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linux/net/l2tp/l2tp_ip.c
James Chapman aa5e17e1f5 l2tp: store l2tpv3 sessions in per-net IDR 
L2TPv3 sessions are currently held in one of two fixed-size hash
lists: either a per-net hashlist (IP-encap), or a per-tunnel hashlist
(UDP-encap), keyed by the L2TPv3 32-bit session_id.

In order to lookup L2TPv3 sessions in UDP-encap tunnels efficiently
without finding the tunnel first via sk_user_data, UDP sessions are
now kept in a per-net session list, keyed by session ID. Convert the
existing per-net hashlist to use an IDR for better performance when
there are many sessions and have L2TPv3 UDP sessions use the same IDR.

Although the L2TPv3 RFC states that the session ID alone identifies
the session, our implementation has allowed the same session ID to be
used in different L2TP UDP tunnels. To retain support for this, a new
per-net session hashtable is used, keyed by the sock and session
ID. If on creating a new session, a session already exists with that
ID in the IDR, the colliding sessions are added to the new hashtable
and the existing IDR entry is flagged. When looking up sessions, the
approach is to first check the IDR and if no unflagged match is found,
check the new hashtable. The sock is made available to session getters
where session ID collisions are to be considered. In this way, the new
hashtable is used only for session ID collisions so can be kept small.

For managing session removal, we need a list of colliding sessions
matching a given ID in order to update or remove the IDR entry of the
ID. This is necessary to detect session ID collisions when future
sessions are created. The list head is allocated on first collision
of a given ID and refcounted.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2024-06-21 11:33:33 +01:00

683 lines
16 KiB
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// SPDX-License-Identifier: GPL-2.0-or-later
/* L2TPv3 IP encapsulation support
*
* Copyright (c) 2008,2009,2010 Katalix Systems Ltd
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <asm/ioctls.h>
#include <linux/icmp.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/random.h>
#include <linux/socket.h>
#include <linux/l2tp.h>
#include <linux/in.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/inet_common.h>
#include <net/tcp_states.h>
#include <net/protocol.h>
#include <net/xfrm.h>
#include "l2tp_core.h"
struct l2tp_ip_sock {
/* inet_sock has to be the first member of l2tp_ip_sock */
struct inet_sock inet;
u32 conn_id;
u32 peer_conn_id;
};
static DEFINE_RWLOCK(l2tp_ip_lock);
static struct hlist_head l2tp_ip_table;
static struct hlist_head l2tp_ip_bind_table;
static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
{
return (struct l2tp_ip_sock *)sk;
}
static struct sock *__l2tp_ip_bind_lookup(const struct net *net, __be32 laddr,
__be32 raddr, int dif, u32 tunnel_id)
{
struct sock *sk;
sk_for_each_bound(sk, &l2tp_ip_bind_table) {
const struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
const struct inet_sock *inet = inet_sk(sk);
int bound_dev_if;
if (!net_eq(sock_net(sk), net))
continue;
bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
if (bound_dev_if && dif && bound_dev_if != dif)
continue;
if (inet->inet_rcv_saddr && laddr &&
inet->inet_rcv_saddr != laddr)
continue;
if (inet->inet_daddr && raddr && inet->inet_daddr != raddr)
continue;
if (l2tp->conn_id != tunnel_id)
continue;
goto found;
}
sk = NULL;
found:
return sk;
}
/* When processing receive frames, there are two cases to
* consider. Data frames consist of a non-zero session-id and an
* optional cookie. Control frames consist of a regular L2TP header
* preceded by 32-bits of zeros.
*
* L2TPv3 Session Header Over IP
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Session ID |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Cookie (optional, maximum 64 bits)...
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* L2TPv3 Control Message Header Over IP
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | (32 bits of zeros) |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |T|L|x|x|S|x|x|x|x|x|x|x| Ver | Length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Control Connection ID |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Ns | Nr |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* All control frames are passed to userspace.
*/
static int l2tp_ip_recv(struct sk_buff *skb)
{
struct net *net = dev_net(skb->dev);
struct sock *sk;
u32 session_id;
u32 tunnel_id;
unsigned char *ptr, *optr;
struct l2tp_session *session;
struct l2tp_tunnel *tunnel = NULL;
struct iphdr *iph;
if (!pskb_may_pull(skb, 4))
goto discard;
/* Point to L2TP header */
optr = skb->data;
ptr = skb->data;
session_id = ntohl(*((__be32 *)ptr));
ptr += 4;
/* RFC3931: L2TP/IP packets have the first 4 bytes containing
* the session_id. If it is 0, the packet is a L2TP control
* frame and the session_id value can be discarded.
