git.meshlink.io Git - utcp/blob - utcp.c

   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
 260         // Add it to the sorted list of connections
 261
 262         utcp->connections[utcp->nconnections++] = c;
 263         qsort(utcp->connections, utcp->nconnections, sizeof *utcp->connections, compare);
 264
 265         return c;
 266 }
 267
 268 struct utcp_connection *utcp_connect(struct utcp *utcp, uint16_t dst, utcp_recv_t recv, void *priv) {
 269         struct utcp_connection *c = allocate_connection(utcp, 0, dst);
 270         if(!c)
 271                 return NULL;
 272
 273         c->recv = recv;
 274
 275         struct hdr hdr;
 276
 277         hdr.src = c->src;
 278         hdr.dst = c->dst;
 279         hdr.seq = c->snd.iss;
 280         hdr.ack = 0;
 281         hdr.ctl = SYN;
 282         hdr.wnd = c->rcv.wnd;
 283
 284         set_state(c, SYN_SENT);
 285
 286         utcp->send(utcp, &hdr, sizeof hdr);
 287
 288         // Set timeout?
 289
 290         return c;
 291 }
 292
 293 void utcp_accept(struct utcp_connection *c, utcp_recv_t recv, void *priv) {
 294         if(c->reapable || c->state != SYN_RECEIVED) {
 295                 fprintf(stderr, "Error: accept() called on invalid connection %p in state %s\n", c, strstate[c->state]);
 296                 return;
 297         }
 298
 299         fprintf(stderr, "%p accepted, %p %p\n", c, recv, priv);
 300         c->recv = recv;
 301         c->priv = priv;
 302         set_state(c, ESTABLISHED);
 303 }
 304
 305 int utcp_send(struct utcp_connection *c, void *data, size_t len) {
 306         if(c->reapable) {
 307                 fprintf(stderr, "Error: send() called on closed connection %p\n", c);
 308                 errno = EBADF;
 309                 return -1;
 310         }
 311
 312         switch(c->state) {
 313         case CLOSED:
 314         case LISTEN:
 315         case SYN_SENT:
 316         case SYN_RECEIVED:
 317                 fprintf(stderr, "Error: send() called on unconnected connection %p\n", c);
 318                 errno = ENOTCONN;
 319                 return -1;
 320         case ESTABLISHED:
 321         case CLOSE_WAIT:
 322                 break;
 323         case FIN_WAIT_1:
 324         case FIN_WAIT_2:
 325         case CLOSING:
 326         case LAST_ACK:
 327         case TIME_WAIT:
 328                 fprintf(stderr, "Error: send() called on closing connection %p\n", c);
 329                 errno = EPIPE;
 330                 return -1;
 331         }
 332
 333         if(!len)
 334                 return 0;
 335
 336         if(!data) {
 337                 errno = EFAULT;
 338                 return -1;
 339         }
 340
 341
 342         struct {
 343                 struct hdr hdr;
 344                 char data[len];
 345         } pkt;
 346
 347         pkt.hdr.src = c->src;
 348         pkt.hdr.dst = c->dst;
 349         pkt.hdr.seq = c->snd.nxt;
 350         pkt.hdr.ack = c->rcv.nxt;
 351         pkt.hdr.wnd = c->snd.wnd;
 352         pkt.hdr.ctl = ACK;
 353
 354         memcpy(pkt.data, data, len);
 355
 356         c->snd.nxt += len;
 357
 358         c->utcp->send(c->utcp, &pkt, sizeof pkt.hdr + len);
 359         //
 360         // Can we add it to the send window?
 361
 362         // Do we need to kick some timers?
