Imported Upstream version 2.15.1
[platform/upstream/git.git] / connect.c
1 #include "git-compat-util.h"
2 #include "cache.h"
3 #include "config.h"
4 #include "pkt-line.h"
5 #include "quote.h"
6 #include "refs.h"
7 #include "run-command.h"
8 #include "remote.h"
9 #include "connect.h"
10 #include "url.h"
11 #include "string-list.h"
12 #include "sha1-array.h"
13 #include "transport.h"
14
15 static char *server_capabilities;
16 static const char *parse_feature_value(const char *, const char *, int *);
17
18 static int check_ref(const char *name, unsigned int flags)
19 {
20         if (!flags)
21                 return 1;
22
23         if (!skip_prefix(name, "refs/", &name))
24                 return 0;
25
26         /* REF_NORMAL means that we don't want the magic fake tag refs */
27         if ((flags & REF_NORMAL) && check_refname_format(name, 0))
28                 return 0;
29
30         /* REF_HEADS means that we want regular branch heads */
31         if ((flags & REF_HEADS) && starts_with(name, "heads/"))
32                 return 1;
33
34         /* REF_TAGS means that we want tags */
35         if ((flags & REF_TAGS) && starts_with(name, "tags/"))
36                 return 1;
37
38         /* All type bits clear means that we are ok with anything */
39         return !(flags & ~REF_NORMAL);
40 }
41
42 int check_ref_type(const struct ref *ref, int flags)
43 {
44         return check_ref(ref->name, flags);
45 }
46
47 static void die_initial_contact(int unexpected)
48 {
49         if (unexpected)
50                 die(_("The remote end hung up upon initial contact"));
51         else
52                 die(_("Could not read from remote repository.\n\n"
53                       "Please make sure you have the correct access rights\n"
54                       "and the repository exists."));
55 }
56
57 static void parse_one_symref_info(struct string_list *symref, const char *val, int len)
58 {
59         char *sym, *target;
60         struct string_list_item *item;
61
62         if (!len)
63                 return; /* just "symref" */
64         /* e.g. "symref=HEAD:refs/heads/master" */
65         sym = xmemdupz(val, len);
66         target = strchr(sym, ':');
67         if (!target)
68                 /* just "symref=something" */
69                 goto reject;
70         *(target++) = '\0';
71         if (check_refname_format(sym, REFNAME_ALLOW_ONELEVEL) ||
72             check_refname_format(target, REFNAME_ALLOW_ONELEVEL))
73                 /* "symref=bogus:pair */
74                 goto reject;
75         item = string_list_append_nodup(symref, sym);
76         item->util = target;
77         return;
78 reject:
79         free(sym);
80         return;
81 }
82
83 static void annotate_refs_with_symref_info(struct ref *ref)
84 {
85         struct string_list symref = STRING_LIST_INIT_DUP;
86         const char *feature_list = server_capabilities;
87
88         while (feature_list) {
89                 int len;
90                 const char *val;
91
92                 val = parse_feature_value(feature_list, "symref", &len);
93                 if (!val)
94                         break;
95                 parse_one_symref_info(&symref, val, len);
96                 feature_list = val + 1;
97         }
98         string_list_sort(&symref);
99
100         for (; ref; ref = ref->next) {
101                 struct string_list_item *item;
102                 item = string_list_lookup(&symref, ref->name);
103                 if (!item)
104                         continue;
105                 ref->symref = xstrdup((char *)item->util);
106         }
107         string_list_clear(&symref, 0);
108 }
109
110 /*
111  * Read all the refs from the other end
112  */
113 struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
114                               struct ref **list, unsigned int flags,
115                               struct oid_array *extra_have,
116                               struct oid_array *shallow_points)
117 {
118         struct ref **orig_list = list;
119
120         /*
121          * A hang-up after seeing some response from the other end
122          * means that it is unexpected, as we know the other end is
123          * willing to talk to us.  A hang-up before seeing any
124          * response does not necessarily mean an ACL problem, though.
