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l2tp: Add L2TPv3 IP encapsulation (no UDP) support

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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>
This commit is contained in:
James Chapman
2010-04-02 06:19:00 +00:00
committed by David S. Miller
parent e0d4435f93
commit 0d76751fad
7 changed files with 850 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files

163
net/l2tp/l2tp_core.c
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@ -36,8 +36,10 @@
#include <linux/inetdevice.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/l2tp.h>
#include <linux/hash.h>
#include <linux/sort.h>
#include <linux/file.h>
@ -48,6 +50,7 @@
#include <net/ip.h>
#include <net/udp.h>
#include <net/xfrm.h>
#include <net/protocol.h>
#include <asm/byteorder.h>
#include <asm/atomic.h>
@ -849,15 +852,21 @@ static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
{
struct l2tp_tunnel *tunnel = session->tunnel;
char *bufp = buf;
char *optr = bufp;
u16 flags = L2TP_HDR_VER_3;
/* Setup L2TP header. */
*((__be16 *) bufp) = htons(flags);
bufp += 2;
*((__be16 *) bufp) = 0;
bufp += 2;
/* Setup L2TP header. The header differs slightly for UDP and
* IP encapsulations. For UDP, there is 4 bytes of flags.
*/
if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
u16 flags = L2TP_HDR_VER_3;
*((__be16 *) bufp) = htons(flags);
bufp += 2;
*((__be16 *) bufp) = 0;
bufp += 2;
}
*((__be32 *) bufp) = htonl(session->peer_session_id);
bufp += 4;
if (session->cookie_len) {
@ -902,10 +911,11 @@ int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, size_t dat
if (session->debug & L2TP_MSG_DATA) {
int i;
unsigned char *datap = skb->data + sizeof(struct udphdr);
int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
unsigned char *datap = skb->data + uhlen;
printk(KERN_DEBUG "%s: xmit:", session->name);
for (i = 0; i < (len - sizeof(struct udphdr)); i++) {
for (i = 0; i < (len - uhlen); i++) {
printk(" %02X", *datap++);
if (i == 31) {
printk(" ...");
@ -956,21 +966,23 @@ static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
{
int data_len = skb->len;
struct sock *sk = session->tunnel->sock;
struct l2tp_tunnel *tunnel = session->tunnel;
struct sock *sk = tunnel->sock;
struct udphdr *uh;
unsigned int udp_len;
struct inet_sock *inet;
__wsum csum;
int old_headroom;
int new_headroom;
int headroom;
int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
int udp_len;
/* Check that there's enough headroom in the skb to insert IP,
* UDP and L2TP headers. If not enough, expand it to
* make room. Adjust truesize.
*/
headroom = NET_SKB_PAD + sizeof(struct iphdr) +
sizeof(struct udphdr) + hdr_len;
uhlen + hdr_len;
old_headroom = skb_headroom(skb);
if (skb_cow_head(skb, headroom))
goto abort;
@ -981,18 +993,8 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
/* Setup L2TP header */
session->build_header(session, __skb_push(skb, hdr_len));
udp_len = sizeof(struct udphdr) + hdr_len + data_len;
/* Setup UDP header */
inet = inet_sk(sk);
__skb_push(skb, sizeof(*uh));
skb_reset_transport_header(skb);
uh = udp_hdr(skb);
uh->source = inet->inet_sport;
uh->dest = inet->inet_dport;
uh->len = htons(udp_len);
uh->check = 0;
/* Reset skb netfilter state */
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
IPSKB_REROUTED);
@ -1001,29 +1003,48 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
/* Get routing info from the tunnel socket */
skb_dst_drop(skb);
skb_dst_set(skb, dst_clone(__sk_dst_get(sk)));
l2tp_skb_set_owner_w(skb, sk);
/* Calculate UDP checksum if configured to do so */
if (sk->sk_no_check == UDP_CSUM_NOXMIT)
skb->ip_summed = CHECKSUM_NONE;
