http-walker.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "pack.h"
   4 #include "walker.h"
   5 #include "http.h"
   6
   7 #define PREV_BUF_SIZE 4096
   8 #define RANGE_HEADER_SIZE 30
   9
  10 struct alt_base
  11 {
  12         char *base;
  13         int got_indices;
  14         struct packed_git *packs;
  15         struct alt_base *next;
  16 };
  17
  18 enum object_request_state {
  19         WAITING,
  20         ABORTED,
  21         ACTIVE,
  22         COMPLETE,
  23 };
  24
  25 struct object_request
  26 {
  27         struct walker *walker;
  28         unsigned char sha1[20];
  29         struct alt_base *repo;
  30         char *url;
  31         char filename[PATH_MAX];
  32         char tmpfile[PATH_MAX];
  33         int local;
  34         enum object_request_state state;
  35         CURLcode curl_result;
  36         char errorstr[CURL_ERROR_SIZE];
  37         long http_code;
  38         unsigned char real_sha1[20];
  39         git_SHA_CTX c;
  40         z_stream stream;
  41         int zret;
  42         int rename;
  43         struct active_request_slot *slot;
  44         struct object_request *next;
  45 };
  46
  47 struct alternates_request {
  48         struct walker *walker;
  49         const char *base;
  50         char *url;
  51         struct strbuf *buffer;
  52         struct active_request_slot *slot;
  53         int http_specific;
  54 };
  55
  56 struct walker_data {
  57         const char *url;
  58         int got_alternates;
  59         struct alt_base *alt;
  60         struct curl_slist *no_pragma_header;
  61 };
  62
  63 static struct object_request *object_queue_head;
  64
  65 static size_t fwrite_sha1_file(void *ptr, size_t eltsize, size_t nmemb,
  66                                void *data)
  67 {
  68         unsigned char expn[4096];
  69         size_t size = eltsize * nmemb;
  70         int posn = 0;
  71         struct object_request *obj_req = (struct object_request *)data;
  72         do {
  73                 ssize_t retval = xwrite(obj_req->local,
  74                                        (char *) ptr + posn, size - posn);
  75                 if (retval < 0)
  76                         return posn;
  77                 posn += retval;
  78         } while (posn < size);
  79
  80         obj_req->stream.avail_in = size;
  81         obj_req->stream.next_in = ptr;
  82         do {
  83                 obj_req->stream.next_out = expn;
  84                 obj_req->stream.avail_out = sizeof(expn);
  85                 obj_req->zret = git_inflate(&obj_req->stream, Z_SYNC_FLUSH);
  86                 git_SHA1_Update(&obj_req->c, expn,
  87                             sizeof(expn) - obj_req->stream.avail_out);
  88         } while (obj_req->stream.avail_in && obj_req->zret == Z_OK);
  89         data_received++;
  90         return size;
  91 }
  92
  93 static void fetch_alternates(struct walker *walker, const char *base);
  94
  95 static void process_object_response(void *callback_data);
  96
  97 static void start_object_request(struct walker *walker,
  98                                  struct object_request *obj_req)
  99 {
 100         char *hex = sha1_to_hex(obj_req->sha1);
 101         char prevfile[PATH_MAX];
 102         char *url;
 103         char *posn;
 104         int prevlocal;
 105         unsigned char prev_buf[PREV_BUF_SIZE];
 106         ssize_t prev_read = 0;
 107         long prev_posn = 0;
 108         char range[RANGE_HEADER_SIZE];
 109         struct curl_slist *range_header = NULL;
 110         struct active_request_slot *slot;
 111         struct walker_data *data = walker->data;
 112
 113         snprintf(prevfile, sizeof(prevfile), "%s.prev", obj_req->filename);
 114         unlink_or_warn(prevfile);
 115         rename(obj_req->tmpfile, prevfile);
 116         unlink_or_warn(obj_req->tmpfile);
 117
 118         if (obj_req->local != -1)
 119                 error("fd leakage in start: %d", obj_req->local);
 120         obj_req->local = open(obj_req->tmpfile,
 121                               O_WRONLY | O_CREAT | O_EXCL, 0666);
 122         /* This could have failed due to the "lazy directory creation";
 123          * try to mkdir the last path component.
