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   1 /*
   2     utcp.c -- Userspace TCP
   3     Copyright (C) 2014 Guus Sliepen <guus@tinc-vpn.org>
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License along
  16     with this program; if not, write to the Free Software Foundation, Inc.,
  17     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 */
  19
  20 #define _GNU_SOURCE
  21
  22 #include <errno.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <stdint.h>
  26 #include <stdbool.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29 #include <sys/time.h>
  30 #include <sys/socket.h>
  31
  32 #define UTCP_INTERNAL
  33 #include "utcp.h"
  34
  35 #define PREP(l) char pkt[(l) + sizeof struct hdr]; struct hdr *hdr = &pkt;
  36
  37 #define SYN 1
  38 #define ACK 2
  39 #define FIN 4
  40 #define RST 8
  41
  42 struct hdr {
  43         uint16_t src; // Source port
  44         uint16_t dst; // Destination port
  45         uint32_t seq; // Sequence number
  46         uint32_t ack; // Acknowledgement number
  47         uint32_t wnd; // Window size
  48         uint16_t ctl; // Flags (SYN, ACK, FIN, RST)
  49         uint16_t aux; // other stuff
  50 };
  51
  52 enum state {
  53         CLOSED,
  54         LISTEN,
  55         SYN_SENT,
  56         SYN_RECEIVED,
  57         ESTABLISHED,
  58         FIN_WAIT_1,
  59         FIN_WAIT_2,
  60         CLOSE_WAIT,
  61         CLOSING,
  62         LAST_ACK,
  63         TIME_WAIT
  64 };
  65
  66 const char *strstate[] = {
  67         "CLOSED",
  68         "LISTEN",
  69         "SYN_SENT",
  70         "SYN_RECEIVED",
  71         "ESTABLISHED",
  72         "FIN_WAIT_1",
  73         "FIN_WAIT_2",
  74         "CLOSE_WAIT",
  75         "CLOSING",
  76         "LAST_ACK",
  77         "TIME_WAIT"
  78 };
  79
  80 struct utcp_connection {
  81         void *priv;
  82         struct utcp *utcp;
  83         bool reapable;
  84
  85         uint16_t src;
  86         uint16_t dst;
  87         enum state state;
  88
  89         // The following two structures form the TCB
  90
  91         struct {
  92                 uint32_t una;
  93                 uint32_t nxt;
  94                 uint32_t wnd;
  95                 uint32_t up;
  96                 uint32_t wl1;
  97                 uint32_t wl2;
  98                 uint32_t iss;
  99         } snd;
 100
 101         struct {
 102                 uint32_t nxt;
 103                 uint32_t wnd;
 104                 uint32_t up;
 105                 uint32_t irs;
 106         } rcv;
 107
 108         utcp_recv_t recv;
 109
 110         struct timeval conn_timeout;
 111         struct timeval rtrx_timeout;
 112
 113         char *sndbuf;
 114         uint32_t sndbufsize;
 115 };
 116
 117 struct utcp {
 118         void *priv;
 119
 120         utcp_accept_t accept;
 121         utcp_pre_accept_t pre_accept;
 122         utcp_send_t send;
 123
 124         uint16_t mtu;
 125
 126         struct utcp_connection **connections;
 127         int nconnections;
 128         int nallocated;
 129         int gap;
 130 };
 131
 132 static void set_state(struct utcp_connection *c, enum state state) {
 133         c->state = state;
 134         fprintf(stderr, "%p new state: %s\n", c->utcp, strstate[state]);
 135 }
 136
 137 static void print_packet(void *pkt, size_t len) {
 138         struct hdr hdr;
 139         if(len < sizeof hdr) {
 140                 fprintf(stderr, "short packet (%zu bytes)\n", len);
 141                 return;
 142         }
 143
 144         memcpy(&hdr, pkt, sizeof hdr);
 145         fprintf (stderr, "src=%u dst=%u seq=%u ack=%u wnd=%u ctl=", hdr.src, hdr.dst, hdr.seq, hdr.ack, hdr.wnd);
 146         if(hdr.ctl & SYN)
 147                 fprintf(stderr, "SYN");
 148         if(hdr.ctl & RST)
 149                 fprintf(stderr, "RST");
 150         if(hdr.ctl & FIN)
 151                 fprintf(stderr, "FIN");
 152         if(hdr.ctl & ACK)
 153                 fprintf(stderr, "ACK");
 154
 155         if(len > sizeof hdr) {
 156                 fprintf(stderr, " data=");
 157                 for(int i = sizeof hdr; i < len; i++) {
 158                         char *data = pkt;
 159                         fprintf(stderr, "%c", data[i] >= 32 ? data[i] : '.');
 160                 }
 161         }
 162
 163         fprintf(stderr, "\n");
 164 }
 165
 166 static void list_connections(struct utcp *utcp) {
 167         fprintf(stderr, "%p has %d connections:\n", utcp, utcp->nconnections);
 168         for(int i = 0; i < utcp->nconnections; i++)
 169                 fprintf(stderr, "  %u -> %u state %s\n", utcp->connections[i]->src, utcp->connections[i]->dst, strstate[utcp->connections[i]->state]);
 170 }
 171
 172 // Connections are stored in a sorted list.