else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
(!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
skb->ip_summed = CHECKSUM_COMPLETE;
csum = skb_checksum(skb, 0, udp_len, 0);
uh->check = csum_tcpudp_magic(inet->inet_saddr,
inet->inet_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_tcpudp_magic(inet->inet_saddr,
inet->inet_daddr,
udp_len, IPPROTO_UDP, 0);
switch (tunnel->encap) {
case L2TP_ENCAPTYPE_UDP:
/* Setup UDP header */
inet = inet_sk(sk);
__skb_push(skb, sizeof(*uh));
skb_reset_transport_header(skb);
uh = udp_hdr(skb);
uh->source = inet->inet_sport;
uh->dest = inet->inet_dport;
udp_len = uhlen + hdr_len + data_len;
uh->len = htons(udp_len);
uh->check = 0;
/* Calculate UDP checksum if configured to do so */
if (sk->sk_no_check == UDP_CSUM_NOXMIT)
skb->ip_summed = CHECKSUM_NONE;
else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
(!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
skb->ip_summed = CHECKSUM_COMPLETE;
csum = skb_checksum(skb, 0, udp_len, 0);
uh->check = csum_tcpudp_magic(inet->inet_saddr,
inet->inet_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_tcpudp_magic(inet->inet_saddr,
inet->inet_daddr,
udp_len, IPPROTO_UDP, 0);
}
break;
case L2TP_ENCAPTYPE_IP:
break;
}
l2tp_skb_set_owner_w(skb, sk);
l2tp_xmit_core(session, skb, data_len);
abort:
@ -1053,9 +1074,15 @@ void l2tp_tunnel_destruct(struct sock *sk)
/* Close all sessions */
l2tp_tunnel_closeall(tunnel);
/* No longer an encapsulation socket. See net/ipv4/udp.c */
(udp_sk(sk))->encap_type = 0;
(udp_sk(sk))->encap_rcv = NULL;
switch (tunnel->encap) {
case L2TP_ENCAPTYPE_UDP:
/* No longer an encapsulation socket. See net/ipv4/udp.c */
(udp_sk(sk))->encap_type = 0;
(udp_sk(sk))->encap_rcv = NULL;
break;
case L2TP_ENCAPTYPE_IP:
break;
}
/* Remove hooks into tunnel socket */
tunnel->sock = NULL;
@ -1168,6 +1195,7 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
struct socket *sock = NULL;
struct sock *sk = NULL;
struct l2tp_net *pn;
enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
/* Get the tunnel socket from the fd, which was opened by
* the userspace L2TP daemon.
@ -1182,18 +1210,27 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
sk = sock->sk;
if (cfg != NULL)
encap = cfg->encap;
/* Quick sanity checks */
err = -EPROTONOSUPPORT;
if (sk->sk_protocol != IPPROTO_UDP) {
printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
goto err;
}
err = -EAFNOSUPPORT;
if (sock->ops->family != AF_INET) {
printk(KERN_ERR "tunl %hu: fd %d wrong family, got %d, expected %d\n",
tunnel_id, fd, sock->ops->family, AF_INET);
goto err;
switch (encap) {
case L2TP_ENCAPTYPE_UDP:
err = -EPROTONOSUPPORT;
if (sk->sk_protocol != IPPROTO_UDP) {
printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
goto err;
}
break;
case L2TP_ENCAPTYPE_IP:
err = -EPROTONOSUPPORT;
if (sk->sk_protocol != IPPROTO_L2TP) {
printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
goto err;
}
break;
}
/* Check if this socket has already been prepped */
@ -1223,12 +1260,16 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
tunnel->l2tp_net = net;
pn = l2tp_pernet(net);
if (cfg)
if (cfg != NULL)
tunnel->debug = cfg->debug;
/* 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;
tunnel->encap = encap;
if (encap == L2TP_ENCAPTYPE_UDP) {
/* 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;
}
sk->sk_user_data = tunnel;
@ -1318,7 +1359,9 @@ void l2tp_session_set_header_len(struct l2tp_session *session, int version)
if (session->send_seq)
session->hdr_len += 4;
} else {
session->hdr_len = 8 + session->cookie_len + session->l2specific_len + session->offset;
session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
session->hdr_len += 4;
}
}