net/l2tp: add support for L2TP over IPv6 UDP

Now that encap_rcv() works on IPv6 UDP sockets, wire L2TP up to IPv6.
Support has been tested with and without hardware offloading.  This
version fixes the L2TP over localhost issue with incorrect checksums
being reported.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 118 insertions, 13 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index f6732b6c758b..e91d55924d94 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -53,6 +53,9 @@
 #include <net/inet_common.h>
 #include <net/xfrm.h>
 #include <net/protocol.h>
+#include <net/inet6_connection_sock.h>
+#include <net/inet_ecn.h>
+#include <net/ip6_route.h>
 
 #include <asm/byteorder.h>
 #include <linux/atomic.h>
@@ -446,21 +449,43 @@ static inline int l2tp_verify_udp_checksum(struct sock *sk,
 {
         struct udphdr *uh = udp_hdr(skb);
         u16 ulen = ntohs(uh->len);
-        struct inet_sock *inet;
         __wsum psum;
 
-        if (sk->sk_no_check || skb_csum_unnecessary(skb) || !uh->check)
-                return 0;
-
-        inet = inet_sk(sk);
-        psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr, ulen,
-                                  IPPROTO_UDP, 0);
-
-        if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
-            !csum_fold(csum_add(psum, skb->csum)))
+        if (sk->sk_no_check || skb_csum_unnecessary(skb))
                 return 0;
 
-        skb->csum = psum;
+#if IS_ENABLED(CONFIG_IPV6)
+        if (sk->sk_family == PF_INET6) {
+                if (!uh->check) {
+                        LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
+                        return 1;
+                }
+                if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
+                    !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
+                                     &ipv6_hdr(skb)->daddr, ulen,
+                                     IPPROTO_UDP, skb->csum)) {
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
+                        return 0;
+                }
+                skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
+                                                         &ipv6_hdr(skb)->daddr,
+                                                         skb->len, IPPROTO_UDP,
+                                                         0));
+        } else
+#endif
+        {
+                struct inet_sock *inet;
+                if (!uh->check)
+                        return 0;
+                inet = inet_sk(sk);
+                psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr,
+                                          ulen, IPPROTO_UDP, 0);
+
+                if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
+                    !csum_fold(csum_add(psum, skb->csum)))
+                        return 0;
+                skb->csum = psum;
+        }
 
         return __skb_checksum_complete(skb);
 }
@@ -988,7 +1013,12 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
 
         /* Queue the packet to IP for output */
         skb->local_df = 1;
-        error = ip_queue_xmit(skb, fl);
+#if IS_ENABLED(CONFIG_IPV6)
+        if (skb->sk->sk_family == PF_INET6)
+                error = inet6_csk_xmit(skb, NULL);
+        else
+#endif
+                error = ip_queue_xmit(skb, fl);
 
         /* Update stats */
         if (error >= 0) {
@@ -1021,6 +1051,31 @@ static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
         skb->destructor = l2tp_sock_wfree;
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
+static void l2tp_xmit_ipv6_csum(struct sock *sk, struct sk_buff *skb,
+                                int udp_len)
+{
+        struct ipv6_pinfo *np = inet6_sk(sk);
+        struct udphdr *uh = udp_hdr(skb);
+
+        if (!skb_dst(skb) || !skb_dst(skb)->dev ||
+            !(skb_dst(skb)->dev->features & NETIF_F_IPV6_CSUM)) {
+                __wsum csum = skb_checksum(skb, 0, udp_len, 0);
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
+                uh->check = csum_ipv6_magic(&np->saddr, &np->daddr, udp_len,
+                                            IPPROTO_UDP, csum);
+                if (uh->check == 0)
+                        uh->check = CSUM_MANGLED_0;
+        } else {
+                skb->ip_summed = CHECKSUM_PARTIAL;
+                skb->csum_start = skb_transport_header(skb) - skb->head;
+                skb->csum_offset = offsetof(struct udphdr, check);
+                uh->check = ~csum_ipv6_magic(&np->saddr, &np->daddr,
+                                             udp_len, IPPROTO_UDP, 0);
+        }
+}
+#endif
+
 /* If caller requires the skb to have a ppp header, the header must be
  * inserted in the skb data before calling this function.
  */
@@ -1089,6 +1144,11 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
                 uh->check = 0;
 
