mdw@git.distorted.org.uk Git - sgt/agedu/blob - httpd.c

   1 /*
   2  * httpd.c: implementation of httpd.h.
   3  */
   4
   5 #include "agedu.h"
   6 #include "alloc.h"
   7 #include "html.h"
   8 #include "httpd.h"
   9
  10 /* --- Logic driving what the web server's responses are. --- */
  11
  12 enum { /* connctx states */
  13     READING_REQ_LINE,
  14     READING_HEADERS,
  15     DONE
  16 };
  17
  18 struct connctx {
  19     const void *t;
  20     char *data;
  21     int datalen, datasize;
  22     char *method, *url, *headers, *auth;
  23     int state;
  24 };
  25
  26 /*
  27  * Called when a new connection arrives on a listening socket.
  28  * Returns a connctx for the new connection.
  29  */
  30 struct connctx *new_connection(const void *t)
  31 {
  32     struct connctx *cctx = snew(struct connctx);
  33     cctx->t = t;
  34     cctx->data = NULL;
  35     cctx->datalen = cctx->datasize = 0;
  36     cctx->state = READING_REQ_LINE;
  37     cctx->method = cctx->url = cctx->headers = cctx->auth = NULL;
  38     return cctx;
  39 }
  40
  41 void free_connection(struct connctx *cctx)
  42 {
  43     sfree(cctx->data);
  44     sfree(cctx);
  45 }
  46
  47 static char *http_error(char *code, char *errmsg, char *extraheader,
  48                         char *errtext, ...)
  49 {
  50     return dupfmt("HTTP/1.1 %s %s\r\n"
  51                   "Date: %D\r\n"
  52                   "Server: " PNAME "\r\n"
  53                   "Connection: close\r\n"
  54                   "%s"
  55                   "Content-Type: text/html; charset=US-ASCII\r\n"
  56                   "\r\n"
  57                   "<!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\r\n"
  58                   "<HTML><HEAD>\r\n"
  59                   "<TITLE>%s %s</TITLE>\r\n"
  60                   "</HEAD><BODY>\r\n"
  61                   "<H1>%s %s</H1>\r\n"
  62                   "<P>%s</P>\r\n"
  63                   "</BODY></HTML>\r\n", code, errmsg,
  64                   extraheader ? extraheader : "",
  65                   code, errmsg, code, errmsg, errtext);
  66 }
  67
  68 static char *http_success(char *mimetype, int stuff_cr, char *document)
  69 {
  70     return dupfmt("HTTP/1.1 200 OK\r\n"
  71                   "Date: %D\r\n"
  72                   "Expires: %D\r\n"
  73                   "Server: " PNAME "\r\n"
  74                   "Connection: close\r\n"
  75                   "Content-Type: %s\r\n"
  76                   "\r\n"
  77                   "%S", mimetype, stuff_cr, document);
  78 }
  79
  80 /*
  81  * Called when data comes in on a connection.
  82  *
  83  * If this function returns NULL, the platform code continues
  84  * reading from the socket. Otherwise, it returns some dynamically
  85  * allocated data which the platform code will then write to the
  86  * socket before closing it.
  87  */
  88 char *got_data(struct connctx *ctx, char *data, int length,
  89                int magic_access, const char *auth_string,
  90                const struct html_config *cfg)
  91 {
  92     char *line, *p, *q, *r, *z1, *z2, c1, c2;
  93     int auth_provided = 0, auth_correct = 0;
  94     unsigned long index;
  95     char *document, *ret;
  96
  97     /*
  98      * Add the data we've just received to our buffer.
  99      */
 100     if (ctx->datasize < ctx->datalen + length) {
 101         ctx->datasize = (ctx->datalen + length) * 3 / 2 + 4096;
 102         ctx->data = sresize(ctx->data, ctx->datasize, char);
 103     }
 104     memcpy(ctx->data + ctx->datalen, data, length);
 105     ctx->datalen += length;
 106
 107     /*
 108      * Gradually process the HTTP request as we receive it.
 109      */
 110     if (ctx->state == READING_REQ_LINE) {
 111         /*
 112          * We're waiting for the first line of the input, which
 113          * contains the main HTTP request. See if we've got it
 114          * yet.
 115          */
 116
 117         line = ctx->data;
 118         /*
 119          * RFC 2616 section 4.1: `In the interest of robustness,
 120          * [...] if the server is reading the protocol stream at
 121          * the beginning of a message and receives a CRLF first,
 122          * it should ignore the CRLF.'
