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wireguard: socket: remove errant restriction on looping to self
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It's already possible to create two different interfaces and loop
packets between them. This has always been possible with tunnels in the
kernel, and isn't specific to wireguard. Therefore, the networking stack
already needs to deal with that. At the very least, the packet winds up
exceeding the MTU and is discarded at that point. So, since this is
already something that happens, there's no need to forbid the not very
exceptional case of routing a packet back to the same interface; this
loop is no different than others, and we shouldn't special case it, but
rather rely on generic handling of loops in general. This also makes it
easier to do interesting things with wireguard such as onion routing.

At the same time, we add a selftest for this, ensuring that both onion
routing works and infinite routing loops do not crash the kernel. We
also add a test case for wireguard interfaces nesting packets and
sending traffic between each other, as well as the loop in this case
too. We make sure to send some throughput-heavy traffic for this use
case, to stress out any possible recursion issues with the locks around
workqueues.

Fixes: e7096c1 ("net: WireGuard secure network tunnel")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Jason A. Donenfeld authored and David S. Miller committed May 7, 2020
1 parent a0fd7cc commit b673e24
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Showing 2 changed files with 51 additions and 15 deletions.
12 changes: 0 additions & 12 deletions drivers/net/wireguard/socket.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -76,12 +76,6 @@ static int send4(struct wg_device *wg, struct sk_buff *skb,
net_dbg_ratelimited("%s: No route to %pISpfsc, error %d\n",
wg->dev->name, &endpoint->addr, ret);
goto err;
} else if (unlikely(rt->dst.dev == skb->dev)) {
ip_rt_put(rt);
ret = -ELOOP;
net_dbg_ratelimited("%s: Avoiding routing loop to %pISpfsc\n",
wg->dev->name, &endpoint->addr);
goto err;
}
if (cache)
dst_cache_set_ip4(cache, &rt->dst, fl.saddr);
Expand Down Expand Up @@ -149,12 +143,6 @@ static int send6(struct wg_device *wg, struct sk_buff *skb,
net_dbg_ratelimited("%s: No route to %pISpfsc, error %d\n",
wg->dev->name, &endpoint->addr, ret);
goto err;
} else if (unlikely(dst->dev == skb->dev)) {
dst_release(dst);
ret = -ELOOP;
net_dbg_ratelimited("%s: Avoiding routing loop to %pISpfsc\n",
wg->dev->name, &endpoint->addr);
goto err;
}
if (cache)
dst_cache_set_ip6(cache, dst, &fl.saddr);
Expand Down
54 changes: 51 additions & 3 deletions tools/testing/selftests/wireguard/netns.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,8 +48,11 @@ cleanup() {
exec 2>/dev/null
printf "$orig_message_cost" > /proc/sys/net/core/message_cost
ip0 link del dev wg0
ip0 link del dev wg1
ip1 link del dev wg0
ip1 link del dev wg1
ip2 link del dev wg0
ip2 link del dev wg1
local to_kill="$(ip netns pids $netns0) $(ip netns pids $netns1) $(ip netns pids $netns2)"
[[ -n $to_kill ]] && kill $to_kill
pp ip netns del $netns1
Expand Down Expand Up @@ -77,18 +80,20 @@ ip0 link set wg0 netns $netns2
key1="$(pp wg genkey)"
key2="$(pp wg genkey)"
key3="$(pp wg genkey)"
key4="$(pp wg genkey)"
pub1="$(pp wg pubkey <<<"$key1")"
pub2="$(pp wg pubkey <<<"$key2")"
pub3="$(pp wg pubkey <<<"$key3")"
pub4="$(pp wg pubkey <<<"$key4")"
psk="$(pp wg genpsk)"
[[ -n $key1 && -n $key2 && -n $psk ]]

configure_peers() {
ip1 addr add 192.168.241.1/24 dev wg0
ip1 addr add fd00::1/24 dev wg0
ip1 addr add fd00::1/112 dev wg0

ip2 addr add 192.168.241.2/24 dev wg0
ip2 addr add fd00::2/24 dev wg0
ip2 addr add fd00::2/112 dev wg0

n1 wg set wg0 \
private-key <(echo "$key1") \
Expand Down Expand Up @@ -230,9 +235,38 @@ n1 ping -W 1 -c 1 192.168.241.2
n1 wg set wg0 private-key <(echo "$key3")
n2 wg set wg0 peer "$pub3" preshared-key <(echo "$psk") allowed-ips 192.168.241.1/32 peer "$pub1" remove
n1 ping -W 1 -c 1 192.168.241.2
n2 wg set wg0 peer "$pub3" remove

