1 /* 2 * Point-to-Point Tunneling Protocol for Linux 3 * 4 * Authors: Dmitry Kozlov <xeb@mail.ru> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 */ 12 13 #include <linux/string.h> 14 #include <linux/module.h> 15 #include <linux/kernel.h> 16 #include <linux/slab.h> 17 #include <linux/errno.h> 18 #include <linux/netdevice.h> 19 #include <linux/net.h> 20 #include <linux/skbuff.h> 21 #include <linux/vmalloc.h> 22 #include <linux/init.h> 23 #include <linux/ppp_channel.h> 24 #include <linux/ppp_defs.h> 25 #include <linux/if_pppox.h> 26 #include <linux/ppp-ioctl.h> 27 #include <linux/notifier.h> 28 #include <linux/file.h> 29 #include <linux/in.h> 30 #include <linux/ip.h> 31 #include <linux/rcupdate.h> 32 #include <linux/spinlock.h> 33 34 #include <net/sock.h> 35 #include <net/protocol.h> 36 #include <net/ip.h> 37 #include <net/icmp.h> 38 #include <net/route.h> 39 #include <net/gre.h> 40 #include <net/pptp.h> 41 42 #include <linux/uaccess.h> 43 44 #define PPTP_DRIVER_VERSION "0.8.5" 45 46 #define MAX_CALLID 65535 47 48 static DECLARE_BITMAP(callid_bitmap, MAX_CALLID + 1); 49 static struct pppox_sock __rcu **callid_sock; 50 51 static DEFINE_SPINLOCK(chan_lock); 52 53 static struct proto pptp_sk_proto __read_mostly; 54 static const struct ppp_channel_ops pptp_chan_ops; 55 static const struct proto_ops pptp_ops; 56 57 static struct pppox_sock *lookup_chan(u16 call_id, __be32 s_addr) 58 { 59 struct pppox_sock *sock; 60 struct pptp_opt *opt; 61 62 rcu_read_lock(); 63 sock = rcu_dereference(callid_sock[call_id]); 64 if (sock) { 65 opt = &sock->proto.pptp; 66 if (opt->dst_addr.sin_addr.s_addr != s_addr) 67 sock = NULL; 68 else 69 sock_hold(sk_pppox(sock)); 70 } 71 rcu_read_unlock(); 72 73 return sock; 74 } 75 76 static int lookup_chan_dst(u16 call_id, __be32 d_addr) 77 { 78 struct pppox_sock *sock; 79 struct pptp_opt *opt; 80 int i; 81 82 rcu_read_lock(); 83 i = 1; 84 for_each_set_bit_from(i, callid_bitmap, MAX_CALLID) { 85 sock = rcu_dereference(callid_sock[i]); 86 if (!sock) 87 continue; 88 opt = &sock->proto.pptp; 89 if (opt->dst_addr.call_id == call_id && 90 opt->dst_addr.sin_addr.s_addr == d_addr) 91 break; 92 } 93 rcu_read_unlock(); 94 95 return i < MAX_CALLID; 96 } 97 98 static int add_chan(struct pppox_sock *sock, 99 struct pptp_addr *sa) 100 { 101 static int call_id; 102 103 spin_lock(&chan_lock); 104 if (!sa->call_id) { 105 call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, call_id + 1); 106 if (call_id == MAX_CALLID) { 107 call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, 1); 108 if (call_id == MAX_CALLID) 109 goto out_err; 110 } 111 sa->call_id = call_id; 112 } else if (test_bit(sa->call_id, callid_bitmap)) { 113 goto out_err; 114 } 115 116 sock->proto.pptp.src_addr = *sa; 117 set_bit(sa->call_id, callid_bitmap); 118 rcu_assign_pointer(callid_sock[sa->call_id], sock); 119 spin_unlock(&chan_lock); 120 121 return 0; 122 123 out_err: 124 spin_unlock(&chan_lock); 125 return -1; 126 } 127 128 static void del_chan(struct pppox_sock *sock) 129 { 130 spin_lock(&chan_lock); 131 clear_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap); 132 RCU_INIT_POINTER(callid_sock[sock->proto.pptp.src_addr.call_id], NULL); 133 spin_unlock(&chan_lock); 134 synchronize_rcu(); 135 } 136 137 static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) 138 { 139 struct sock *sk = (struct sock *) chan->private; 140 struct pppox_sock *po = pppox_sk(sk); 141 struct net *net = sock_net(sk); 142 struct pptp_opt *opt = &po->proto.pptp; 143 struct pptp_gre_header *hdr; 144 