                 /* Calculate UDP checksum if configured to do so */
+#if IS_ENABLED(CONFIG_IPV6)
+                if (sk->sk_family == PF_INET6)
+                        l2tp_xmit_ipv6_csum(sk, skb, udp_len);
+                else
+#endif
                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
                         skb->ip_summed = CHECKSUM_NONE;
                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
@@ -1424,6 +1484,11 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
+#if IS_ENABLED(CONFIG_IPV6)
+                if (sk->sk_family == PF_INET6)
+                        udpv6_encap_enable();
+                else
+#endif
                 udp_encap_enable();
         }
 
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 1addd9f3f40a..27b9dec9d254 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -916,7 +916,7 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
         }
 
         inet = inet_sk(tunnel->sock);
-        if (tunnel->version == 2) {
+        if ((tunnel->version == 2) && (tunnel->sock->sk_family == AF_INET)) {
                 struct sockaddr_pppol2tp sp;
                 len = sizeof(sp);
                 memset(&sp, 0, len);
@@ -932,6 +932,46 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
                 sp.pppol2tp.addr.sin_port = inet->inet_dport;
                 sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
                 memcpy(uaddr, &sp, len);
+#if IS_ENABLED(CONFIG_IPV6)
+        } else if ((tunnel->version == 2) &&
+                   (tunnel->sock->sk_family == AF_INET6)) {
+                struct ipv6_pinfo *np = inet6_sk(tunnel->sock);
+                struct sockaddr_pppol2tpin6 sp;
+                len = sizeof(sp);
+                memset(&sp, 0, len);
+                sp.sa_family    = AF_PPPOX;
+                sp.sa_protocol  = PX_PROTO_OL2TP;
+                sp.pppol2tp.fd  = tunnel->fd;
+                sp.pppol2tp.pid = pls->owner;
+                sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+                sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+                sp.pppol2tp.s_session = session->session_id;
+                sp.pppol2tp.d_session = session->peer_session_id;
+                sp.pppol2tp.addr.sin6_family = AF_INET6;
+                sp.pppol2tp.addr.sin6_port = inet->inet_dport;
+                memcpy(&sp.pppol2tp.addr.sin6_addr, &np->daddr,
+                       sizeof(np->daddr));
+                memcpy(uaddr, &sp, len);
+        } else if ((tunnel->version == 3) &&
+                   (tunnel->sock->sk_family == AF_INET6)) {
+                struct ipv6_pinfo *np = inet6_sk(tunnel->sock);
+                struct sockaddr_pppol2tpv3in6 sp;
+                len = sizeof(sp);
+                memset(&sp, 0, len);
+                sp.sa_family    = AF_PPPOX;
+                sp.sa_protocol  = PX_PROTO_OL2TP;
+                sp.pppol2tp.fd  = tunnel->fd;
+                sp.pppol2tp.pid = pls->owner;
+                sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+                sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+                sp.pppol2tp.s_session = session->session_id;
+                sp.pppol2tp.d_session = session->peer_session_id;
+                sp.pppol2tp.addr.sin6_family = AF_INET6;
+                sp.pppol2tp.addr.sin6_port = inet->inet_dport;
+                memcpy(&sp.pppol2tp.addr.sin6_addr, &np->daddr,
+                       sizeof(np->daddr));
+                memcpy(uaddr, &sp, len);
+#endif
         } else if (tunnel->version == 3) {
                 struct sockaddr_pppol2tpv3 sp;
                 len = sizeof(sp);