ppp.c

   1 // L2TPNS PPP Stuff
   2 // $Id: ppp.c,v 1.2 2004-03-05 00:09:03 fred_nerk Exp $
   3
   4 #include <stdio.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7 #include <errno.h>
   8 #include <stdlib.h>
   9 #include "l2tpns.h"
  10 #include "constants.h"
  11 #include "plugin.h"
  12 #include "util.h"
  13
  14 extern tunnelt *tunnel;
  15 extern sessiont *session;
  16 extern radiust *radius;
  17 extern int tapfd;
  18 extern char hostname[1000];
  19 extern struct Tstats *_statistics;
  20 extern unsigned long eth_tx;
  21 extern time_t time_now;
  22 extern struct configt *config;
  23
  24 // Process PAP messages
  25 void processpap(tunnelidt t, sessionidt s, u8 * p, u16 l)
  26 {
  27         char user[129];
  28         char pass[129];
  29
  30 #ifdef STAT_CALLS
  31         STAT(call_processpap);
  32 #endif
  33         log_hex(5, "PAP", p, l);
  34         if (l < 4)
  35         {
  36                 log(1, 0, s, t, "Short PAP %u bytes", l);
  37                 STAT(tunnel_rx_errors);
  38                 return ;
  39         }
  40         if (*p != 1)
  41         {
  42                 log(1, 0, s, t, "Unexpected PAP code %d\n", *p);
  43                 STAT(tunnel_rx_errors);
  44                 return ;
  45         }
  46         if (ntohs(*(u16 *) (p + 2)) > l)
  47         {
  48                 log(1, 0, s, t, "Length mismatch PAP %d/%d\n", ntohs(*(u16 *) (p + 2)), l);
  49                 STAT(tunnel_rx_errors);
  50                 return ;
  51         }
  52         {
  53                 u8 *b = p;
  54                 b += 4;
  55                 if (*b && *b < sizeof(user))
  56                         memcpy(user, b + 1, *b);
  57                 user[*b] = 0;
  58                 b += 1 + *b;
  59                 if (*b && *b < sizeof(pass))
  60                         memcpy(pass, b + 1, *b);
  61                 pass[*b] = 0;
  62                 log(3, 0, s, t, "PAP login %s/%s\n", user, pass);
  63         }
  64         if (session[s].ip || !session[s].radius)
  65         {
  66                 // respond now, either no RADIUS available or already authenticated
  67                 u8 b[MAXCONTROL];
  68                 u8 id = p[1];
  69                 u8 *p = makeppp(b, 0, 0, t, s, PPPPAP);
  70                 if (session[s].ip)
  71                         *p = 2;              // ACK
  72                 else
  73                         *p = 3;              // cant authorise
  74                 p[1] = id;
  75                 *(u16 *) (p + 2) = htons(5); // length
  76                 p[4] = 0;               // no message
  77                 if (session[s].ip)
  78                 {
  79                     log(3, session[s].ip, s, t, "%d Already an IP allocated: %s (%d)\n", getpid(), inet_toa(htonl(session[s].ip)), session[s].ip_pool_index);
  80                 }
  81                 else
  82                 {
  83                     log(1, 0, s, t, "No radius session available to authenticate session...\n");
  84                 }
  85                 log(3, 0, s, t, "Fallback response to PAP (%s)\n", (session[s].ip) ? "ACK" : "NAK");
  86                 tunnelsend(b, 5 + (p - b), t); // send it
  87         }
  88         else
  89         {                          // set up RADIUS request
  90                 u8 r = session[s].radius;
  91
  92                 // Run PRE_AUTH plugins
  93                 struct param_pre_auth packet = { &tunnel[t], &session[s], strdup(user), strdup(pass), PPPPAP, 1 };
  94                 run_plugins(PLUGIN_PRE_AUTH, &packet);
  95                 if (!packet.continue_auth)
  96                 {
  97                         log(3, 0, s, t, "A plugin rejected PRE_AUTH\n");
  98                         if (packet.username) free(packet.username);
  99                         if (packet.password) free(packet.password);
 100                         return;
 101                 }
 102
 103                 strncpy(session[s].user, packet.username, sizeof(session[s].user) - 1);
 104                 strncpy(radius[r].pass, packet.password, sizeof(radius[r].pass) - 1);
 105
 106                 free(packet.username);
 107                 free(packet.password);
 108
 109                 radius[r].id = p[1];
 110                 log(3, 0, s, t, "Sending login for %s/%s to radius\n", user, pass);
 111                 radiussend(r, RADIUSAUTH);
 112         }
 113 }
 114
 115 // Process CHAP messages
