connect.c

   1 #include "git-compat-util.h"
   2 #include "cache.h"
   3 #include "pkt-line.h"
   4 #include "quote.h"
   5 #include "refs.h"
   6 #include "run-command.h"
   7 #include "remote.h"
   8 #include "connect.h"
   9 #include "url.h"
  10 #include "string-list.h"
  11 #include "sha1-array.h"
  12 #include "transport.h"
  13
  14 static char *server_capabilities;
  15 static const char *parse_feature_value(const char *, const char *, int *);
  16
  17 static int check_ref(const char *name, unsigned int flags)
  18 {
  19         if (!flags)
  20                 return 1;
  21
  22         if (!skip_prefix(name, "refs/", &name))
  23                 return 0;
  24
  25         /* REF_NORMAL means that we don't want the magic fake tag refs */
  26         if ((flags & REF_NORMAL) && check_refname_format(name, 0))
  27                 return 0;
  28
  29         /* REF_HEADS means that we want regular branch heads */
  30         if ((flags & REF_HEADS) && starts_with(name, "heads/"))
  31                 return 1;
  32
  33         /* REF_TAGS means that we want tags */
  34         if ((flags & REF_TAGS) && starts_with(name, "tags/"))
  35                 return 1;
  36
  37         /* All type bits clear means that we are ok with anything */
  38         return !(flags & ~REF_NORMAL);
  39 }
  40
  41 int check_ref_type(const struct ref *ref, int flags)
  42 {
  43         return check_ref(ref->name, flags);
  44 }
  45
  46 static void die_initial_contact(int unexpected)
  47 {
  48         if (unexpected)
  49                 die(_("The remote end hung up upon initial contact"));
  50         else
  51                 die(_("Could not read from remote repository.\n\n"
  52                       "Please make sure you have the correct access rights\n"
  53                       "and the repository exists."));
  54 }
  55
  56 static void parse_one_symref_info(struct string_list *symref, const char *val, int len)
  57 {
  58         char *sym, *target;
  59         struct string_list_item *item;
  60
  61         if (!len)
  62                 return; /* just "symref" */
  63         /* e.g. "symref=HEAD:refs/heads/master" */
  64         sym = xmemdupz(val, len);
  65         target = strchr(sym, ':');
  66         if (!target)
  67                 /* just "symref=something" */
  68                 goto reject;
  69         *(target++) = '\0';
  70         if (check_refname_format(sym, REFNAME_ALLOW_ONELEVEL) ||
  71             check_refname_format(target, REFNAME_ALLOW_ONELEVEL))
  72                 /* "symref=bogus:pair */
  73                 goto reject;
  74         item = string_list_append(symref, sym);
  75         item->util = target;
  76         return;
  77 reject:
  78         free(sym);
  79         return;
  80 }
  81
  82 static void annotate_refs_with_symref_info(struct ref *ref)
  83 {
  84         struct string_list symref = STRING_LIST_INIT_DUP;
  85         const char *feature_list = server_capabilities;
  86
  87         while (feature_list) {
  88                 int len;
  89                 const char *val;
  90
  91                 val = parse_feature_value(feature_list, "symref", &len);
  92                 if (!val)
  93                         break;
  94                 parse_one_symref_info(&symref, val, len);
  95                 feature_list = val + 1;
  96         }
  97         string_list_sort(&symref);
  98
  99         for (; ref; ref = ref->next) {
 100                 struct string_list_item *item;
 101                 item = string_list_lookup(&symref, ref->name);
 102                 if (!item)
 103                         continue;
 104                 ref->symref = xstrdup((char *)item->util);
 105         }
 106         string_list_clear(&symref, 0);
 107 }
 108
 109 /*
 110  * Read all the refs from the other end
 111  */
 112 struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 113                               struct ref **list, unsigned int flags,
 114                               struct sha1_array *extra_have,
 115                               struct sha1_array *shallow_points)
 116 {
 117         struct ref **orig_list = list;
 118
 119         /*
 120          * A hang-up after seeing some response from the other end
 121          * means that it is unexpected, as we know the other end is
 122          * willing to talk to us.  A hang-up before seeing any
 123          * response does not necessarily mean an ACL problem, though.