125          */
126         int saw_response;
127         int got_dummy_ref_with_capabilities_declaration = 0;
128
129         *list = NULL;
130         for (saw_response = 0; ; saw_response = 1) {
131                 struct ref *ref;
132                 struct object_id old_oid;
133                 char *name;
134                 int len, name_len;
135                 char *buffer = packet_buffer;
136                 const char *arg;
137
138                 len = packet_read(in, &src_buf, &src_len,
139                                   packet_buffer, sizeof(packet_buffer),
140                                   PACKET_READ_GENTLE_ON_EOF |
141                                   PACKET_READ_CHOMP_NEWLINE);
142                 if (len < 0)
143                         die_initial_contact(saw_response);
144
145                 if (!len)
146                         break;
147
148                 if (len > 4 && skip_prefix(buffer, "ERR ", &arg))
149                         die("remote error: %s", arg);
150
151                 if (len == GIT_SHA1_HEXSZ + strlen("shallow ") &&
152                         skip_prefix(buffer, "shallow ", &arg)) {
153                         if (get_oid_hex(arg, &old_oid))
154                                 die("protocol error: expected shallow sha-1, got '%s'", arg);
155                         if (!shallow_points)
156                                 die("repository on the other end cannot be shallow");
157                         oid_array_append(shallow_points, &old_oid);
158                         continue;
159                 }
160
161                 if (len < GIT_SHA1_HEXSZ + 2 || get_oid_hex(buffer, &old_oid) ||
162                         buffer[GIT_SHA1_HEXSZ] != ' ')
163                         die("protocol error: expected sha/ref, got '%s'", buffer);
164                 name = buffer + GIT_SHA1_HEXSZ + 1;
165
166                 name_len = strlen(name);
167                 if (len != name_len + GIT_SHA1_HEXSZ + 1) {
168                         free(server_capabilities);
169                         server_capabilities = xstrdup(name + name_len + 1);
170                 }
171
172                 if (extra_have && !strcmp(name, ".have")) {
173                         oid_array_append(extra_have, &old_oid);
174                         continue;
175                 }
176
177                 if (!strcmp(name, "capabilities^{}")) {
178                         if (saw_response)
179                                 die("protocol error: unexpected capabilities^{}");
180                         if (got_dummy_ref_with_capabilities_declaration)
181                                 die("protocol error: multiple capabilities^{}");
182                         got_dummy_ref_with_capabilities_declaration = 1;
183                         continue;
184                 }
185
186                 if (!check_ref(name, flags))
187                         continue;
188
189                 if (got_dummy_ref_with_capabilities_declaration)
190                         die("protocol error: unexpected ref after capabilities^{}");
191
192                 ref = alloc_ref(buffer + GIT_SHA1_HEXSZ + 1);
193                 oidcpy(&ref->old_oid, &old_oid);
194                 *list = ref;
195                 list = &ref->next;
196         }
197
198         annotate_refs_with_symref_info(*orig_list);
199
200         return list;
201 }
202
203 static const char *parse_feature_value(const char *feature_list, const char *feature, int *lenp)
204 {
205         int len;
206
207         if (!feature_list)
208                 return NULL;
209
210         len = strlen(feature);
211         while (*feature_list) {
212                 const char *found = strstr(feature_list, feature);
213                 if (!found)
214                         return NULL;
215                 if (feature_list == found || isspace(found[-1])) {
216                         const char *value = found + len;
217                         /* feature with no value (e.g., "thin-pack") */
218                         if (!*value || isspace(*value)) {
219                                 if (lenp)
220                                         *lenp = 0;
221                                 return value;
222                         }
223                         /* feature with a value (e.g., "agent=git/1.2.3") */
224                         else if (*value == '=') {
225                                 value++;
226                                 if (lenp)
