CVE-2024-50038: netfilter: xtables: avoid NFPROTO_UNSPEC where needed

In the Linux kernel, the following vulnerability has been resolved:

netfilter: xtables: avoid NFPROTOUNSPEC where needed

syzbot managed to call xtcluster match via ebtables:

WARNING: CPU: 0 PID: 11 at net/netfilter/xtcluster.c:72 xtclustermt+0x196/0x780 [..] ebtdotable+0x174b/0x2a40

Module registers to NFPROTOUNSPEC, but it assumes ipv4/ipv6 packet processing. As this is only useful to restrict locally terminating TCP/UDP traffic, register this for ipv4 and ipv6 family only.

Pablo points out that this is a general issue, direct users of the set/getsockopt interface can call into targets/matches that were only intended for use with ip(6)tables.

Check all UNSPEC matches and targets for similar issues:

- matches and targets are fine except if they assume skbnetworkheader() is valid -- this is only true when called from inet layer: ip(6) stack pulls the ip/ipv6 header into linear data area. - targets that return XTCONTINUE or other xtables verdicts must be restricted too, they are incompatbile with the ebtables traverser, e.g. EBTCONTINUE is a completely different value than XTCONTINUE.

Most matches/targets are changed to register for NFPROTOIPV4/IPV6, as they are provided for use by ip(6)tables.

The MARK target is also used by arptables, so register for NFPROTOARP too.

While at it, bail out if connbytes fails to enable the corresponding conntrack family.

This change passes the selftests in iptables.git.