 116 void processchap(tunnelidt t, sessionidt s, u8 * p, u16 l)
 117 {
 118         u8 r;
 119         u16 len;
 120
 121 #ifdef STAT_CALLS
 122         STAT(call_processchap);
 123 #endif
 124         log_hex(5, "CHAP", p, l);
 125         r = session[s].radius;
 126         if (!r)
 127         {
 128                 log(1, 0, s, t, "Unexpected CHAP message\n");
 129                 STAT(tunnel_rx_errors);
 130                 return;
 131         }
 132         if (*p != 2)
 133         {
 134                 log(1, 0, s, t, "Unexpected CHAP response code %d\n", *p);
 135                 STAT(tunnel_rx_errors);
 136                 return;
 137         }
 138         if (p[1] != radius[r].id)
 139         {
 140                 log(1, 0, s, t, "Wrong CHAP response ID %d (should be %d) (%d)\n", p[1], radius[r].id, r);
 141                 STAT(tunnel_rx_errors);
 142                 return ;
 143         }
 144         len = ntohs(*(u16 *) (p + 2));
 145         if (len > l)
 146         {
 147                 log(1, 0, s, t, "Bad CHAP length %d\n", len);
 148                 STAT(tunnel_rx_errors);
 149                 return ;
 150         }
 151         if (p[4] != 16)
 152         {
 153                 log(1, 0, s, t, "Bad CHAP response length %d\n", p[4]);
 154                 STAT(tunnel_rx_errors);
 155                 return ;
 156         }
 157         if (len - 21 >= sizeof(session[s].user))
 158         {
 159                 log(1, 0, s, t, "CHAP user too long %d\n", len - 21);
 160                 STAT(tunnel_rx_errors);
 161                 return ;
 162         }
 163
 164         // Run PRE_AUTH plugins
 165         {
 166                 struct param_pre_auth packet = { &tunnel[t], &session[s], NULL, NULL, PPPCHAP, 1 };
 167
 168                 packet.username = calloc(len-20, 1);
 169                 packet.password = calloc(16, 1);
 170                 memcpy(packet.username, p + 21, len - 21);
 171                 memcpy(packet.password, p + 5, 16);
 172
 173                 run_plugins(PLUGIN_PRE_AUTH, &packet);
 174                 if (!packet.continue_auth)
 175                 {
 176                         log(3, 0, s, t, "A plugin rejected PRE_AUTH\n");
 177                         if (packet.username) free(packet.username);
 178                         if (packet.password) free(packet.password);
 179                         return;
 180                 }
 181
 182                 strncpy(session[s].user, packet.username, sizeof(session[s].user) - 1);
 183                 memcpy(radius[r].pass, packet.password, 16);
 184
 185                 free(packet.username);
 186                 free(packet.password);
 187         }
 188
 189         radius[r].chap = 1;
 190         radiussend(r, RADIUSAUTH);
 191         log(3, 0, s, t, "CHAP login %s\n", session[s].user);
 192 }
 193
 194 char *ppp_lcp_types[] = {
 195         NULL,
 196         "ConfigReq",
 197         "ConfigAck",
 198         "ConfigNak",
 199         "ConfigRej",
 200         "TerminateReq",
 201         "TerminateAck",
 202         "CodeRej",
 203         "ProtocolRej",
 204         "EchoReq",
 205         "EchoReply",
 206         "DiscardRequest",
 207 };
 208
 209 void dumplcp(char *p, int l)
 210 {
 211         signed int x = l - 3;
 212         char *o = (p + 3);
 213
 214         log_hex(5, "PPP LCP Packet", p, l);
 215         log(4, 0, 0, 0, "PPP LCP Packet type %d (%s)\n", *p, ppp_lcp_types[(int)*p]);
 216         log(4, 0, 0, 0, "Length: %d\n", l);
 217         if (*p != ConfigReq && *p != ConfigRej && *p != ConfigAck)
 218                 return;
 219
 220         while (x > 2)
 221         {
 222                 int type = *(u8 *)(o);
 223                 int length = *(u8 *)(o + 1);
 224                 if (length == 0)
 225                 {
 226                         log(4, 0, 0, 0, "       Option length is 0...\n");
 227                         break;
 228                 }
 229                 if (type == 0)
 230                 {
 231                         log(4, 0, 0, 0, "       Option type is 0...\n");
 232                         x -= length;
 233                         o += length;
 234                         continue;
 235                 }
 236                 switch (type)
 237                 {
 238                         case 1: // Maximum-Receive-Unit
 239                                 log(4, 0, 0, 0, "    %s %d\n", lcp_types[type], ntohs(*(u16 *)(o + 2)));
 240                                 break;