 124          */
 125         int saw_response;
 126         int got_dummy_ref_with_capabilities_declaration = 0;
 127
 128         *list = NULL;
 129         for (saw_response = 0; ; saw_response = 1) {
 130                 struct ref *ref;
 131                 struct object_id old_oid;
 132                 char *name;
 133                 int len, name_len;
 134                 char *buffer = packet_buffer;
 135                 const char *arg;
 136
 137                 len = packet_read(in, &src_buf, &src_len,
 138                                   packet_buffer, sizeof(packet_buffer),
 139                                   PACKET_READ_GENTLE_ON_EOF |
 140                                   PACKET_READ_CHOMP_NEWLINE);
 141                 if (len < 0)
 142                         die_initial_contact(saw_response);
 143
 144                 if (!len)
 145                         break;
 146
 147                 if (len > 4 && skip_prefix(buffer, "ERR ", &arg))
 148                         die("remote error: %s", arg);
 149
 150                 if (len == GIT_SHA1_HEXSZ + strlen("shallow ") &&
 151                         skip_prefix(buffer, "shallow ", &arg)) {
 152                         if (get_oid_hex(arg, &old_oid))
 153                                 die("protocol error: expected shallow sha-1, got '%s'", arg);
 154                         if (!shallow_points)
 155                                 die("repository on the other end cannot be shallow");
 156                         sha1_array_append(shallow_points, old_oid.hash);
 157                         continue;
 158                 }
 159
 160                 if (len < GIT_SHA1_HEXSZ + 2 || get_oid_hex(buffer, &old_oid) ||
 161                         buffer[GIT_SHA1_HEXSZ] != ' ')
 162                         die("protocol error: expected sha/ref, got '%s'", buffer);
 163                 name = buffer + GIT_SHA1_HEXSZ + 1;
 164
 165                 name_len = strlen(name);
 166                 if (len != name_len + GIT_SHA1_HEXSZ + 1) {
 167                         free(server_capabilities);
 168                         server_capabilities = xstrdup(name + name_len + 1);
 169                 }
 170
 171                 if (extra_have && !strcmp(name, ".have")) {
 172                         sha1_array_append(extra_have, old_oid.hash);
 173                         continue;
 174                 }
 175
 176                 if (!strcmp(name, "capabilities^{}")) {
 177                         if (saw_response)
 178                                 die("protocol error: unexpected capabilities^{}");
 179                         if (got_dummy_ref_with_capabilities_declaration)
 180                                 die("protocol error: multiple capabilities^{}");
 181                         got_dummy_ref_with_capabilities_declaration = 1;
 182                         continue;
 183                 }
 184
 185                 if (!check_ref(name, flags))
 186                         continue;
 187
 188                 if (got_dummy_ref_with_capabilities_declaration)
 189                         die("protocol error: unexpected ref after capabilities^{}");
 190
 191                 ref = alloc_ref(buffer + GIT_SHA1_HEXSZ + 1);
 192                 oidcpy(&ref->old_oid, &old_oid);
 193                 *list = ref;
 194                 list = &ref->next;
 195         }
 196
 197         annotate_refs_with_symref_info(*orig_list);
 198
 199         return list;
 200 }
 201
 202 static const char *parse_feature_value(const char *feature_list, const char *feature, int *lenp)
 203 {
 204         int len;
 205
 206         if (!feature_list)
 207                 return NULL;
 208
 209         len = strlen(feature);
 210         while (*feature_list) {
 211                 const char *found = strstr(feature_list, feature);
 212                 if (!found)
 213                         return NULL;
 214                 if (feature_list == found || isspace(found[-1])) {
 215                         const char *value = found + len;
 216                         /* feature with no value (e.g., "thin-pack") */
 217                         if (!*value || isspace(*value)) {
 218                                 if (lenp)
 219                                         *lenp = 0;
 220                                 return value;
 221                         }
 222                         /* feature with a value (e.g., "agent=git/1.2.3") */
 223                         else if (*value == '=') {
 224                                 value++;
 225                                 if (lenp)