 124          */
 125         if (obj_req->local < 0 && errno == ENOENT) {
 126                 char *dir = strrchr(obj_req->tmpfile, '/');
 127                 if (dir) {
 128                         *dir = 0;
 129                         mkdir(obj_req->tmpfile, 0777);
 130                         *dir = '/';
 131                 }
 132                 obj_req->local = open(obj_req->tmpfile,
 133                                       O_WRONLY | O_CREAT | O_EXCL, 0666);
 134         }
 135
 136         if (obj_req->local < 0) {
 137                 obj_req->state = ABORTED;
 138                 error("Couldn't create temporary file %s for %s: %s",
 139                       obj_req->tmpfile, obj_req->filename, strerror(errno));
 140                 return;
 141         }
 142
 143         memset(&obj_req->stream, 0, sizeof(obj_req->stream));
 144
 145         git_inflate_init(&obj_req->stream);
 146
 147         git_SHA1_Init(&obj_req->c);
 148
 149         url = xmalloc(strlen(obj_req->repo->base) + 51);
 150         obj_req->url = xmalloc(strlen(obj_req->repo->base) + 51);
 151         strcpy(url, obj_req->repo->base);
 152         posn = url + strlen(obj_req->repo->base);
 153         strcpy(posn, "/objects/");
 154         posn += 9;
 155         memcpy(posn, hex, 2);
 156         posn += 2;
 157         *(posn++) = '/';
 158         strcpy(posn, hex + 2);
 159         strcpy(obj_req->url, url);
 160
 161         /* If a previous temp file is present, process what was already
 162            fetched. */
 163         prevlocal = open(prevfile, O_RDONLY);
 164         if (prevlocal != -1) {
 165                 do {
 166                         prev_read = xread(prevlocal, prev_buf, PREV_BUF_SIZE);
 167                         if (prev_read>0) {
 168                                 if (fwrite_sha1_file(prev_buf,
 169                                                      1,
 170                                                      prev_read,
 171                                                      obj_req) == prev_read) {
 172                                         prev_posn += prev_read;
 173                                 } else {
 174                                         prev_read = -1;
 175                                 }
 176                         }
 177                 } while (prev_read > 0);
 178                 close(prevlocal);
 179         }
 180         unlink_or_warn(prevfile);
 181
 182         /* Reset inflate/SHA1 if there was an error reading the previous temp
 183            file; also rewind to the beginning of the local file. */
 184         if (prev_read == -1) {
 185                 memset(&obj_req->stream, 0, sizeof(obj_req->stream));
 186                 git_inflate_init(&obj_req->stream);
 187                 git_SHA1_Init(&obj_req->c);
 188                 if (prev_posn>0) {
 189                         prev_posn = 0;
 190                         lseek(obj_req->local, 0, SEEK_SET);
 191                         ftruncate(obj_req->local, 0);
 192                 }
 193         }
 194
 195         slot = get_active_slot();
 196         slot->callback_func = process_object_response;
 197         slot->callback_data = obj_req;
 198         obj_req->slot = slot;
 199
 200         curl_easy_setopt(slot->curl, CURLOPT_FILE, obj_req);
 201         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
 202         curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, obj_req->errorstr);
 203         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 204         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
 205
 206         /* If we have successfully processed data from a previous fetch
 207            attempt, only fetch the data we don't already have. */
 208         if (prev_posn>0) {
 209                 if (walker->get_verbosely)
 210                         fprintf(stderr,
 211                                 "Resuming fetch of object %s at byte %ld\n",
 212                                 hex, prev_posn);
 213                 sprintf(range, "Range: bytes=%ld-", prev_posn);
 214                 range_header = curl_slist_append(range_header, range);
 215                 curl_easy_setopt(slot->curl,
 216                                  CURLOPT_HTTPHEADER, range_header);
 217         }
 218
 219         /* Try to get the request started, abort the request on error */
 220         obj_req->state = ACTIVE;
 221         if (!start_active_slot(slot)) {
 222                 obj_req->state = ABORTED;
 223                 obj_req->slot = NULL;
 224                 close(obj_req->local); obj_req->local = -1;
 225                 free(obj_req->url);
 226                 return;
 227         }
 228 }
 229
 230 static void finish_object_request(struct object_request *obj_req)
 231 {
 232         struct stat st;
 233
 234         close(obj_req->local); obj_req->local = -1;