unsigned int header_len = sizeof(*hdr); 145 struct flowi4 fl4; 146 int islcp; 147 int len; 148 unsigned char *data; 149 __u32 seq_recv; 150 151 152 struct rtable *rt; 153 struct net_device *tdev; 154 struct iphdr *iph; 155 int max_headroom; 156 157 if (sk_pppox(po)->sk_state & PPPOX_DEAD) 158 goto tx_error; 159 160 rt = ip_route_output_ports(net, &fl4, NULL, 161 opt->dst_addr.sin_addr.s_addr, 162 opt->src_addr.sin_addr.s_addr, 163 0, 0, IPPROTO_GRE, 164 RT_TOS(0), 0); 165 if (IS_ERR(rt)) 166 goto tx_error; 167 168 tdev = rt->dst.dev; 169 170 max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(*iph) + sizeof(*hdr) + 2; 171 172 if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) { 173 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom); 174 if (!new_skb) { 175 ip_rt_put(rt); 176 goto tx_error; 177 } 178 if (skb->sk) 179 skb_set_owner_w(new_skb, skb->sk); 180 consume_skb(skb); 181 skb = new_skb; 182 } 183 184 data = skb->data; 185 islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7; 186 187 /* compress protocol field */ 188 if ((opt->ppp_flags & SC_COMP_PROT) && data[0] == 0 && !islcp) 189 skb_pull(skb, 1); 190 191 /* Put in the address/control bytes if necessary */ 192 if ((opt->ppp_flags & SC_COMP_AC) == 0 || islcp) { 193 data = skb_push(skb, 2); 194 data[0] = PPP_ALLSTATIONS; 195 data[1] = PPP_UI; 196 } 197 198 len = skb->len; 199 200 seq_recv = opt->seq_recv; 201 202 if (opt->ack_sent == seq_recv) 203 header_len -= sizeof(hdr->ack); 204 205 /* Push down and install GRE header */ 206 skb_push(skb, header_len); 207 hdr = (struct pptp_gre_header *)(skb->data); 208 209 hdr->gre_hd.flags = GRE_KEY | GRE_VERSION_1 | GRE_SEQ; 210 hdr->gre_hd.protocol = GRE_PROTO_PPP; 211 hdr->call_id = htons(opt->dst_addr.call_id); 212 213 hdr->seq = htonl(++opt->seq_sent); 214 if (opt->ack_sent != seq_recv) { 215 /* send ack with this message */ 216 hdr->gre_hd.flags |= GRE_ACK; 217 hdr->ack = htonl(seq_recv); 218 opt->ack_sent = seq_recv; 219 } 220 hdr->payload_len = htons(len); 221 222 /* Push down and install the IP header. */ 223 224 skb_reset_transport_header(skb); 225 skb_push(skb, sizeof(*iph)); 226 skb_reset_network_header(skb); 227 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt)); 228 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED); 229 230 iph = ip_hdr(skb); 231 iph->version = 4; 232 iph->ihl = sizeof(struct iphdr) >> 2; 233 if (ip_dont_fragment(sk, &rt->dst)) 234 iph->frag_off = htons(IP_DF); 235 else 236 iph->frag_off = 0; 237 iph->protocol = IPPROTO_GRE; 238 iph->tos = 0; 239 iph->daddr = fl4.daddr; 240 iph->saddr = fl4.saddr; 241 iph->ttl = ip4_dst_hoplimit(&rt->dst); 242 iph->tot_len = htons(skb->len); 243 244 skb_dst_drop(skb); 245 skb_dst_set(skb, &rt->dst); 246 247 nf_reset(skb); 248 249 skb->ip_summed = CHECKSUM_NONE; 250 ip_select_ident(net, skb, NULL); 251 ip_send_check(iph); 252 253 ip_local_out(net, skb->sk, skb); 254 return 1; 255 256 tx_error: 257 kfree_skb(skb); 258 return 1; 259 } 260 261 static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb) 262 { 263 struct pppox_sock *po = pppox_sk(sk); 264 struct pptp_opt *opt = &po->proto.pptp; 265 int headersize, payload_len, seq; 266 __u8 *payload; 267 struct pptp_gre_header *header; 268 269 if (!