 226                                         *lenp = strcspn(value, " \t\n");
 227                                 return value;
 228                         }
 229                         /*
 230                          * otherwise we matched a substring of another feature;
 231                          * keep looking
 232                          */
 233                 }
 234                 feature_list = found + 1;
 235         }
 236         return NULL;
 237 }
 238
 239 int parse_feature_request(const char *feature_list, const char *feature)
 240 {
 241         return !!parse_feature_value(feature_list, feature, NULL);
 242 }
 243
 244 const char *server_feature_value(const char *feature, int *len)
 245 {
 246         return parse_feature_value(server_capabilities, feature, len);
 247 }
 248
 249 int server_supports(const char *feature)
 250 {
 251         return !!server_feature_value(feature, NULL);
 252 }
 253
 254 enum protocol {
 255         PROTO_LOCAL = 1,
 256         PROTO_FILE,
 257         PROTO_SSH,
 258         PROTO_GIT
 259 };
 260
 261 int url_is_local_not_ssh(const char *url)
 262 {
 263         const char *colon = strchr(url, ':');
 264         const char *slash = strchr(url, '/');
 265         return !colon || (slash && slash < colon) ||
 266                 has_dos_drive_prefix(url);
 267 }
 268
 269 static const char *prot_name(enum protocol protocol)
 270 {
 271         switch (protocol) {
 272                 case PROTO_LOCAL:
 273                 case PROTO_FILE:
 274                         return "file";
 275                 case PROTO_SSH:
 276                         return "ssh";
 277                 case PROTO_GIT:
 278                         return "git";
 279                 default:
 280                         return "unknown protocol";
 281         }
 282 }
 283
 284 static enum protocol get_protocol(const char *name)
 285 {
 286         if (!strcmp(name, "ssh"))
 287                 return PROTO_SSH;
 288         if (!strcmp(name, "git"))
 289                 return PROTO_GIT;
 290         if (!strcmp(name, "git+ssh")) /* deprecated - do not use */
 291                 return PROTO_SSH;
 292         if (!strcmp(name, "ssh+git")) /* deprecated - do not use */
 293                 return PROTO_SSH;
 294         if (!strcmp(name, "file"))
 295                 return PROTO_FILE;
 296         die("I don't handle protocol '%s'", name);
 297 }
 298
 299 static char *host_end(char **hoststart, int removebrackets)
 300 {
 301         char *host = *hoststart;
 302         char *end;
 303         char *start = strstr(host, "@[");
 304         if (start)
 305                 start++; /* Jump over '@' */
 306         else
 307                 start = host;
 308         if (start[0] == '[') {
 309                 end = strchr(start + 1, ']');
 310                 if (end) {
 311                         if (removebrackets) {
 312                                 *end = 0;
 313                                 memmove(start, start + 1, end - start);
 314                                 end++;
 315                         }
 316                 } else
 317                         end = host;
 318         } else
 319                 end = host;
 320         return end;
 321 }
 322
 323 #define STR_(s) # s
 324 #define STR(s)  STR_(s)
 325
 326 static void get_host_and_port(char **host, const char **port)
 327 {
 328         char *colon, *end;
 329         end = host_end(host, 1);
 330         colon = strchr(end, ':');
 331         if (colon) {
 332                 long portnr = strtol(colon + 1, &end, 10);
 333                 if (end != colon + 1 && *end == '\0' && 0 <= portnr && portnr < 65536) {
 334                         *colon = 0;
 335                         *port = colon + 1;
 336                 } else if (!colon[1]) {
 337                         *colon = 0;
 338                 }
 339         }
 340 }
 341
 342 static void enable_keepalive(int sockfd)
 343 {
 344         int ka = 1;
 345
 346         if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &ka, sizeof(ka)) < 0)
 347                 fprintf(stderr, "unable to set SO_KEEPALIVE on socket: %s\n",
 348                         strerror(errno));
 349 }
 350
 351 #ifndef NO_IPV6
 352
 353 static const char *ai_name(const struct addrinfo *ai)
 354 {
 355         static char addr[NI_MAXHOST];
 356         if (getnameinfo(ai->ai_addr, ai->ai_addrlen, addr, sizeof(addr), NULL, 0,
 357                         NI_NUMERICHOST) != 0)
 358                 xsnprintf(addr, sizeof(addr), "(unknown)");
 359
 360         return addr;
 361 }
 362
 363 /*
 364  * Returns a connected socket() fd, or else die()s.