 123          */
 124         while (line - ctx->data < ctx->datalen &&
 125                (*line == '\r' || *line == '\n'))
 126             line++;
 127         q = line;
 128         while (q - ctx->data < ctx->datalen && *q != '\n')
 129             q++;
 130         if (q - ctx->data >= ctx->datalen)
 131             return NULL;               /* not got request line yet */
 132
 133         /*
 134          * We've got the first line of the request. Zero-terminate
 135          * and parse it into method, URL and optional HTTP
 136          * version.
 137          */
 138         *q = '\0';
 139         ctx->headers = q+1;
 140         if (q > line && q[-1] == '\r')
 141             *--q = '\0';
 142         z1 = z2 = q;
 143         c1 = c2 = *q;
 144         p = line;
 145         while (*p && !isspace((unsigned char)*p)) p++;
 146         if (*p) {
 147             z1 = p++;
 148             c1 = *z1;
 149             *z1 = '\0';
 150         }
 151         while (*p && isspace((unsigned char)*p)) p++;
 152         q = p;
 153         while (*q && !isspace((unsigned char)*q)) q++;
 154         z2 = q++;
 155         c2 = *z2;
 156         *z2 = '\0';
 157         while (*q && isspace((unsigned char)*q)) q++;
 158
 159         /*
 160          * Now `line' points at the method name; p points at the
 161          * URL, if any; q points at the HTTP version, if any.
 162          */
 163
 164         /*
 165          * There should _be_ a URL, on any request type at all.
 166          */
 167         if (!*p) {
 168             char *ret, *text;
 169             /* Restore the request to the way we received it. */
 170             *z2 = c2;
 171             *z1 = c1;
 172             text = dupfmt("<code>" PNAME "</code> received the HTTP request"
 173                           " \"<code>%h</code>\", which contains no URL.",
 174                           line);
 175             ret = http_error("400", "Bad request", NULL, text);
 176             sfree(text);
 177             return ret;
 178         }
 179
 180         ctx->method = line;
 181         ctx->url = p;
 182
 183         /*
 184          * If there was an HTTP version, we might need to see
 185          * headers. Otherwise, the request is done.
 186          */
 187         if (*q) {
 188             ctx->state = READING_HEADERS;
 189         } else {
 190             ctx->state = DONE;
 191         }
 192     }
 193
 194     if (ctx->state == READING_HEADERS) {
 195         /*
 196          * While we're receiving the HTTP request headers, all we
 197          * do is to keep scanning to see if we find two newlines
 198          * next to each other.
 199          */
 200         q = ctx->data + ctx->datalen;
 201         for (p = ctx->headers; p < q; p++) {
 202             if (*p == '\n' &&
 203                 ((p+1 < q && p[1] == '\n') ||
 204                  (p+2 < q && p[1] == '\r' && p[2] == '\n'))) {
 205                 p[1] = '\0';
 206                 ctx->state = DONE;
 207                 break;
 208             }
 209         }
 210     }
 211
 212     if (ctx->state == DONE) {
 213         /*
 214          * Now we have the entire HTTP request. Decide what to do
 215          * with it.
 216          */
 217         if (auth_string) {
 218             /*
 219              * Search the request headers for Authorization.