 241                         case 3: // Authentication-Protocol
 242                                 {
 243                                         int proto = ntohs(*(u16 *)(o + 2));
 244                                         log(4, 0, 0, 0, "    %s %s\n", lcp_types[type],
 245                                                         proto == 0xC223 ? "CHAP" : "PAP");
 246                                         break;
 247                                 }
 248                         case 5: // Magic-Number
 249                                 {
 250                                         u32 magicno = ntohl(*(u32 *)(o + 2));
 251                                         log(4, 0, 0, 0, "    %s %x\n", lcp_types[type], magicno);
 252                                         break;
 253                                 }
 254                         case 4: // Quality-Protocol
 255                                 {
 256                                         u32 qp = ntohl(*(u32 *)(o + 2));
 257                                         log(4, 0, 0, 0, "    %s %x\n", lcp_types[type], qp);
 258                                         break;
 259                                 }
 260                         case 7: // Protocol-Field-Compression
 261                                 {
 262                                         u32 pfc = ntohl(*(u32 *)(o + 2));
 263                                         log(4, 0, 0, 0, "    %s %x\n", lcp_types[type], pfc);
 264                                         break;
 265                                 }
 266                         case 8: // Address-And-Control-Field-Compression
 267                                 {
 268                                         u32 afc = ntohl(*(u32 *)(o + 2));
 269                                         log(4, 0, 0, 0, "    %s %x\n", lcp_types[type], afc);
 270                                         break;
 271                                 }
 272                         default:
 273                                 log(2, 0, 0, 0, "    Unknown PPP LCP Option type %d\n", type);
 274                                 break;
 275                 }
 276                 x -= length;
 277                 o += length;
 278         }
 279 }
 280
 281 // Process LCP messages
 282 void processlcp(tunnelidt t, sessionidt s, u8 * p, u16 l)
 283 {
 284         u8 b[MAXCONTROL];
 285         u8 *q = NULL;
 286
 287 #ifdef STAT_CALLS
 288         STAT(call_processlcp);
 289 #endif
 290         log_hex(5, "LCP", p, l);
 291         if (l < 4)
 292         {
 293                 log(1, session[s].ip, s, t, "Short LCP %d bytes", l);
 294                 STAT(tunnel_rx_errors);
 295                 return ;
 296         }
 297         if (*p == ConfigAck)
 298         {
 299                 log(3, session[s].ip, s, t, "LCP: Discarding ConfigAck\n");
 300         }
 301         else if (*p == ConfigReq)
 302         {
 303                 signed int x = l - 1;
 304                 char *o = (p + 1);
 305
 306                 log(3, session[s].ip, s, t, "LCP: ConfigReq (%d bytes)...\n", l);
 307
 308                 while (x > 2)
 309                 {
 310                         int type = *(u8 *)(o);
 311                         int length = *(u8 *)(o + 1);
 312                         if (length == 0 || type == 0) break;
 313                         switch (type)
 314                         {
 315                                 case 1: // Maximum-Receive-Unit
 316                                         session[s].mru = ntohs(*(u16 *)(o + 2));
 317                                         break;
 318                                 case 3: // Authentication-Protocol
 319                                         {
 320                                                 int proto = ntohs(*(u16 *)(o + 2));
 321                                                 if (proto == 0xC223)
 322                                                 {
 323                                                         log(2, session[s].ip, s, t, "    Remote end is trying to do CHAP. Rejecting it.\n");
 324
 325                                                         if (!q)
 326                                                         {
 327                                                                 q = makeppp(b, p, l, t, s, PPPLCP);
 328                                                                 *q++ = ConfigNak;
 329                                                         }