 365  */
 366 static int git_tcp_connect_sock(char *host, int flags)
 367 {
 368         struct strbuf error_message = STRBUF_INIT;
 369         int sockfd = -1;
 370         const char *port = STR(DEFAULT_GIT_PORT);
 371         struct addrinfo hints, *ai0, *ai;
 372         int gai;
 373         int cnt = 0;
 374
 375         get_host_and_port(&host, &port);
 376         if (!*port)
 377                 port = "<none>";
 378
 379         memset(&hints, 0, sizeof(hints));
 380         if (flags & CONNECT_IPV4)
 381                 hints.ai_family = AF_INET;
 382         else if (flags & CONNECT_IPV6)
 383                 hints.ai_family = AF_INET6;
 384         hints.ai_socktype = SOCK_STREAM;
 385         hints.ai_protocol = IPPROTO_TCP;
 386
 387         if (flags & CONNECT_VERBOSE)
 388                 fprintf(stderr, "Looking up %s ... ", host);
 389
 390         gai = getaddrinfo(host, port, &hints, &ai);
 391         if (gai)
 392                 die("Unable to look up %s (port %s) (%s)", host, port, gai_strerror(gai));
 393
 394         if (flags & CONNECT_VERBOSE)
 395                 fprintf(stderr, "done.\nConnecting to %s (port %s) ... ", host, port);
 396
 397         for (ai0 = ai; ai; ai = ai->ai_next, cnt++) {
 398                 sockfd = socket(ai->ai_family,
 399                                 ai->ai_socktype, ai->ai_protocol);
 400                 if ((sockfd < 0) ||
 401                     (connect(sockfd, ai->ai_addr, ai->ai_addrlen) < 0)) {
 402                         strbuf_addf(&error_message, "%s[%d: %s]: errno=%s\n",
 403                                     host, cnt, ai_name(ai), strerror(errno));
 404                         if (0 <= sockfd)
 405                                 close(sockfd);
 406                         sockfd = -1;
 407                         continue;
 408                 }
 409                 if (flags & CONNECT_VERBOSE)
 410                         fprintf(stderr, "%s ", ai_name(ai));
 411                 break;
 412         }
 413
 414         freeaddrinfo(ai0);
 415
 416         if (sockfd < 0)
 417                 die("unable to connect to %s:\n%s", host, error_message.buf);
 418
 419         enable_keepalive(sockfd);
 420
 421         if (flags & CONNECT_VERBOSE)
 422                 fprintf(stderr, "done.\n");
 423
 424         strbuf_release(&error_message);
 425
 426         return sockfd;
 427 }
 428
 429 #else /* NO_IPV6 */
 430
 431 /*
 432  * Returns a connected socket() fd, or else die()s.