 173 // This gives O(log(N)) lookup time, O(N log(N)) insertion time and O(N) deletion time.
 174
 175 static int compare(const void *va, const void *vb) {
 176         const struct utcp_connection *a = *(struct utcp_connection **)va;
 177         const struct utcp_connection *b = *(struct utcp_connection **)vb;
 178         if(!a->src || !b->src)
 179                 abort();
 180         int c = (int)a->src - (int)b->src;
 181         if(c)
 182                 return c;
 183         c = (int)a->dst - (int)b->dst;
 184         return c;
 185 }
 186
 187 static struct utcp_connection *find_connection(const struct utcp *utcp, uint16_t src, uint16_t dst) {
 188         if(!utcp->nconnections)
 189                 return NULL;
 190         struct utcp_connection key = {
 191                 .src = src,
 192                 .dst = dst,
 193         }, *keyp = &key;
 194         struct utcp_connection **match = bsearch(&keyp, utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
 195         return match ? *match : NULL;
 196 }
 197
 198 static void free_connection(struct utcp_connection *c) {
 199         struct utcp *utcp = c->utcp;
 200         struct utcp_connection **cp = bsearch(&c, utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
 201         if(!cp)
 202                 abort();
 203
 204         int i = cp - utcp->connections;
 205         memmove(cp + i, cp + i + 1, (utcp->nconnections - i - 1) * sizeof *cp);
 206         utcp->nconnections--;
 207
 208         free(c);
 209 }
 210
 211 static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t src, uint16_t dst) {
 212         // Check whether this combination of src and dst is free
 213
 214         if(src) {
 215                 if(find_connection(utcp, src, dst)) {
 216                         errno = EADDRINUSE;
 217                         return NULL;
 218                 }
 219         } else { // If src == 0, generate a random port number with the high bit set
 220                 if(utcp->nconnections >= 32767) {
 221                         errno = ENOMEM;
 222                         return NULL;
 223                 }
 224                 src = rand() | 0x8000;
 225                 while(find_connection(utcp, src, dst))
 226                         src++;
 227         }
 228
 229         // Allocate memory for the new connection
 230
 231         if(utcp->nconnections >= utcp->nallocated) {
 232                 if(!utcp->nallocated)
 233                         utcp->nallocated = 4;
 234                 else
 235                         utcp->nallocated *= 2;
 236                 struct utcp_connection **new_array = realloc(utcp->connections, utcp->nallocated * sizeof *utcp->connections);
 237                 if(!new_array) {
 238                         errno = ENOMEM;
 239                         return NULL;
 240                 }
 241                 utcp->connections = new_array;
 242         }
 243
 244         struct utcp_connection *c = calloc(1, sizeof *c);
 245         if(!c) {
 246                 errno = ENOMEM;
 247                 return NULL;
 248         }
 249
 250         // Fill in the details
 251
 252         c->src = src;
 253         c->dst = dst;
 254         c->snd.iss = rand();
 255         c->snd.una = c->snd.iss;
 256         c->snd.nxt = c->snd.iss + 1;
 257         c->rcv.wnd = utcp->mtu;
 258         c->utcp = utcp;
 259         c->sndbufsize = 65536;
 260         c->sndbuf = malloc(c->sndbufsize);
 261         if(!c->sndbuf)
 262                 c->sndbufsize = 0;
 263
 264         // Add it to the sorted list of connections
 265
 266         utcp->connections[utcp->nconnections++] = c;
 267         qsort(utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
 268
 269         return c;
 270 }
 271
 272 struct utcp_connection *utcp_connect(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv) {
 273         struct utcp_connection *c = allocate_connection(utcp, 0, dst);
 274         if(!c)
 275                 return NULL;
 276
 277         c->recv = recv;
 278
 279         struct hdr hdr;
 280
 281         hdr.src = c->src;
 282         hdr.dst = c->dst;
 283         hdr.seq = c->snd.iss;
 284         hdr.ack = 0;
 285         hdr.ctl = SYN;
 286         hdr.wnd = c->rcv.wnd;
 287
 288         set_state(c, SYN_SENT);
 289
 290         utcp->send(utcp, &hdr, sizeof hdr);
 291
 292         // Set timeout?
