src/socket-proxy/socket-proxyd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <getopt.h>
   6 #include <netdb.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <sys/socket.h>
  11 #include <sys/un.h>
  12 #include <unistd.h>
  13
  14 #include "sd-daemon.h"
  15 #include "sd-event.h"
  16 #include "sd-resolve.h"
  17
  18 #include "alloc-util.h"
  19 #include "fd-util.h"
  20 #include "log.h"
  21 #include "main-func.h"
  22 #include "parse-util.h"
  23 #include "path-util.h"
  24 #include "pretty-print.h"
  25 #include "resolve-private.h"
  26 #include "set.h"
  27 #include "socket-util.h"
  28 #include "string-util.h"
  29 #include "util.h"
  30
  31 #define BUFFER_SIZE (256 * 1024)
  32 static unsigned arg_connections_max = 256;
  33
  34 static const char *arg_remote_host = NULL;
  35
  36 typedef struct Context {
  37         sd_event *event;
  38         sd_resolve *resolve;
  39
  40         Set *listen;
  41         Set *connections;
  42 } Context;
  43
  44 typedef struct Connection {
  45         Context *context;
  46
  47         int server_fd, client_fd;
  48         int server_to_client_buffer[2]; /* a pipe */
  49         int client_to_server_buffer[2]; /* a pipe */
  50
  51         size_t server_to_client_buffer_full, client_to_server_buffer_full;
  52         size_t server_to_client_buffer_size, client_to_server_buffer_size;
  53
  54         sd_event_source *server_event_source, *client_event_source;
  55
  56         sd_resolve_query *resolve_query;
  57 } Connection;
  58
  59 static void connection_free(Connection *c) {
  60         assert(c);
  61
  62         if (c->context)
  63                 set_remove(c->context->connections, c);
  64
  65         sd_event_source_unref(c->server_event_source);
  66         sd_event_source_unref(c->client_event_source);
  67
  68         safe_close(c->server_fd);
  69         safe_close(c->client_fd);
  70
  71         safe_close_pair(c->server_to_client_buffer);
  72         safe_close_pair(c->client_to_server_buffer);
  73
  74         sd_resolve_query_unref(c->resolve_query);
  75
  76         free(c);
  77 }
  78
  79 static void context_clear(Context *context) {
  80         assert(context);
  81
  82         set_free_with_destructor(context->listen, sd_event_source_unref);
  83         set_free_with_destructor(context->connections, connection_free);
  84
  85         sd_event_unref(context->event);
  86         sd_resolve_unref(context->resolve);
  87 }
  88
  89 static int connection_create_pipes(Connection *c, int buffer[static 2], size_t *sz) {
  90         int r;
  91
  92         assert(c);
  93         assert(buffer);
  94         assert(sz);
  95
  96         if (buffer[0] >= 0)
  97                 return 0;
  98
  99         r = pipe2(buffer, O_CLOEXEC|O_NONBLOCK);
 100         if (r < 0)
 101                 return log_error_errno(errno, "Failed to allocate pipe buffer: %m");
 102
 103         (void) fcntl(buffer[0], F_SETPIPE_SZ, BUFFER_SIZE);
 104
 105         r = fcntl(buffer[0], F_GETPIPE_SZ);
 106         if (r < 0)
 107                 return log_error_errno(errno, "Failed to get pipe buffer size: %m");
 108
 109         assert(r > 0);
 110         *sz = r;
 111
 112         return 0;
 113 }
 114
 115 static int connection_shovel(
 116                 Connection *c,
 117                 int *from, int buffer[2], int *to,
 118                 size_t *full, size_t *sz,
 119                 sd_event_source **from_source, sd_event_source **to_source) {
 120
 121         bool shoveled;
 122
 123         assert(c);
 124         assert(from);
 125         assert(buffer);
 126         assert(buffer[0] >= 0);
 127         assert(buffer[1] >= 0);
 128         assert(to);
 129         assert(full);
 130         assert(sz);
 131         assert(from_source);
 132         assert(to_source);
 133
 134         do {
 135                 ssize_t z;
 136
 137                 shoveled = false;
 138
 139                 if (*full < *sz && *from >= 0 && *to >= 0) {
 140                         z = splice(*from, NULL, buffer[1], NULL, *sz - *full, SPLICE_F_MOVE|SPLICE_F_NONBLOCK);
 141                         if (z > 0) {
 142                                 *full += z;
 143                                 shoveled = true;
 144                         } else if (z == 0 || IN_SET(errno, EPIPE, ECONNRESET)) {
 145                                 *from_source = sd_event_source_unref(*from_source);
 146                                 *from = safe_close(*from);
 147                         } else if (!IN_SET(errno, EAGAIN, EINTR))
 148                                 return log_error_errno(errno, "Failed to splice: %m");
 149                 }
 150