 330                                                         memcpy(q, o, length);
 331                                                         *(u16 *)(q += 2) = htons(0xC023); // NAK -> Use PAP instead
 332                                                         q += length;
 333                                                 }
 334                                                 break;
 335                                         }
 336                                 case 5: // Magic-Number
 337                                         {
 338 //                                              u32 magicno = ntohl(*(u32 *)(o + 2));
 339                                                 break;
 340                                         }
 341                                 case 4: // Quality-Protocol
 342                                         {
 343 //                                              u32 qp = ntohl(*(u32 *)(o + 2));
 344                                                 break;
 345                                         }
 346                                 case 7: // Protocol-Field-Compression
 347                                         {
 348 //                                              u32 pfc = ntohl(*(u32 *)(o + 2));
 349                                                 break;
 350                                         }
 351                                 case 8: // Address-And-Control-Field-Compression
 352                                         {
 353 //                                              u32 afc = ntohl(*(u32 *)(o + 2));
 354                                                 break;
 355                                         }
 356                                 default:
 357                                         log(2, session[s].ip, s, t, "    Unknown PPP LCP Option type %d\n", type);
 358                                         break;
 359                         }
 360                         x -= length;
 361                         o += length;
 362                 }
 363
 364                 if (!q)
 365                 {
 366                         // Send back a ConfigAck
 367                         log(3, session[s].ip, s, t, "ConfigReq accepted, sending as Ack\n");
 368                         q = makeppp(b, p, l, t, s, PPPLCP);
 369                         *q = ConfigAck;
 370                         tunnelsend(b, l + (q - b), t);
 371                 }
 372                 else
 373                 {
 374                         // Already built a ConfigNak... send it
 375                         log(3, session[s].ip, s, t, "Sending ConfigNak\n");
 376                         tunnelsend(b, l + (q - b), t);
 377
 378                         log(3, session[s].ip, s, t, "Sending ConfigReq, requesting PAP login\n");
 379                         q = makeppp(b, NULL, 0, t, s, PPPLCP);
 380                         *q++ = ConfigReq;
 381                         *(u8 *)(q++) = 3;
 382                         *(u8 *)(q++) = 4;
 383                         *(u16 *)(q += 2) = htons(0xC023);
 384                         tunnelsend(b, l + (q - b), t);
 385                 }
 386         }
 387         else if (*p == ConfigNak)
 388         {
 389                 log(1, session[s].ip, s, t, "Remote end sent a ConfigNak. Ignoring\n");
 390                 dumplcp(p, l);
 391                 return ;
 392         }
 393         else if (*p == TerminateReq)
 394         {
 395                 *p = TerminateAck;     // close
 396                 q = makeppp(b, p, l, t, s, PPPLCP);
 397                 log(3, session[s].ip, s, t, "LCP: Received TerminateReq. Sending TerminateAck\n");
 398                 sessionshutdown(s, "Remote end closed connection.");
 399                 tunnelsend(b, l + (q - b), t); // send it
 400         }
 401         else if (*p == TerminateReq)
 402         {
 403                 sessionshutdown(s, "Remote end closed connection.");
 404         }
 405         else if (*p == EchoReq)
 406         {
 407                 *p = EchoReply;      // reply
 408                 *(u32 *) (p + 4) = htonl(session[s].magic); // our magic number
 409                 q = makeppp(b, p, l, t, s, PPPLCP);
 410                 log(4, session[s].ip, s, t, "LCP: Received EchoReq. Sending EchoReply\n");
 411                 tunnelsend(b, l + (q - b), t); // send it
 412         }
 413         else if (*p == EchoReply)
 414         {
 415                 // Ignore it, last_packet time is set earlier than this.
