At one point, a member here -- when asked what the difference in
defining rules in nftables between the two systems -- said "they are the
same."
As I read the documentation on wiki.nftables.org: NO!
The hooker here is the requirement thatt IPv6 header examination
requires "nexthdr" to examine tcp, udp, and icmp packets. How about
other protocols: do I need to do something like this?
nexthdr inet protocol {gre, esp, ah} jump other_protocols
If this is the case, than the "inet" combined table is useless, as my
filters will need to be in separate "ip" and "ip6" tables.
Fortunately, I'm building a parameter-based firewall generator, so
details like this can be hidden from the person specifying the pinholes
for the firewall, if this is the case.
Or does nft(8) do the smart thing and, for IPv6, put the "nexthop" in
the v6 rules for you?
Maybe this excerpt from wiki.nftables.org answers my question:
inet
Tables of this family see both IPv4 and IPv6 traffic/packets, simplifying dual stack support.
Within a table of inet family, both IPv4 and IPv6 packets traverse the same rules. Rules for IPv4 packets don't affect IPv6 packets. Rules for both L3 protocols affect both.
Examples:
# This rule affects only IPv4 packets:
add rule inet filter input ip saddr 1.1.1.1 counter accept
# This rule affects only IPv6 packets:
add rule inet filter input ip6 daddr fe00::2 counter accept
# These rules affect both IPv4 and IPv6 packets:
add rule inet filter input ct state established,related counter accept
add rule inet filter input udp dport 53 accept
The thing is, the specification of "inet" is shorthand for inserting the
same rule into two tables, "ip" and "ip6". So, if I'm constructing a
table I need to separate the "inet" table into two separate tables, "ip"
and "ip6".
Someone please disabuse me of any incorrect notions.