227                                         *lenp = strcspn(value, " \t\n");
228                                 return value;
229                         }
230                         /*
231                          * otherwise we matched a substring of another feature;
232                          * keep looking
233                          */
234                 }
235                 feature_list = found + 1;
236         }
237         return NULL;
238 }
239
240 int parse_feature_request(const char *feature_list, const char *feature)
241 {
242         return !!parse_feature_value(feature_list, feature, NULL);
243 }
244
245 const char *server_feature_value(const char *feature, int *len)
246 {
247         return parse_feature_value(server_capabilities, feature, len);
248 }
249
250 int server_supports(const char *feature)
251 {
252         return !!server_feature_value(feature, NULL);
253 }
254
255 enum protocol {
256         PROTO_LOCAL = 1,
257         PROTO_FILE,
258         PROTO_SSH,
259         PROTO_GIT
260 };
261
262 int url_is_local_not_ssh(const char *url)
263 {
264         const char *colon = strchr(url, ':');
265         const char *slash = strchr(url, '/');
266         return !colon || (slash && slash < colon) ||
267                 has_dos_drive_prefix(url);
268 }
269
270 static const char *prot_name(enum protocol protocol)
271 {
272         switch (protocol) {
273                 case PROTO_LOCAL:
274                 case PROTO_FILE:
275                         return "file";
276                 case PROTO_SSH:
277                         return "ssh";
278                 case PROTO_GIT:
279                         return "git";
280                 default:
281                         return "unknown protocol";
282         }
283 }
284
285 static enum protocol get_protocol(const char *name)
286 {
287         if (!strcmp(name, "ssh"))
288                 return PROTO_SSH;
289         if (!strcmp(name, "git"))
290                 return PROTO_GIT;
291         if (!strcmp(name, "git+ssh")) /* deprecated - do not use */
292                 return PROTO_SSH;
293         if (!strcmp(name, "ssh+git")) /* deprecated - do not use */
294                 return PROTO_SSH;
295         if (!strcmp(name, "file"))
296                 return PROTO_FILE;
297         die("I don't handle protocol '%s'", name);
298 }
299
300 static char *host_end(char **hoststart, int removebrackets)
301 {
302         char *host = *hoststart;
303         char *end;
304         char *start = strstr(host, "@[");
305         if (start)
306                 start++; /* Jump over '@' */
307         else
308                 start = host;
309         if (start[0] == '[') {
310                 end = strchr(start + 1, ']');
311                 if (end) {
312                         if (removebrackets) {
313                                 *end = 0;
314                                 memmove(start, start + 1, end - start);
315                                 end++;
316                         }
317                 } else
318                         end = host;
319         } else
320                 end = host;
321         return end;
322 }
323
324 #define STR_(s) # s
325 #define STR(s)  STR_(s)
326
327 static void get_host_and_port(char **host, const char **port)
328 {
329         char *colon, *end;
330         end = host_end(host, 1);
331         colon = strchr(end, ':');
332         if (colon) {
333                 long portnr = strtol(colon + 1, &end, 10);
334                 if (end != colon + 1 && *end == '\0' && 0 <= portnr && portnr < 65536) {
335                         *colon = 0;
336                         *port = colon + 1;
337                 } else if (!colon[1]) {
338                         *colon = 0;
339                 }
340         }
341 }
342
343 static void enable_keepalive(int sockfd)
344 {
345         int ka = 1;
346
347         if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &ka, sizeof(ka)) < 0)
348                 fprintf(stderr, "unable to set SO_KEEPALIVE on socket: %s\n",
349                         strerror(errno));
350 }
351
352 #ifndef NO_IPV6
353
354 static const char *ai_name(const struct addrinfo *ai)
355 {
356         static char addr[NI_MAXHOST];
357         if (getnameinfo(ai->ai_addr, ai->ai_addrlen, addr, sizeof(addr), NULL, 0,
358                         NI_NUMERICHOST) != 0)
359                 xsnprintf(addr, sizeof(addr), "(unknown)");
360
361         return addr;
362 }
363
364 /*
365  * Returns a connected socket() fd, or else die()s.