 416         }
 417         else
 418         {
 419                 log(1, session[s].ip, s, t, "Unexpected LCP code %d\n", *p);
 420                 STAT(tunnel_rx_errors);
 421                 return ;
 422         }
 423 }
 424
 425 // Process IPCP messages
 426 void processipcp(tunnelidt t, sessionidt s, u8 * p, u16 l)
 427 {
 428 #ifdef STAT_CALLS
 429         STAT(call_processipcp);
 430 #endif
 431         log_hex(5, "IPCP", p, l);
 432         if (l < 5)
 433         {
 434                 log(1, 0, s, t, "Short IPCP %d bytes", l);
 435                 STAT(tunnel_rx_errors);
 436                 return ;
 437         }
 438         if (*p == ConfigAck)
 439         {                          // happy with our IPCP
 440                 u8 r = session[s].radius;
 441                 if ((!r || radius[r].state == RADIUSIPCP) && !session[s].servicenet)
 442                         if (!r)
 443                                 r = radiusnew(s);
 444                         if (r)
 445                                 radiussend(r, RADIUSSTART); // send radius start, having got IPCP at last
 446                 return ;                 // done
 447         }
 448         if (*p != ConfigReq)
 449         {
 450                 log(1, 0, s, t, "Unexpected IPCP code %d\n", *p);
 451                 STAT(tunnel_rx_errors);
 452                 return ;
 453         }
 454         if (ntohs(*(u16 *) (p + 2)) > l)
 455         {
 456                 log(1, 0, s, t, "Length mismatch IPCP %d/%d\n", ntohs(*(u16 *) (p + 2)), l);
 457                 STAT(tunnel_rx_errors);
 458                 return ;
 459         }
 460         if (!session[s].ip)
 461         {
 462                 log(3, 0, s, t, "Waiting on radius reply\n");
 463                 return ;                   // have to wait on RADIUS eply
 464         }
 465         // form a config reply quoting the IP in the session
 466         {
 467                 u8 b[MAXCONTROL];
 468                 u8 *i,
 469                 *q;
 470
 471                 q = p + 4;
 472                 i = p + l;
 473                 while (q < i && q[1])
 474                 {
 475                         if (*q != 0x81 && *q != 0x83 && *q != 3)
 476                                 break;
 477                         q += q[1];
 478                 }
 479                 if (q < i)
 480                 {                       // reject
 481                         u16 n = 4;
 482                         i = p + l;
 483                         q = makeppp(b, p, l, t, s, PPPIPCP);
 484                         *q = ConfigRej;
 485                         p += 4;
 486                         while (p < i && p[1])
 487                         {
 488                                 if (*p != 0x81 && *p != 0x83 && *p != 3)
 489                                 {
 490                                         log(2, 0, s, t, "IPCP reject %d\n", *p);
 491                                         memcpy(q + n, p, p[1]);
 492                                         n += p[1];
 493                                 }
 494                                 p += p[1];
 495                         }
 496                         *(u16 *) (q + 2) = htons(n);
 497                         tunnelsend(b, n + (q - b), t); // send it
 498                 }
 499                 else
 500                 {
 501                         *p = ConfigAck;
 502                         i = findppp(p, 0x81); // Primary DNS address
 503                         if (i)
 504                         {
 505                                 if (*(u32 *) (i + 2) != htonl(session[s].dns1))
 506                                 {
 507                                         *(u32 *) (i + 2) = htonl(session[s].dns1);
 508                                         *p = ConfigNak;
 509                                 }
 510                         }