 151                 if (*full > 0 && *to >= 0) {
 152                         z = splice(buffer[0], NULL, *to, NULL, *full, SPLICE_F_MOVE|SPLICE_F_NONBLOCK);
 153                         if (z > 0) {
 154                                 *full -= z;
 155                                 shoveled = true;
 156                         } else if (z == 0 || IN_SET(errno, EPIPE, ECONNRESET)) {
 157                                 *to_source = sd_event_source_unref(*to_source);
 158                                 *to = safe_close(*to);
 159                         } else if (!IN_SET(errno, EAGAIN, EINTR))
 160                                 return log_error_errno(errno, "Failed to splice: %m");
 161                 }
 162         } while (shoveled);
 163
 164         return 0;
 165 }
 166
 167 static int connection_enable_event_sources(Connection *c);
 168
 169 static int traffic_cb(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 170         Connection *c = userdata;
 171         int r;
 172
 173         assert(s);
 174         assert(fd >= 0);
 175         assert(c);
 176
 177         r = connection_shovel(c,
 178                               &c->server_fd, c->server_to_client_buffer, &c->client_fd,
 179                               &c->server_to_client_buffer_full, &c->server_to_client_buffer_size,
 180                               &c->server_event_source, &c->client_event_source);
 181         if (r < 0)
 182                 goto quit;
 183
 184         r = connection_shovel(c,
 185                               &c->client_fd, c->client_to_server_buffer, &c->server_fd,
 186                               &c->client_to_server_buffer_full, &c->client_to_server_buffer_size,
 187                               &c->client_event_source, &c->server_event_source);
 188         if (r < 0)
 189                 goto quit;
 190
 191         /* EOF on both sides? */
 192         if (c->server_fd == -1 && c->client_fd == -1)
 193                 goto quit;
 194
 195         /* Server closed, and all data written to client? */
 196         if (c->server_fd == -1 && c->server_to_client_buffer_full <= 0)
 197                 goto quit;
 198
 199         /* Client closed, and all data written to server? */
 200         if (c->client_fd == -1 && c->client_to_server_buffer_full <= 0)
 201                 goto quit;
 202
 203         r = connection_enable_event_sources(c);
 204         if (r < 0)
 205                 goto quit;
 206
 207         return 1;
 208
 209 quit:
 210         connection_free(c);
 211         return 0; /* ignore errors, continue serving */
 212 }
 213
 214 static int connection_enable_event_sources(Connection *c) {
 215         uint32_t a = 0, b = 0;
 216         int r;
 217
 218         assert(c);
 219
 220         if (c->server_to_client_buffer_full > 0)
 221                 b |= EPOLLOUT;
 222         if (c->server_to_client_buffer_full < c->server_to_client_buffer_size)
 223                 a |= EPOLLIN;
 224
 225         if (c->client_to_server_buffer_full > 0)
 226                 a |= EPOLLOUT;
 227         if (c->client_to_server_buffer_full < c->client_to_server_buffer_size)
 228                 b |= EPOLLIN;
 229
 230         if (c->server_event_source)
 231                 r = sd_event_source_set_io_events(c->server_event_source, a);
 232         else if (c->server_fd >= 0)
 233                 r = sd_event_add_io(c->context->event, &c->server_event_source, c->server_fd, a, traffic_cb, c);
 234         else
 235                 r = 0;
 236
 237         if (r < 0)
 238                 return log_error_errno(r, "Failed to set up server event source: %m");
 239
 240         if (c->client_event_source)
 241                 r = sd_event_source_set_io_events(c->client_event_source, b);
 242         else if (c->client_fd >= 0)
 243                 r = sd_event_add_io(c->context->event, &c->client_event_source, c->client_fd, b, traffic_cb, c);
 244         else
 245                 r = 0;
 246
 247         if (r < 0)
 248                 return log_error_errno(r, "Failed to set up client event source: %m");
 249
 250         return 0;
 251 }
 252
 253 static int connection_complete(Connection *c) {
 254         int r;
 255
 256         assert(c);
 257
 258         r = connection_create_pipes(c, c->server_to_client_buffer, &c->server_to_client_buffer_size);
 259         if (r < 0)
 260                 goto fail;
 261
 262         r = connection_create_pipes(c, c->client_to_server_buffer, &c->client_to_server_buffer_size);
 263         if (r < 0)
 264                 goto fail;
 265
 266         r = connection_enable_event_sources(c);
 267         if (r < 0)
 268                 goto fail;
 269