366  */
367 static int git_tcp_connect_sock(char *host, int flags)
368 {
369         struct strbuf error_message = STRBUF_INIT;
370         int sockfd = -1;
371         const char *port = STR(DEFAULT_GIT_PORT);
372         struct addrinfo hints, *ai0, *ai;
373         int gai;
374         int cnt = 0;
375
376         get_host_and_port(&host, &port);
377         if (!*port)
378                 port = "<none>";
379
380         memset(&hints, 0, sizeof(hints));
381         if (flags & CONNECT_IPV4)
382                 hints.ai_family = AF_INET;
383         else if (flags & CONNECT_IPV6)
384                 hints.ai_family = AF_INET6;
385         hints.ai_socktype = SOCK_STREAM;
386         hints.ai_protocol = IPPROTO_TCP;
387
388         if (flags & CONNECT_VERBOSE)
389                 fprintf(stderr, "Looking up %s ... ", host);
390
391         gai = getaddrinfo(host, port, &hints, &ai);
392         if (gai)
393                 die("Unable to look up %s (port %s) (%s)", host, port, gai_strerror(gai));
394
395         if (flags & CONNECT_VERBOSE)
396                 fprintf(stderr, "done.\nConnecting to %s (port %s) ... ", host, port);
397
398         for (ai0 = ai; ai; ai = ai->ai_next, cnt++) {
399                 sockfd = socket(ai->ai_family,
400                                 ai->ai_socktype, ai->ai_protocol);
401                 if ((sockfd < 0) ||
402                     (connect(sockfd, ai->ai_addr, ai->ai_addrlen) < 0)) {
403                         strbuf_addf(&error_message, "%s[%d: %s]: errno=%s\n",
404                                     host, cnt, ai_name(ai), strerror(errno));
405                         if (0 <= sockfd)
406                                 close(sockfd);
407                         sockfd = -1;
408                         continue;
409                 }
410                 if (flags & CONNECT_VERBOSE)
411                         fprintf(stderr, "%s ", ai_name(ai));
412                 break;
413         }
414
415         freeaddrinfo(ai0);
416
417         if (sockfd < 0)
418                 die("unable to connect to %s:\n%s", host, error_message.buf);
419
420         enable_keepalive(sockfd);
421
422         if (flags & CONNECT_VERBOSE)
423                 fprintf(stderr, "done.\n");
424
425         strbuf_release(&error_message);
426
427         return sockfd;
428 }
429
430 #else /* NO_IPV6 */
431
432 /*
433  * Returns a connected socket() fd, or else die()s.
434  */
435 static int git_tcp_connect_sock(char *host, int flags)
436 {
437         struct strbuf error_message = STRBUF_INIT;
438         int sockfd = -1;
439         const char *port = STR(DEFAULT_GIT_PORT);
440         char *ep;
441         struct hostent *he;
442         struct sockaddr_in sa;
443         char **ap;
444         unsigned int nport;
445         int cnt;
446
447         get_host_and_port(&host, &port);
448
449         if (flags & CONNECT_VERBOSE)
450                 fprintf(stderr, "Looking up %s ... ", host);
451
452         he = gethostbyname(host);
453         if (!he)
454                 die("Unable to look up %s (%s)", host, hstrerror(h_errno));
455         nport = strtoul(port, &ep, 10);
456         if ( ep == port || *ep ) {
457                 /* Not numeric */
458                 struct servent *se = getservbyname(port,"tcp");
459                 if ( !se )
460                         die("Unknown port %s", port);
461                 nport = se->s_port;
462         }
463
