l2tp: Add L2TPv3 IP encapsulation (no UDP) support

This patch adds a new L2TPIP socket family and modifies the core to
handle the case where there is no UDP header in the L2TP
packet. L2TP/IP uses IP protocol 115. Since L2TP/UDP and L2TP/IP
packets differ in layout, the datapath packet handling code needs
changes too. Userspace uses an L2TPIP socket instead of a UDP socket
when IP encapsulation is required.

We can't use raw sockets for this because the semantics of raw sockets
don't lend themselves to the socket-per-tunnel model - we need to

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index e5b531266541..63fc62baeeb9 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -305,6 +305,7 @@ static int pppol2tp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msgh
         struct l2tp_session *session;
         struct l2tp_tunnel *tunnel;
         struct pppol2tp_session *ps;
+        int uhlen;
 
         error = -ENOTCONN;
         if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
@@ -321,10 +322,12 @@ static int pppol2tp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msgh
         if (tunnel == NULL)
                 goto error_put_sess;
 
+        uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
+
         /* Allocate a socket buffer */
         error = -ENOMEM;
         skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
-                           sizeof(struct udphdr) + session->hdr_len +
+                           uhlen + session->hdr_len +
                            sizeof(ppph) + total_len,
                            0, GFP_KERNEL);
         if (!skb)
@@ -335,7 +338,7 @@ static int pppol2tp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msgh
         skb_reset_network_header(skb);
         skb_reserve(skb, sizeof(struct iphdr));
         skb_reset_transport_header(skb);
-        skb_reserve(skb, sizeof(struct udphdr));
+        skb_reserve(skb, uhlen);
 
         /* Add PPP header */
         skb->data[0] = ppph[0];