 220              */
 221             q = ctx->data + ctx->datalen;
 222             for (p = ctx->headers; p < q; p++) {
 223                 const char *hdr = "Authorization:";
 224                 int i;
 225                 for (i = 0; hdr[i]; i++) {
 226                     if (p >= q || tolower((unsigned char)*p) !=
 227                         tolower((unsigned char)hdr[i]))
 228                         break;
 229                     p++;
 230                 }
 231                 if (!hdr[i])
 232                     break;             /* found our header */
 233                 p = memchr(p, '\n', q - p);
 234                 if (!p)
 235                     p = q;
 236             }
 237             if (p < q) {
 238                 auth_provided = 1;
 239                 while (p < q && isspace((unsigned char)*p))
 240                     p++;
 241                 r = p;
 242                 while (p < q && !isspace((unsigned char)*p))
 243                     p++;
 244                 if (p < q) {
 245                     *p++ = '\0';
 246                     if (!strcasecmp(r, "Basic")) {
 247                         while (p < q && isspace((unsigned char)*p))
 248                             p++;
 249                         r = p;
 250                         while (p < q && !isspace((unsigned char)*p))
 251                             p++;
 252                         if (p < q) {
 253                             *p++ = '\0';
 254                             if (!strcmp(r, auth_string))
 255                                 auth_correct = 1;
 256                         }
 257                     }
 258                 }
 259             }
 260         }
 261
 262         if (!magic_access && !auth_correct) {
 263             if (auth_string) {
 264                 ret = http_error("401", "Unauthorized",
 265                                  "WWW-Authenticate: Basic realm=\""PNAME"\"\r",
 266                                  "\nYou must authenticate to view these pages.");
 267             } else {
 268                 ret = http_error("403", "Forbidden", NULL,
 269                                  "This is a restricted-access set of pages.");
 270             }
 271         } else {
 272             p = ctx->url;
 273             p += strspn(p, "/?");
 274             index = strtoul(p, NULL, 10);
 275             document = html_query(ctx->t, index, cfg);
 276             if (document) {
 277                 ret = http_success("text/html", 1, document);
 278                 sfree(document);
 279             } else {
 280                 ret = http_error("404", "Not Found", NULL,
 281                                  "Pathname index out of range.");
 282             }
 283         }
 284         return ret;
 285     } else
 286         return NULL;
 287 }
 288
 289 /* --- Platform support for running a web server. --- */
 290
 291 enum { FD_CLIENT, FD_LISTENER, FD_CONNECTION };
 292
 293 struct fd {
 294     int fd;
 295     int type;
 296     int deleted;
 297     char *wdata;
 298     int wdatalen, wdatapos;
 299     int magic_access;
 300     struct connctx *cctx;
 301 };
 302
 303 struct fd *fds = NULL;
 304 int nfds = 0, fdsize = 0;
 305
 306 struct fd *new_fdstruct(int fd, int type)
 307 {
 308     struct fd *ret;
 309
 310     if (nfds >= fdsize) {
 311         fdsize = nfds * 3 / 2 + 32;
 312         fds = sresize(fds, fdsize, struct fd);
 313     }
 314
 315     ret = &fds[nfds++];
 316
 317     ret->fd = fd;
 318     ret->type = type;
 319     ret->wdata = NULL;
 320     ret->wdatalen = ret->wdatapos = 0;
 321     ret->cctx = NULL;
 322     ret->deleted = 0;
 323     ret->magic_access = 0;
 324
 325     return ret;
 326 }
 327
 328 int check_owning_uid(int fd, int flip)
 329 {
 330     struct sockaddr_in sock, peer;
 331     socklen_t addrlen;
 332     char linebuf[4096], matchbuf[80];
 333     FILE *fp;
 334
 335     addrlen = sizeof(sock);
 336     if (getsockname(fd, (struct sockaddr *)&sock, &addrlen)) {
 337         fprintf(stderr, "getsockname: %s\n", strerror(errno));
 338         exit(1);
 339     }
 340     addrlen = sizeof(peer);
 341     if (getpeername(fd, (struct sockaddr *)&peer, &addrlen)) {
 342         if (errno == ENOTCONN) {
 343             peer.sin_addr.s_addr = htonl(0);
 344             peer.sin_port = htons(0);
 345         } else {
 346             fprintf(stderr, "getpeername: %s\n", strerror(errno));
 347             exit(1);
 348         }
 349     }
 350
 351     if (flip) {
 352         struct sockaddr_in tmp = sock;
 353         sock = peer;
 354         peer = tmp;
 355     }
 356
 357     sprintf(matchbuf, "%08X:%04X %08X:%04X",
 358             peer.sin_addr.s_addr, ntohs(peer.sin_port),
 359             sock.sin_addr.s_addr, ntohs(sock.sin_port));
 360     fp = fopen("/proc/net/tcp", "r");
 361     if (fp) {
 362         while (fgets(linebuf, sizeof(linebuf), fp)) {
 363             if (strlen(linebuf) >= 75 &&
 364                 !strncmp(linebuf+6, matchbuf, strlen(matchbuf))) {
 365                 return atoi(linebuf + 75);
 366             }
 367         }
 368     }
 369
 370     return -1;
 371 }
 372
 373 void check_magic_access(struct fd *fd)
 374 {
 375     if (check_owning_uid(fd->fd, 0) == getuid())
 376         fd->magic_access = 1;
 377 }
 378
 379 static void base64_encode_atom(unsigned char *data, int n, char *out)
 380 {
 381     static const char base64_chars[] =
 382         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 383
 384     unsigned word;
 385
 386     word = data[0] << 16;
 387     if (n > 1)
 388         word |= data[1] << 8;
 389     if (n > 2)
 390         word |= data[2];
 391     out[0] = base64_chars[(word >> 18) & 0x3F];
 392     out[1] = base64_chars[(word >> 12) & 0x3F];
 393     if (n > 1)
 394         out[2] = base64_chars[(word >> 6) & 0x3F];
 395     else
 396         out[2] = '=';
 397     if (n > 2)
 398         out[3] = base64_chars[word & 0x3F];
 399     else
 400         out[3] = '=';
 401 }
 402
 403 void run_httpd(const void *t, int authmask, const struct httpd_config *dcfg,
 404                const struct html_config *incfg)
 405 {
 406     int fd, ret;
 407     int authtype;
 408     char *authstring = NULL;
 409     unsigned long ipaddr;
 410     struct fd *f;
 411     struct sockaddr_in addr;
 412     socklen_t addrlen;
 413     struct html_config cfg = *incfg;
 414
 415     cfg.format = "%.0lu";
 416
 417     /*
 418      * Establish the listening socket and retrieve its port
 419      * number.