464         if (flags & CONNECT_VERBOSE)
465                 fprintf(stderr, "done.\nConnecting to %s (port %s) ... ", host, port);
466
467         for (cnt = 0, ap = he->h_addr_list; *ap; ap++, cnt++) {
468                 memset(&sa, 0, sizeof sa);
469                 sa.sin_family = he->h_addrtype;
470                 sa.sin_port = htons(nport);
471                 memcpy(&sa.sin_addr, *ap, he->h_length);
472
473                 sockfd = socket(he->h_addrtype, SOCK_STREAM, 0);
474                 if ((sockfd < 0) ||
475                     connect(sockfd, (struct sockaddr *)&sa, sizeof sa) < 0) {
476                         strbuf_addf(&error_message, "%s[%d: %s]: errno=%s\n",
477                                 host,
478                                 cnt,
479                                 inet_ntoa(*(struct in_addr *)&sa.sin_addr),
480                                 strerror(errno));
481                         if (0 <= sockfd)
482                                 close(sockfd);
483                         sockfd = -1;
484                         continue;
485                 }
486                 if (flags & CONNECT_VERBOSE)
487                         fprintf(stderr, "%s ",
488                                 inet_ntoa(*(struct in_addr *)&sa.sin_addr));
489                 break;
490         }
491
492         if (sockfd < 0)
493                 die("unable to connect to %s:\n%s", host, error_message.buf);
494
495         enable_keepalive(sockfd);
496
497         if (flags & CONNECT_VERBOSE)
498                 fprintf(stderr, "done.\n");
499
500         return sockfd;
501 }
502
503 #endif /* NO_IPV6 */
504
505
506 static void git_tcp_connect(int fd[2], char *host, int flags)
507 {
508         int sockfd = git_tcp_connect_sock(host, flags);
509
510         fd[0] = sockfd;
511         fd[1] = dup(sockfd);
512 }
513
514
515 static char *git_proxy_command;
516
517 static int git_proxy_command_options(const char *var, const char *value,
518                 void *cb)
519 {
520         if (!strcmp(var, "core.gitproxy")) {
521                 const char *for_pos;
522                 int matchlen = -1;
523                 int hostlen;
524                 const char *rhost_name = cb;
525                 int rhost_len = strlen(rhost_name);
526
527                 if (git_proxy_command)
528                         return 0;
529                 if (!value)
530                         return config_error_nonbool(var);
531                 /* [core]
532                  * ;# matches www.kernel.org as well
533                  * gitproxy = netcatter-1 for kernel.org
534                  * gitproxy = netcatter-2 for sample.xz
535                  * gitproxy = netcatter-default
536                  */
537                 for_pos = strstr(value, " for ");
538                 if (!for_pos)
539                         /* matches everybody */
540                         matchlen = strlen(value);
541                 else {
542                         hostlen = strlen(for_pos + 5);
543                         if (rhost_len < hostlen)
544                                 matchlen = -1;
545                         else if (!strncmp(for_pos + 5,
546                                           rhost_name + rhost_len - hostlen,
547                                           hostlen) &&
548                                  ((rhost_len == hostlen) ||
549                                   rhost_name[rhost_len - hostlen -1] == '.'))