 235
 236         if (obj_req->http_code == 416) {
 237                 fprintf(stderr, "Warning: requested range invalid; we may already have all the data.\n");
 238         } else if (obj_req->curl_result != CURLE_OK) {
 239                 if (stat(obj_req->tmpfile, &st) == 0)
 240                         if (st.st_size == 0)
 241                                 unlink_or_warn(obj_req->tmpfile);
 242                 return;
 243         }
 244
 245         git_inflate_end(&obj_req->stream);
 246         git_SHA1_Final(obj_req->real_sha1, &obj_req->c);
 247         if (obj_req->zret != Z_STREAM_END) {
 248                 unlink_or_warn(obj_req->tmpfile);
 249                 return;
 250         }
 251         if (hashcmp(obj_req->sha1, obj_req->real_sha1)) {
 252                 unlink_or_warn(obj_req->tmpfile);
 253                 return;
 254         }
 255         obj_req->rename =
 256                 move_temp_to_file(obj_req->tmpfile, obj_req->filename);
 257
 258         if (obj_req->rename == 0)
 259                 walker_say(obj_req->walker, "got %s\n", sha1_to_hex(obj_req->sha1));
 260 }
 261
 262 static void process_object_response(void *callback_data)
 263 {
 264         struct object_request *obj_req =
 265                 (struct object_request *)callback_data;
 266         struct walker *walker = obj_req->walker;
 267         struct walker_data *data = walker->data;
 268         struct alt_base *alt = data->alt;
 269
 270         obj_req->curl_result = obj_req->slot->curl_result;
 271         obj_req->http_code = obj_req->slot->http_code;
 272         obj_req->slot = NULL;
 273         obj_req->state = COMPLETE;
 274
 275         /* Use alternates if necessary */
 276         if (missing_target(obj_req)) {
 277                 fetch_alternates(walker, alt->base);
 278                 if (obj_req->repo->next != NULL) {
 279                         obj_req->repo =
 280                                 obj_req->repo->next;
 281                         close(obj_req->local);
 282                         obj_req->local = -1;
 283                         start_object_request(walker, obj_req);
 284                         return;
 285                 }
 286         }
 287
 288         finish_object_request(obj_req);
 289 }
 290
 291 static void release_object_request(struct object_request *obj_req)
 292 {
 293         struct object_request *entry = object_queue_head;
 294
 295         if (obj_req->local != -1)
 296                 error("fd leakage in release: %d", obj_req->local);
 297         if (obj_req == object_queue_head) {
 298                 object_queue_head = obj_req->next;
 299         } else {
 300                 while (entry->next != NULL && entry->next != obj_req)
 301                         entry = entry->next;
 302                 if (entry->next == obj_req)
 303                         entry->next = entry->next->next;
 304         }
 305
 306         free(obj_req->url);
 307         free(obj_req);
 308 }
 309
 310 #ifdef USE_CURL_MULTI
 311 static int fill_active_slot(struct walker *walker)
 312 {
 313         struct object_request *obj_req;
 314
 315         for (obj_req = object_queue_head; obj_req; obj_req = obj_req->next) {
 316                 if (obj_req->state == WAITING) {
 317                         if (has_sha1_file(obj_req->sha1))
 318                                 obj_req->state = COMPLETE;
 319                         else {
 320                                 start_object_request(walker, obj_req);
 321                                 return 1;
 322                         }
 323                 }
 324         }
 325         return 0;
 326 }
 327 #endif
 328
 329 static void prefetch(struct walker *walker, unsigned char *sha1)
 330 {
 331         struct object_request *newreq;
 332         struct object_request *tail;
 333         struct walker_data *data = walker->data;
 334         char *filename = sha1_file_name(sha1);
 335
 336         newreq = xmalloc(sizeof(*newreq));
 337         newreq->walker = walker;
 338         hashcpy(newreq->sha1, sha1);
 339         newreq->repo = data->alt;
 340         newreq->url = NULL;
 341         newreq->local = -1;
 342         newreq->state = WAITING;
 343         snprintf(newreq->filename, sizeof(newreq->filename), "%s", filename);
 344         snprintf(newreq->tmpfile, sizeof(newreq->tmpfile),
 345                  "%s.temp", filename);
 346         newreq->slot = NULL;
 347         newreq->next = NULL;
 348
 349         if (object_queue_head == NULL) {
 350                 object_queue_head = newreq;
 351         } else {
 352                 tail = object_queue_head;
 353                 while (tail->next != NULL) {
 354                         tail = tail->next;
 355                 }
 356                 tail->next = newreq;
 357         }
 358
 359 #ifdef USE_CURL_MULTI