 433  */
 434 static int git_tcp_connect_sock(char *host, int flags)
 435 {
 436         struct strbuf error_message = STRBUF_INIT;
 437         int sockfd = -1;
 438         const char *port = STR(DEFAULT_GIT_PORT);
 439         char *ep;
 440         struct hostent *he;
 441         struct sockaddr_in sa;
 442         char **ap;
 443         unsigned int nport;
 444         int cnt;
 445
 446         get_host_and_port(&host, &port);
 447
 448         if (flags & CONNECT_VERBOSE)
 449                 fprintf(stderr, "Looking up %s ... ", host);
 450
 451         he = gethostbyname(host);
 452         if (!he)
 453                 die("Unable to look up %s (%s)", host, hstrerror(h_errno));
 454         nport = strtoul(port, &ep, 10);
 455         if ( ep == port || *ep ) {
 456                 /* Not numeric */
 457                 struct servent *se = getservbyname(port,"tcp");
 458                 if ( !se )
 459                         die("Unknown port %s", port);
 460                 nport = se->s_port;
 461         }
 462
 463         if (flags & CONNECT_VERBOSE)
 464                 fprintf(stderr, "done.\nConnecting to %s (port %s) ... ", host, port);
 465
 466         for (cnt = 0, ap = he->h_addr_list; *ap; ap++, cnt++) {
 467                 memset(&sa, 0, sizeof sa);
 468                 sa.sin_family = he->h_addrtype;
 469                 sa.sin_port = htons(nport);
 470                 memcpy(&sa.sin_addr, *ap, he->h_length);
 471
 472                 sockfd = socket(he->h_addrtype, SOCK_STREAM, 0);
 473                 if ((sockfd < 0) ||
 474                     connect(sockfd, (struct sockaddr *)&sa, sizeof sa) < 0) {
 475                         strbuf_addf(&error_message, "%s[%d: %s]: errno=%s\n",
 476                                 host,
 477                                 cnt,
 478                                 inet_ntoa(*(struct in_addr *)&sa.sin_addr),
 479                                 strerror(errno));
 480                         if (0 <= sockfd)
 481                                 close(sockfd);
 482                         sockfd = -1;
 483                         continue;
 484                 }
 485                 if (flags & CONNECT_VERBOSE)
 486                         fprintf(stderr, "%s ",
 487                                 inet_ntoa(*(struct in_addr *)&sa.sin_addr));
 488                 break;
 489         }
 490
 491         if (sockfd < 0)
 492                 die("unable to connect to %s:\n%s", host, error_message.buf);
 493
 494         enable_keepalive(sockfd);
 495
 496         if (flags & CONNECT_VERBOSE)
 497                 fprintf(stderr, "done.\n");
 498
 499         return sockfd;
 500 }
 501
 502 #endif /* NO_IPV6 */
 503
 504
 505 static void git_tcp_connect(int fd[2], char *host, int flags)
 506 {
 507         int sockfd = git_tcp_connect_sock(host, flags);
 508
 509         fd[0] = sockfd;
 510         fd[1] = dup(sockfd);
 511 }
 512
 513
 514 static char *git_proxy_command;
 515
 516 static int git_proxy_command_options(const char *var, const char *value,
 517                 void *cb)
 518 {
 519         if (!strcmp(var, "core.gitproxy")) {
 520                 const char *for_pos;
 521                 int matchlen = -1;
 522                 int hostlen;
 523                 const char *rhost_name = cb;
 524                 int rhost_len = strlen(rhost_name);
 525
 526                 if (git_proxy_command)
 527                         return 0;
 528                 if (!value)
 529                         return config_error_nonbool(var);
 530                 /* [core]
 531                  * ;# matches www.kernel.org as well
 532                  * gitproxy = netcatter-1 for kernel.org
 533                  * gitproxy = netcatter-2 for sample.xz
 534                  * gitproxy = netcatter-default
 535                  */
 536                 for_pos = strstr(value, " for ");
 537                 if (!for_pos)
 538                         /* matches everybody */
 539                         matchlen = strlen(value);
 540                 else {
 541                         hostlen = strlen(for_pos + 5);
 542                         if (rhost_len < hostlen)
 543                                 matchlen = -1;
 544                         else if (!strncmp(for_pos + 5,
 545                                           rhost_name + rhost_len - hostlen,
 546                                           hostlen) &&
 547                                  ((rhost_len == hostlen) ||
 548                                   rhost_name[rhost_len - hostlen -1] == '.'))
