This reverts commit 878aed8db3.
This change breaks existing setups where conntrack is used with
asymmetric paths.
In these cases, the NAT transformation occurs on the syn-ack instead of
the syn:
1. SYN x:12345 -> y -> 443 // sent by initiator, receiverd by responder
2. SYNACK y:443 -> x:12345 // First packet seen by conntrack, as sent by responder
3. tuple_force_port_remap() gets called, sees:
'tcp from 443 to port 12345 NAT' -> pick a new source port, inititor receives
4. SYNACK y:$RANDOM -> x:12345 // connection is never established
While its possible to avoid the breakage with NOTRACK rules, a kernel
update should not break working setups.
An alternative to the revert is to augment conntrack to tag
mid-stream connections plus more code in the nat core to skip NAT
for such connections, however, this leads to more interaction/integration
between conntrack and NAT.
Therefore, revert, users will need to add explicit nat rules to avoid
port shadowing.
Link: https://lore.kernel.org/netfilter-devel/20220302105908.GA5852@breakpoint.cc/#R
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2051413
Signed-off-by: Florian Westphal <fw@strlen.de>
a82c25c366