 420      */
 421     fd = socket(PF_INET, SOCK_STREAM, 0);
 422     if (fd < 0) {
 423         fprintf(stderr, "socket(PF_INET): %s\n", strerror(errno));
 424         exit(1);
 425     }
 426     addr.sin_family = AF_INET;
 427     if (!dcfg->address) {
 428         srand(0L);
 429         ipaddr = 0x7f000000;
 430         ipaddr += (1 + rand() % 255) << 16;
 431         ipaddr += (1 + rand() % 255) << 8;
 432         ipaddr += (1 + rand() % 255);
 433         addr.sin_addr.s_addr = htonl(ipaddr);
 434         addr.sin_port = htons(0);
 435
 436     } else {
 437         addr.sin_addr.s_addr = inet_addr(dcfg->address);
 438         addr.sin_port = dcfg->port ? htons(dcfg->port) : 0;
 439     }
 440     addrlen = sizeof(addr);
 441     ret = bind(fd, (const struct sockaddr *)&addr, addrlen);
 442     if (ret < 0 && errno == EADDRNOTAVAIL && !dcfg->address) {
 443         /*
 444          * Some systems don't like us binding to random weird
 445          * localhost-space addresses. Try again with the official
 446          * INADDR_LOOPBACK.
 447          */
 448         addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 449         addr.sin_port = htons(0);
 450         ret = bind(fd, (const struct sockaddr *)&addr, addrlen);
 451     }
 452     if (ret < 0) {
 453         fprintf(stderr, "bind: %s\n", strerror(errno));
 454         exit(1);
 455     }
 456     if (listen(fd, 5) < 0) {
 457         fprintf(stderr, "listen: %s\n", strerror(errno));
 458         exit(1);
 459     }
 460     addrlen = sizeof(addr);
 461     if (getsockname(fd, (struct sockaddr *)&addr, &addrlen)) {
 462         fprintf(stderr, "getsockname: %s\n", strerror(errno));
 463         exit(1);
 464     }
 465     if ((authmask & HTTPD_AUTH_MAGIC) &&
 466         (check_owning_uid(fd, 1) == getuid())) {
 467         authtype = HTTPD_AUTH_MAGIC;
 468         if (authmask != HTTPD_AUTH_MAGIC)
 469             printf("Using Linux /proc/net magic authentication\n");
 470     } else if ((authmask & HTTPD_AUTH_BASIC)) {
 471         char username[128], password[128], userpassbuf[259];
 472         const char *userpass;
 473         const char *rname;
 474         unsigned char passbuf[10];
 475         int i, j, k, fd;
 476
 477         authtype = HTTPD_AUTH_BASIC;
 478
 479         if (authmask != HTTPD_AUTH_BASIC)
 480             printf("Using HTTP Basic authentication\n");
 481
 482         if (dcfg->basicauthdata) {
 483             userpass = dcfg->basicauthdata;
 484         } else {
 485             strcpy(username, PNAME);
 486             rname = "/dev/urandom";
 487             fd = open(rname, O_RDONLY);
 488             if (fd < 0) {
 489                 int err = errno;
 490                 rname = "/dev/random";
 491                 fd = open(rname, O_RDONLY);
 492                 if (fd < 0) {
 493                     int err2 = errno;
 494                     fprintf(stderr, "/dev/urandom: open: %s\n", strerror(err));
 495                     fprintf(stderr, "/dev/random: open: %s\n", strerror(err2));
 496                     exit(1);
 497                 }
 498             }
 499             for (i = 0; i < 10 ;) {
 500                 j = read(fd, passbuf + i, 10 - i);
 501                 if (j <= 0) {
 502                     fprintf(stderr, "%s: read: %s\n", rname,
 503                             j < 0 ? strerror(errno) : "unexpected EOF");
 504                     exit(1);
 505                 }
 506                 i += j;
 507             }
 508             close(fd);
 509             for (i = 0; i < 16; i++) {
 510                 /*
 511                  * 32 characters out of the 36 alphanumerics gives
 512                  * me the latitude to discard i,l,o for being too
 513                  * numeric-looking, and w because it has two too
 514                  * many syllables and one too many presidential
 515                  * associations.
