nft_ipv{4,6}_xlate: Respect prefix lengths

This was an annoying bug in the translator since it silently dropped
crucial information which is easily overlooked:

| $ iptables-translate -A INPUT -s 192.168.0.0/24 -j ACCEPT
| nft add rule ip filter INPUT ip saddr 192.168.0.0 counter accept
| $ ip6tables-translate -A INPUT -s feed:babe::/64 -j ACCEPT
| nft add rule ip6 filter INPUT ip6 saddr feed:babe:: counter accept

To my surprise, this fix works really well in all kinds of situations:

| $ iptables-translate -A INPUT -s 1.2.3.4/0 -j ACCEPT
| nft add rule ip filter INPUT counter accept
|
| $ iptables-translate -A INPUT -s 1.2.3.4/23 -j ACCEPT
| nft add rule ip filter INPUT ip saddr 1.2.2.0/23 counter accept
|
| $ iptables-translate -A INPUT -s 1.2.3.4/24 -j ACCEPT
| nft add rule ip filter INPUT ip saddr 1.2.3.0/24 counter accept
|
| $ iptables-translate -A INPUT -s 1.2.3.4/32 -j ACCEPT
| nft add rule ip filter INPUT ip saddr 1.2.3.4 counter accept
|
| $ iptables-translate -A INPUT -s 1.2.3.4/255.255.0.0 -j ACCEPT
| nft add rule ip filter INPUT ip saddr 1.2.0.0/16 counter accept

Ditto for IPv6.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2 files changed