drivers/net/pppolac.c

   1 /* drivers/net/pppolac.c
   2  *
   3  * Driver for PPP on L2TP Access Concentrator / PPPoLAC Socket (RFC 2661)
   4  *
   5  * Copyright (C) 2009 Google, Inc.
   6  *
   7  * This software is licensed under the terms of the GNU General Public
   8  * License version 2, as published by the Free Software Foundation, and
   9  * may be copied, distributed, and modified under those terms.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  */
  16
  17 /* This driver handles L2TP data packets between a UDP socket and a PPP channel.
  18  * To keep things simple, only one session per socket is permitted. Packets are
  19  * sent via the socket, so it must keep connected to the same address. One must
  20  * not set sequencing in ICCN but let LNS controll it. Currently this driver
  21  * only works on IPv4 due to the lack of UDP encapsulation support in IPv6. */
  22
  23 #include <linux/module.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/skbuff.h>
  26 #include <linux/file.h>
  27 #include <linux/netdevice.h>
  28 #include <linux/net.h>
  29 #include <linux/udp.h>
  30 #include <linux/ppp_defs.h>
  31 #include <linux/if_ppp.h>
  32 #include <linux/if_pppox.h>
  33 #include <linux/ppp_channel.h>
  34 #include <net/tcp_states.h>
  35 #include <asm/uaccess.h>
  36
  37 #define L2TP_CONTROL_BIT        0x80
  38 #define L2TP_LENGTH_BIT         0x40
  39 #define L2TP_SEQUENCE_BIT       0x08
  40 #define L2TP_OFFSET_BIT         0x02
  41 #define L2TP_VERSION            0x02
  42 #define L2TP_VERSION_MASK       0x0F
  43
  44 #define PPP_ADDR        0xFF
  45 #define PPP_CTRL        0x03
  46
  47 union unaligned {
  48         __u32 u32;
  49 } __attribute__((packed));
  50
  51 static inline union unaligned *unaligned(void *ptr)
  52 {
  53         return (union unaligned *)ptr;
  54 }
  55
  56 static int pppolac_recv_core(struct sock *sk_udp, struct sk_buff *skb)
  57 {
  58         struct sock *sk = (struct sock *)sk_udp->sk_user_data;
  59         struct pppolac_opt *opt = &pppox_sk(sk)->proto.lac;
  60         __u8 bits;
  61         __u8 *ptr;
  62
  63         /* Drop the packet if it is too short. */
  64         if (skb->len < sizeof(struct udphdr) + 6)
  65                 goto drop;
  66
  67         /* Put it back if it is a control packet. */
  68         if (skb->data[sizeof(struct udphdr)] & L2TP_CONTROL_BIT)
  69                 return opt->backlog_rcv(sk_udp, skb);
  70
  71         /* Skip UDP header. */
  72         skb_pull(skb, sizeof(struct udphdr));
  73
  74         /* Check the version. */
  75         if ((skb->data[1] & L2TP_VERSION_MASK) != L2TP_VERSION)
  76                 goto drop;
  77         bits = skb->data[0];
  78         ptr = &skb->data[2];
  79
  80         /* Check the length if it is present. */
  81         if (bits & L2TP_LENGTH_BIT) {
  82                 if ((ptr[0] << 8 | ptr[1]) != skb->len)
  83                         goto drop;
  84                 ptr += 2;
  85         }
  86
  87         /* Skip all fields including optional ones. */
  88         if (!skb_pull(skb, 6 + (bits & L2TP_SEQUENCE_BIT ? 4 : 0) +
  89                         (bits & L2TP_LENGTH_BIT ? 2 : 0) +
  90                         (bits & L2TP_OFFSET_BIT ? 2 : 0)))
  91                 goto drop;
  92
  93         /* Skip the offset padding if it is present. */
  94         if (bits & L2TP_OFFSET_BIT &&
  95                         !skb_pull(skb, skb->data[-2] << 8 | skb->data[-1]))
  96                 goto drop;
  97
  98         /* Check the tunnel and the session. */
  99         if (unaligned(ptr)->u32 != opt->local)
 100                 goto drop;
 101
 102         /* Check the sequence if it is present. According to RFC 2661 section
 103          * 5.4, the only thing to do is to update opt->sequencing. */
 104         opt->sequencing = bits & L2TP_SEQUENCE_BIT;
 105
 106         /* Skip PPP address and control if they are present. */
 107         if (skb->len >= 2 && skb->data[0] == PPP_ADDR &&
 108                         skb->data[1] == PPP_CTRL)
 109                 skb_pull(skb, 2);
 110
 111         /* Fix PPP protocol if it is compressed. */
 112         if (skb->len >= 1 && skb->data[0] & 1)
 113                 skb_push(skb, 1)[0] = 0;
 114
 115         /* Finally, deliver the packet to PPP channel. */
 116         skb_orphan(skb);
 117         ppp_input(&pppox_sk(sk)->chan, skb);
 118         return NET_RX_SUCCESS;
 119 drop:
 120         kfree_skb(skb);
 121         return NET_RX_DROP;
 122 }
 123