 511                         i = findppp(p, 0x83); // Secondary DNS address (TBA, is it)
 512                         if (i)
 513                         {
 514                                 if (*(u32 *) (i + 2) != htonl(session[s].dns2))
 515                                 {
 516                                         *(u32 *) (i + 2) = htonl(session[s].dns2);
 517                                         *p = ConfigNak;
 518                                 }
 519                         }
 520                         i = findppp(p, 3);   // IP address
 521                         if (!i || i[1] != 6)
 522                         {
 523                                 log(1, 0, s, t, "No IP in IPCP request\n");
 524                                 STAT(tunnel_rx_errors);
 525                                 return ;
 526                         }
 527                         if (*(u32 *) (i + 2) != htonl(session[s].ip))
 528                         {
 529                                 *(u32 *) (i + 2) = htonl(session[s].ip);
 530                                 *p = ConfigNak;
 531                         }
 532                         q = makeppp(b, p, l, t, s, PPPIPCP);
 533                         tunnelsend(b, l + (q - b), t); // send it
 534                 }
 535         }
 536 }
 537
 538 // process IP packet received
 539 void processipin(tunnelidt t, sessionidt s, u8 * p, u16 l)
 540 {
 541 #ifdef STAT_CALLS
 542         STAT(call_processipin);
 543 #endif
 544         log_hex(5, "IP", p, l);
 545
 546         if (l > MAXETHER)
 547         {
 548                 log(1, *(u32 *)(p + 12), s, t, "IP packet too long %d\n", l);
 549                 STAT(tunnel_rx_errors);
 550                 return ;
 551         }
 552
 553         session[s].cin += l;
 554         session[s].total_cin += l;
 555         session[s].pin++;
 556         eth_tx += l;
 557
 558         // Add on the tun header
 559         p -= 4;
 560         *(u32 *)p = htonl(0x00000800);
 561         l += 4;
 562
 563         // Plugin hook
 564         {
 565                 struct param_packet_rx packet = { &tunnel[t], &session[s], p, l };
 566                 run_plugins(PLUGIN_PACKET_TX, &packet);
 567         }
 568
 569         // send to ethernet
 570         if (write(tapfd, p, l) < 0)
 571         {
 572                 STAT(tap_tx_errors);
 573                 log(0, 0, s, t, "Error writing %d bytes to TAP device: %s (tapfd=%d, p=%p)\n",
 574                         l, strerror(errno), tapfd, p);
 575         }
 576
 577         if (session[s].snoop)
 578         {
 579                 // Snooping this session, send it to ASIO
 580                 snoop_send_packet(p, l);
 581         }
 582         STAT(tap_tx_packets);
 583         INC_STAT(tap_tx_bytes, l);
 584 }
 585
 586 // Process LCP messages
 587 void processccp(tunnelidt t, sessionidt s, u8 * p, u16 l)
 588 {
 589 #ifdef STAT_CALLS
 590         STAT(call_processccp);
 591 #endif
 592         log_hex(5, "CCP", p, l);
 593         if (l < 2 || (*p != ConfigReq && *p != TerminateReq))
 594         {
 595                 log(1, 0, s, t, "Unexpecetd CCP request code %d\n", *p);
 596                 STAT(tunnel_rx_errors);
 597                 return ;
 598         }
 599         // reject
 600         {
 601                 u8 b[MAXCONTROL];
 602                 u8 *q;
 603                 if (*p == ConfigReq)
 604                 {
 605                         if (l < 6)
 606                         {
 607                                 *p = ConfigAck;         // accept no compression
 608                         }
 609                         else
 610                         {
 611                                 *p = ConfigRej;        // reject
 612                         }
 613                 }
 614                 else
 615                         *p = TerminateAck;     // close