550                                 matchlen = for_pos - value;
551                         else
552                                 matchlen = -1;
553                 }
554                 if (0 <= matchlen) {
555                         /* core.gitproxy = none for kernel.org */
556                         if (matchlen == 4 &&
557                             !memcmp(value, "none", 4))
558                                 matchlen = 0;
559                         git_proxy_command = xmemdupz(value, matchlen);
560                 }
561                 return 0;
562         }
563
564         return git_default_config(var, value, cb);
565 }
566
567 static int git_use_proxy(const char *host)
568 {
569         git_proxy_command = getenv("GIT_PROXY_COMMAND");
570         git_config(git_proxy_command_options, (void*)host);
571         return (git_proxy_command && *git_proxy_command);
572 }
573
574 static struct child_process *git_proxy_connect(int fd[2], char *host)
575 {
576         const char *port = STR(DEFAULT_GIT_PORT);
577         struct child_process *proxy;
578
579         get_host_and_port(&host, &port);
580
581         if (looks_like_command_line_option(host))
582                 die("strange hostname '%s' blocked", host);
583         if (looks_like_command_line_option(port))
584                 die("strange port '%s' blocked", port);
585
586         proxy = xmalloc(sizeof(*proxy));
587         child_process_init(proxy);
588         argv_array_push(&proxy->args, git_proxy_command);
589         argv_array_push(&proxy->args, host);
590         argv_array_push(&proxy->args, port);
591         proxy->in = -1;
592         proxy->out = -1;
593         if (start_command(proxy))
594                 die("cannot start proxy %s", git_proxy_command);
595         fd[0] = proxy->out; /* read from proxy stdout */
596         fd[1] = proxy->in;  /* write to proxy stdin */
597         return proxy;
598 }
599
600 static char *get_port(char *host)
601 {
602         char *end;
603         char *p = strchr(host, ':');
604
605         if (p) {
606                 long port = strtol(p + 1, &end, 10);
607                 if (end != p + 1 && *end == '\0' && 0 <= port && port < 65536) {
608                         *p = '\0';
609                         return p+1;
610                 }
611         }
612
613         return NULL;
614 }
615
616 /*
617  * Extract protocol and relevant parts from the specified connection URL.
618  * The caller must free() the returned strings.
619  */
620 static enum protocol parse_connect_url(const char *url_orig, char **ret_host,
621                                        char **ret_path)
622 {
623         char *url;
624         char *host, *path;
625         char *end;
626         int separator = '/';
627         enum protocol protocol = PROTO_LOCAL;
628
629         if (is_url(url_orig))
630                 url = url_decode(url_orig);
631         else
632                 url = xstrdup(url_orig);
633
634         host = strstr(url, "://");
635         if (host) {
636                 *host = '\0';
637                 protocol = get_protocol(url);
638                 host += 3;
639         } else {
640                 host = url;
641                 if (!url_is_local_not_ssh(url)) {
642                         protocol = PROTO_SSH;
643                         separator = ':';
644                 }
645         }
646
647         /*
648          * Don't do destructive transforms as protocol code does
649          * '[]' unwrapping in get_host_and_port()
650          */
651         end = host_end(&host, 0);
652
653         if (protocol == PROTO_LOCAL)
654                 path = end;
655         else if (protocol == PROTO_FILE && has_dos_drive_prefix(end))
656                 path = end; /* "file://$(pwd)" may be "file://C:/projects/repo" */
657         else
658                 path = strchr(end, separator);
659
660         if (!path || !*path)
661                 die("No path specified. See 'man git-pull' for valid url syntax");
662
663         /*
664          * null-terminate hostname and point path to ~ for URL's like this:
665          *    ssh://host.xz/~user/repo
666          */
667
668         end = path; /* Need to \0 terminate host here */
669         if (separator == ':')
670                 path++; /* path starts after ':' */
671         if (protocol == PROTO_GIT || protocol == PROTO_SSH) {
672                 if (path[1] == '~')
673                         path++;
674         }
675
676         path = xstrdup(path);
677         *end = '\0';
678
679         *ret_host = xstrdup(host);
680         *ret_path = path;
681         free(url);
682         return protocol;
683 }
684
685 static struct child_process no_fork = CHILD_PROCESS_INIT;
686
687 static const char *get_ssh_command(void)
688 {
689         const char *ssh;
690
691         if ((ssh = getenv("GIT_SSH_COMMAND")))
692                 return ssh;
693
694         if (!git_config_get_string_const("core.sshcommand", &ssh))
695                 return ssh;
696
697         return NULL;
698 }
699
700 static int override_ssh_variant(int *port_option, int *needs_batch)
701 {
702         char *variant;
703
704         variant = xstrdup_or_null(getenv("GIT_SSH_VARIANT"));
705         if (!variant &&
706             git_config_get_string("ssh.variant", &variant))
707                 return 0;
708
709         if (!strcmp(variant, "plink") || !strcmp(variant, "putty")) {
710                 *port_option = 'P';
711                 *needs_batch = 0;
712         } else if (!strcmp(variant, "tortoiseplink")) {
713                 *port_option = 'P';
714                 *needs_batch = 1;
715         } else {
716                 *port_option = 'p';
717                 *needs_batch = 0;
718         }
719         free(variant);
720         return 1;
721 }
722
723 static void handle_ssh_variant(const char *ssh_command, int is_cmdline,
724                                int *port_option, int *needs_batch)
725 {
726         const char *variant;
727         char *p = NULL;
728
729         if (override_ssh_variant(port_option, needs_batch))
730                 return;
731
732         if (!is_cmdline) {
733                 p = xstrdup(ssh_command);
734                 variant = basename(p);
735         } else {
736                 const char **ssh_argv;
737
738                 p = xstrdup(ssh_command);
739                 if (split_cmdline(p, &ssh_argv) > 0) {
740                         variant = basename((char *)ssh_argv[0]);
741                         /*
742                          * At this point, variant points into the buffer
743                          * referenced by p, hence we do not need ssh_argv
744                          * any longer.