 293
 294         return c;
 295 }
 296
 297 void utcp_accept(struct utcp_connection *c, utcp_recv_t recv, void *priv) {
 298         if(c->reapable || c->state != SYN_RECEIVED) {
 299                 fprintf(stderr, "Error: accept() called on invalid connection %p in state %s\n", c, strstate[c->state]);
 300                 return;
 301         }
 302
 303         fprintf(stderr, "%p accepted, %p %p\n", c, recv, priv);
 304         c->recv = recv;
 305         c->priv = priv;
 306         set_state(c, ESTABLISHED);
 307 }
 308
 309 ssize_t utcp_send(struct utcp_connection *c, void *data, size_t len) {
 310         if(c->reapable) {
 311                 fprintf(stderr, "Error: send() called on closed connection %p\n", c);
 312                 errno = EBADF;
 313                 return -1;
 314         }
 315
 316         switch(c->state) {
 317         case CLOSED:
 318         case LISTEN:
 319         case SYN_SENT:
 320         case SYN_RECEIVED:
 321                 fprintf(stderr, "Error: send() called on unconnected connection %p\n", c);
 322                 errno = ENOTCONN;
 323                 return -1;
 324         case ESTABLISHED:
 325         case CLOSE_WAIT:
 326                 break;
 327         case FIN_WAIT_1:
 328         case FIN_WAIT_2:
 329         case CLOSING:
 330         case LAST_ACK:
 331         case TIME_WAIT:
 332                 fprintf(stderr, "Error: send() called on closing connection %p\n", c);
 333                 errno = EPIPE;
 334                 return -1;
 335         }
 336
 337         // Add data to send buffer
 338
 339         if(!len)
 340                 return 0;
 341
 342         if(!data) {
 343                 errno = EFAULT;
 344                 return -1;
 345         }
 346
 347         uint32_t bufused = c->snd.nxt - c->snd.una;
 348
 349         if(len > c->sndbufsize - bufused)
 350                 len = c->sndbufsize - bufused;
 351
 352         memcpy(c->sndbuf + (c->snd.nxt - c->snd.una), data, len);
 353
 354         // Send segments
 355
 356         struct {
 357                 struct hdr hdr;
 358                 char data[c->utcp->mtu];
 359         } pkt;
 360
 361         pkt.hdr.src = c->src;
 362         pkt.hdr.dst = c->dst;
 363         pkt.hdr.ack = c->rcv.nxt;
 364         pkt.hdr.wnd = c->snd.wnd;
 365         pkt.hdr.ctl = ACK;
 366
 367         uint32_t left = len;
 368
 369         while(left) {
 370                 uint32_t seglen = left > c->utcp->mtu ? c->utcp->mtu : left;
 371                 pkt.hdr.seq = c->snd.nxt;
 372
 373                 memcpy(pkt.data, data, seglen);
 374
 375                 c->snd.nxt += seglen;
 376                 data += seglen;
 377                 left -= seglen;
 378
 379                 c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + seglen);
 380         }
 381
 382         fprintf(stderr, "len=%u\n", len);
 383         return len;
 384 }
 385
 386 static void swap_ports(struct hdr *hdr) {
 387         uint16_t tmp = hdr->src;
 388         hdr->src = hdr->dst;
 389         hdr->dst = tmp;
 390 }
 391
 392 static int16_t seqdiff(uint16_t a, uint16_t b) {
 393         return a -b;
 394 }
 395
 396 int utcp_recv(struct utcp *utcp, void *data, size_t len) {
 397         if(!utcp) {
 398                 errno = EFAULT;
 399                 return -1;
 400         }
 401
 402         if(!len)
 403                 return 0;
 404
 405         if(!data) {
 406                 errno = EFAULT;
 407                 return -1;
 408         }
 409
 410         fprintf(stderr, "%p got: ", utcp);
 411         print_packet(data, len);
 412
 413         struct hdr hdr;
 414         if(len < sizeof hdr) {
 415                 errno = EBADMSG;
 416                 return -1;
 417         }
 418
 419         memcpy(&hdr, data, sizeof hdr);
 420         data += sizeof hdr;
 421         len -= sizeof hdr;
 422
 423         if(hdr.ctl & ~(SYN | ACK | RST | FIN)) {
 424                 errno = EBADMSG;
 425                 return -1;
 426         }
 427
 428         //list_connections(utcp);
 429
 430         struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
 431
 432         // Is it for a new connection?
