ipv6: Define dscp_t and stop taking ECN bits into account in fib6-rules

Define a dscp_t type and its appropriate helpers that ensure ECN bits
are not taken into account when handling DSCP.

Use this new type to replace the tclass field of struct fib6_rule, so
that fib6-rules don't get influenced by ECN bits anymore.

Before this patch, fib6-rules didn't make any distinction between the
DSCP and ECN bits. Therefore, rules specifying a DSCP (tos or dsfield
options in iproute2) stopped working as soon a packets had at least one
of its ECN bits set (as a work around one could create four rules for
each DSCP value to match, one for each possible ECN value).

After this patch fib6-rules only compare the DSCP bits. ECN doesn't
influence the result anymore. Also, fib6-rules now must have the ECN
bits cleared or they will be rejected.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Acked-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 29 insertions, 1 deletions

diff --git a/tools/testing/selftests/net/fib_rule_tests.sh b/tools/testing/selftests/net/fib_rule_tests.sh
index 3b0489910422..d7a9ab3be1d3 100755
--- a/tools/testing/selftests/net/fib_rule_tests.sh
+++ b/tools/testing/selftests/net/fib_rule_tests.sh
@@ -114,10 +114,25 @@ fib_rule6_test_match_n_redirect()
 	log_test $? 0 "rule6 del by pref: $description"
 }
 
+fib_rule6_test_reject()
+{
+	local match="$1"
+	local rc
+
+	$IP -6 rule add $match table $RTABLE 2>/dev/null
+	rc=$?
+	log_test $rc 2 "rule6 check: $match"
+
+	if [ $rc -eq 0 ]; then
+		$IP -6 rule del $match table $RTABLE
+	fi
+}
+
 fib_rule6_test()
 {
 	local getmatch
 	local match
+	local cnt
 
 	# setup the fib rule redirect route
 	$IP -6 route add table $RTABLE default via $GW_IP6 dev $DEV onlink
@@ -128,8 +143,21 @@ fib_rule6_test()
 	match="from $SRC_IP6 iif $DEV"
 	fib_rule6_test_match_n_redirect "$match" "$match" "iif redirect to table"
 
+	# Reject dsfield (tos) options which have ECN bits set
+	for cnt in $(seq 1 3); do
+		match="dsfield $cnt"
+		fib_rule6_test_reject "$match"
+	done
+
+	# Don't take ECN bits into account when matching on dsfield
 	match="tos 0x10"
-	fib_rule6_test_match_n_redirect "$match" "$match" "tos redirect to table"
+	for cnt in "0x10" "0x11" "0x12" "0x13"; do
+		# Using option 'tos' instead of 'dsfield' as old iproute2
+		# versions don't support 'dsfield' in ip rule show.
+		getmatch="tos $cnt"
+		fib_rule6_test_match_n_redirect "$match" "$getmatch" \
+						"$getmatch redirect to table"
+	done
 
 	match="fwmark 0x64"
 	getmatch="mark 0x64"