 363
 364         return 0;
 365 }
 366
 367 static void swap_ports(struct hdr *hdr) {
 368         uint16_t tmp = hdr->src;
 369         hdr->src = hdr->dst;
 370         hdr->dst = tmp;
 371 }
 372
 373 static int16_t seqdiff(uint16_t a, uint16_t b) {
 374         return a -b;
 375 }
 376
 377 int utcp_recv(struct utcp *utcp, void *data, size_t len) {
 378         if(!utcp) {
 379                 errno = EFAULT;
 380                 return -1;
 381         }
 382
 383         if(!len)
 384                 return 0;
 385
 386         if(!data) {
 387                 errno = EFAULT;
 388                 return -1;
 389         }
 390
 391         fprintf(stderr, "%p got: ", utcp);
 392         print_packet(data, len);
 393
 394         struct hdr hdr;
 395         if(len < sizeof hdr) {
 396                 errno = EBADMSG;
 397                 return -1;
 398         }
 399
 400         memcpy(&hdr, data, sizeof hdr);
 401         data += sizeof hdr;
 402         len -= sizeof hdr;
 403
 404         if(hdr.ctl & ~(SYN | ACK | RST | FIN)) {
 405                 errno = EBADMSG;
 406                 return -1;
 407         }
 408
 409         //list_connections(utcp);
 410
 411         struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
 412
 413         // Is it for a new connection?
 414
 415         if(!c) {
 416                 if(hdr.ctl & RST)
 417                         return 0;
 418
 419                 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
 420                         // Return SYN+ACK
 421                         c->snd.wnd = hdr.wnd;
 422                         c->rcv.irs = hdr.seq;
 423                         c->rcv.nxt = c->rcv.irs + 1;
 424                         set_state(c, SYN_RECEIVED);
 425
 426                         hdr.dst = c->dst;
 427                         hdr.src = c->src;
 428                         hdr.ack = c->rcv.irs + 1;
 429                         hdr.seq = c->snd.iss;
 430                         hdr.ctl = SYN | ACK;
 431                         utcp->send(utcp, &hdr, sizeof hdr);
 432                         return 0;
 433                 } else { // CLOSED
 434                         len = 1;
 435                         goto reset;
 436                 }
 437         }
 438
 439         fprintf(stderr, "%p state %s\n", c->utcp, strstate[c->state]);
 440
 441         if(c->state == CLOSED) {
 442                 fprintf(stderr, "Error: packet recv()d on closed connection %p\n", c);
 443                 errno = EBADF;
 444                 return -1;
 445         }
 446
 447         // It is for an existing connection.
 448
 449         if(c->state == SYN_SENT) {
 450                 if(hdr.ctl & ACK) {
 451                         if(seqdiff(hdr.ack, c->snd.iss) <= 0 || seqdiff(hdr.ack, c->snd.nxt) > 0) {
 452                                 fprintf(stderr, "Invalid ACK, %u %u %u\n", hdr.ack, c->snd.iss, c->snd.nxt);
 453                                 goto reset;
 454                         }
 455                 }
 456                 if(hdr.ctl & RST) {
 457                         if(!(hdr.ctl & ACK))
 458                                 return 0;
 459                         set_state(c, CLOSED);
 460                         errno = ECONNREFUSED;
 461                         c->recv(c, NULL, 0);
 462                         return 0;
 463                 }
 464                 if(hdr.ctl & SYN) {
 465                         c->dst = hdr.src;
 466                         c->rcv.nxt = hdr.seq + 1;
 467                         c->rcv.irs = hdr.seq;
 468                         c->snd.wnd = hdr.wnd;
 469
 470                         if(hdr.ctl & ACK)
 471                                 c->snd.una = hdr.ack;
 472                         if(seqdiff(c->snd.una, c->snd.iss) > 0) {
 473                                 set_state(c, ESTABLISHED);
 474                                 // TODO: signal app?
 475                                 swap_ports(&hdr);
 476                                 hdr.seq = c->snd.nxt;
 477                                 hdr.ack = c->rcv.nxt;
 478                                 hdr.ctl = ACK;
 479                         } else {
 480                                 set_state(c, SYN_RECEIVED);
 481                                 swap_ports(&hdr);
 482                                 hdr.seq = c->snd.iss;
 483                                 hdr.ack = c->rcv.nxt;
 484                                 hdr.ctl = SYN | ACK;
 485                         }
 486                         utcp->send(utcp, &hdr, sizeof hdr);
 487                         // TODO: queue any data?