 270         return 0;
 271
 272 fail:
 273         connection_free(c);
 274         return 0; /* ignore errors, continue serving */
 275 }
 276
 277 static int connect_cb(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 278         Connection *c = userdata;
 279         socklen_t solen;
 280         int error, r;
 281
 282         assert(s);
 283         assert(fd >= 0);
 284         assert(c);
 285
 286         solen = sizeof(error);
 287         r = getsockopt(fd, SOL_SOCKET, SO_ERROR, &error, &solen);
 288         if (r < 0) {
 289                 log_error_errno(errno, "Failed to issue SO_ERROR: %m");
 290                 goto fail;
 291         }
 292
 293         if (error != 0) {
 294                 log_error_errno(error, "Failed to connect to remote host: %m");
 295                 goto fail;
 296         }
 297
 298         c->client_event_source = sd_event_source_unref(c->client_event_source);
 299
 300         return connection_complete(c);
 301
 302 fail:
 303         connection_free(c);
 304         return 0; /* ignore errors, continue serving */
 305 }
 306
 307 static int connection_start(Connection *c, struct sockaddr *sa, socklen_t salen) {
 308         int r;
 309
 310         assert(c);
 311         assert(sa);
 312         assert(salen);
 313
 314         c->client_fd = socket(sa->sa_family, SOCK_STREAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0);
 315         if (c->client_fd < 0) {
 316                 log_error_errno(errno, "Failed to get remote socket: %m");
 317                 goto fail;
 318         }
 319
 320         r = connect(c->client_fd, sa, salen);
 321         if (r < 0) {
 322                 if (errno == EINPROGRESS) {
 323                         r = sd_event_add_io(c->context->event, &c->client_event_source, c->client_fd, EPOLLOUT, connect_cb, c);
 324                         if (r < 0) {
 325                                 log_error_errno(r, "Failed to add connection socket: %m");
 326                                 goto fail;
 327                         }
 328
 329                         r = sd_event_source_set_enabled(c->client_event_source, SD_EVENT_ONESHOT);
 330                         if (r < 0) {
 331                                 log_error_errno(r, "Failed to enable oneshot event source: %m");
 332                                 goto fail;
 333                         }
 334                 } else {
 335                         log_error_errno(errno, "Failed to connect to remote host: %m");
 336                         goto fail;
 337                 }
 338         } else {
 339                 r = connection_complete(c);
 340                 if (r < 0)
 341                         goto fail;
 342         }
 343
 344         return 0;
 345
 346 fail:
 347         connection_free(c);
 348         return 0; /* ignore errors, continue serving */
 349 }
 350
 351 static int resolve_handler(sd_resolve_query *q, int ret, const struct addrinfo *ai, Connection *c) {
 352         assert(q);
 353         assert(c);
 354
 355         if (ret != 0) {
 356                 log_error("Failed to resolve host: %s", gai_strerror(ret));
 357                 goto fail;
 358         }
 359
 360         c->resolve_query = sd_resolve_query_unref(c->resolve_query);
 361
 362         return connection_start(c, ai->ai_addr, ai->ai_addrlen);
 363
 364 fail:
 365         connection_free(c);
 366         return 0; /* ignore errors, continue serving */
 367 }
 368
 369 static int resolve_remote(Connection *c) {
 370
 371         static const struct addrinfo hints = {
 372                 .ai_family = AF_UNSPEC,
 373                 .ai_socktype = SOCK_STREAM,
 374                 .ai_flags = AI_ADDRCONFIG
 375         };
 376
 377         union sockaddr_union sa = {};
 378         const char *node, *service;
 379         int r;
 380
 381         if (IN_SET(arg_remote_host[0], '/', '@')) {
 382                 int salen;
 383
 384                 salen = sockaddr_un_set_path(&sa.un, arg_remote_host);
 385                 if (salen < 0) {
 386                         log_error_errno(salen, "Specified address doesn't fit in an AF_UNIX address, refusing: %m");
 387                         goto fail;
 388                 }
 389
 390                 return connection_start(c, &sa.sa, salen);
 391         }
 392
 393         service = strrchr(arg_remote_host, ':');
 394         if (service) {
 395                 node = strndupa(arg_remote_host, service - arg_remote_host);
 396                 service++;
 397         } else {
 398                 node = arg_remote_host;
 399                 service = "80";
 400         }
 401
 402         log_debug("Looking up address info for %s:%s", node, service);