 516                  */
 517                 static const char chars[32] =
 518                     "0123456789abcdefghjkmnpqrstuvxyz";
 519                 int v = 0;
 520
 521                 k = i / 8 * 5;
 522                 for (j = 0; j < 5; j++)
 523                     v |= ((passbuf[k+j] >> (i%8)) & 1) << j;
 524
 525                 password[i] = chars[v];
 526             }
 527             password[i] = '\0';
 528
 529             sprintf(userpassbuf, "%s:%s", username, password);
 530             userpass = userpassbuf;
 531
 532             printf("Username: %s\nPassword: %s\n", username, password);
 533         }
 534
 535         k = strlen(userpass);
 536         authstring = snewn(k * 4 / 3 + 16, char);
 537         for (i = j = 0; i < k ;) {
 538             int s = k-i < 3 ? k-i : 3;
 539             base64_encode_atom((unsigned char *)(userpass+i), s, authstring+j);
 540             i += s;
 541             j += 4;
 542         }
 543         authstring[j] = '\0';
 544     } else if ((authmask & HTTPD_AUTH_NONE)) {
 545         authtype = HTTPD_AUTH_NONE;
 546         if (authmask != HTTPD_AUTH_NONE)
 547             printf("Web server is unauthenticated\n");
 548     } else {
 549         fprintf(stderr, PNAME ": authentication method not supported\n");
 550         exit(1);
 551     }
 552     if (ntohs(addr.sin_addr.s_addr) == INADDR_ANY) {
 553         printf("Server port: %d\n", ntohs(addr.sin_port));
 554     } else if (ntohs(addr.sin_port) == 80) {
 555         printf("URL: http://%s/\n", inet_ntoa(addr.sin_addr));
 556     } else {
 557         printf("URL: http://%s:%d/\n",
 558                inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
 559     }
 560
 561     /*
 562      * Now construct an fd structure to hold it.
 563      */
 564     f = new_fdstruct(fd, FD_LISTENER);
 565
 566     /*
 567      * Read from standard input, and treat EOF as a notification
 568      * to exit.
 569      */
 570     new_fdstruct(0, FD_CLIENT);
 571
 572     /*
 573      * Now we're ready to run our main loop. Keep looping round on
 574      * select.
 575      */
 576     while (1) {
 577         fd_set rfds, wfds;
 578         int i, j;
 579         SELECT_TYPE_ARG1 maxfd;
 580         int ret;
 581
 582 #define FD_SET_MAX(fd, set, max) \
 583         do { FD_SET((fd),(set)); (max) = ((max)<=(fd)?(fd)+1:(max)); } while(0)
 584
 585         /*
 586          * Loop round the fd list putting fds into our select
 587          * sets. Also in this loop we remove any that were marked
 588          * as deleted in the previous loop.
 589          */
 590         FD_ZERO(&rfds);
 591         FD_ZERO(&wfds);
 592         maxfd = 0;
 593         for (i = j = 0; j < nfds; j++) {
 594
 595             if (fds[j].deleted) {
 596                 sfree(fds[j].wdata);
 597                 free_connection(fds[j].cctx);
 598                 continue;
 599             }
 600             fds[i] = fds[j];
 601
 602             switch (fds[i].type) {
 603               case FD_CLIENT:
 604                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 605                 break;
 606               case FD_LISTENER:
 607                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 608                 break;
 609               case FD_CONNECTION:
 610                 /*
 611                  * Always read from a connection socket. Even
 612                  * after we've started writing, the peer might
 613                  * still be sending (e.g. because we shamefully
 614                  * jumped the gun before waiting for the end of
 615                  * the HTTP request) and so we should be prepared
 616                  * to read data and throw it away.
 617                  */
 618                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 619                 /*
 620                  * Also attempt to write, if we have data to write.