 488                 }
 489
 490                 return 0;
 491         }
 492
 493         bool acceptable;
 494
 495         if(len == 0)
 496                 if(c->rcv.wnd == 0)
 497                         acceptable = hdr.seq == c->rcv.nxt;
 498                 else
 499                         acceptable = (hdr.seq >= c->rcv.nxt && hdr.seq < c->rcv.nxt + c->rcv.wnd);
 500         else
 501                 if(c->rcv.wnd == 0)
 502                         acceptable = false;
 503                 else
 504                         acceptable = (hdr.seq >= c->rcv.nxt && hdr.seq < c->rcv.nxt + c->rcv.wnd)
 505                                 || (hdr.seq + len - 1 >= c->rcv.nxt && hdr.seq + len - 1 < c->rcv.nxt + c->rcv.wnd);
 506
 507         if(!acceptable) {
 508                 fprintf(stderr, "Packet not acceptable, %u %u %u %zu\n", hdr.seq, c->rcv.nxt, c->rcv.wnd, len);
 509                 if(hdr.ctl & RST)
 510                         return 0;
 511                 goto ack_and_drop;
 512         }
 513
 514         c->snd.wnd = hdr.wnd;
 515
 516         // TODO: check whether segment really starts at rcv.nxt, otherwise trim it.
 517
 518         if(hdr.ctl & RST) {
 519                 switch(c->state) {
 520                 case SYN_RECEIVED:
 521                         // TODO: delete connection?
 522                         break;
 523                 case ESTABLISHED:
 524                 case FIN_WAIT_1:
 525                 case FIN_WAIT_2:
 526                 case CLOSE_WAIT:
 527                         set_state(c, CLOSED);
 528                         errno = ECONNRESET;
 529                         c->recv(c, NULL, 0);
 530                         break;
 531                 case CLOSING:
 532                 case LAST_ACK:
 533                 case TIME_WAIT:
 534                         // TODO: delete connection?
 535                         break;
 536                 default:
 537                         // TODO: wtf?
 538                         return 0;
 539                 }
 540                 set_state(c, CLOSED);
 541                 return 0;
 542         }
 543
 544         if(hdr.ctl & SYN) {
 545                 switch(c->state) {
 546                 case SYN_RECEIVED:
 547                 case ESTABLISHED:
 548                 case FIN_WAIT_1:
 549                 case FIN_WAIT_2:
 550                 case CLOSE_WAIT:
 551                 case CLOSING:
 552                 case LAST_ACK:
 553                 case TIME_WAIT:
 554                         set_state(c, CLOSED);
 555                         errno = ECONNRESET;
 556                         c->recv(c, NULL, 0);
 557                         goto reset;
 558                         break;
 559                 default:
 560                         // TODO: wtf?
 561                         return 0;
 562                 }
 563         }
 564
 565         if(!(hdr.ctl & ACK))
 566                 return 0;
 567
 568         switch(c->state) {
 569         case SYN_RECEIVED:
 570                 if(seqdiff(hdr.ack, c->snd.una) >= 0 && seqdiff(hdr.ack, c->snd.nxt) <= 0)
 571                         c->utcp->accept(c, hdr.dst);
 572
 573                 if(c->state != ESTABLISHED)
 574                         goto reset;
 575                 break;
 576         case ESTABLISHED:
 577         case CLOSE_WAIT:
 578                 if(seqdiff(hdr.ack, c->snd.una) < 0)
 579                         return 0;
 580                 if(seqdiff(hdr.ack, c->snd.nxt) > 0)
 581                         goto ack_and_drop;
 582                 if(seqdiff(hdr.ack, c->snd.una) > 0 && seqdiff(hdr.ack, c->snd.nxt) <= 0) {
 583                         c->snd.una = hdr.ack;
 584                         if(seqdiff(c->snd.wl1, hdr.seq) < 0 || (c->snd.wl1 == hdr.seq && seqdiff(c->snd.wl2, hdr.ack) <= 0)) {
 585                                 c->snd.wnd = hdr.wnd;
 586                                 c->snd.wl1 = hdr.seq;
 587                                 c->snd.wl2 = hdr.ack;
 588                         }
 589                 }
 590                 break;
 591         case FIN_WAIT_1:
 592                 if(hdr.ack == c->snd.nxt)
 593                         set_state(c, FIN_WAIT_2);
 594                 break;
 595         case FIN_WAIT_2:
 596                 // TODO: If nothing left to send, close.