 433
 434         if(!c) {
 435                 if(hdr.ctl & RST)
 436                         return 0;
 437
 438                 if(hdr.ctl & SYN && !(hdr.ctl & ACK) && utcp->accept && (!utcp->pre_accept || utcp->pre_accept(utcp, hdr.dst)) && (c = allocate_connection(utcp, hdr.dst, hdr.src))) { // LISTEN
 439                         // Return SYN+ACK
 440                         c->snd.wnd = hdr.wnd;
 441                         c->rcv.irs = hdr.seq;
 442                         c->rcv.nxt = c->rcv.irs + 1;
 443                         set_state(c, SYN_RECEIVED);
 444
 445                         hdr.dst = c->dst;
 446                         hdr.src = c->src;
 447                         hdr.ack = c->rcv.irs + 1;
 448                         hdr.seq = c->snd.iss;
 449                         hdr.ctl = SYN | ACK;
 450                         utcp->send(utcp, &hdr, sizeof hdr);
 451                         return 0;
 452                 } else { // CLOSED
 453                         len = 1;
 454                         goto reset;
 455                 }
 456         }
 457
 458         fprintf(stderr, "%p state %s\n", c->utcp, strstate[c->state]);
 459
 460         if(c->state == CLOSED) {
 461                 fprintf(stderr, "Error: packet recv()d on closed connection %p\n", c);
 462                 errno = EBADF;
 463                 return -1;
 464         }
 465
 466         // It is for an existing connection.
 467
 468         if(c->state == SYN_SENT) {
 469                 if(hdr.ctl & ACK) {
 470                         if(seqdiff(hdr.ack, c->snd.iss) <= 0 || seqdiff(hdr.ack, c->snd.nxt) > 0) {
 471                                 fprintf(stderr, "Invalid ACK, %u %u %u\n", hdr.ack, c->snd.iss, c->snd.nxt);
 472                                 goto reset;
 473                         }
 474                 }
 475                 if(hdr.ctl & RST) {
 476                         if(!(hdr.ctl & ACK))
 477                                 return 0;
 478                         set_state(c, CLOSED);
 479                         errno = ECONNREFUSED;
 480                         c->recv(c, NULL, 0);
 481                         return 0;
 482                 }
 483                 if(hdr.ctl & SYN) {
 484                         c->dst = hdr.src;
 485                         c->rcv.nxt = hdr.seq + 1;
 486                         c->rcv.irs = hdr.seq;
 487                         c->snd.wnd = hdr.wnd;
 488
 489                         if(hdr.ctl & ACK)
 490                                 c->snd.una = hdr.ack;
 491                         if(seqdiff(c->snd.una, c->snd.iss) > 0) {
 492                                 set_state(c, ESTABLISHED);
 493                                 // TODO: signal app?
 494                                 swap_ports(&hdr);
 495                                 hdr.seq = c->snd.nxt;
 496                                 hdr.ack = c->rcv.nxt;
 497                                 hdr.ctl = ACK;
 498                         } else {
 499                                 set_state(c, SYN_RECEIVED);
 500                                 swap_ports(&hdr);
 501                                 hdr.seq = c->snd.iss;
 502                                 hdr.ack = c->rcv.nxt;
 503                                 hdr.ctl = SYN | ACK;
 504                         }
 505                         utcp->send(utcp, &hdr, sizeof hdr);
 506                         // TODO: queue any data?