(sk->sk_state & PPPOX_CONNECTED)) { 270 if (sock_queue_rcv_skb(sk, skb)) 271 goto drop; 272 return NET_RX_SUCCESS; 273 } 274 275 header = (struct pptp_gre_header *)(skb->data); 276 headersize = sizeof(*header); 277 278 /* test if acknowledgement present */ 279 if (GRE_IS_ACK(header->gre_hd.flags)) { 280 __u32 ack; 281 282 if (!pskb_may_pull(skb, headersize)) 283 goto drop; 284 header = (struct pptp_gre_header *)(skb->data); 285 286 /* ack in different place if S = 0 */ 287 ack = GRE_IS_SEQ(header->gre_hd.flags) ? header->ack : header->seq; 288 289 ack = ntohl(ack); 290 291 if (ack > opt->ack_recv) 292 opt->ack_recv = ack; 293 /* also handle sequence number wrap-around */ 294 if (WRAPPED(ack, opt->ack_recv)) 295 opt->ack_recv = ack; 296 } else { 297 headersize -= sizeof(header->ack); 298 } 299 /* test if payload present */ 300 if (!GRE_IS_SEQ(header->gre_hd.flags)) 301 goto drop; 302 303 payload_len = ntohs(header->payload_len); 304 seq = ntohl(header->seq); 305 306 /* check for incomplete packet (length smaller than expected) */ 307 if (!pskb_may_pull(skb, headersize + payload_len)) 308 goto drop; 309 310 payload = skb->data + headersize; 311 /* check for expected sequence number */ 312 if (seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq)) { 313 if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) && 314 (PPP_PROTOCOL(payload) == PPP_LCP) && 315 ((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP))) 316 goto allow_packet; 317 } else { 318 opt->seq_recv = seq; 319 allow_packet: 320 skb_pull(skb, headersize); 321 322 if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) { 323 /* chop off address/control */ 324 if (skb->len < 3) 325 goto drop; 326 skb_pull(skb, 2); 327 } 328 329 if ((*skb->data) & 1) { 330 /* protocol is compressed */ 331 skb_push(skb, 1)[0] = 0; 332 } 333 334 skb->ip_summed = CHECKSUM_NONE; 335 skb_set_network_header(skb, skb->head-skb->data); 336 ppp_input(&po->chan, skb); 337 338 return NET_RX_SUCCESS; 339 } 340 drop: 341 kfree_skb(skb); 342 return NET_RX_DROP; 343 } 344 345 static int pptp_rcv(struct sk_buff *skb) 346 { 347 struct pppox_sock *po; 348 struct pptp_gre_header *header; 349 struct iphdr *iph; 350 351 if (skb->pkt_type != PACKET_HOST) 352 goto drop; 353 354 if (!pskb_may_pull(skb, 12)) 355 goto drop; 356 357 iph = ip_hdr(skb); 358 359 header = (struct pptp_gre_header *)skb->data; 360 361 if (header->gre_hd.protocol != GRE_PROTO_PPP || /* PPTP-GRE protocol for PPTP */ 362 GRE_IS_CSUM(header->gre_hd.flags) || /* flag CSUM should be clear */ 363 GRE_IS_ROUTING(header->gre_hd.flags) || /* flag ROUTING should be clear */ 364 !GRE_IS_KEY(header->gre_hd.flags) || /* flag KEY should be set */ 365 (header->gre_hd.flags & GRE_FLAGS)) /* flag Recursion Ctrl should be clear */ 366 /* if invalid, discard this packet */ 367 goto drop; 368 369 po = lookup_chan(htons(header->call_id), iph->saddr); 370 if (po) { 371 skb_dst_drop(skb); 372 nf_reset(skb); 373 return sk_receive_skb(sk_pppox(po), skb, 0); 374 } 375 drop: 376 kfree_skb(skb); 377 return NET_RX_DROP; 378 } 379 380 static int pptp_bind(struct socket *sock, struct sockaddr *uservaddr, 381 int sockaddr_len) 382 { 383 struct sock *sk = sock->sk; 384 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; 385 struct pppox_sock *po = pppox_sk(sk); 386 int error = 0; 387 388 if (sockaddr_len < sizeof(struct sockaddr_pppox)) 389 return -EINVAL; 390 391 lock_sock(sk); 392 393 if (sk->sk_state & PPPOX_DEAD) { 394 error = -EALREADY; 395 goto out; 396 } 397 398 if (sk->sk_state & PPPOX_BOUND) { 399 error = -EBUSY; 400 goto out; 401 } 402 403 if (add_chan(po, &sp->sa_addr.pptp)) 404 error = -EBUSY; 405 else 406 sk->sk_state |= PPPOX_BOUND; 407 408 out: 409 release_sock(sk); 410 return error; 411 } 412 413 static int pptp_connect(struct socket *sock, struct sockaddr *uservaddr, 