Skip to content

Commit

Permalink
l2tp: Add L2TPv3 IP encapsulation (no UDP) support
Browse files Browse the repository at this point in the history 
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 <[email protected]>
  • Loading branch information
@j-c-h @davem330
j-c-h authored and davem330 committed Apr 3, 2010
1 parent e0d4435 commit 0d76751
Show file tree
Hide file tree
Showing 7 changed files with 850 additions and 62 deletions.
38 changes: 38 additions & 0 deletions include/linux/l2tp.h
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
/*
* L2TP-over-IP socket for L2TPv3.
*
* Author: James Chapman <[email protected]>
*/

#ifndef _LINUX_L2TP_H_
#define _LINUX_L2TP_H_

#include <linux/types.h>
#ifdef __KERNEL__
#include <linux/socket.h>
#include <linux/in.h>
#endif

#define IPPROTO_L2TP 115

/**
* struct sockaddr_l2tpip - the sockaddr structure for L2TP-over-IP sockets
* @l2tp_family: address family number AF_L2TPIP.
* @l2tp_addr: protocol specific address information
* @l2tp_conn_id: connection id of tunnel
*/
struct sockaddr_l2tpip {
/* The first fields must match struct sockaddr_in */
sa_family_t l2tp_family; /* AF_INET */
__be16 l2tp_unused; /* INET port number (unused) */
struct in_addr l2tp_addr; /* Internet address */

__u32 l2tp_conn_id; /* Connection ID of tunnel */

/* Pad to size of `struct sockaddr'. */
unsigned char __pad[sizeof(struct sockaddr) - sizeof(sa_family_t) -
sizeof(__be16) - sizeof(struct in_addr) -
sizeof(__u32)];
};

#endif
17 changes: 17 additions & 0 deletions net/l2tp/Kconfig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,3 +51,20 @@ config L2TP_V3
If you are connecting to L2TPv3 equipment, or you want to
tunnel raw ethernet frames using L2TP, say Y here. If
unsure, say N.

config L2TP_IP
tristate "L2TP IP encapsulation for L2TPv3"
depends on L2TP_V3
help
Support for L2TP-over-IP socket family.

The L2TPv3 protocol defines two possible encapsulations for
L2TP frames, namely UDP and plain IP (without UDP). This
driver provides a new L2TPIP socket family with which
userspace L2TPv3 daemons may create L2TP/IP tunnel sockets
when UDP encapsulation is not required. When L2TP is carried
in IP packets, it used IP protocol number 115, so this port
must be enabled in firewalls.

To compile this driver as a module, choose M here. The module
will be called l2tp_ip.
1 change: 1 addition & 0 deletions net/l2tp/Makefile
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,3 +6,4 @@ obj-$(CONFIG_L2TP) += l2tp_core.o

# Build l2tp as modules if L2TP is M
obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_PPPOL2TP)) += l2tp_ppp.o
obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_IP)) += l2tp_ip.o
163 changes: 103 additions & 60 deletions net/l2tp/l2tp_core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -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>
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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(" ...");
Expand Down Expand Up @@ -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;
Expand All @@ -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);
Expand All @@ -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:
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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.
Expand All @@ -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 */
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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;
}

}
Expand Down
7 changes: 7 additions & 0 deletions net/l2tp/l2tp_core.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,11 @@ enum l2tp_l2spec_type {
L2TP_L2SPECTYPE_DEFAULT,
};

enum l2tp_encap_type {
L2TP_ENCAPTYPE_UDP,
L2TP_ENCAPTYPE_IP,
};

struct sk_buff;

struct l2tp_stats {
Expand Down Expand Up @@ -155,6 +160,7 @@ struct l2tp_session {
struct l2tp_tunnel_cfg {
int debug; /* bitmask of debug message
* categories */
enum l2tp_encap_type encap;
};

struct l2tp_tunnel {
Expand All @@ -170,6 +176,7 @@ struct l2tp_tunnel {
char name[20]; /* for logging */
int debug; /* bitmask of debug message
* categories */
enum l2tp_encap_type encap;
struct l2tp_stats stats;

struct list_head list; /* Keep a list of all tunnels */
Expand Down
Loading

0 comments on commit 0d76751

Please sign in to comment.