- 根目录:
- drivers
- net
- ppp
- pppopns.c
/* drivers/net/pppopns.c
*
* Driver for PPP on PPTP Network Server / PPPoPNS Socket (RFC 2637)
*
* Copyright (C) 2009 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
/* This driver handles PPTP data packets between a RAW socket and a PPP channel.
* The socket is created in the kernel space and connected to the same address
* of the control socket. Outgoing packets are always sent with sequences but
* without acknowledgements. Incoming packets with sequences are reordered
* within a sliding window of one second. Currently reordering only happens when
* a packet is received. It is done for simplicity since no additional locks or
* threads are required. This driver should work on both IPv4 and IPv6. */
#include <linux/module.h>
#include <linux/jiffies.h>
#include <linux/workqueue.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/netdevice.h>
#include <linux/net.h>
#include <linux/ppp_defs.h>
#include <linux/if.h>
#include <linux/if_ppp.h>
#include <linux/if_pppox.h>
#include <linux/ppp_channel.h>
#include <asm/uaccess.h>
#define GRE_HEADER_SIZE 8
#define PPTP_GRE_BITS htons(0x2001)
#define PPTP_GRE_BITS_MASK htons(0xEF7F)
#define PPTP_GRE_SEQ_BIT htons(0x1000)
#define PPTP_GRE_ACK_BIT htons(0x0080)
#define PPTP_GRE_TYPE htons(0x880B)
#define PPP_ADDR 0xFF
#define PPP_CTRL 0x03
struct header {
__u16 bits;
__u16 type;
__u16 length;
__u16 call;
__u32 sequence;
} __attribute__((packed));
struct meta {
__u32 sequence;
__u32 timestamp;
};
static inline struct meta *skb_meta(struct sk_buff *skb)
{
return (struct meta *)skb->cb;
}
/******************************************************************************/
static int pppopns_recv_core(struct sock *sk_raw, struct sk_buff *skb)
{
struct sock *sk = (struct sock *)sk_raw->sk_user_data;
struct pppopns_opt *opt = &pppox_sk(sk)->proto.pns;
struct meta *meta = skb_meta(skb);
__u32 now = jiffies;
struct header *hdr;
/* Skip transport header */
skb_pull(skb, skb_transport_header(skb) - skb->data);
/* Drop the packet if GRE header is missing. */
if (skb->len < GRE_HEADER_SIZE)
goto drop;
hdr = (struct header *)skb->data;
/* Check the header. */
if (hdr->type != PPTP_GRE_TYPE || hdr->call != opt->local ||
(hdr->bits & PPTP_GRE_BITS_MASK) != PPTP_GRE_BITS)
goto drop;
/* Skip all fields including optional ones. */
if (!skb_pull(skb, GRE_HEADER_SIZE +
(hdr->bits & PPTP_GRE_SEQ_BIT ? 4 : 0) +
(hdr->bits & PPTP_GRE_ACK_BIT ? 4 : 0)))
goto drop;
/* Check the length. */
if (skb->len != ntohs(hdr->length))
goto drop;
/* Check the sequence if it is present. */
if (hdr->bits & PPTP_GRE_SEQ_BIT) {
meta->sequence = ntohl(hdr->sequence);
if ((__s32)(meta->sequence - opt->recv_sequence) < 0)
goto drop;
}
/* Skip PPP address and control if they are present. */
if (skb->len >= 2 && skb->data[0] == PPP_ADDR &&
skb->data[1] == PPP_CTRL)
skb_pull(skb, 2);
/* Fix PPP protocol if it is compressed. */
if (skb->len >= 1 && skb->data[0] & 1)
skb_push(skb, 1)[0] = 0;
/* Drop the packet if PPP protocol is missing. */
if (skb->len < 2)
goto drop;
/* Perform reordering if sequencing is enabled. */
if (hdr->bits & PPTP_GRE_SEQ_BIT) {
struct sk_buff *skb1;
/* Insert the packet into receive queue in order. */
skb_set_owner_r(skb, sk);
skb_queue_walk(&sk->sk_receive_queue, skb1) {
struct meta *meta1 = skb_meta(skb1);
__s32 order = meta->sequence - meta1->sequence;
if (order == 0)
goto drop;
if (order < 0) {
meta->timestamp = meta1->timestamp;
skb_insert(skb1, skb, &sk->sk_receive_queue);