414 int sockaddr_len, int flags) 415 { 416 struct sock *sk = sock->sk; 417 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; 418 struct pppox_sock *po = pppox_sk(sk); 419 struct pptp_opt *opt = &po->proto.pptp; 420 struct rtable *rt; 421 struct flowi4 fl4; 422 int error = 0; 423 424 if (sockaddr_len < sizeof(struct sockaddr_pppox)) 425 return -EINVAL; 426 427 if (sp->sa_protocol != PX_PROTO_PPTP) 428 return -EINVAL; 429 430 if (lookup_chan_dst(sp->sa_addr.pptp.call_id, sp->sa_addr.pptp.sin_addr.s_addr)) 431 return -EALREADY; 432 433 lock_sock(sk); 434 /* Check for already bound sockets */ 435 if (sk->sk_state & PPPOX_CONNECTED) { 436 error = -EBUSY; 437 goto end; 438 } 439 440 /* Check for already disconnected sockets, on attempts to disconnect */ 441 if (sk->sk_state & PPPOX_DEAD) { 442 error = -EALREADY; 443 goto end; 444 } 445 446 if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr) { 447 error = -EINVAL; 448 goto end; 449 } 450 451 po->chan.private = sk; 452 po->chan.ops = &pptp_chan_ops; 453 454 rt = ip_route_output_ports(sock_net(sk), &fl4, sk, 455 opt->dst_addr.sin_addr.s_addr, 456 opt->src_addr.sin_addr.s_addr, 457 0, 0, 458 IPPROTO_GRE, RT_CONN_FLAGS(sk), 0); 459 if (IS_ERR(rt)) { 460 error = -EHOSTUNREACH; 461 goto end; 462 } 463 sk_setup_caps(sk, &rt->dst); 464 465 po->chan.mtu = dst_mtu(&rt->dst); 466 if (!po->chan.mtu) 467 po->chan.mtu = PPP_MRU; 468 ip_rt_put(rt); 469 po->chan.mtu -= PPTP_HEADER_OVERHEAD; 470 471 po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header); 472 error = ppp_register_channel(&po->chan); 473 if (error) { 474 pr_err("PPTP: failed to register PPP channel (%d)\n", error); 475 goto end; 476 } 477 478 opt->dst_addr = sp->sa_addr.pptp; 479 sk->sk_state |= PPPOX_CONNECTED; 480 481 end: 482 release_sock(sk); 483 return error; 484 } 485 486 static int pptp_getname(struct socket *sock, struct sockaddr *uaddr, 487 int *usockaddr_len, int peer) 488 { 489 int len = sizeof(struct sockaddr_pppox); 490 struct sockaddr_pppox sp; 491 492 memset(&sp.sa_addr, 0, sizeof(sp.sa_addr)); 493 494 sp.sa_family = AF_PPPOX; 495 sp.sa_protocol = PX_PROTO_PPTP; 496 sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr; 497 498 memcpy(uaddr, &sp, len); 499 500 *usockaddr_len = len; 501 502 return 0; 503 } 504 505 static int pptp_release(struct socket *sock) 506 { 507 struct sock *sk = sock->sk; 508 struct pppox_sock *po; 509 struct pptp_opt *opt; 510 int error = 0; 511 512 if (!sk) 513 return 0; 514 515 lock_sock(sk); 516 517 if (sock_flag(sk, SOCK_DEAD)) { 518 release_sock(sk); 519 return -EBADF; 520 } 521 522 po = pppox_sk(sk); 523 opt = &po->proto.pptp; 524 del_chan(po); 525 526 pppox_unbind_sock(sk); 527 sk->sk_state = PPPOX_DEAD; 528 529 sock_orphan(sk); 530 sock->sk = NULL; 531 532 release_sock(sk); 533 sock_put(sk); 534 535 return error; 536 } 537 538 static void pptp_sock_destruct(struct sock *sk) 539 { 540 if (!(sk->sk_state & PPPOX_DEAD)) { 541 del_chan(pppox_sk(sk)); 542 pppox_unbind_sock(sk); 543 } 544 skb_queue_purge(&sk->sk_receive_queue); 545 } 546 547 static int pptp_create(struct net *net, struct socket *sock, int kern) 548 { 549 int error = -ENOMEM; 550 struct sock *sk; 551 struct pppox_sock *po; 552 struct pptp_opt *opt; 553 554 sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto, kern); 555 if (!sk) 556 goto out; 557 558 sock_init_data(sock, sk); 559 560 sock->state = SS_UNCONNECTED; 561 sock->ops = &pptp_ops; 562 563 sk->sk_backlog_rcv = pptp_rcv_core; 564 sk->sk_state = PPPOX_NONE; 565 sk->sk_type = SOCK_STREAM; 