 616                 q = makeppp(b, p, l, t, s, PPPCCP);
 617                 tunnelsend(b, l + (q - b), t); // send it
 618         }
 619 }
 620
 621 // send a CHAP PP packet
 622 void sendchap(tunnelidt t, sessionidt s)
 623 {
 624         u8 b[MAXCONTROL];
 625         u8 r = session[s].radius;
 626         u8 *q;
 627 #ifdef STAT_CALLS
 628         STAT(call_sendchap);
 629 #endif
 630         if (!r)
 631         {
 632                 log(1, 0, s, t, "No RADIUS to send challenge\n");
 633                 STAT(tunnel_tx_errors);
 634                 return ;
 635         }
 636         log(1, 0, s, t, "Send CHAP challenge\n");
 637         {                            // new challenge
 638                 int n;
 639                 for (n = 0; n < 15; n++)
 640                         radius[r].auth[n] = rand();
 641         }
 642         radius[r].chap = 1;          // CHAP not PAP
 643         radius[r].id++;
 644         if (radius[r].state != RADIUSCHAP)
 645                 radius[r].try = 0;
 646         radius[r].state = RADIUSCHAP;
 647         radius[r].retry = backoff(radius[r].try++);
 648         if (radius[r].try > 5)
 649         {
 650                 sessionshutdown(s, "Timeout CHAP");
 651                 STAT(tunnel_tx_errors);
 652                 return ;
 653         }
 654         q = makeppp(b, 0, 0, t, s, PPPCHAP);
 655         *q = 1;                      // challenhe
 656         q[1] = radius[r].id;         // ID
 657         q[4] = 16;                   // length
 658         memcpy(q + 5, radius[r].auth, 16); // challenge
 659         strcpy(q + 21, hostname);    // our name
 660         *(u16 *) (q + 2) = htons(strlen(hostname) + 21); // length
 661         tunnelsend(b, strlen(hostname) + 21 + (q - b), t); // send it
 662 }
 663
 664 // fill in a L2TP message with a PPP frame,
 665 // copies existing PPP message and changes magic number if seen
 666 // returns start of PPP frame
 667 u8 *makeppp(u8 * b, u8 * p, int l, tunnelidt t, sessionidt s, u16 mtype)
 668 {
 669         *(u16 *) (b + 0) = htons(0x0002); // L2TP with no options
 670         *(u16 *) (b + 2) = htons(tunnel[t].far); // tunnel
 671         *(u16 *) (b + 4) = htons(session[s].far); // session
 672         b += 6;
 673         if (mtype != PPPLCP && !(session[s].flags & SESSIONACFC))
 674         {
 675                 *(u16 *) b = htons(0xFF03); // HDLC header
 676                 b += 2;
 677         }
 678         if (mtype < 0x100 && session[s].flags & SESSIONPFC)
 679                 *b++ = mtype;
 680         else
 681         {
 682                 *(u16 *) b = htons(mtype);
 683                 b += 2;
 684         }
 685         if (p && l)
 686                 memcpy(b, p, l);
 687         return b;
 688 }
 689
 690 // find a PPP option, returns point to option, or 0 if not found
 691 u8 *findppp(u8 * b, u8 mtype)
 692 {
 693         u16 l = ntohs(*(u16 *) (b + 2));
 694         if (l < 4)
 695                 return 0;
 696         b += 4;
 697         l -= 4;
 698         while (l)
 699         {
 700                 if (l < b[1] || !b[1])
 701                         return 0;            // faulty
 702                 if (*b == mtype)
 703                         return b;
 704                 l -= b[1];
 705                 b += b[1];
 706         }
 707         return 0;
 708 }
 709
 710 // Send initial LCP ConfigReq
 711 void initlcp(tunnelidt t, sessionidt s)
 712 {
 713         char b[500] = {0}, *q;
 714
 715         q = makeppp(b, NULL, 0, t, s, PPPLCP);
 716         log(4, 0, s, t, "Sending LCP ConfigReq for PAP\n");
 717         *q = ConfigReq;
 718         *(u8 *)(q + 1) = (time_now % 255) + 1; // ID
 719         *(u16 *)(q + 2) = htons(8); // Length
 720         *(u8 *)(q + 4) = 3;
 721         *(u8 *)(q + 5) = 4;
 722         *(u16 *)(q + 6) = htons(0xC023); // PAP
 723         tunnelsend(b, 12 + 8, t);
 724 }
 725