*/
if (session_id == 0) {
__skb_pull(skb, 4);
goto pass_up;
}
/* Ok, this is a data packet. Lookup the session. */
session = l2tp_v3_session_get(net, NULL, session_id);
if (!session)
goto discard;
tunnel = session->tunnel;
if (!tunnel)
goto discard_sess;
if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
goto discard_sess;
l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
l2tp_session_dec_refcount(session);
return 0;
pass_up:
/* Get the tunnel_id from the L2TP header */
if (!pskb_may_pull(skb, 12))
goto discard;
if ((skb->data[0] & 0xc0) != 0xc0)
goto discard;
tunnel_id = ntohl(*(__be32 *)&skb->data[4]);
iph = (struct iphdr *)skb_network_header(skb);
read_lock_bh(&l2tp_ip_lock);
sk = __l2tp_ip_bind_lookup(net, iph->daddr, iph->saddr, inet_iif(skb),
tunnel_id);
if (!sk) {
read_unlock_bh(&l2tp_ip_lock);
goto discard;
}
sock_hold(sk);
read_unlock_bh(&l2tp_ip_lock);
if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
goto discard_put;
nf_reset_ct(skb);
return sk_receive_skb(sk, skb, 1);
discard_sess:
l2tp_session_dec_refcount(session);
goto discard;
discard_put:
sock_put(sk);
discard:
kfree_skb(skb);
return 0;
}
static int l2tp_ip_hash(struct sock *sk)
{
if (sk_unhashed(sk)) {
write_lock_bh(&l2tp_ip_lock);
sk_add_node(sk, &l2tp_ip_table);
write_unlock_bh(&l2tp_ip_lock);
}
return 0;
}
static void l2tp_ip_unhash(struct sock *sk)
{
if (sk_unhashed(sk))
return;
write_lock_bh(&l2tp_ip_lock);
sk_del_node_init(sk);
write_unlock_bh(&l2tp_ip_lock);
}
static int l2tp_ip_open(struct sock *sk)
{
/* Prevent autobind. We don't have ports. */
inet_sk(sk)->inet_num = IPPROTO_L2TP;
l2tp_ip_hash(sk);
return 0;
}
static void l2tp_ip_close(struct sock *sk, long timeout)
{
write_lock_bh(&l2tp_ip_lock);
hlist_del_init(&sk->sk_bind_node);
sk_del_node_init(sk);
write_unlock_bh(&l2tp_ip_lock);
sk_common_release(sk);
}
static void l2tp_ip_destroy_sock(struct sock *sk)
{
struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
struct sk_buff *skb;
while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
kfree_skb(skb);
if (tunnel)
l2tp_tunnel_delete(tunnel);
}
static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
struct inet_sock *inet = inet_sk(sk);
struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *)uaddr;
struct net *net = sock_net(sk);
int ret;
int chk_addr_ret;
if (addr_len < sizeof(struct sockaddr_l2tpip))
return -EINVAL;
if (addr->l2tp_family != AF_INET)
return -EINVAL;
lock_sock(sk);
ret = -EINVAL;
if (!sock_flag(sk, SOCK_ZAPPED))
goto out;
if (sk->sk_state != TCP_CLOSE)
goto out;
chk_addr_ret = inet_addr_type(net, addr->l2tp_addr.s_addr);
ret = -EADDRNOTAVAIL;
if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL &&
chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST)
goto out;
if (addr->l2tp_addr.s_addr) {
inet->inet_rcv_saddr = addr->l2tp_addr.s_addr;
inet->inet_saddr = addr->l2tp_addr.s_addr;
}
if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST)
inet->inet_saddr = 0; /* Use device */
write_lock_bh(&l2tp_ip_lock);
if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr, 0,
sk->sk_bound_dev_if, addr->l2tp_conn_id)) {
write_unlock_bh(&l2tp_ip_lock);
ret = -EADDRINUSE;
goto out;
}
sk_dst_reset(sk);
l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id;
sk_add_bind_node(sk, &l2tp_ip_bind_table);
sk_del_node_init(sk);
write_unlock_bh(&l2tp_ip_lock);
ret = 0;
sock_reset_flag(sk, SOCK_ZAPPED);
out:
release_sock(sk);
return ret;
}
static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
int rc;
if (addr_len < sizeof(*lsa))
return -EINVAL;
if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
return -EINVAL;
lock_sock(sk);
/* Must bind first - autobinding does not work */
