net: Force PPPoLAC and PPPoPNS to bind an interface before creating PPP channel.

It is common to manipulate the routing table after configuring PPP device.
Since both PPPoLAC and PPPoPNS run over IP, care must be taken to make sure
that there is no loop in the routing table.
Although this can be done by adding a host route, it might still cause
problems when the interface is down for some reason.

To solve this, this patch forces both drivers to bind an interface before
creating PPP channel, so the system will not re-route the tunneling sockets
to another interface when the original one is down. Another benefit is that
now the host route is no longer required, so there is no need to remove it
when PPP channel is closed.

Signed-off-by: Chia-chi Yeh <chiachi@android.com>

2 files changed, 21 insertions, 2 deletions

diff --git a/drivers/net/pppolac.c b/drivers/net/pppolac.c
index 1f522270fd33..b4d879d8b8eb 100644
--- a/drivers/net/pppolac.c
+++ b/drivers/net/pppolac.c
@@ -220,6 +220,14 @@ static int pppolac_connect(struct socket *sock, struct sockaddr *useraddr,
 	error = -EBUSY;
 	if (udp_sk(sk_udp)->encap_type || sk_udp->sk_user_data)
 		goto out;
+	if (!sk_udp->sk_bound_dev_if) {
+		struct dst_entry *dst = sk_dst_get(sk_udp);
+		error = -ENODEV;
+		if (!dst)
+			goto out;
+		sk_udp->sk_bound_dev_if = dst->dev->ifindex;
+		dst_release(dst);
+	}
 
 	po->chan.hdrlen = 12;
 	po->chan.private = sk_udp;
diff --git a/drivers/net/pppopns.c b/drivers/net/pppopns.c
index 7edff027d0cc..eae4bdab0b62 100644
--- a/drivers/net/pppopns.c
+++ b/drivers/net/pppopns.c
@@ -161,6 +161,7 @@ static int pppopns_connect(struct socket *sock, struct sockaddr *useraddr,
 	struct sockaddr_storage ss;
 	struct socket *sock_tcp = NULL;
 	struct socket *sock_raw = NULL;
+	struct sock *sk_tcp;
 	struct sock *sk_raw;
 	int error;
 
@@ -175,21 +176,31 @@ static int pppopns_connect(struct socket *sock, struct sockaddr *useraddr,
 	sock_tcp = sockfd_lookup(addr->tcp_socket, &error);
 	if (!sock_tcp)
 		goto out;
+	sk_tcp = sock_tcp->sk;
 	error = -EPROTONOSUPPORT;
-	if (sock_tcp->sk->sk_protocol != IPPROTO_TCP)
+	if (sk_tcp->sk_protocol != IPPROTO_TCP)
 		goto out;
 	addrlen = sizeof(struct sockaddr_storage);
 	error = kernel_getpeername(sock_tcp, (struct sockaddr *)&ss, &addrlen);
 	if (error)
 		goto out;
+	if (!sk_tcp->sk_bound_dev_if) {
+		struct dst_entry *dst = sk_dst_get(sk_tcp);
+		error = -ENODEV;
+		if (!dst)
+			goto out;
+		sk_tcp->sk_bound_dev_if = dst->dev->ifindex;
+		dst_release(dst);
+	}
 
 	error = sock_create(ss.ss_family, SOCK_RAW, IPPROTO_GRE, &sock_raw);
 	if (error)
 		goto out;
+	sk_raw = sock_raw->sk;
+	sk_raw->sk_bound_dev_if = sk_tcp->sk_bound_dev_if;
 	error = kernel_connect(sock_raw, (struct sockaddr *)&ss, addrlen, 0);
 	if (error)
 		goto out;
-	sk_raw = sock_raw->sk;
 
 	po->chan.hdrlen = 14;
 	po->chan.private = sk_raw;