 597                 break;
 598         case CLOSING:
 599                 if(hdr.ack == c->snd.nxt) {
 600                         set_state(c, TIME_WAIT);
 601                 }
 602                 break;
 603         case LAST_ACK:
 604                 if(hdr.ack == c->snd.nxt) {
 605                         set_state(c, CLOSED);
 606                 }
 607                 return 0;
 608         case TIME_WAIT:
 609                 // TODO: retransmission of remote FIN, ACK and restart 2 MSL timeout
 610                 break;
 611         default:
 612                 goto reset;
 613         }
 614
 615         // Process data
 616
 617         switch(c->state) {
 618         case ESTABLISHED:
 619         case FIN_WAIT_1:
 620         case FIN_WAIT_2:
 621                 // TODO: process the data, see page 74
 622                 break;
 623         case CLOSE_WAIT:
 624         case CLOSING:
 625         case LAST_ACK:
 626         case TIME_WAIT:
 627                 break;
 628         default:
 629                 abort();
 630         }
 631
 632         if(hdr.ctl & FIN) {
 633                 switch(c->state) {
 634                 case CLOSED:
 635                 case LISTEN:
 636                 case SYN_SENT:
 637                         return 0;
 638                 case SYN_RECEIVED:
 639                 case ESTABLISHED:
 640                         set_state(c, CLOSE_WAIT);
 641                         c->rcv.nxt++;
 642                         goto ack_and_drop;
 643                 case FIN_WAIT_1:
 644                         set_state(c, CLOSING);
 645                         c->rcv.nxt++;
 646                         goto ack_and_drop;
 647                 case FIN_WAIT_2:
 648                         set_state(c, TIME_WAIT);
 649                         c->rcv.nxt++;
 650                         goto ack_and_drop;
 651                 case CLOSE_WAIT:
 652                 case CLOSING:
 653                 case LAST_ACK:
 654                 case TIME_WAIT:
 655                         break;
 656                 default:
 657                         abort();
 658                 }
 659         }
 660
 661         // Process the data
 662
 663         if(len && c->recv) {
 664                 c->recv(c, data, len);
 665                 c->rcv.nxt += len;
 666                 goto ack_and_drop;
 667         }
 668
 669         return 0;
 670
 671 reset:
 672         swap_ports(&hdr);
 673         hdr.wnd = 0;
 674         if(hdr.ctl & ACK) {
 675                 hdr.seq = hdr.ack;
 676                 hdr.ctl = RST;
 677         } else {
 678                 hdr.ack = hdr.seq + len;
 679                 hdr.seq = 0;
 680                 hdr.ctl = RST | ACK;
 681         }
 682         utcp->send(utcp, &hdr, sizeof hdr);
 683         return 0;
 684
 685 ack_and_drop:
 686         swap_ports(&hdr);
 687         hdr.seq = c->snd.nxt;
 688         hdr.ack = c->rcv.nxt;
 689         hdr.ctl = ACK;
 690         utcp->send(utcp, &hdr, sizeof hdr);
 691         if(c->state == CLOSE_WAIT || c->state == TIME_WAIT) {
 692                 errno = 0;
 693                 c->recv(c, NULL, 0);
 694         }
 695         return 0;
 696 }
 697
 698 int utcp_shutdown(struct utcp_connection *c, int dir) {
 699         if(!c) {
 700                 errno = EFAULT;
 701                 return -1;
 702         }
 703
 704         if(c->reapable) {
 705                 fprintf(stderr, "Error: shutdown() called on closed connection %p\n", c);
 706                 errno = EBADF;
 707                 return -1;
 708         }
 709
 710         // TODO: handle dir
 711
 712         switch(c->state) {
 713         case CLOSED:
 714                 return 0;
 715         case LISTEN:
 716         case SYN_SENT:
 717                 set_state(c, CLOSED);
 718                 return 0;
 719
 720         case SYN_RECEIVED:
 721         case ESTABLISHED:
 722                 set_state(c, FIN_WAIT_1);
 723                 break;
 724         case FIN_WAIT_1:
 725         case FIN_WAIT_2:
 726                 return 0;
 727         case CLOSE_WAIT:
 728                 set_state(c, LAST_ACK);
 729                 break;
 730
 731         case CLOSING:
 732         case LAST_ACK:
 733         case TIME_WAIT:
 734                 return 0;
 735         }
 736
 737         // Send FIN
 738
 739         struct hdr hdr;
 740
 741         hdr.src = c->src;
 742         hdr.dst = c->dst;
 743         hdr.seq = c->snd.nxt;
 744         hdr.ack = c->rcv.nxt;
 745         hdr.wnd = c->snd.wnd;
 746         hdr.ctl = FIN | ACK;
 747
 748         c->snd.nxt += 1;
 749
 750         c->utcp->send(c->utcp, &hdr, sizeof hdr);
 751         return 0;
 752 }
 753
 754 int utcp_close(struct utcp_connection *c) {
 755         if(utcp_shutdown(c, SHUT_RDWR))
 756                 return -1;
 757         c->reapable = true;
 758         return 0;
 759 }
 760
 761 int utcp_abort(struct utcp_connection *c) {
 762         if(!c) {
 763                 errno = EFAULT;
 764                 return -1;
 765         }
 766
 767         if(c->reapable) {
 768                 fprintf(stderr, "Error: abort() called on closed connection %p\n", c);
 769                 errno = EBADF;
 770                 return -1;
 771         }
 772
 773         c->reapable = true;
 774
 775         switch(c->state) {
 776         case CLOSED:
 777                 return 0;
 778         case LISTEN:
 779         case SYN_SENT:
 780         case CLOSING:
 781         case LAST_ACK:
 782         case TIME_WAIT:
 783                 set_state(c, CLOSED);
 784                 return 0;
 785
 786         case SYN_RECEIVED:
 787         case ESTABLISHED:
 788         case FIN_WAIT_1:
 789         case FIN_WAIT_2:
 790         case CLOSE_WAIT:
 791                 set_state(c, CLOSED);
 792                 break;
 793         }
 794
 795         // Send RST
 796
 797         struct hdr hdr;
 798
 799         hdr.src = c->src;
 800         hdr.dst = c->dst;
 801         hdr.seq = c->snd.nxt;
 802         hdr.ack = 0;
 803         hdr.wnd = 0;
 804         hdr.ctl = RST;
 805
 806         c->utcp->send(c->utcp, &hdr, sizeof hdr);
 807         return 0;
 808 }
 809
 810 void utcp_timeout(struct utcp *utcp) {
 811         struct timeval now;
 812         gettimeofday(&now, NULL);
 813
 814         for(int i = 0; i < utcp->nconnections; i++) {
 815                 struct utcp_connection *c = utcp->connections[i];
 816                 if(!c)
 817                         continue;
 818
 819                 if(c->reapable) {
 820                         fprintf(stderr, "Reaping %p\n", c);
 821                         free_connection(c);
 822                         continue;
 823                 }
 824
 825                 if(c->state == CLOSED)
 826                         return;
 827
 828                 if(c->conn_timeout.tv_sec && timercmp(&c->conn_timeout, &now, <)) {
 829                         if(!c->reapable) {
 830                                 errno = ETIMEDOUT;
 831                                 c->recv(c, NULL, 0);
 832                         }
 833                         c->state = CLOSED;
 834                         return;
 835                 }
 836
 837                 if(c->rtrx_timeout.tv_sec && timercmp(&c->rtrx_timeout, &now, <)) {
 838                         // TODO: retransmit stuff;
 839                 }
 840         }
 841 }
 842
 843 struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_send_t send, void *priv) {
 844         struct utcp *utcp = calloc(1, sizeof *utcp);
 845         if(!utcp)
 846                 return NULL;
 847
 848         utcp->accept = accept;
 849         utcp->pre_accept = pre_accept;
 850         utcp->send = send;
 851         utcp->priv = priv;
 852         utcp->gap = -1;
 853         utcp->mtu = 1000;
 854
 855         return utcp;
 856 }
 857
 858 void utcp_exit(struct utcp *utcp) {
 859         if(!utcp)
 860                 return;
 861         for(int i = 0; i < utcp->nconnections; i++)
 862                 free_connection(utcp->connections[i]);
 863         free(utcp);
 864 }