 360         fill_active_slots();
 361         step_active_slots();
 362 #endif
 363 }
 364
 365 static int fetch_index(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 366 {
 367         char *hex = sha1_to_hex(sha1);
 368         char *filename;
 369         char *url;
 370         char tmpfile[PATH_MAX];
 371         long prev_posn = 0;
 372         char range[RANGE_HEADER_SIZE];
 373         struct curl_slist *range_header = NULL;
 374         struct walker_data *data = walker->data;
 375
 376         FILE *indexfile;
 377         struct active_request_slot *slot;
 378         struct slot_results results;
 379
 380         if (has_pack_index(sha1))
 381                 return 0;
 382
 383         if (walker->get_verbosely)
 384                 fprintf(stderr, "Getting index for pack %s\n", hex);
 385
 386         url = xmalloc(strlen(repo->base) + 64);
 387         sprintf(url, "%s/objects/pack/pack-%s.idx", repo->base, hex);
 388
 389         filename = sha1_pack_index_name(sha1);
 390         snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
 391         indexfile = fopen(tmpfile, "a");
 392         if (!indexfile)
 393                 return error("Unable to open local file %s for pack index",
 394                              tmpfile);
 395
 396         slot = get_active_slot();
 397         slot->results = &results;
 398         curl_easy_setopt(slot->curl, CURLOPT_FILE, indexfile);
 399         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
 400         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 401         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
 402         slot->local = indexfile;
 403
 404         /* If there is data present from a previous transfer attempt,
 405            resume where it left off */
 406         prev_posn = ftell(indexfile);
 407         if (prev_posn>0) {
 408                 if (walker->get_verbosely)
 409                         fprintf(stderr,
 410                                 "Resuming fetch of index for pack %s at byte %ld\n",
 411                                 hex, prev_posn);
 412                 sprintf(range, "Range: bytes=%ld-", prev_posn);
 413                 range_header = curl_slist_append(range_header, range);
 414                 curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
 415         }
 416
 417         if (start_active_slot(slot)) {
 418                 run_active_slot(slot);
 419                 if (results.curl_result != CURLE_OK) {
 420                         fclose(indexfile);
 421                         return error("Unable to get pack index %s\n%s", url,
 422                                      curl_errorstr);
 423                 }
 424         } else {
 425                 fclose(indexfile);
 426                 return error("Unable to start request");
 427         }
 428
 429         fclose(indexfile);
 430
 431         return move_temp_to_file(tmpfile, filename);
 432 }
 433
 434 static int setup_index(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 435 {
 436         struct packed_git *new_pack;
 437         if (has_pack_file(sha1))
 438                 return 0; /* don't list this as something we can get */
 439
 440         if (fetch_index(walker, repo, sha1))
 441                 return -1;
 442
 443         new_pack = parse_pack_index(sha1);
 444         if (!new_pack)
 445                 return -1; /* parse_pack_index() already issued error message */
 446         new_pack->next = repo->packs;
 447         repo->packs = new_pack;
 448         return 0;
 449 }
 450
 451 static void process_alternates_response(void *callback_data)
 452 {
 453         struct alternates_request *alt_req =
 454                 (struct alternates_request *)callback_data;
 455         struct walker *walker = alt_req->walker;
 456         struct walker_data *cdata = walker->data;
 457         struct active_request_slot *slot = alt_req->slot;
 458         struct alt_base *tail = cdata->alt;
 459         const char *base = alt_req->base;
 460         static const char null_byte = '\0';
 461         char *data;
 462         int i = 0;
 463
 464         if (alt_req->http_specific) {
 465                 if (slot->curl_result != CURLE_OK ||
 466                     !alt_req->buffer->len) {
 467
 468                         /* Try reusing the slot to get non-http alternates */
 469                         alt_req->http_specific = 0;
 470                         sprintf(alt_req->url, "%s/objects/info/alternates",
 471                                 base);
 472                         curl_easy_setopt(slot->curl, CURLOPT_URL,
 473                                          alt_req->url);
 474                         active_requests++;
 475                         slot->in_use = 1;
 476                         if (slot->finished != NULL)
 477                                 (*slot->finished) = 0;