skb = NULL;
break;
}
}
if (skb) {
meta->timestamp = now;
skb_queue_tail(&sk->sk_receive_queue, skb);
}
/* Remove packets from receive queue as long as
* 1. the receive buffer is full,
* 2. they are queued longer than one second, or
* 3. there are no missing packets before them. */
skb_queue_walk_safe(&sk->sk_receive_queue, skb, skb1) {
meta = skb_meta(skb);
if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
now - meta->timestamp < HZ &&
meta->sequence != opt->recv_sequence)
break;
skb_unlink(skb, &sk->sk_receive_queue);
opt->recv_sequence = meta->sequence + 1;
skb_orphan(skb);
ppp_input(&pppox_sk(sk)->chan, skb);
}
return NET_RX_SUCCESS;
}
/* Flush receive queue if sequencing is disabled. */
skb_queue_purge(&sk->sk_receive_queue);
skb_orphan(skb);
ppp_input(&pppox_sk(sk)->chan, skb);
return NET_RX_SUCCESS;
drop:
kfree_skb(skb);
return NET_RX_DROP;
}
static void pppopns_recv(struct sock *sk_raw, int length)
{
struct sk_buff *skb;
while ((skb = skb_dequeue(&sk_raw->sk_receive_queue))) {
sock_hold(sk_raw);
sk_receive_skb(sk_raw, skb, 0);
}
}
static struct sk_buff_head delivery_queue;
static void pppopns_xmit_core(struct work_struct *delivery_work)
{
mm_segment_t old_fs = get_fs();
struct sk_buff *skb;
set_fs(KERNEL_DS);
while ((skb = skb_dequeue(&delivery_queue))) {
struct sock *sk_raw = skb->sk;
struct kvec iov = {.iov_base = skb->data, .iov_len = skb->len};
struct msghdr msg = {
.msg_iov = (struct iovec *)&iov,
.msg_iovlen = 1,
.msg_flags = MSG_NOSIGNAL | MSG_DONTWAIT,
};
sk_raw->sk_prot->sendmsg(NULL, sk_raw, &msg, skb->len);
kfree_skb(skb);
}
set_fs(old_fs);
}
static DECLARE_WORK(delivery_work, pppopns_xmit_core);
static int pppopns_xmit(struct ppp_channel *chan, struct sk_buff *skb)
{
struct sock *sk_raw = (struct sock *)chan->private;
struct pppopns_opt *opt = &pppox_sk(sk_raw->sk_user_data)->proto.pns;
struct header *hdr;
__u16 length;
/* Install PPP address and control. */
skb_push(skb, 2);
skb->data[0] = PPP_ADDR;
skb->data[1] = PPP_CTRL;
length = skb->len;
/* Install PPTP GRE header. */
hdr = (struct header *)skb_push(skb, 12);
hdr->bits = PPTP_GRE_BITS | PPTP_GRE_SEQ_BIT;
hdr->type = PPTP_GRE_TYPE;
hdr->length = htons(length);
hdr->call = opt->remote;
hdr->sequence = htonl(opt->xmit_sequence);
opt->xmit_sequence++;
/* Now send the packet via the delivery queue. */
skb_set_owner_w(skb, sk_raw);
skb_queue_tail(&delivery_queue, skb);
schedule_work(&delivery_work);
return 1;
}
/******************************************************************************/
static struct ppp_channel_ops pppopns_channel_ops = {
.start_xmit = pppopns_xmit,
};
static int pppopns_connect(struct socket *sock, struct sockaddr *useraddr,
int addrlen, int flags)
{
struct sock *sk = sock->sk;
struct pppox_sock *po = pppox_sk(sk);
struct sockaddr_pppopns *addr = (struct sockaddr_pppopns *)useraddr;
struct sockaddr_storage ss;
struct socket *sock_tcp = NULL;
struct socket *sock_raw = NULL;
struct sock *sk_tcp;
struct sock *sk_raw;
int error;
if (addrlen != sizeof(struct sockaddr_pppopns))
return -EINVAL;
lock_sock(sk);
error = -EALREADY;
if (sk->sk_state != PPPOX_NONE)
goto out;
sock_tcp = sockfd_lookup(addr->tcp_socket, &error);
if (!sock_tcp)
goto out;
sk_tcp = sock_tcp->sk;
error = -EPROTONOSUPPORT;
if (sk_tcp->sk_protocol != IPPROTO_TCP)
goto out;
addrlen = sizeof(struct sockaddr_storage);
error = kernel_getpeername(sock_tcp, (struct sockaddr *)&ss, &addrlen);
if (error)
goto out;
if (!sk_tcp->sk_bound_dev_if) {
struct dst_entry *dst = sk_dst_get(sk_tcp);
