diff options
author | Florian Westphal <fw@strlen.de> | 2022-03-08 13:52:11 +0100 |
---|---|---|
committer | Florian Westphal <fw@strlen.de> | 2022-03-08 13:52:11 +0100 |
commit | a82c25c366b0963d33ddf699196e6cf57f6d89b1 (patch) | |
tree | 0ee98e723ff4d4695dac75185365806a79e2ef64 /tools/testing | |
parent | f8e9bd34cedd89b93b1167aa32ab8ecd6c2ccf4a (diff) | |
download | linux-stable-a82c25c366b0963d33ddf699196e6cf57f6d89b1.tar.gz linux-stable-a82c25c366b0963d33ddf699196e6cf57f6d89b1.tar.bz2 linux-stable-a82c25c366b0963d33ddf699196e6cf57f6d89b1.zip |
Revert "netfilter: nat: force port remap to prevent shadowing well-known ports"
This reverts commit 878aed8db324bec64f3c3f956e64d5ae7375a5de.
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>
Diffstat (limited to 'tools/testing')
-rwxr-xr-x | tools/testing/selftests/netfilter/nft_nat.sh | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/tools/testing/selftests/netfilter/nft_nat.sh b/tools/testing/selftests/netfilter/nft_nat.sh index 79fe627b9e81..eb8543b9a5c4 100755 --- a/tools/testing/selftests/netfilter/nft_nat.sh +++ b/tools/testing/selftests/netfilter/nft_nat.sh @@ -880,9 +880,8 @@ EOF return $ksft_skip fi - # test default behaviour. Packet from ns1 to ns0 is not redirected - # due to automatic port translation. - test_port_shadow "default" "ROUTER" + # test default behaviour. Packet from ns1 to ns0 is redirected to ns2. + test_port_shadow "default" "CLIENT" # test packet filter based mitigation: prevent forwarding of # packets claiming to come from the service port. |