 478                         if (!start_active_slot(slot)) {
 479                                 cdata->got_alternates = -1;
 480                                 slot->in_use = 0;
 481                                 if (slot->finished != NULL)
 482                                         (*slot->finished) = 1;
 483                         }
 484                         return;
 485                 }
 486         } else if (slot->curl_result != CURLE_OK) {
 487                 if (!missing_target(slot)) {
 488                         cdata->got_alternates = -1;
 489                         return;
 490                 }
 491         }
 492
 493         fwrite_buffer(&null_byte, 1, 1, alt_req->buffer);
 494         alt_req->buffer->len--;
 495         data = alt_req->buffer->buf;
 496
 497         while (i < alt_req->buffer->len) {
 498                 int posn = i;
 499                 while (posn < alt_req->buffer->len && data[posn] != '\n')
 500                         posn++;
 501                 if (data[posn] == '\n') {
 502                         int okay = 0;
 503                         int serverlen = 0;
 504                         struct alt_base *newalt;
 505                         char *target = NULL;
 506                         if (data[i] == '/') {
 507                                 /* This counts
 508                                  * http://git.host/pub/scm/linux.git/
 509                                  * -----------here^
 510                                  * so memcpy(dst, base, serverlen) will
 511                                  * copy up to "...git.host".
 512                                  */
 513                                 const char *colon_ss = strstr(base,"://");
 514                                 if (colon_ss) {
 515                                         serverlen = (strchr(colon_ss + 3, '/')
 516                                                      - base);
 517                                         okay = 1;
 518                                 }
 519                         } else if (!memcmp(data + i, "../", 3)) {
 520                                 /* Relative URL; chop the corresponding
 521                                  * number of subpath from base (and ../
 522                                  * from data), and concatenate the result.
 523                                  *
 524                                  * The code first drops ../ from data, and
 525                                  * then drops one ../ from data and one path
 526                                  * from base.  IOW, one extra ../ is dropped
 527                                  * from data than path is dropped from base.
 528                                  *
 529                                  * This is not wrong.  The alternate in
 530                                  *     http://git.host/pub/scm/linux.git/
 531                                  * to borrow from
 532                                  *     http://git.host/pub/scm/linus.git/
 533                                  * is ../../linus.git/objects/.  You need
 534                                  * two ../../ to borrow from your direct
 535                                  * neighbour.
 536                                  */
 537                                 i += 3;
 538                                 serverlen = strlen(base);
 539                                 while (i + 2 < posn &&
 540                                        !memcmp(data + i, "../", 3)) {
 541                                         do {
 542                                                 serverlen--;
 543                                         } while (serverlen &&
 544                                                  base[serverlen - 1] != '/');
 545                                         i += 3;
 546                                 }
 547                                 /* If the server got removed, give up. */
 548                                 okay = strchr(base, ':') - base + 3 <
 549                                         serverlen;
 550                         } else if (alt_req->http_specific) {
 551                                 char *colon = strchr(data + i, ':');
 552                                 char *slash = strchr(data + i, '/');
 553                                 if (colon && slash && colon < data + posn &&
 554                                     slash < data + posn && colon < slash) {
 555                                         okay = 1;
 556                                 }
 557                         }
 558                         /* skip "objects\n" at end */
 559                         if (okay) {
 560                                 target = xmalloc(serverlen + posn - i - 6);
 561                                 memcpy(target, base, serverlen);