error = -ENODEV;
if (!dst)
goto out;
sk_tcp->sk_bound_dev_if = dst->dev->ifindex;
dst_release(dst);
}
error = sock_create(ss.ss_family, SOCK_RAW, IPPROTO_GRE, &sock_raw);
if (error)
goto out;
sk_raw = sock_raw->sk;
sk_raw->sk_bound_dev_if = sk_tcp->sk_bound_dev_if;
error = kernel_connect(sock_raw, (struct sockaddr *)&ss, addrlen, 0);
if (error)
goto out;
po->chan.hdrlen = 14;
po->chan.private = sk_raw;
po->chan.ops = &pppopns_channel_ops;
po->chan.mtu = PPP_MRU - 80;
po->proto.pns.local = addr->local;
po->proto.pns.remote = addr->remote;
po->proto.pns.data_ready = sk_raw->sk_data_ready;
po->proto.pns.backlog_rcv = sk_raw->sk_backlog_rcv;
error = ppp_register_channel(&po->chan);
if (error)
goto out;
sk->sk_state = PPPOX_CONNECTED;
lock_sock(sk_raw);
sk_raw->sk_data_ready = pppopns_recv;
sk_raw->sk_backlog_rcv = pppopns_recv_core;
sk_raw->sk_user_data = sk;
release_sock(sk_raw);
out:
if (sock_tcp)
sockfd_put(sock_tcp);
if (error && sock_raw)
sock_release(sock_raw);
release_sock(sk);
return error;
}
static int pppopns_release(struct socket *sock)
{
struct sock *sk = sock->sk;
if (!sk)
return 0;
lock_sock(sk);
if (sock_flag(sk, SOCK_DEAD)) {
release_sock(sk);
return -EBADF;
}
if (sk->sk_state != PPPOX_NONE) {
struct sock *sk_raw = (struct sock *)pppox_sk(sk)->chan.private;
lock_sock(sk_raw);
skb_queue_purge(&sk->sk_receive_queue);
pppox_unbind_sock(sk);
sk_raw->sk_data_ready = pppox_sk(sk)->proto.pns.data_ready;
sk_raw->sk_backlog_rcv = pppox_sk(sk)->proto.pns.backlog_rcv;
sk_raw->sk_user_data = NULL;
release_sock(sk_raw);
sock_release(sk_raw->sk_socket);
}
sock_orphan(sk);
sock->sk = NULL;
release_sock(sk);
sock_put(sk);
return 0;
}
/******************************************************************************/
static struct proto pppopns_proto = {
.name = "PPPOPNS",
.owner = THIS_MODULE,
.obj_size = sizeof(struct pppox_sock),
};
static struct proto_ops pppopns_proto_ops = {
.family = PF_PPPOX,
.owner = THIS_MODULE,
.release = pppopns_release,
.bind = sock_no_bind,
.connect = pppopns_connect,
.socketpair = sock_no_socketpair,
.accept = sock_no_accept,
.getname = sock_no_getname,
.poll = sock_no_poll,
.ioctl = pppox_ioctl,
.listen = sock_no_listen,
.shutdown = sock_no_shutdown,
.setsockopt = sock_no_setsockopt,
.getsockopt = sock_no_getsockopt,
.sendmsg = sock_no_sendmsg,
.recvmsg = sock_no_recvmsg,
.mmap = sock_no_mmap,
};
static int pppopns_create(struct net *net, struct socket *sock)
{
struct sock *sk;
sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppopns_proto);
if (!sk)
return -ENOMEM;
sock_init_data(sock, sk);
sock->state = SS_UNCONNECTED;
sock->ops = &pppopns_proto_ops;
sk->sk_protocol = PX_PROTO_OPNS;
sk->sk_state = PPPOX_NONE;
return 0;
}
/******************************************************************************/
static struct pppox_proto pppopns_pppox_proto = {
.create = pppopns_create,
.owner = THIS_MODULE,
};
static int __init pppopns_init(void)
{
int error;
error = proto_register(&pppopns_proto, 0);
if (error)
return error;
error = register_pppox_proto(PX_PROTO_OPNS, &pppopns_pppox_proto);
if (error)
proto_unregister(&pppopns_proto);
else
skb_queue_head_init(&delivery_queue);
return error;
}
static void __exit pppopns_exit(void)
{
unregister_pppox_proto(PX_PROTO_OPNS);
proto_unregister(&pppopns_proto);
}
module_init(pppopns_init);
module_exit(pppopns_exit);
MODULE_DESCRIPTION("PPP on PPTP Network Server (PPPoPNS)");
MODULE_AUTHOR("Chia-chi Yeh <chiachi@android.com>");
MODULE_LICENSE("GPL");