 507                 }
 508
 509                 return 0;
 510         }
 511
 512         bool acceptable;
 513
 514         if(len == 0)
 515                 if(c->rcv.wnd == 0)
 516                         acceptable = hdr.seq == c->rcv.nxt;
 517                 else
 518                         acceptable = (hdr.seq >= c->rcv.nxt && hdr.seq < c->rcv.nxt + c->rcv.wnd);
 519         else
 520                 if(c->rcv.wnd == 0)
 521                         acceptable = false;
 522                 else
 523                         acceptable = (hdr.seq >= c->rcv.nxt && hdr.seq < c->rcv.nxt + c->rcv.wnd)
 524                                 || (hdr.seq + len - 1 >= c->rcv.nxt && hdr.seq + len - 1 < c->rcv.nxt + c->rcv.wnd);
 525
 526         if(!acceptable) {
 527                 fprintf(stderr, "Packet not acceptable, %u %u %u %zu\n", hdr.seq, c->rcv.nxt, c->rcv.wnd, len);
 528                 if(hdr.ctl & RST)
 529                         return 0;
 530                 goto ack_and_drop;
 531         }
 532
 533         c->snd.wnd = hdr.wnd;
 534
 535         // TODO: check whether segment really starts at rcv.nxt, otherwise trim it.
 536
 537         if(hdr.ctl & RST) {
 538                 switch(c->state) {
 539                 case SYN_RECEIVED:
 540                         // TODO: delete connection?
 541                         break;
 542                 case ESTABLISHED:
 543                 case FIN_WAIT_1:
 544                 case FIN_WAIT_2:
 545                 case CLOSE_WAIT:
 546                         set_state(c, CLOSED);
 547                         errno = ECONNRESET;
 548                         c->recv(c, NULL, 0);
 549                         break;
 550                 case CLOSING:
 551                 case LAST_ACK:
 552                 case TIME_WAIT:
 553                         // TODO: delete connection?
 554                         break;
 555                 default:
 556                         // TODO: wtf?
 557                         return 0;
 558                 }
 559                 set_state(c, CLOSED);
 560                 return 0;
 561         }
 562
 563         if(hdr.ctl & SYN) {
 564                 switch(c->state) {
 565                 case SYN_RECEIVED:
 566                 case ESTABLISHED:
 567                 case FIN_WAIT_1:
 568                 case FIN_WAIT_2:
 569                 case CLOSE_WAIT:
 570                 case CLOSING:
 571                 case LAST_ACK:
 572                 case TIME_WAIT:
 573                         set_state(c, CLOSED);
 574                         errno = ECONNRESET;
 575                         c->recv(c, NULL, 0);
 576                         goto reset;
 577                         break;
 578                 default:
 579                         // TODO: wtf?
 580                         return 0;
 581                 }
 582         }
 583
 584         if(!(hdr.ctl & ACK))
 585                 return 0;
 586
 587         switch(c->state) {
 588         case SYN_RECEIVED:
 589                 if(seqdiff(hdr.ack, c->snd.una) >= 0 && seqdiff(hdr.ack, c->snd.nxt) <= 0)
 590                         c->utcp->accept(c, hdr.dst);
 591
 592                 if(c->state != ESTABLISHED)
 593                         goto reset;
 594                 break;
 595         case ESTABLISHED:
 596         case CLOSE_WAIT:
 597                 if(seqdiff(hdr.ack, c->snd.una) < 0)
 598                         return 0;
 599                 if(seqdiff(hdr.ack, c->snd.nxt) > 0)
 600                         goto ack_and_drop;
 601                 if(seqdiff(hdr.ack, c->snd.una) > 0 && seqdiff(hdr.ack, c->snd.nxt) <= 0) {
 602                         c->snd.una = hdr.ack;
 603                         if(seqdiff(c->snd.wl1, hdr.seq) < 0 || (c->snd.wl1 == hdr.seq && seqdiff(c->snd.wl2, hdr.ack) <= 0)) {
 604                                 c->snd.wnd = hdr.wnd;
 605                                 c->snd.wl1 = hdr.seq;
 606                                 c->snd.wl2 = hdr.ack;
 607                         }
 608                 }
 609                 break;
 610         case FIN_WAIT_1:
 611                 if(hdr.ack == c->snd.nxt)
 612                         set_state(c, FIN_WAIT_2);
 613                 break;
 614         case FIN_WAIT_2:
 615                 // TODO: If nothing left to send, close.