 403         r = resolve_getaddrinfo(c->context->resolve, &c->resolve_query, node, service, &hints, resolve_handler, NULL, c);
 404         if (r < 0) {
 405                 log_error_errno(r, "Failed to resolve remote host: %m");
 406                 goto fail;
 407         }
 408
 409         return 0;
 410
 411 fail:
 412         connection_free(c);
 413         return 0; /* ignore errors, continue serving */
 414 }
 415
 416 static int add_connection_socket(Context *context, int fd) {
 417         Connection *c;
 418         int r;
 419
 420         assert(context);
 421         assert(fd >= 0);
 422
 423         if (set_size(context->connections) > arg_connections_max) {
 424                 log_warning("Hit connection limit, refusing connection.");
 425                 safe_close(fd);
 426                 return 0;
 427         }
 428
 429         r = set_ensure_allocated(&context->connections, NULL);
 430         if (r < 0) {
 431                 log_oom();
 432                 return 0;
 433         }
 434
 435         c = new0(Connection, 1);
 436         if (!c) {
 437                 log_oom();
 438                 return 0;
 439         }
 440
 441         c->context = context;
 442         c->server_fd = fd;
 443         c->client_fd = -1;
 444         c->server_to_client_buffer[0] = c->server_to_client_buffer[1] = -1;
 445         c->client_to_server_buffer[0] = c->client_to_server_buffer[1] = -1;
 446
 447         r = set_put(context->connections, c);
 448         if (r < 0) {
 449                 free(c);
 450                 log_oom();
 451                 return 0;
 452         }
 453
 454         return resolve_remote(c);
 455 }
 456
 457 static int accept_cb(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 458         _cleanup_free_ char *peer = NULL;
 459         Context *context = userdata;
 460         int nfd = -1, r;
 461
 462         assert(s);
 463         assert(fd >= 0);
 464         assert(revents & EPOLLIN);
 465         assert(context);
 466
 467         nfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
 468         if (nfd < 0) {
 469                 if (errno != -EAGAIN)
 470                         log_warning_errno(errno, "Failed to accept() socket: %m");
 471         } else {
 472                 getpeername_pretty(nfd, true, &peer);
 473                 log_debug("New connection from %s", strna(peer));
 474
 475                 r = add_connection_socket(context, nfd);
 476                 if (r < 0) {
 477                         log_error_errno(r, "Failed to accept connection, ignoring: %m");
 478                         safe_close(fd);
 479                 }
 480         }
 481
 482         r = sd_event_source_set_enabled(s, SD_EVENT_ONESHOT);
 483         if (r < 0) {
 484                 log_error_errno(r, "Error while re-enabling listener with ONESHOT: %m");
 485                 sd_event_exit(context->event, r);
 486                 return r;
 487         }
 488
 489         return 1;
 490 }
 491
 492 static int add_listen_socket(Context *context, int fd) {
 493         sd_event_source *source;
 494         int r;
 495
 496         assert(context);
 497         assert(fd >= 0);
 498
 499         r = set_ensure_allocated(&context->listen, NULL);
 500         if (r < 0) {
 501                 log_oom();
 502                 return r;
 503         }
 504
 505         r = sd_is_socket(fd, 0, SOCK_STREAM, 1);
 506         if (r < 0)
 507                 return log_error_errno(r, "Failed to determine socket type: %m");
 508         if (r == 0)
 509                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
 510                                        "Passed in socket is not a stream socket.");
 511
 512         r = fd_nonblock(fd, true);
 513         if (r < 0)
 514                 return log_error_errno(r, "Failed to mark file descriptor non-blocking: %m");
 515
 516         r = sd_event_add_io(context->event, &source, fd, EPOLLIN, accept_cb, context);
 517         if (r < 0)
 518                 return log_error_errno(r, "Failed to add event source: %m");
 519
 520         r = set_put(context->listen, source);
 521         if (r < 0) {
 522                 log_error_errno(r, "Failed to add source to set: %m");
 523                 sd_event_source_unref(source);
 524                 return r;
 525         }
 526
 527         /* Set the watcher to oneshot in case other processes are also
 528          * watching to accept(). */
 529         r = sd_event_source_set_enabled(source, SD_EVENT_ONESHOT);
 530         if (r < 0)
 531                 return log_error_errno(r, "Failed to enable oneshot mode: %m");
 532
 533         return 0;
 534 }
