netfilter: ipset: Copy the right MAC address in bitmap:ip,mac and hash:ip,mac sets

netfilter: ipset: Copy the right MAC address in bitmap:ip,mac and hash:ip,mac sets

In commit 8cc4ccf58379 ("ipset: Allow matching on destination MAC address
for mac and ipmac sets"), ipset.git commit 1543514c46a7, I added to the
KADT functions for sets matching on MAC addreses the copy of source or
destination MAC address depending on the configured match.

This was done correctly for hash:mac, but for hash:ip,mac and
bitmap:ip,mac, copying and pasting the same code block presents an
obvious problem: in these two set types, the MAC address is the second
dimension, not the first one, and we are actually selecting the MAC
address depending on whether the first dimension (IP address) specifies
source or destination.

Fix this by checking for the IPSET_DIM_TWO_SRC flag in option flags.

This way, mixing source and destination matches for the two dimensions
of ip,mac set types works as expected. With this setup:

  ip netns add A
  ip link add veth1 type veth peer name veth2 netns A
  ip addr add 192.0.2.1/24 dev veth1
  ip -net A addr add 192.0.2.2/24 dev veth2
  ip link set veth1 up
  ip -net A link set veth2 up

  dst=$(ip netns exec A cat /sys/class/net/veth2/address)

  ip netns exec A ipset create test_bitmap bitmap:ip,mac range 192.0.0.0/16
  ip netns exec A ipset add test_bitmap 192.0.2.1,${dst}
  ip netns exec A iptables -A INPUT -m set ! --match-set test_bitmap src,dst -j DROP

  ip netns exec A ipset create test_hash hash:ip,mac
  ip netns exec A ipset add test_hash 192.0.2.1,${dst}
  ip netns exec A iptables -A INPUT -m set ! --match-set test_hash src,dst -j DROP

ipset correctly matches a test packet:

  # ping -c1 192.0.2.2 >/dev/null
  # echo $?
  0

Reported-by: Chen Yi <yiche@redhat.com>
Fixes: 8cc4ccf58379 ("ipset: Allow matching on destination MAC address for mac and ipmac sets")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>