 562                                 memcpy(target + serverlen, data + i,
 563                                        posn - i - 7);
 564                                 target[serverlen + posn - i - 7] = 0;
 565                                 if (walker->get_verbosely)
 566                                         fprintf(stderr,
 567                                                 "Also look at %s\n", target);
 568                                 newalt = xmalloc(sizeof(*newalt));
 569                                 newalt->next = NULL;
 570                                 newalt->base = target;
 571                                 newalt->got_indices = 0;
 572                                 newalt->packs = NULL;
 573
 574                                 while (tail->next != NULL)
 575                                         tail = tail->next;
 576                                 tail->next = newalt;
 577                         }
 578                 }
 579                 i = posn + 1;
 580         }
 581
 582         cdata->got_alternates = 1;
 583 }
 584
 585 static void fetch_alternates(struct walker *walker, const char *base)
 586 {
 587         struct strbuf buffer = STRBUF_INIT;
 588         char *url;
 589         struct active_request_slot *slot;
 590         struct alternates_request alt_req;
 591         struct walker_data *cdata = walker->data;
 592
 593         /* If another request has already started fetching alternates,
 594            wait for them to arrive and return to processing this request's
 595            curl message */
 596 #ifdef USE_CURL_MULTI
 597         while (cdata->got_alternates == 0) {
 598                 step_active_slots();
 599         }
 600 #endif
 601
 602         /* Nothing to do if they've already been fetched */
 603         if (cdata->got_alternates == 1)
 604                 return;
 605
 606         /* Start the fetch */
 607         cdata->got_alternates = 0;
 608
 609         if (walker->get_verbosely)
 610                 fprintf(stderr, "Getting alternates list for %s\n", base);
 611
 612         url = xmalloc(strlen(base) + 31);
 613         sprintf(url, "%s/objects/info/http-alternates", base);
 614
 615         /* Use a callback to process the result, since another request
 616            may fail and need to have alternates loaded before continuing */
 617         slot = get_active_slot();
 618         slot->callback_func = process_alternates_response;
 619         alt_req.walker = walker;
 620         slot->callback_data = &alt_req;
 621
 622         curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
 623         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 624         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 625
 626         alt_req.base = base;
 627         alt_req.url = url;
 628         alt_req.buffer = &buffer;
 629         alt_req.http_specific = 1;
 630         alt_req.slot = slot;
 631
 632         if (start_active_slot(slot))
 633                 run_active_slot(slot);
 634         else
 635                 cdata->got_alternates = -1;
 636
 637         strbuf_release(&buffer);
 638         free(url);
 639 }
 640
 641 static int fetch_indices(struct walker *walker, struct alt_base *repo)
 642 {
 643         unsigned char sha1[20];
 644         char *url;
 645         struct strbuf buffer = STRBUF_INIT;
 646         char *data;
 647         int i = 0;
 648         int ret = 0;
 649
 650         struct active_request_slot *slot;
 651         struct slot_results results;
 652
 653         if (repo->got_indices)
 654                 return 0;
 655
 656         if (walker->get_verbosely)
 657                 fprintf(stderr, "Getting pack list for %s\n", repo->base);
 658
 659         url = xmalloc(strlen(repo->base) + 21);
 660         sprintf(url, "%s/objects/info/packs", repo->base);
 661
 662         slot = get_active_slot();
 663         slot->results = &results;
 664         curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
 665         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 666         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 667         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, NULL);
 668         if (start_active_slot(slot)) {
 669                 run_active_slot(slot);
 670                 if (results.curl_result != CURLE_OK) {
 671                         if (missing_target(&results)) {
 672                                 repo->got_indices = 1;
 673                                 goto cleanup;
 674                         } else {
 675                                 repo->got_indices = 0;
 676                                 ret = error("%s", curl_errorstr);
 677                                 goto cleanup;
 678                         }
 679                 }
 680         } else {
 681                 repo->got_indices = 0;
 682                 ret = error("Unable to start request");
