937f
--- /dev/null
+++ b/tests/py/inet/snat.t.payload
@@ -0,0 +1,42 @@
+# iifname "eth0" tcp dport 81 snat ip to 192.168.3.2
+inet test-inet postrouting
+  [ meta load iifname => reg 1 ]
+  [ cmp eq reg 1 0x30687465 0x00000000 0x00000000 0x00000000 ]
+  [ meta load l4proto => reg 1 ]
+  [ cmp eq reg 1 0x00000006 ]
+  [ payload load 2b @ transport header + 2 => reg 1 ]
+  [ cmp eq reg 1 0x00005100 ]
+  [ immediate reg 1 0x0203a8c0 ]
+  [ nat snat ip addr_min reg 1 addr_max reg 0 ]
+
+# iifname "eth0" tcp dport 81 ip saddr 10.1.1.1 snat to 192.168.3.2
+inet test-inet postrouting
+  [ meta load iifname => reg 1 ]
+  [ cmp eq reg 1 0x30687465 0x00000000 0x00000000 0x00000000 ]
+  [ meta load l4proto => reg 1 ]
+  [ cmp eq reg 1 0x00000006 ]
+  [ payload load 2b @ transport header + 2 => reg 1 ]
+  [ cmp eq reg 1 0x00005100 ]
+  [ meta load nfproto => reg 1 ]
+  [ cmp eq reg 1 0x00000002 ]
+  [ payload load 4b @ network header + 12 => reg 1 ]
+  [ cmp eq reg 1 0x0101010a ]
+  [ immediate reg 1 0x0203a8c0 ]
+  [ nat snat ip addr_min reg 1 addr_max reg 0 ]
+
+# iifname "eth0" tcp dport 81 snat ip6 to dead::beef
+inet test-inet postrouting
+  [ meta load iifname => reg 1 ]
+  [ cmp eq reg 1 0x30687465 0x00000000 0x00000000 0x00000000 ]
+  [ meta load l4proto => reg 1 ]
+  [ cmp eq reg 1 0x00000006 ]
+  [ payload load 2b @ transport header + 2 => reg 1 ]
+  [ cmp eq reg 1 0x00005100 ]
+  [ immediate reg 1 0x0000adde 0x00000000 0x00000000 0xefbe0000 ]
+  [ nat snat ip6 addr_min reg 1 addr_max reg 0 ]
+
+# iifname "foo" masquerade random
+inet test-inet postrouting
+  [ meta load iifname => reg 1 ]
+  [ cmp eq reg 1 0x006f6f66 0x00000000 0x00000000 0x00000000 ]
+  [ masq flags 0x4 ]