# Test that we can route wg through wg
ip1 addr flush dev wg0
ip2 addr flush dev wg0
ip1 addr add fd00::5:1/112 dev wg0
ip2 addr add fd00::5:2/112 dev wg0
n1 wg set wg0 private-key <(echo "$key1") peer "$pub2" preshared-key <(echo "$psk") allowed-ips fd00::5:2/128 endpoint 127.0.0.1:2
n2 wg set wg0 private-key <(echo "$key2") listen-port 2 peer "$pub1" preshared-key <(echo "$psk") allowed-ips fd00::5:1/128 endpoint 127.212.121.99:9998
ip1 link add wg1 type wireguard
ip2 link add wg1 type wireguard
ip1 addr add 192.168.241.1/24 dev wg1
ip1 addr add fd00::1/112 dev wg1
ip2 addr add 192.168.241.2/24 dev wg1
ip2 addr add fd00::2/112 dev wg1
ip1 link set mtu 1340 up dev wg1
ip2 link set mtu 1340 up dev wg1
n1 wg set wg1 listen-port 5 private-key <(echo "$key3") peer "$pub4" allowed-ips 192.168.241.2/32,fd00::2/128 endpoint [fd00::5:2]:5
n2 wg set wg1 listen-port 5 private-key <(echo "$key4") peer "$pub3" allowed-ips 192.168.241.1/32,fd00::1/128 endpoint [fd00::5:1]:5
tests
# Try to set up a routing loop between the two namespaces
ip1 link set netns $netns0 dev wg1
ip0 addr add 192.168.241.1/24 dev wg1
ip0 link set up dev wg1
n0 ping -W 1 -c 1 192.168.241.2
n1 wg set wg0 peer "$pub2" endpoint 192.168.241.2:7
ip2 link del wg0
ip2 link del wg1
! n0 ping -W 1 -c 10 -f 192.168.241.2 || false # Should not crash kernel

ip0 link del wg1
ip1 link del wg0
ip2 link del wg0

# Test using NAT. We now change the topology to this:
# ┌────────────────────────────────────────┐ ┌────────────────────────────────────────────────┐ ┌────────────────────────────────────────┐
Expand Down Expand Up @@ -282,6 +316,20 @@ pp sleep 3
n2 ping -W 1 -c 1 192.168.241.1
n1 wg set wg0 peer "$pub2" persistent-keepalive 0

# Test that onion routing works, even when it loops
n1 wg set wg0 peer "$pub3" allowed-ips 192.168.242.2/32 endpoint 192.168.241.2:5
ip1 addr add 192.168.242.1/24 dev wg0
ip2 link add wg1 type wireguard
ip2 addr add 192.168.242.2/24 dev wg1
n2 wg set wg1 private-key <(echo "$key3") listen-port 5 peer "$pub1" allowed-ips 192.168.242.1/32
ip2 link set wg1 up
n1 ping -W 1 -c 1 192.168.242.2
ip2 link del wg1
n1 wg set wg0 peer "$pub3" endpoint 192.168.242.2:5
! n1 ping -W 1 -c 1 192.168.242.2 || false # Should not crash kernel
n1 wg set wg0 peer "$pub3" remove
ip1 addr del 192.168.242.1/24 dev wg0

# Do a wg-quick(8)-style policy routing for the default route, making sure vethc has a v6 address to tease out bugs.
ip1 -6 addr add fc00::9/96 dev vethc
ip1 -6 route add default via fc00::1
Expand Down

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