 621                  */
 622                 if (fds[i].wdatapos < fds[i].wdatalen)
 623                     FD_SET_MAX(fds[i].fd, &wfds, maxfd);
 624                 break;
 625             }
 626
 627             i++;
 628         }
 629         nfds = i;
 630
 631         ret = select(maxfd, SELECT_TYPE_ARG234 &rfds,
 632                      SELECT_TYPE_ARG234 &wfds, SELECT_TYPE_ARG234 NULL,
 633                      SELECT_TYPE_ARG5 NULL);
 634         if (ret <= 0) {
 635             if (ret < 0 && (errno != EINTR)) {
 636                 fprintf(stderr, "select: %s", strerror(errno));
 637                 exit(1);
 638             }
 639             continue;
 640         }
 641
 642         for (i = 0; i < nfds; i++) {
 643             switch (fds[i].type) {
 644               case FD_CLIENT:
 645                 if (FD_ISSET(fds[i].fd, &rfds)) {
 646                     char buf[4096];
 647                     int ret = read(fds[i].fd, buf, sizeof(buf));
 648                     if (ret <= 0) {
 649                         if (ret < 0) {
 650                             fprintf(stderr, "standard input: read: %s\n",
 651                                     strerror(errno));
 652                             exit(1);
 653                         }
 654                         return;
 655                     }
 656                 }
 657                 break;
 658               case FD_LISTENER:
 659                 if (FD_ISSET(fds[i].fd, &rfds)) {
 660                     /*
 661                      * New connection has come in. Accept it.
 662                      */
 663                     struct fd *f;
 664                     struct sockaddr_in addr;
 665                     socklen_t addrlen = sizeof(addr);
 666                     int newfd = accept(fds[i].fd, (struct sockaddr *)&addr,
 667                                        &addrlen);
 668                     if (newfd < 0)
 669                         break;         /* not sure what happened there */
 670
 671                     f = new_fdstruct(newfd, FD_CONNECTION);
 672                     f->cctx = new_connection(t);
 673                     if (authtype == HTTPD_AUTH_MAGIC)
 674                         check_magic_access(f);
 675                 }
 676                 break;
 677               case FD_CONNECTION:
 678                 if (FD_ISSET(fds[i].fd, &rfds)) {
 679                     /*
 680                      * There's data to be read.
 681                      */
 682                     char readbuf[4096];
 683                     int ret;
 684
 685                     ret = read(fds[i].fd, readbuf, sizeof(readbuf));
 686                     if (ret <= 0) {
 687                         /*
 688                          * This shouldn't happen in a sensible
 689                          * HTTP connection, so we abandon the
 690                          * connection if it does.
 691                          */
 692                         close(fds[i].fd);
 693                         fds[i].deleted = 1;
 694                         break;
 695                     } else {
 696                         if (!fds[i].wdata) {
 697                             /*
 698                              * If we haven't got an HTTP response
 699                              * yet, keep processing data in the
 700                              * hope of acquiring one.
 701                              */
 702                             fds[i].wdata = got_data
 703                                 (fds[i].cctx, readbuf, ret,
 704                                  (authtype == HTTPD_AUTH_NONE ||
 705                                   fds[i].magic_access), authstring, &cfg);
 706                             if (fds[i].wdata) {
 707                                 fds[i].wdatalen = strlen(fds[i].wdata);
 708                                 fds[i].wdatapos = 0;
 709                             }
 710                         } else {
 711                             /*
 712                              * Otherwise, just drop our read data
 713                              * on the floor.
 714                              */
 715                         }
 716                     }
 717                 }
 718                 if (FD_ISSET(fds[i].fd, &wfds) &&
 719                     fds[i].wdatapos < fds[i].wdatalen) {
 720                     /*
 721                      * The socket is writable, and we have data to
 722                      * write. Write it.
 723                      */
 724                     int ret = write(fds[i].fd, fds[i].wdata + fds[i].wdatapos,
 725                                     fds[i].wdatalen - fds[i].wdatapos);
 726                     if (ret <= 0) {
 727                         /*
 728                          * Shouldn't happen; abandon the connection.
 729                          */
 730                         close(fds[i].fd);
 731                         fds[i].deleted = 1;
 732                         break;
 733                     } else {
 734                         fds[i].wdatapos += ret;
 735                         if (fds[i].wdatapos == fds[i].wdatalen) {
 736                             shutdown(fds[i].fd, SHUT_WR);
 737                         }
 738                     }
 739                 }
 740                 break;
 741             }
 742         }
 743
 744     }
 745 }