 124 static int pppolac_recv(struct sock *sk_udp, struct sk_buff *skb)
 125 {
 126         sock_hold(sk_udp);
 127         sk_receive_skb(sk_udp, skb, 0);
 128         return 0;
 129 }
 130
 131 static struct sk_buff_head delivery_queue;
 132
 133 static void pppolac_xmit_core(struct work_struct *delivery_work)
 134 {
 135         mm_segment_t old_fs = get_fs();
 136         struct sk_buff *skb;
 137
 138         set_fs(KERNEL_DS);
 139         while ((skb = skb_dequeue(&delivery_queue))) {
 140                 struct sock *sk_udp = skb->sk;
 141                 struct kvec iov = {.iov_base = skb->data, .iov_len = skb->len};
 142                 struct msghdr msg = {
 143                         .msg_iov = (struct iovec *)&iov,
 144                         .msg_iovlen = 1,
 145                         .msg_flags = MSG_NOSIGNAL | MSG_DONTWAIT,
 146                 };
 147                 sk_udp->sk_prot->sendmsg(NULL, sk_udp, &msg, skb->len);
 148                 kfree_skb(skb);
 149         }
 150         set_fs(old_fs);
 151 }
 152
 153 static DECLARE_WORK(delivery_work, pppolac_xmit_core);
 154
 155 static int pppolac_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 156 {
 157         struct sock *sk_udp = (struct sock *)chan->private;
 158         struct pppolac_opt *opt = &pppox_sk(sk_udp->sk_user_data)->proto.lac;
 159
 160         /* Install PPP address and control. */
 161         skb_push(skb, 2);
 162         skb->data[0] = PPP_ADDR;
 163         skb->data[1] = PPP_CTRL;
 164
 165         /* Install L2TP header. */
 166         if (opt->sequencing) {
 167                 skb_push(skb, 10);
 168                 skb->data[0] = L2TP_SEQUENCE_BIT;
 169                 skb->data[6] = opt->sequence >> 8;
 170                 skb->data[7] = opt->sequence;
 171                 skb->data[8] = 0;
 172                 skb->data[9] = 0;
 173                 opt->sequence++;
 174         } else {
 175                 skb_push(skb, 6);
 176                 skb->data[0] = 0;
 177         }
 178         skb->data[1] = L2TP_VERSION;
 179         unaligned(&skb->data[2])->u32 = opt->remote;
 180
 181         /* Now send the packet via the delivery queue. */
 182         skb_set_owner_w(skb, sk_udp);
 183         skb_queue_tail(&delivery_queue, skb);
 184         schedule_work(&delivery_work);
 185         return 1;
 186 }
 187
 188 /******************************************************************************/
 189
 190 static struct ppp_channel_ops pppolac_channel_ops = {
 191         .start_xmit = pppolac_xmit,
 192 };
 193
 194 static int pppolac_connect(struct socket *sock, struct sockaddr *useraddr,
 195         int addrlen, int flags)
 196 {
 197         struct sock *sk = sock->sk;
 198         struct pppox_sock *po = pppox_sk(sk);
 199         struct sockaddr_pppolac *addr = (struct sockaddr_pppolac *)useraddr;
 200         struct socket *sock_udp = NULL;
 201         struct sock *sk_udp;
 202         int error;
 203
 204         if (addrlen != sizeof(struct sockaddr_pppolac) ||
 205                         !addr->local.tunnel || !addr->local.session ||
 206                         !addr->remote.tunnel || !addr->remote.session) {
 207                 return -EINVAL;
 208         }
 209
 210         lock_sock(sk);
 211         error = -EALREADY;
 212         if (sk->sk_state != PPPOX_NONE)
 213                 goto out;
 214
 215         sock_udp = sockfd_lookup(addr->udp_socket, &error);
 216         if (!sock_udp)
 217                 goto out;
 218         sk_udp = sock_udp->sk;
 219         lock_sock(sk_udp);
 220
 221         /* Remove this check when IPv6 supports UDP encapsulation. */
 222         error = -EAFNOSUPPORT;
 223         if (sk_udp->sk_family != AF_INET)
 224                 goto out;
 225         error = -EPROTONOSUPPORT;
 226         if (sk_udp->sk_protocol != IPPROTO_UDP)
 227                 goto out;
 228         error = -EDESTADDRREQ;
 229         if (sk_udp->sk_state != TCP_ESTABLISHED)
 230                 goto out;
 231         error = -EBUSY;
 232         if (udp_sk(sk_udp)->encap_type || sk_udp->sk_user_data)
 233                 goto out;
 234         if (!sk_udp->sk_bound_dev_if) {
 235                 struct dst_entry *dst = sk_dst_get(sk_udp);
 236                 error = -ENODEV;
 237                 if (!dst)
 238                         goto out;
 239                 sk_udp->sk_bound_dev_if = dst->dev->ifindex;
 240                 dst_release(dst);
 241         }
 242
 243         po->chan.hdrlen = 12;
 244         po->chan.private = sk_udp;