if (sock_flag(sk, SOCK_ZAPPED)) {
rc = -EINVAL;
goto out_sk;
}
rc = __ip4_datagram_connect(sk, uaddr, addr_len);
if (rc < 0)
goto out_sk;
l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
write_lock_bh(&l2tp_ip_lock);
hlist_del_init(&sk->sk_bind_node);
sk_add_bind_node(sk, &l2tp_ip_bind_table);
write_unlock_bh(&l2tp_ip_lock);
out_sk:
release_sock(sk);
return rc;
}
static int l2tp_ip_disconnect(struct sock *sk, int flags)
{
if (sock_flag(sk, SOCK_ZAPPED))
return 0;
return __udp_disconnect(sk, flags);
}
static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr,
int peer)
{
struct sock *sk = sock->sk;
struct inet_sock *inet = inet_sk(sk);
struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk);
struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
memset(lsa, 0, sizeof(*lsa));
lsa->l2tp_family = AF_INET;
if (peer) {
if (!inet->inet_dport)
return -ENOTCONN;
lsa->l2tp_conn_id = lsk->peer_conn_id;
lsa->l2tp_addr.s_addr = inet->inet_daddr;
} else {
__be32 addr = inet->inet_rcv_saddr;
if (!addr)
addr = inet->inet_saddr;
lsa->l2tp_conn_id = lsk->conn_id;
lsa->l2tp_addr.s_addr = addr;
}
return sizeof(*lsa);
}
static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb)
{
int rc;
/* Charge it to the socket, dropping if the queue is full. */
rc = sock_queue_rcv_skb(sk, skb);
if (rc < 0)
goto drop;
return 0;
drop:
IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
kfree_skb(skb);
return 0;
}
/* Userspace will call sendmsg() on the tunnel socket to send L2TP
* control frames.
*/
static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
struct sk_buff *skb;
int rc;
struct inet_sock *inet = inet_sk(sk);
struct rtable *rt = NULL;
struct flowi4 *fl4;
int connected = 0;
__be32 daddr;
lock_sock(sk);
rc = -ENOTCONN;
if (sock_flag(sk, SOCK_DEAD))
goto out;
/* Get and verify the address. */
if (msg->msg_name) {
DECLARE_SOCKADDR(struct sockaddr_l2tpip *, lip, msg->msg_name);
rc = -EINVAL;
if (msg->msg_namelen < sizeof(*lip))
goto out;
if (lip->l2tp_family != AF_INET) {
rc = -EAFNOSUPPORT;
if (lip->l2tp_family != AF_UNSPEC)
goto out;
}
daddr = lip->l2tp_addr.s_addr;
} else {
rc = -EDESTADDRREQ;
if (sk->sk_state != TCP_ESTABLISHED)
goto out;
daddr = inet->inet_daddr;
connected = 1;
}
/* Allocate a socket buffer */
rc = -ENOMEM;
skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) +
4 + len, 0, GFP_KERNEL);
if (!skb)
goto error;
/* Reserve space for headers, putting IP header on 4-byte boundary. */
skb_reserve(skb, 2 + NET_SKB_PAD);
skb_reset_network_header(skb);
skb_reserve(skb, sizeof(struct iphdr));
skb_reset_transport_header(skb);
/* Insert 0 session_id */
*((__be32 *)skb_put(skb, 4)) = 0;
/* Copy user data into skb */
rc = memcpy_from_msg(skb_put(skb, len), msg, len);
if (rc < 0) {
kfree_skb(skb);
goto error;
}
fl4 = &inet->cork.fl.u.ip4;
if (connected)
rt = dst_rtable(__sk_dst_check(sk, 0));
rcu_read_lock();
if (!rt) {
const struct ip_options_rcu *inet_opt;
inet_opt = rcu_dereference(inet->inet_opt);
/* Use correct destination address if we have options. */
if (inet_opt && inet_opt->opt.srr)
daddr = inet_opt->opt.faddr;
/* If this fails, retransmit mechanism of transport layer will
* keep trying until route appears or the connection times
* itself out.
*/
rt = ip_route_output_ports(sock_net(sk), fl4, sk,
daddr, inet->inet_saddr,
inet->inet_dport, inet->inet_sport,
sk->sk_protocol, ip_sock_rt_tos(sk),
sk->sk_bound_dev_if);
if (IS_ERR(rt))
goto no_route;
if (connected) {
sk_setup_caps(sk, &rt->dst);
} else {
skb_dst_set(skb, &rt->dst);
goto xmit;
}
}
/* We don't need to clone dst here, it is guaranteed to not disappear.
* __dev_xmit_skb() might force a refcount if needed.