566 sk->sk_family = PF_PPPOX; 567 sk->sk_protocol = PX_PROTO_PPTP; 568 sk->sk_destruct = pptp_sock_destruct; 569 570 po = pppox_sk(sk); 571 opt = &po->proto.pptp; 572 573 opt->seq_sent = 0; opt->seq_recv = 0xffffffff; 574 opt->ack_recv = 0; opt->ack_sent = 0xffffffff; 575 576 error = 0; 577 out: 578 return error; 579 } 580 581 static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd, 582 unsigned long arg) 583 { 584 struct sock *sk = (struct sock *) chan->private; 585 struct pppox_sock *po = pppox_sk(sk); 586 struct pptp_opt *opt = &po->proto.pptp; 587 void __user *argp = (void __user *)arg; 588 int __user *p = argp; 589 int err, val; 590 591 err = -EFAULT; 592 switch (cmd) { 593 case PPPIOCGFLAGS: 594 val = opt->ppp_flags; 595 if (put_user(val, p)) 596 break; 597 err = 0; 598 break; 599 case PPPIOCSFLAGS: 600 if (get_user(val, p)) 601 break; 602 opt->ppp_flags = val & ~SC_RCV_BITS; 603 err = 0; 604 break; 605 default: 606 err = -ENOTTY; 607 } 608 609 return err; 610 } 611 612 static const struct ppp_channel_ops pptp_chan_ops = { 613 .start_xmit = pptp_xmit, 614 .ioctl = pptp_ppp_ioctl, 615 }; 616 617 static struct proto pptp_sk_proto __read_mostly = { 618 .name = "PPTP", 619 .owner = THIS_MODULE, 620 .obj_size = sizeof(struct pppox_sock), 621 }; 622 623 static const struct proto_ops pptp_ops = { 624 .family = AF_PPPOX, 625 .owner = THIS_MODULE, 626 .release = pptp_release, 627 .bind = pptp_bind, 628 .connect = pptp_connect, 629 .socketpair = sock_no_socketpair, 630 .accept = sock_no_accept, 631 .getname = pptp_getname, 632 .poll = sock_no_poll, 633 .listen = sock_no_listen, 634 .shutdown = sock_no_shutdown, 635 .setsockopt = sock_no_setsockopt, 636 .getsockopt = sock_no_getsockopt, 637 .sendmsg = sock_no_sendmsg, 638 .recvmsg = sock_no_recvmsg, 639 .mmap = sock_no_mmap, 640 .ioctl = pppox_ioctl, 641 }; 642 643 static const struct pppox_proto pppox_pptp_proto = { 644 .create = pptp_create, 645 .owner = THIS_MODULE, 646 }; 647 648 static const struct gre_protocol gre_pptp_protocol = { 649 .handler = pptp_rcv, 650 }; 651 652 static int __init pptp_init_module(void) 653 { 654 int err = 0; 655 pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n"); 656 657 callid_sock = vzalloc((MAX_CALLID + 1) * sizeof(void *)); 658 if (!callid_sock) 659 return -ENOMEM; 660 661 err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 662 if (err) { 663 pr_err("PPTP: can't add gre protocol\n"); 664 goto out_mem_free; 665 } 666 667 err = proto_register(&pptp_sk_proto, 0); 668 if (err) { 669 pr_err("PPTP: can't register sk_proto\n"); 670 goto out_gre_del_protocol; 671 } 672 673 err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto); 674 if (err) { 675 pr_err("PPTP: can't register pppox_proto\n"); 676 goto out_unregister_sk_proto; 677 } 678 679 return 0; 680 681 out_unregister_sk_proto: 682 proto_unregister(&pptp_sk_proto); 683 out_gre_del_protocol: 684 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 685 out_mem_free: 686 vfree(callid_sock); 687 688 return err; 689 } 690 691 static void __exit pptp_exit_module(void) 692 { 693 unregister_pppox_proto(PX_PROTO_PPTP); 694 proto_unregister(&pptp_sk_proto); 695 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 696 vfree(callid_sock); 697 } 698 699 module_init(pptp_init_module); 700 module_exit(pptp_exit_module); 701 702 MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol"); 703 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 704 MODULE_LICENSE("GPL"); 705 MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP); 706