netdev - [PATCH nf 1/2] wireguard: selftests: check that route_me

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Message-Id: <20201029025606.3523771-2-Jason@zx2c4.com>
Date:   Thu, 29 Oct 2020 03:56:05 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Chen Minqiang <ptpt52@...il.com>
Subject: [PATCH nf 1/2] wireguard: selftests: check that route_me_harder packets use the right sk

If netfilter changes the packet mark, the packet is rerouted. The
ip_route_me_harder family of functions fails to use the right sk, opting
to instead use skb->sk, resulting in a routing loop when used with
tunnels. With the next change fixing this issue in netfilter, test for
the relevant condition inside our test suite, since wireguard was where
the bug was discovered.

Reported-by: Chen Minqiang <ptpt52@...il.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 tools/testing/selftests/wireguard/netns.sh           | 8 ++++++++
 tools/testing/selftests/wireguard/qemu/kernel.config | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/tools/testing/selftests/wireguard/netns.sh b/tools/testing/selftests/wireguard/netns.sh
index d77f4829f1e0..74c69b75f6f5 100755
--- a/tools/testing/selftests/wireguard/netns.sh
+++ b/tools/testing/selftests/wireguard/netns.sh
@@ -316,6 +316,14 @@ pp sleep 3
 n2 ping -W 1 -c 1 192.168.241.1
 n1 wg set wg0 peer "$pub2" persistent-keepalive 0
 
+# Test that sk_bound_dev_if works
+n1 ping -I wg0 -c 1 -W 1 192.168.241.2
+# What about when the mark changes and the packet must be rerouted?
+n1 iptables -t mangle -I OUTPUT -j MARK --set-xmark 1
+n1 ping -c 1 -W 1 192.168.241.2 # First the boring case
+n1 ping -I wg0 -c 1 -W 1 192.168.241.2 # Then the sk_bound_dev_if case
+n1 iptables -t mangle -D OUTPUT -j MARK --set-xmark 1
+
 # Test that onion routing works, even when it loops
 n1 wg set wg0 peer "$pub3" allowed-ips 192.168.242.2/32 endpoint 192.168.241.2:5
 ip1 addr add 192.168.242.1/24 dev wg0
diff --git a/tools/testing/selftests/wireguard/qemu/kernel.config b/tools/testing/selftests/wireguard/qemu/kernel.config
index d531de13c95b..4eecb432a66c 100644
--- a/tools/testing/selftests/wireguard/qemu/kernel.config
+++ b/tools/testing/selftests/wireguard/qemu/kernel.config
@@ -18,10 +18,12 @@ CONFIG_NF_NAT=y
 CONFIG_NETFILTER_XTABLES=y
 CONFIG_NETFILTER_XT_NAT=y
 CONFIG_NETFILTER_XT_MATCH_LENGTH=y
+CONFIG_NETFILTER_XT_MARK=y
 CONFIG_NF_CONNTRACK_IPV4=y
 CONFIG_NF_NAT_IPV4=y
 CONFIG_IP_NF_IPTABLES=y
 CONFIG_IP_NF_FILTER=y
+CONFIG_IP_NF_MANGLE=y
 CONFIG_IP_NF_NAT=y
 CONFIG_IP_ADVANCED_ROUTER=y
 CONFIG_IP_MULTIPLE_TABLES=y
-- 
2.29.1