 549                                 matchlen = for_pos - value;
 550                         else
 551                                 matchlen = -1;
 552                 }
 553                 if (0 <= matchlen) {
 554                         /* core.gitproxy = none for kernel.org */
 555                         if (matchlen == 4 &&
 556                             !memcmp(value, "none", 4))
 557                                 matchlen = 0;
 558                         git_proxy_command = xmemdupz(value, matchlen);
 559                 }
 560                 return 0;
 561         }
 562
 563         return git_default_config(var, value, cb);
 564 }
 565
 566 static int git_use_proxy(const char *host)
 567 {
 568         git_proxy_command = getenv("GIT_PROXY_COMMAND");
 569         git_config(git_proxy_command_options, (void*)host);
 570         return (git_proxy_command && *git_proxy_command);
 571 }
 572
 573 static struct child_process *git_proxy_connect(int fd[2], char *host)
 574 {
 575         const char *port = STR(DEFAULT_GIT_PORT);
 576         struct child_process *proxy;
 577
 578         get_host_and_port(&host, &port);
 579
 580         if (looks_like_command_line_option(host))
 581                 die("strange hostname '%s' blocked", host);
 582         if (looks_like_command_line_option(port))
 583                 die("strange port '%s' blocked", port);
 584
 585         proxy = xmalloc(sizeof(*proxy));
 586         child_process_init(proxy);
 587         argv_array_push(&proxy->args, git_proxy_command);
 588         argv_array_push(&proxy->args, host);
 589         argv_array_push(&proxy->args, port);
 590         proxy->in = -1;
 591         proxy->out = -1;
 592         if (start_command(proxy))
 593                 die("cannot start proxy %s", git_proxy_command);
 594         fd[0] = proxy->out; /* read from proxy stdout */
 595         fd[1] = proxy->in;  /* write to proxy stdin */
 596         return proxy;
 597 }
 598
 599 static char *get_port(char *host)
 600 {
 601         char *end;
 602         char *p = strchr(host, ':');
 603
 604         if (p) {
 605                 long port = strtol(p + 1, &end, 10);
 606                 if (end != p + 1 && *end == '\0' && 0 <= port && port < 65536) {
 607                         *p = '\0';
 608                         return p+1;
 609                 }
 610         }
 611
 612         return NULL;
 613 }
 614
 615 /*
 616  * Extract protocol and relevant parts from the specified connection URL.
 617  * The caller must free() the returned strings.
 618  */
 619 static enum protocol parse_connect_url(const char *url_orig, char **ret_host,
 620                                        char **ret_path)
 621 {
 622         char *url;
 623         char *host, *path;
 624         char *end;
 625         int separator = '/';
 626         enum protocol protocol = PROTO_LOCAL;
 627
 628         if (is_url(url_orig))
 629                 url = url_decode(url_orig);
 630         else
 631                 url = xstrdup(url_orig);
 632
 633         host = strstr(url, "://");
 634         if (host) {
 635                 *host = '\0';
 636                 protocol = get_protocol(url);
 637                 host += 3;
 638         } else {
 639                 host = url;
 640                 if (!url_is_local_not_ssh(url)) {
 641                         protocol = PROTO_SSH;
 642                         separator = ':';
 643                 }
 644         }
 645
 646         /*
 647          * Don't do destructive transforms as protocol code does
 648          * '[]' unwrapping in get_host_and_port()
 649          */
 650         end = host_end(&host, 0);
 651
 652         if (protocol == PROTO_LOCAL)
 653                 path = end;
 654         else if (protocol == PROTO_FILE && has_dos_drive_prefix(end))
 655                 path = end; /* "file://$(pwd)" may be "file://C:/projects/repo" */
 656         else
 657                 path = strchr(end, separator);
 658
 659         if (!path || !*path)
