vrf: Revert "Reset skb conntrack connection..."

stable inclusion
from stable-5.10.78
commit b9c85a71e1b4898e978c594a44e881456313a855
bugzilla: 185700 https://gitee.com/openeuler/kernel/issues/I4IAU2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b9c85a71e1b4898e978c594a44e881456313a855



--------------------------------

commit 55161e67 upstream.

This reverts commit 09e856d5.

When an interface is enslaved in a VRF, prerouting conntrack hook is
called twice: once in the context of the original input interface, and
once in the context of the VRF interface. If no special precausions are
taken, this leads to creation of two conntrack entries instead of one,
and breaks SNAT.

Commit above was intended to avoid creation of extra conntrack entries
when input interface is enslaved in a VRF. It did so by resetting
conntrack related data associated with the skb when it enters VRF context.

However it breaks netfilter operation. Imagine a use case when conntrack
zone must be assigned based on the original input interface, rather than
VRF interface (that would make original interfaces indistinguishable). One
could create netfilter rules similar to these:

        chain rawprerouting {
                type filter hook prerouting priority raw;
                iif realiface1 ct zone set 1 return
                iif realiface2 ct zone set 2 return
        }

This works before the mentioned commit, but not after: zone assignment
is "forgotten", and any subsequent NAT or filtering that is dependent
on the conntrack zone does not work.

Here is a reproducer script that demonstrates the difference in behaviour.

==========

IPIN=172.30.30.1
IPOUT=172.30.30.2
PFXL=30

ip li sh vein >/dev/null 2>&1 && ip li del vein
ip li sh tvrf >/dev/null 2>&1 && ip li del tvrf
nft list table testct >/dev/null 2>&1 && nft delete table testct

ip li add vein type veth peer veout
ip li add tvrf type vrf table 9876
ip li set veout master tvrf
ip li set vein up
ip li set veout up
ip li set tvrf up
/sbin/sysctl -w net.ipv4.conf.veout.accept_local=1
/sbin/sysctl -w net.ipv4.conf.veout.rp_filter=0
ip addr add $IPIN/$PFXL dev vein
ip addr add $IPOUT/$PFXL dev veout

nft -f - <<__END__
table testct {
	chain rawpre {
		type filter hook prerouting priority raw;
		iif { veout, tvrf } meta nftrace set 1
		iif veout ct zone set 1 return
		iif tvrf ct zone set 2 return
		notrack
	}
	chain rawout {
		type filter hook output priority raw;
		notrack
	}
}
__END__

uname -rv
conntrack -F
ping -W 1 -c 1 -I vein $IPOUT
conntrack -L

Signed-off-by: Eugene Crosser <crosser@average.org>
Acked-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>

Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>