 535
 536 static int help(void) {
 537         _cleanup_free_ char *link = NULL;
 538         int r;
 539
 540         r = terminal_urlify_man("systemd-socket-proxyd", "8", &link);
 541         if (r < 0)
 542                 return log_oom();
 543
 544         printf("%1$s [HOST:PORT]\n"
 545                "%1$s [SOCKET]\n\n"
 546                "Bidirectionally proxy local sockets to another (possibly remote) socket.\n\n"
 547                "  -c --connections-max=  Set the maximum number of connections to be accepted\n"
 548                "  -h --help              Show this help\n"
 549                "     --version           Show package version\n"
 550                "\nSee the %2$s for details.\n"
 551                , program_invocation_short_name
 552                , link
 553         );
 554
 555         return 0;
 556 }
 557
 558 static int parse_argv(int argc, char *argv[]) {
 559
 560         enum {
 561                 ARG_VERSION = 0x100,
 562                 ARG_IGNORE_ENV
 563         };
 564
 565         static const struct option options[] = {
 566                 { "connections-max", required_argument, NULL, 'c'           },
 567                 { "help",            no_argument,       NULL, 'h'           },
 568                 { "version",         no_argument,       NULL, ARG_VERSION   },
 569                 {}
 570         };
 571
 572         int c, r;
 573
 574         assert(argc >= 0);
 575         assert(argv);
 576
 577         while ((c = getopt_long(argc, argv, "c:h", options, NULL)) >= 0)
 578
 579                 switch (c) {
 580
 581                 case 'h':
 582                         return help();
 583
 584                 case ARG_VERSION:
 585                         return version();
 586
 587                 case 'c':
 588                         r = safe_atou(optarg, &arg_connections_max);
 589                         if (r < 0) {
 590                                 log_error("Failed to parse --connections-max= argument: %s", optarg);
 591                                 return r;
 592                         }
 593
 594                         if (arg_connections_max < 1)
 595                                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
 596                                                        "Connection limit is too low.");
 597
 598                         break;
 599
 600                 case '?':
 601                         return -EINVAL;
 602
 603                 default:
 604                         assert_not_reached("Unhandled option");
 605                 }
 606
 607         if (optind >= argc)
 608                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
 609                                        "Not enough parameters.");
 610
 611         if (argc != optind+1)
 612                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
 613                                        "Too many parameters.");
 614
 615         arg_remote_host = argv[optind];
 616         return 1;
 617 }
 618
 619 static int run(int argc, char *argv[]) {
 620         _cleanup_(context_clear) Context context = {};
 621         int r, n, fd;
 622
 623         log_parse_environment();
 624         log_open();
 625
 626         r = parse_argv(argc, argv);
 627         if (r <= 0)
 628                 return r;
 629
 630         r = sd_event_default(&context.event);
 631         if (r < 0)
 632                 return log_error_errno(r, "Failed to allocate event loop: %m");
 633
 634         r = sd_resolve_default(&context.resolve);
 635         if (r < 0)
 636                 return log_error_errno(r, "Failed to allocate resolver: %m");
 637
 638         r = sd_resolve_attach_event(context.resolve, context.event, 0);
 639         if (r < 0)
 640                 return log_error_errno(r, "Failed to attach resolver: %m");
 641
 642         sd_event_set_watchdog(context.event, true);
 643
 644         r = sd_listen_fds(1);
 645         if (r < 0)
 646                 return log_error_errno(r, "Failed to receive sockets from parent.");
 647         if (r == 0)
 648                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Didn't get any sockets passed in.");
 649
 650         n = r;
 651
 652         for (fd = SD_LISTEN_FDS_START; fd < SD_LISTEN_FDS_START + n; fd++) {
 653                 r = add_listen_socket(&context, fd);
 654                 if (r < 0)
 655                         return r;
 656         }
 657
 658         r = sd_event_loop(context.event);
 659         if (r < 0)
 660                 return log_error_errno(r, "Failed to run event loop: %m");
 661
 662         return 0;
 663 }
 664
 665 DEFINE_MAIN_FUNCTION(run);