745                          */
746                         free(ssh_argv);
747                 } else {
748                         free(p);
749                         return;
750                 }
751         }
752
753         if (!strcasecmp(variant, "plink") ||
754             !strcasecmp(variant, "plink.exe"))
755                 *port_option = 'P';
756         else if (!strcasecmp(variant, "tortoiseplink") ||
757                  !strcasecmp(variant, "tortoiseplink.exe")) {
758                 *port_option = 'P';
759                 *needs_batch = 1;
760         }
761         free(p);
762 }
763
764 /*
765  * This returns a dummy child_process if the transport protocol does not
766  * need fork(2), or a struct child_process object if it does.  Once done,
767  * finish the connection with finish_connect() with the value returned from
768  * this function (it is safe to call finish_connect() with NULL to support
769  * the former case).
770  *
771  * If it returns, the connect is successful; it just dies on errors (this
772  * will hopefully be changed in a libification effort, to return NULL when
773  * the connection failed).
774  */
775 struct child_process *git_connect(int fd[2], const char *url,
776                                   const char *prog, int flags)
777 {
778         char *hostandport, *path;
779         struct child_process *conn = &no_fork;
780         enum protocol protocol;
781
782         /* Without this we cannot rely on waitpid() to tell
783          * what happened to our children.
784          */
785         signal(SIGCHLD, SIG_DFL);
786
787         protocol = parse_connect_url(url, &hostandport, &path);
788         if ((flags & CONNECT_DIAG_URL) && (protocol != PROTO_SSH)) {
789                 printf("Diag: url=%s\n", url ? url : "NULL");
790                 printf("Diag: protocol=%s\n", prot_name(protocol));
791                 printf("Diag: hostandport=%s\n", hostandport ? hostandport : "NULL");
792                 printf("Diag: path=%s\n", path ? path : "NULL");
793                 conn = NULL;
794         } else if (protocol == PROTO_GIT) {
795                 /*
796                  * Set up virtual host information based on where we will
797                  * connect, unless the user has overridden us in
798                  * the environment.
799                  */
800                 char *target_host = getenv("GIT_OVERRIDE_VIRTUAL_HOST");
801                 if (target_host)
802                         target_host = xstrdup(target_host);
803                 else
804                         target_host = xstrdup(hostandport);
805
806                 transport_check_allowed("git");
807
808                 /* These underlying connection commands die() if they
809                  * cannot connect.
810                  */
811                 if (git_use_proxy(hostandport))
812                         conn = git_proxy_connect(fd, hostandport);
813                 else
814                         git_tcp_connect(fd, hostandport, flags);
815                 /*
816                  * Separate original protocol components prog and path
817                  * from extended host header with a NUL byte.
818                  *
819                  * Note: Do not add any other headers here!  Doing so
820                  * will cause older git-daemon servers to crash.