 660                 die("No path specified. See 'man git-pull' for valid url syntax");
 661
 662         /*
 663          * null-terminate hostname and point path to ~ for URL's like this:
 664          *    ssh://host.xz/~user/repo
 665          */
 666
 667         end = path; /* Need to \0 terminate host here */
 668         if (separator == ':')
 669                 path++; /* path starts after ':' */
 670         if (protocol == PROTO_GIT || protocol == PROTO_SSH) {
 671                 if (path[1] == '~')
 672                         path++;
 673         }
 674
 675         path = xstrdup(path);
 676         *end = '\0';
 677
 678         *ret_host = xstrdup(host);
 679         *ret_path = path;
 680         free(url);
 681         return protocol;
 682 }
 683
 684 static struct child_process no_fork = CHILD_PROCESS_INIT;
 685
 686 static const char *get_ssh_command(void)
 687 {
 688         const char *ssh;
 689
 690         if ((ssh = getenv("GIT_SSH_COMMAND")))
 691                 return ssh;
 692
 693         if (!git_config_get_string_const("core.sshcommand", &ssh))
 694                 return ssh;
 695
 696         return NULL;
 697 }
 698
 699 /*
 700  * This returns a dummy child_process if the transport protocol does not
 701  * need fork(2), or a struct child_process object if it does.  Once done,
 702  * finish the connection with finish_connect() with the value returned from
 703  * this function (it is safe to call finish_connect() with NULL to support
 704  * the former case).
 705  *
 706  * If it returns, the connect is successful; it just dies on errors (this
 707  * will hopefully be changed in a libification effort, to return NULL when
 708  * the connection failed).
 709  */
 710 struct child_process *git_connect(int fd[2], const char *url,
 711                                   const char *prog, int flags)
 712 {
 713         char *hostandport, *path;
 714         struct child_process *conn = &no_fork;
 715         enum protocol protocol;
 716         struct strbuf cmd = STRBUF_INIT;
 717
 718         /* Without this we cannot rely on waitpid() to tell
 719          * what happened to our children.
 720          */
 721         signal(SIGCHLD, SIG_DFL);
 722
 723         protocol = parse_connect_url(url, &hostandport, &path);
 724         if ((flags & CONNECT_DIAG_URL) && (protocol != PROTO_SSH)) {
 725                 printf("Diag: url=%s\n", url ? url : "NULL");
 726                 printf("Diag: protocol=%s\n", prot_name(protocol));
 727                 printf("Diag: hostandport=%s\n", hostandport ? hostandport : "NULL");
 728                 printf("Diag: path=%s\n", path ? path : "NULL");
 729                 conn = NULL;
 730         } else if (protocol == PROTO_GIT) {
 731                 /*
 732                  * Set up virtual host information based on where we will
 733                  * connect, unless the user has overridden us in
 734                  * the environment.
 735                  */
 736                 char *target_host = getenv("GIT_OVERRIDE_VIRTUAL_HOST");
 737                 if (target_host)
 738                         target_host = xstrdup(target_host);
 739                 else
 740                         target_host = xstrdup(hostandport);
 741
 742                 transport_check_allowed("git");
 743
 744                 /* These underlying connection commands die() if they
 745                  * cannot connect.
 746                  */
 747                 if (git_use_proxy(hostandport))
 748                         conn = git_proxy_connect(fd, hostandport);
 749                 else
 750                         git_tcp_connect(fd, hostandport, flags);
 751                 /*
 752                  * Separate original protocol components prog and path
 753                  * from extended host header with a NUL byte.
 754                  *
 755                  * Note: Do not add any other headers here!  Doing so
 756                  * will cause older git-daemon servers to crash.
