socket: fix compat for 4.1 v6 sockets

It turns out 4.1 is even more broken than expected. While both 4.1 and
4.2 need to jigger the sysctl nob temporarily, it turns out that in 4.1
it's looking in the wrong namespace for the nob value. So, we have to
account for the different namespace semantics in the different versions.
Super ugly. But, all this code goes away once we upstream.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/socket.c b/src/socket.c
index 9dd1683..aa17c1b 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -423,6 +423,7 @@ int socket_init(struct wireguard_device *wg)
 	int ret = 0;
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
 	int old_bindv6only;
+	struct net *nobns;
 #endif
 
 	mutex_lock(&wg->socket_update_lock);
@@ -453,15 +454,20 @@ int socket_init(struct wireguard_device *wg)
 
 #if IS_ENABLED(CONFIG_IPV6)
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 2, 0)
+	nobns = &init_net;
+#else
+	nobns = wg->creating_net;
+#endif
 	/* Since udp_port_cfg only learned of ipv6_v6only in 4.3, we do this horrible
 	 * hack here and set the sysctl variable temporarily to something that will
 	 * set the right option for us in sock_create. It's super racey! */
-	old_bindv6only = wg->creating_net->ipv6.sysctl.bindv6only;
-	wg->creating_net->ipv6.sysctl.bindv6only = 1;
+	old_bindv6only = nobns->ipv6.sysctl.bindv6only;
+	nobns->ipv6.sysctl.bindv6only = 1;
 #endif
 	ret = udp_sock_create(wg->creating_net, &port6, &new6);
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
-	wg->creating_net->ipv6.sysctl.bindv6only = old_bindv6only;
+	nobns->ipv6.sysctl.bindv6only = old_bindv6only;
 #endif
 	if (ret < 0) {
 		pr_err("Could not create IPv6 socket\n");