[PATCH 5.11 045/152] flow_dissector: fix TTL and TOS dissection on IPv4 fragments

Greg Kroah-Hartman
2021-04-05T09:16:48Z

From: Davide Caratti <dcaratti@redhat.com>

[ Upstream commit d2126838050ccd1dadf310ffb78b2204f3b032b9 ]

the following command:

# tc filter add dev $h2 ingress protocol ip pref 1 handle 101 flower \
$tcflags dst_ip 192.0.2.2 ip_ttl 63 action drop

doesn't drop all IPv4 packets that match the configured TTL / destination
address. In particular, if "fragment offset" or "more fragments" have non
zero value in the IPv4 header, setting of FLOW_DISSECTOR_KEY_IP is simply
ignored. Fix this dissecting IPv4 TTL and TOS before fragment info; while
at it, add a selftest for tc flower's match on 'ip_ttl' that verifies the
correct behavior.

Fixes: 518d8a2e9bad ("net/flow_dissector: add support for dissection of misc ip header fields")
Reported-by: Shuang Li <shuali@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/flow_dissector.c | 6 +--
.../selftests/net/forwarding/tc_flower.sh | 38 ++++++++++++++++++-
2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 7a06d4301617..180be5102efc 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1050,6 +1050,9 @@ proto_again:
key_control->addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
}

+ __skb_flow_dissect_ipv4(skb, flow_dissector,
+ target_container, data, iph);
+
if (ip_is_fragment(iph)) {
key_control->flags |= FLOW_DIS_IS_FRAGMENT;

@@ -1066,9 +1069,6 @@ proto_again:
}
}

- __skb_flow_dissect_ipv4(skb, flow_dissector,
- target_container, data, iph);
-
break;
}
case htons(ETH_P_IPV6): {
diff --git a/tools/testing/selftests/net/forwarding/tc_flower.sh b/tools/testing/selftests/net/forwarding/tc_flower.sh
index 058c746ee300..b11d8e6b5bc1 100755
--- a/tools/testing/selftests/net/forwarding/tc_flower.sh
+++ b/tools/testing/selftests/net/forwarding/tc_flower.sh
@@ -3,7 +3,7 @@

ALL_TESTS="match_dst_mac_test match_src_mac_test match_dst_ip_test \
match_src_ip_test match_ip_flags_test match_pcp_test match_vlan_test \
- match_ip_tos_test match_indev_test"
+ match_ip_tos_test match_indev_test match_ip_ttl_test"
NUM_NETIFS=2
source tc_common.sh
source lib.sh
@@ -310,6 +310,42 @@ match_ip_tos_test()
log_test "ip_tos match ($tcflags)"
}

+match_ip_ttl_test()
+{
+ RET=0
+
+ tc filter add dev $h2 ingress protocol ip pref 1 handle 101 flower \
+ $tcflags dst_ip 192.0.2.2 ip_ttl 63 action drop
+ tc filter add dev $h2 ingress protocol ip pref 2 handle 102 flower \
+ $tcflags dst_ip 192.0.2.2 action drop
+
+ $MZ $h1 -c 1 -p 64 -a $h1mac -b $h2mac -A 192.0.2.1 -B 192.0.2.2 \
+ -t ip "ttl=63" -q
+
+ $MZ $h1 -c 1 -p 64 -a $h1mac -b $h2mac -A 192.0.2.1 -B 192.0.2.2 \
+ -t ip "ttl=63,mf,frag=256" -q
+
+ tc_check_packets "dev $h2 ingress" 102 1
+ check_fail $? "Matched on the wrong filter (no check on ttl)"
+
+ tc_check_packets "dev $h2 ingress" 101 2
+ check_err $? "Did not match on correct filter (ttl=63)"
+
+ $MZ $h1 -c 1 -p 64 -a $h1mac -b $h2mac -A 192.0.2.1 -B 192.0.2.2 \
+ -t ip "ttl=255" -q
+
+ tc_check_packets "dev $h2 ingress" 101 3
+ check_fail $? "Matched on a wrong filter (ttl=63)"
+
+ tc_check_packets "dev $h2 ingress" 102 1
+ check_err $? "Did not match on correct filter (no check on ttl)"
+
+ tc filter del dev $h2 ingress protocol ip pref 2 handle 102 flower
+ tc filter del dev $h2 ingress protocol ip pref 1 handle 101 flower
+
+ log_test "ip_ttl match ($tcflags)"
+}
+
match_indev_test()
{
RET=0
--
2.30.1