 757                  */
 758                 packet_write_fmt(fd[1],
 759                              "%s %s%chost=%s%c",
 760                              prog, path, 0,
 761                              target_host, 0);
 762                 free(target_host);
 763         } else {
 764                 conn = xmalloc(sizeof(*conn));
 765                 child_process_init(conn);
 766
 767                 if (looks_like_command_line_option(path))
 768                         die("strange pathname '%s' blocked", path);
 769
 770                 strbuf_addstr(&cmd, prog);
 771                 strbuf_addch(&cmd, ' ');
 772                 sq_quote_buf(&cmd, path);
 773
 774                 /* remove repo-local variables from the environment */
 775                 conn->env = local_repo_env;
 776                 conn->use_shell = 1;
 777                 conn->in = conn->out = -1;
 778                 if (protocol == PROTO_SSH) {
 779                         const char *ssh;
 780                         int putty = 0, tortoiseplink = 0;
 781                         char *ssh_host = hostandport;
 782                         const char *port = NULL;
 783                         transport_check_allowed("ssh");
 784                         get_host_and_port(&ssh_host, &port);
 785
 786                         if (!port)
 787                                 port = get_port(ssh_host);
 788
 789                         if (flags & CONNECT_DIAG_URL) {
 790                                 printf("Diag: url=%s\n", url ? url : "NULL");
 791                                 printf("Diag: protocol=%s\n", prot_name(protocol));
 792                                 printf("Diag: userandhost=%s\n", ssh_host ? ssh_host : "NULL");
 793                                 printf("Diag: port=%s\n", port ? port : "NONE");
 794                                 printf("Diag: path=%s\n", path ? path : "NULL");
 795
 796                                 free(hostandport);
 797                                 free(path);
 798                                 free(conn);
 799                                 return NULL;
 800                         }
 801
 802                         if (looks_like_command_line_option(ssh_host))
 803                                 die("strange hostname '%s' blocked", ssh_host);
 804
 805                         ssh = get_ssh_command();
 806                         if (!ssh) {
 807                                 const char *base;
 808                                 char *ssh_dup;
 809
 810                                 /*
 811                                  * GIT_SSH is the no-shell version of
 812                                  * GIT_SSH_COMMAND (and must remain so for
 813                                  * historical compatibility).
 814                                  */
 815                                 conn->use_shell = 0;
 816
 817                                 ssh = getenv("GIT_SSH");
 818                                 if (!ssh)
 819                                         ssh = "ssh";
 820
 821                                 ssh_dup = xstrdup(ssh);
 822                                 base = basename(ssh_dup);
 823
 824                                 tortoiseplink = !strcasecmp(base, "tortoiseplink") ||
 825                                         !strcasecmp(base, "tortoiseplink.exe");
 826                                 putty = tortoiseplink ||
 827                                         !strcasecmp(base, "plink") ||
 828                                         !strcasecmp(base, "plink.exe");
 829
 830                                 free(ssh_dup);
 831                         }
 832
 833                         argv_array_push(&conn->args, ssh);
 834                         if (flags & CONNECT_IPV4)
 835                                 argv_array_push(&conn->args, "-4");
 836                         else if (flags & CONNECT_IPV6)
 837                                 argv_array_push(&conn->args, "-6");
 838                         if (tortoiseplink)
 839                                 argv_array_push(&conn->args, "-batch");
 840                         if (port) {
 841                                 /* P is for PuTTY, p is for OpenSSH */
 842                                 argv_array_push(&conn->args, putty ? "-P" : "-p");
 843                                 argv_array_push(&conn->args, port);
 844                         }
 845                         argv_array_push(&conn->args, ssh_host);
 846                 } else {
 847                         transport_check_allowed("file");
 848                 }
 849                 argv_array_push(&conn->args, cmd.buf);
 850
 851                 if (start_command(conn))
 852                         die("unable to fork");
 853
 854                 fd[0] = conn->out; /* read from child's stdout */
 855                 fd[1] = conn->in;  /* write to child's stdin */
 856                 strbuf_release(&cmd);
 857         }
 858         free(hostandport);
 859         free(path);
 860         return conn;
 861 }
 862
 863 int git_connection_is_socket(struct child_process *conn)
 864 {
 865         return conn == &no_fork;
 866 }
 867
 868 int finish_connect(struct child_process *conn)
 869 {
 870         int code;
 871         if (!conn || git_connection_is_socket(conn))
 872                 return 0;
 873
 874         code = finish_command(conn);
 875         free(conn);
 876         return code;
 877 }