*/
skb_dst_set_noref(skb, &rt->dst);
xmit:
/* Queue the packet to IP for output */
rc = ip_queue_xmit(sk, skb, &inet->cork.fl);
rcu_read_unlock();
error:
if (rc >= 0)
rc = len;
out:
release_sock(sk);
return rc;
no_route:
rcu_read_unlock();
IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
kfree_skb(skb);
rc = -EHOSTUNREACH;
goto out;
}
static int l2tp_ip_recvmsg(struct sock *sk, struct msghdr *msg,
size_t len, int flags, int *addr_len)
{
struct inet_sock *inet = inet_sk(sk);
size_t copied = 0;
int err = -EOPNOTSUPP;
DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
struct sk_buff *skb;
if (flags & MSG_OOB)
goto out;
skb = skb_recv_datagram(sk, flags, &err);
if (!skb)
goto out;
copied = skb->len;
if (len < copied) {
msg->msg_flags |= MSG_TRUNC;
copied = len;
}
err = skb_copy_datagram_msg(skb, 0, msg, copied);
if (err)
goto done;
sock_recv_timestamp(msg, sk, skb);
/* Copy the address. */
if (sin) {
sin->sin_family = AF_INET;
sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
sin->sin_port = 0;
memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
*addr_len = sizeof(*sin);
}
if (inet_cmsg_flags(inet))
ip_cmsg_recv(msg, skb);
if (flags & MSG_TRUNC)
copied = skb->len;
done:
skb_free_datagram(sk, skb);
out:
return err ? err : copied;
}
int l2tp_ioctl(struct sock *sk, int cmd, int *karg)
{
struct sk_buff *skb;
switch (cmd) {
case SIOCOUTQ:
*karg = sk_wmem_alloc_get(sk);
break;
case SIOCINQ:
spin_lock_bh(&sk->sk_receive_queue.lock);
skb = skb_peek(&sk->sk_receive_queue);
*karg = skb ? skb->len : 0;
spin_unlock_bh(&sk->sk_receive_queue.lock);
break;
default:
return -ENOIOCTLCMD;
}
return 0;
}
EXPORT_SYMBOL_GPL(l2tp_ioctl);
static struct proto l2tp_ip_prot = {
.name = "L2TP/IP",
.owner = THIS_MODULE,
.init = l2tp_ip_open,
.close = l2tp_ip_close,
.bind = l2tp_ip_bind,
.connect = l2tp_ip_connect,
.disconnect = l2tp_ip_disconnect,
.ioctl = l2tp_ioctl,
.destroy = l2tp_ip_destroy_sock,
.setsockopt = ip_setsockopt,
.getsockopt = ip_getsockopt,
.sendmsg = l2tp_ip_sendmsg,
.recvmsg = l2tp_ip_recvmsg,
.backlog_rcv = l2tp_ip_backlog_recv,
.hash = l2tp_ip_hash,
.unhash = l2tp_ip_unhash,
.obj_size = sizeof(struct l2tp_ip_sock),
};
static const struct proto_ops l2tp_ip_ops = {
.family = PF_INET,
.owner = THIS_MODULE,
.release = inet_release,
.bind = inet_bind,
.connect = inet_dgram_connect,
.socketpair = sock_no_socketpair,
.accept = sock_no_accept,
.getname = l2tp_ip_getname,
.poll = datagram_poll,
.ioctl = inet_ioctl,
.gettstamp = sock_gettstamp,
.listen = sock_no_listen,
.shutdown = inet_shutdown,
.setsockopt = sock_common_setsockopt,
.getsockopt = sock_common_getsockopt,
.sendmsg = inet_sendmsg,
.recvmsg = sock_common_recvmsg,
.mmap = sock_no_mmap,
};
static struct inet_protosw l2tp_ip_protosw = {
.type = SOCK_DGRAM,
.protocol = IPPROTO_L2TP,
.prot = &l2tp_ip_prot,
.ops = &l2tp_ip_ops,
};
static struct net_protocol l2tp_ip_protocol __read_mostly = {
.handler = l2tp_ip_recv,
};
static int __init l2tp_ip_init(void)
{
int err;
pr_info("L2TP IP encapsulation support (L2TPv3)\n");
err = proto_register(&l2tp_ip_prot, 1);
if (err != 0)
goto out;
err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
if (err)
goto out1;
inet_register_protosw(&l2tp_ip_protosw);
return 0;
out1:
proto_unregister(&l2tp_ip_prot);
out:
return err;
}
static void __exit l2tp_ip_exit(void)
{
inet_unregister_protosw(&l2tp_ip_protosw);
inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
proto_unregister(&l2tp_ip_prot);
}
module_init(l2tp_ip_init);
module_exit(l2tp_ip_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("L2TP over IP");
MODULE_VERSION("1.0");
/* Use the values of SOCK_DGRAM (2) as type and IPPROTO_L2TP (115) as protocol,
* because __stringify doesn't like enums
*/
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 115, 2);
MODULE_ALIAS_NET_PF_PROTO(PF_INET, 115);
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