 616                 break;
 617         case CLOSING:
 618                 if(hdr.ack == c->snd.nxt) {
 619                         set_state(c, TIME_WAIT);
 620                 }
 621                 break;
 622         case LAST_ACK:
 623                 if(hdr.ack == c->snd.nxt) {
 624                         set_state(c, CLOSED);
 625                 }
 626                 return 0;
 627         case TIME_WAIT:
 628                 // TODO: retransmission of remote FIN, ACK and restart 2 MSL timeout
 629                 break;
 630         default:
 631                 goto reset;
 632         }
 633
 634         // Process data
 635
 636         switch(c->state) {
 637         case ESTABLISHED:
 638         case FIN_WAIT_1:
 639         case FIN_WAIT_2:
 640                 // TODO: process the data, see page 74
 641                 break;
 642         case CLOSE_WAIT:
 643         case CLOSING:
 644         case LAST_ACK:
 645         case TIME_WAIT:
 646                 break;
 647         default:
 648                 abort();
 649         }
 650
 651         if(hdr.ctl & FIN) {
 652                 switch(c->state) {
 653                 case CLOSED:
 654                 case LISTEN:
 655                 case SYN_SENT:
 656                         return 0;
 657                 case SYN_RECEIVED:
 658                 case ESTABLISHED:
 659                         set_state(c, CLOSE_WAIT);
 660                         c->rcv.nxt++;
 661                         goto ack_and_drop;
 662                 case FIN_WAIT_1:
 663                         set_state(c, CLOSING);
 664                         c->rcv.nxt++;
 665                         goto ack_and_drop;
 666                 case FIN_WAIT_2:
 667                         set_state(c, TIME_WAIT);
 668                         c->rcv.nxt++;
 669                         goto ack_and_drop;
 670                 case CLOSE_WAIT:
 671                 case CLOSING:
 672                 case LAST_ACK:
 673                 case TIME_WAIT:
 674                         break;
 675                 default:
 676                         abort();
 677                 }
 678         }
 679
 680         // Process the data
 681
 682         if(len && c->recv) {
 683                 c->recv(c, data, len);
 684                 c->rcv.nxt += len;
 685                 goto ack_and_drop;
 686         }
 687
 688         return 0;
 689
 690 reset:
 691         swap_ports(&hdr);
 692         hdr.wnd = 0;
 693         if(hdr.ctl & ACK) {
 694                 hdr.seq = hdr.ack;
 695                 hdr.ctl = RST;
 696         } else {
 697                 hdr.ack = hdr.seq + len;
 698                 hdr.seq = 0;
 699                 hdr.ctl = RST | ACK;
 700         }
 701         utcp->send(utcp, &hdr, sizeof hdr);
 702         return 0;
 703
 704 ack_and_drop:
 705         swap_ports(&hdr);
 706         hdr.seq = c->snd.nxt;
 707         hdr.ack = c->rcv.nxt;
 708         hdr.ctl = ACK;
 709         utcp->send(utcp, &hdr, sizeof hdr);
 710         if(c->state == CLOSE_WAIT || c->state == TIME_WAIT) {
 711                 errno = 0;
 712                 c->recv(c, NULL, 0);
 713         }
 714         return 0;
 715 }
 716
 717 int utcp_shutdown(struct utcp_connection *c, int dir) {
 718         if(!c) {
 719                 errno = EFAULT;
 720                 return -1;
 721         }
 722
 723         if(c->reapable) {
 724                 fprintf(stderr, "Error: shutdown() called on closed connection %p\n", c);
 725                 errno = EBADF;
 726                 return -1;
 727         }
 728
 729         // TODO: handle dir
 730
 731         switch(c->state) {
 732         case CLOSED:
 733                 return 0;
 734         case LISTEN:
 735         case SYN_SENT:
 736                 set_state(c, CLOSED);
 737                 return 0;
 738
 739         case SYN_RECEIVED:
 740         case ESTABLISHED:
 741                 set_state(c, FIN_WAIT_1);
 742                 break;
 743         case FIN_WAIT_1:
 744         case FIN_WAIT_2:
 745                 return 0;
 746         case CLOSE_WAIT:
 747                 set_state(c, LAST_ACK);
 748                 break;
 749
 750         case CLOSING:
 751         case LAST_ACK:
 752         case TIME_WAIT:
 753                 return 0;
 754         }
 755
 756         // Send FIN
 757
 758         struct hdr hdr;
 759
 760         hdr.src = c->src;
 761         hdr.dst = c->dst;
 762         hdr.seq = c->snd.nxt;
 763         hdr.ack = c->rcv.nxt;
 764         hdr.wnd = c->snd.wnd;
 765         hdr.ctl = FIN | ACK;
 766
 767         c->snd.nxt += 1;
 768
 769         c->utcp->send(c->utcp, &hdr, sizeof hdr);
 770         return 0;
 771 }
 772
 773 int utcp_close(struct utcp_connection *c) {
 774         if(utcp_shutdown(c, SHUT_RDWR))
 775                 return -1;
 776         c->reapable = true;
 777         return 0;
 778 }
 779
 780 int utcp_abort(struct utcp_connection *c) {
 781         if(!c) {
 782                 errno = EFAULT;
 783                 return -1;
 784         }
 785
 786         if(c->reapable) {
 787                 fprintf(stderr, "Error: abort() called on closed connection %p\n", c);
 788                 errno = EBADF;
 789                 return -1;
 790         }
 791
 792         c->reapable = true;
 793
 794         switch(c->state) {
 795         case CLOSED:
 796                 return 0;
 797         case LISTEN:
 798         case SYN_SENT:
 799         case CLOSING:
 800         case LAST_ACK:
 801         case TIME_WAIT:
 802                 set_state(c, CLOSED);
 803                 return 0;
 804
 805         case SYN_RECEIVED:
 806         case ESTABLISHED:
 807         case FIN_WAIT_1:
 808         case FIN_WAIT_2:
 809         case CLOSE_WAIT:
 810                 set_state(c, CLOSED);
 811                 break;
 812         }
 813
 814         // Send RST
 815
 816         struct hdr hdr;
 817
 818         hdr.src = c->src;
 819         hdr.dst = c->dst;
 820         hdr.seq = c->snd.nxt;
 821         hdr.ack = 0;
 822         hdr.wnd = 0;
 823         hdr.ctl = RST;
 824
 825         c->utcp->send(c->utcp, &hdr, sizeof hdr);
 826         return 0;
 827 }
 828
 829 void utcp_timeout(struct utcp *utcp) {
 830         struct timeval now;
 831         gettimeofday(&now, NULL);
 832
 833         for(int i = 0; i < utcp->nconnections; i++) {
 834                 struct utcp_connection *c = utcp->connections[i];
 835                 if(!c)
 836                         continue;
 837
 838                 if(c->reapable) {
 839                         fprintf(stderr, "Reaping %p\n", c);
 840                         free_connection(c);
 841                         continue;
 842                 }
 843
 844                 if(c->state == CLOSED)
 845                         return;
 846
 847                 if(c->conn_timeout.tv_sec && timercmp(&c->conn_timeout, &now, <)) {
 848                         if(!c->reapable) {
 849                                 errno = ETIMEDOUT;
 850                                 c->recv(c, NULL, 0);
 851                         }
 852                         c->state = CLOSED;
 853                         return;
 854                 }
 855
 856                 if(c->rtrx_timeout.tv_sec && timercmp(&c->rtrx_timeout, &now, <)) {
 857                         // TODO: retransmit stuff;
 858                 }
 859         }
 860 }
 861
 862 struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_send_t send, void *priv) {
 863         struct utcp *utcp = calloc(1, sizeof *utcp);
 864         if(!utcp)
 865                 return NULL;
 866
 867         utcp->accept = accept;
 868         utcp->pre_accept = pre_accept;
 869         utcp->send = send;
 870         utcp->priv = priv;
 871         utcp->gap = -1;
 872         utcp->mtu = 1000;
 873
 874         return utcp;
 875 }
 876
 877 void utcp_exit(struct utcp *utcp) {
 878         if(!utcp)
 879                 return;
 880         for(int i = 0; i < utcp->nconnections; i++)
 881                 free_connection(utcp->connections[i]);
 882         free(utcp);
 883 }