 683                 goto cleanup;
 684         }
 685
 686         data = buffer.buf;
 687         while (i < buffer.len) {
 688                 switch (data[i]) {
 689                 case 'P':
 690                         i++;
 691                         if (i + 52 <= buffer.len &&
 692                             !prefixcmp(data + i, " pack-") &&
 693                             !prefixcmp(data + i + 46, ".pack\n")) {
 694                                 get_sha1_hex(data + i + 6, sha1);
 695                                 setup_index(walker, repo, sha1);
 696                                 i += 51;
 697                                 break;
 698                         }
 699                 default:
 700                         while (i < buffer.len && data[i] != '\n')
 701                                 i++;
 702                 }
 703                 i++;
 704         }
 705
 706         repo->got_indices = 1;
 707 cleanup:
 708         strbuf_release(&buffer);
 709         free(url);
 710         return ret;
 711 }
 712
 713 static int fetch_pack(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 714 {
 715         char *url;
 716         struct packed_git *target;
 717         struct packed_git **lst;
 718         FILE *packfile;
 719         char *filename;
 720         char tmpfile[PATH_MAX];
 721         int ret;
 722         long prev_posn = 0;
 723         char range[RANGE_HEADER_SIZE];
 724         struct curl_slist *range_header = NULL;
 725         struct walker_data *data = walker->data;
 726
 727         struct active_request_slot *slot;
 728         struct slot_results results;
 729
 730         if (fetch_indices(walker, repo))
 731                 return -1;
 732         target = find_sha1_pack(sha1, repo->packs);
 733         if (!target)
 734                 return -1;
 735
 736         if (walker->get_verbosely) {
 737                 fprintf(stderr, "Getting pack %s\n",
 738                         sha1_to_hex(target->sha1));
 739                 fprintf(stderr, " which contains %s\n",
 740                         sha1_to_hex(sha1));
 741         }
 742
 743         url = xmalloc(strlen(repo->base) + 65);
 744         sprintf(url, "%s/objects/pack/pack-%s.pack",
 745                 repo->base, sha1_to_hex(target->sha1));
 746
 747         filename = sha1_pack_name(target->sha1);
 748         snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
 749         packfile = fopen(tmpfile, "a");
 750         if (!packfile)
 751                 return error("Unable to open local file %s for pack",
 752                              tmpfile);
 753
 754         slot = get_active_slot();
 755         slot->results = &results;
 756         curl_easy_setopt(slot->curl, CURLOPT_FILE, packfile);
 757         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
 758         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 759         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
 760         slot->local = packfile;
 761
 762         /* If there is data present from a previous transfer attempt,
 763            resume where it left off */
 764         prev_posn = ftell(packfile);
 765         if (prev_posn>0) {
 766                 if (walker->get_verbosely)
 767                         fprintf(stderr,
 768                                 "Resuming fetch of pack %s at byte %ld\n",
 769                                 sha1_to_hex(target->sha1), prev_posn);
 770                 sprintf(range, "Range: bytes=%ld-", prev_posn);
 771                 range_header = curl_slist_append(range_header, range);
 772                 curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
 773         }
 774
 775         if (start_active_slot(slot)) {
 776                 run_active_slot(slot);
 777                 if (results.curl_result != CURLE_OK) {
 778                         fclose(packfile);
 779                         return error("Unable to get pack file %s\n%s", url,
 780                                      curl_errorstr);
 781                 }
 782         } else {
 783                 fclose(packfile);
 784                 return error("Unable to start request");
 785         }
 786
 787         target->pack_size = ftell(packfile);
 788         fclose(packfile);
 789
 790         ret = move_temp_to_file(tmpfile, filename);
 791         if (ret)
 792                 return ret;
 793
 794         lst = &repo->packs;
 795         while (*lst != target)
 796                 lst = &((*lst)->next);
 797         *lst = (*lst)->next;
 798
 799         if (verify_pack(target))
 800                 return -1;
 801         install_packed_git(target);
 802
 803         return 0;
 804 }
 805
 806 static void abort_object_request(struct object_request *obj_req)
 807 {
 808         if (obj_req->local >= 0) {
 809                 close(obj_req->local);