821                  */
822                 packet_write_fmt(fd[1],
823                              "%s %s%chost=%s%c",
824                              prog, path, 0,
825                              target_host, 0);
826                 free(target_host);
827         } else {
828                 struct strbuf cmd = STRBUF_INIT;
829
830                 conn = xmalloc(sizeof(*conn));
831                 child_process_init(conn);
832
833                 if (looks_like_command_line_option(path))
834                         die("strange pathname '%s' blocked", path);
835
836                 strbuf_addstr(&cmd, prog);
837                 strbuf_addch(&cmd, ' ');
838                 sq_quote_buf(&cmd, path);
839
840                 /* remove repo-local variables from the environment */
841                 conn->env = local_repo_env;
842                 conn->use_shell = 1;
843                 conn->in = conn->out = -1;
844                 if (protocol == PROTO_SSH) {
845                         const char *ssh;
846                         int needs_batch = 0;
847                         int port_option = 'p';
848                         char *ssh_host = hostandport;
849                         const char *port = NULL;
850                         transport_check_allowed("ssh");
851                         get_host_and_port(&ssh_host, &port);
852
853                         if (!port)
854                                 port = get_port(ssh_host);
855
856                         if (flags & CONNECT_DIAG_URL) {
857                                 printf("Diag: url=%s\n", url ? url : "NULL");
858                                 printf("Diag: protocol=%s\n", prot_name(protocol));
859                                 printf("Diag: userandhost=%s\n", ssh_host ? ssh_host : "NULL");
860                                 printf("Diag: port=%s\n", port ? port : "NONE");
861                                 printf("Diag: path=%s\n", path ? path : "NULL");
862
863                                 free(hostandport);
864                                 free(path);
865                                 free(conn);
866                                 strbuf_release(&cmd);
867                                 return NULL;
868                         }
869
870                         if (looks_like_command_line_option(ssh_host))
871                                 die("strange hostname '%s' blocked", ssh_host);
872
873                         ssh = get_ssh_command();
874                         if (ssh)
875                                 handle_ssh_variant(ssh, 1, &port_option,
876                                                    &needs_batch);
877                         else {
878                                 /*
879                                  * GIT_SSH is the no-shell version of
880                                  * GIT_SSH_COMMAND (and must remain so for
881                                  * historical compatibility).
882                                  */
883                                 conn->use_shell = 0;
884
885                                 ssh = getenv("GIT_SSH");
886                                 if (!ssh)
887                                         ssh = "ssh";
888                                 else
889                                         handle_ssh_variant(ssh, 0,
890                                                            &port_option,
891                                                            &needs_batch);
892                         }
893
894                         argv_array_push(&conn->args, ssh);
895                         if (flags & CONNECT_IPV4)
896                                 argv_array_push(&conn->args, "-4");
897                         else if (flags & CONNECT_IPV6)
898                                 argv_array_push(&conn->args, "-6");
899                         if (needs_batch)
900                                 argv_array_push(&conn->args, "-batch");
901                         if (port) {
902                                 argv_array_pushf(&conn->args,
903                                                  "-%c", port_option);
904                                 argv_array_push(&conn->args, port);
905                         }
906                         argv_array_push(&conn->args, ssh_host);
907                 } else {
908                         transport_check_allowed("file");
909                 }
910                 argv_array_push(&conn->args, cmd.buf);
911
912                 if (start_command(conn))
913                         die("unable to fork");
914
915                 fd[0] = conn->out; /* read from child's stdout */
916                 fd[1] = conn->in;  /* write to child's stdin */
917                 strbuf_release(&cmd);
918         }
919         free(hostandport);
920         free(path);
921         return conn;
922 }
923
924 int git_connection_is_socket(struct child_process *conn)
925 {
926         return conn == &no_fork;
927 }
928
929 int finish_connect(struct child_process *conn)
930 {
931         int code;
932         if (!conn || git_connection_is_socket(conn))
933                 return 0;
934
935         code = finish_command(conn);
936         free(conn);
937         return code;
938 }