 245         po->chan.ops = &pppolac_channel_ops;
 246         po->chan.mtu = PPP_MTU - 80;
 247         po->proto.lac.local = unaligned(&addr->local)->u32;
 248         po->proto.lac.remote = unaligned(&addr->remote)->u32;
 249         po->proto.lac.backlog_rcv = sk_udp->sk_backlog_rcv;
 250
 251         error = ppp_register_channel(&po->chan);
 252         if (error)
 253                 goto out;
 254
 255         sk->sk_state = PPPOX_CONNECTED;
 256         udp_sk(sk_udp)->encap_type = UDP_ENCAP_L2TPINUDP;
 257         udp_sk(sk_udp)->encap_rcv = pppolac_recv;
 258         sk_udp->sk_backlog_rcv = pppolac_recv_core;
 259         sk_udp->sk_user_data = sk;
 260 out:
 261         if (sock_udp) {
 262                 release_sock(sk_udp);
 263                 if (error)
 264                         sockfd_put(sock_udp);
 265         }
 266         release_sock(sk);
 267         return error;
 268 }
 269
 270 static int pppolac_release(struct socket *sock)
 271 {
 272         struct sock *sk = sock->sk;
 273
 274         if (!sk)
 275                 return 0;
 276
 277         lock_sock(sk);
 278         if (sock_flag(sk, SOCK_DEAD)) {
 279                 release_sock(sk);
 280                 return -EBADF;
 281         }
 282
 283         if (sk->sk_state != PPPOX_NONE) {
 284                 struct sock *sk_udp = (struct sock *)pppox_sk(sk)->chan.private;
 285                 lock_sock(sk_udp);
 286                 pppox_unbind_sock(sk);
 287                 udp_sk(sk_udp)->encap_type = 0;
 288                 udp_sk(sk_udp)->encap_rcv = NULL;
 289                 sk_udp->sk_backlog_rcv = pppox_sk(sk)->proto.lac.backlog_rcv;
 290                 sk_udp->sk_user_data = NULL;
 291                 release_sock(sk_udp);
 292                 sockfd_put(sk_udp->sk_socket);
 293         }
 294
 295         sock_orphan(sk);
 296         sock->sk = NULL;
 297         release_sock(sk);
 298         sock_put(sk);
 299         return 0;
 300 }
 301
 302 /******************************************************************************/
 303
 304 static struct proto pppolac_proto = {
 305         .name = "PPPOLAC",
 306         .owner = THIS_MODULE,
 307         .obj_size = sizeof(struct pppox_sock),
 308 };
 309
 310 static struct proto_ops pppolac_proto_ops = {
 311         .family = PF_PPPOX,
 312         .owner = THIS_MODULE,
 313         .release = pppolac_release,
 314         .bind = sock_no_bind,
 315         .connect = pppolac_connect,
 316         .socketpair = sock_no_socketpair,
 317         .accept = sock_no_accept,
 318         .getname = sock_no_getname,
 319         .poll = sock_no_poll,
 320         .ioctl = pppox_ioctl,
 321         .listen = sock_no_listen,
 322         .shutdown = sock_no_shutdown,
 323         .setsockopt = sock_no_setsockopt,
 324         .getsockopt = sock_no_getsockopt,
 325         .sendmsg = sock_no_sendmsg,
 326         .recvmsg = sock_no_recvmsg,
 327         .mmap = sock_no_mmap,
 328 };
 329
 330 static int pppolac_create(struct net *net, struct socket *sock)
 331 {
 332         struct sock *sk;
 333
 334         sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppolac_proto);
 335         if (!sk)
 336                 return -ENOMEM;
 337
 338         sock_init_data(sock, sk);
 339         sock->state = SS_UNCONNECTED;
 340         sock->ops = &pppolac_proto_ops;
 341         sk->sk_protocol = PX_PROTO_OLAC;
 342         sk->sk_state = PPPOX_NONE;
 343         return 0;
 344 }
 345
 346 /******************************************************************************/
 347
 348 static struct pppox_proto pppolac_pppox_proto = {
 349         .create = pppolac_create,
 350         .owner = THIS_MODULE,
 351 };
 352
 353 static int __init pppolac_init(void)
 354 {
 355         int error;
 356
 357         error = proto_register(&pppolac_proto, 0);
 358         if (error)
 359                 return error;
 360
 361         error = register_pppox_proto(PX_PROTO_OLAC, &pppolac_pppox_proto);
 362         if (error)
 363                 proto_unregister(&pppolac_proto);
 364         else
 365                 skb_queue_head_init(&delivery_queue);
 366         return error;
 367 }
 368
 369 static void __exit pppolac_exit(void)
 370 {
 371         unregister_pppox_proto(PX_PROTO_OLAC);
 372         proto_unregister(&pppolac_proto);
 373 }
 374
 375 module_init(pppolac_init);
 376 module_exit(pppolac_exit);
 377
 378 MODULE_DESCRIPTION("PPP on L2TP Access Concentrator (PPPoLAC)");
 379 MODULE_AUTHOR("Chia-chi Yeh <chiachi@android.com>");
 380 MODULE_LICENSE("GPL");