 810                 obj_req->local = -1;
 811         }
 812         unlink_or_warn(obj_req->tmpfile);
 813         if (obj_req->slot) {
 814                 release_active_slot(obj_req->slot);
 815                 obj_req->slot = NULL;
 816         }
 817         release_object_request(obj_req);
 818 }
 819
 820 static int fetch_object(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 821 {
 822         char *hex = sha1_to_hex(sha1);
 823         int ret = 0;
 824         struct object_request *obj_req = object_queue_head;
 825
 826         while (obj_req != NULL && hashcmp(obj_req->sha1, sha1))
 827                 obj_req = obj_req->next;
 828         if (obj_req == NULL)
 829                 return error("Couldn't find request for %s in the queue", hex);
 830
 831         if (has_sha1_file(obj_req->sha1)) {
 832                 abort_object_request(obj_req);
 833                 return 0;
 834         }
 835
 836 #ifdef USE_CURL_MULTI
 837         while (obj_req->state == WAITING) {
 838                 step_active_slots();
 839         }
 840 #else
 841         start_object_request(walker, obj_req);
 842 #endif
 843
 844         while (obj_req->state == ACTIVE) {
 845                 run_active_slot(obj_req->slot);
 846         }
 847         if (obj_req->local != -1) {
 848                 close(obj_req->local); obj_req->local = -1;
 849         }
 850
 851         if (obj_req->state == ABORTED) {
 852                 ret = error("Request for %s aborted", hex);
 853         } else if (obj_req->curl_result != CURLE_OK &&
 854                    obj_req->http_code != 416) {
 855                 if (missing_target(obj_req))
 856                         ret = -1; /* Be silent, it is probably in a pack. */
 857                 else
 858                         ret = error("%s (curl_result = %d, http_code = %ld, sha1 = %s)",
 859                                     obj_req->errorstr, obj_req->curl_result,
 860                                     obj_req->http_code, hex);
 861         } else if (obj_req->zret != Z_STREAM_END) {
 862                 walker->corrupt_object_found++;
 863                 ret = error("File %s (%s) corrupt", hex, obj_req->url);
 864         } else if (hashcmp(obj_req->sha1, obj_req->real_sha1)) {
 865                 ret = error("File %s has bad hash", hex);
 866         } else if (obj_req->rename < 0) {
 867                 ret = error("unable to write sha1 filename %s",
 868                             obj_req->filename);
 869         }
 870
 871         release_object_request(obj_req);
 872         return ret;
 873 }
 874
 875 static int fetch(struct walker *walker, unsigned char *sha1)
 876 {
 877         struct walker_data *data = walker->data;
 878         struct alt_base *altbase = data->alt;
 879
 880         if (!fetch_object(walker, altbase, sha1))
 881                 return 0;
 882         while (altbase) {
 883                 if (!fetch_pack(walker, altbase, sha1))
 884                         return 0;
 885                 fetch_alternates(walker, data->alt->base);
 886                 altbase = altbase->next;
 887         }
 888         return error("Unable to find %s under %s", sha1_to_hex(sha1),
 889                      data->alt->base);
 890 }
 891
 892 static int fetch_ref(struct walker *walker, struct ref *ref)
 893 {
 894         struct walker_data *data = walker->data;
 895         return http_fetch_ref(data->alt->base, ref);
 896 }
 897
 898 static void cleanup(struct walker *walker)
 899 {
 900         struct walker_data *data = walker->data;
 901         http_cleanup();
 902
 903         curl_slist_free_all(data->no_pragma_header);
 904 }
 905
 906 struct walker *get_http_walker(const char *url, struct remote *remote)
 907 {
 908         char *s;
 909         struct walker_data *data = xmalloc(sizeof(struct walker_data));
 910         struct walker *walker = xmalloc(sizeof(struct walker));
 911
 912         http_init(remote);
 913
 914         data->no_pragma_header = curl_slist_append(NULL, "Pragma:");
 915
 916         data->alt = xmalloc(sizeof(*data->alt));
 917         data->alt->base = xmalloc(strlen(url) + 1);
 918         strcpy(data->alt->base, url);
 919         for (s = data->alt->base + strlen(data->alt->base) - 1; *s == '/'; --s)
 920                 *s = 0;
 921
 922         data->alt->got_indices = 0;
 923         data->alt->packs = NULL;
 924         data->alt->next = NULL;
 925         data->got_alternates = -1;
 926
 927         walker->corrupt_object_found = 0;
 928         walker->fetch = fetch;
 929         walker->fetch_ref = fetch_ref;
 930         walker->prefetch = prefetch;
 931         walker->cleanup = cleanup;
 932         walker->data = data;
 933
 934 #ifdef USE_CURL_MULTI
 935         add_fill_function(walker, (int (*)(void *)) fill_active_slot);
 936 #endif
 937
 938         return walker;
 939 }