Jeremy Kerr | f403c42 | 2018-07-26 12:14:56 +0800 | [diff] [blame] | 1 | /* Copyright 2018 IBM Corp. |
| 2 | * |
| 3 | * Author: Jeremy Kerr <jk@ozlabs.org> |
| 4 | * |
| 5 | * Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 6 | * use this file except in compliance with the License. You may obtain a copy |
| 7 | * of the License at |
| 8 | * |
| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | * |
| 11 | * Unless required by applicable law or agreed to in writing, software |
| 12 | * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| 13 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 14 | * License for the specific language governing permissions and limitations |
| 15 | * under the License. |
| 16 | */ |
| 17 | |
| 18 | #define _GNU_SOURCE |
| 19 | |
| 20 | #include <err.h> |
| 21 | #include <errno.h> |
| 22 | #include <fcntl.h> |
| 23 | #include <signal.h> |
| 24 | #include <stdbool.h> |
| 25 | #include <stdint.h> |
| 26 | #include <stdio.h> |
| 27 | #include <stdlib.h> |
| 28 | #include <string.h> |
| 29 | #include <unistd.h> |
| 30 | |
| 31 | #include <sys/poll.h> |
| 32 | #include <sys/socket.h> |
| 33 | #include <sys/stat.h> |
| 34 | #include <sys/un.h> |
| 35 | #include <sys/wait.h> |
| 36 | |
| 37 | #include "config.h" |
| 38 | |
| 39 | struct ctx { |
| 40 | int sock; |
| 41 | int sock_client; |
| 42 | int signal_pipe[2]; |
| 43 | char *sock_path; |
| 44 | pid_t nbd_client_pid; |
| 45 | uint8_t *buf; |
| 46 | size_t bufsize; |
| 47 | }; |
| 48 | |
| 49 | static const char *sockpath_tmpl = RUNSTATEDIR "/nbd.%d.sock"; |
| 50 | static const char *dev_path = "/dev/nbd0"; |
| 51 | static const size_t bufsize = 0x20000; |
Jeremy Kerr | 09295f2 | 2018-07-27 16:29:38 +0800 | [diff] [blame^] | 52 | static const int nbd_timeout = 30; |
Jeremy Kerr | f403c42 | 2018-07-26 12:14:56 +0800 | [diff] [blame] | 53 | |
| 54 | static int open_nbd_socket(struct ctx *ctx) |
| 55 | { |
| 56 | struct sockaddr_un addr; |
| 57 | char *path; |
| 58 | int sd, rc; |
| 59 | |
| 60 | rc = asprintf(&path, sockpath_tmpl, getpid()); |
| 61 | if (rc < 0) |
| 62 | return -1; |
| 63 | |
| 64 | sd = socket(AF_UNIX, SOCK_STREAM, 0); |
| 65 | if (sd < 0) { |
| 66 | warn("can't create socket"); |
| 67 | goto err_free; |
| 68 | } |
| 69 | |
| 70 | rc = fchmod(sd, S_IRUSR | S_IWUSR); |
| 71 | if (rc) { |
| 72 | warn("can't set permissions on socket"); |
| 73 | goto err_close; |
| 74 | } |
| 75 | |
| 76 | addr.sun_family = AF_UNIX; |
| 77 | strncpy(addr.sun_path, path, sizeof(addr.sun_path)); |
| 78 | |
| 79 | rc = bind(sd, (struct sockaddr *)&addr, sizeof(addr)); |
| 80 | if (rc) { |
| 81 | warn("can't bind to path %s", path); |
| 82 | goto err_close; |
| 83 | } |
| 84 | |
| 85 | rc = listen(sd, 1); |
| 86 | if (rc) { |
| 87 | warn("can't listen on socket %s", path); |
| 88 | goto err_unlink; |
| 89 | } |
| 90 | |
| 91 | ctx->sock = sd; |
| 92 | ctx->sock_path = path; |
| 93 | return 0; |
| 94 | |
| 95 | err_unlink: |
| 96 | unlink(path); |
| 97 | err_close: |
| 98 | close(sd); |
| 99 | err_free: |
| 100 | free(path); |
| 101 | return -1; |
| 102 | } |
| 103 | |
| 104 | static int start_nbd_client(struct ctx *ctx) |
| 105 | { |
| 106 | pid_t pid; |
| 107 | |
| 108 | pid = fork(); |
| 109 | if (pid < 0) { |
| 110 | warn("can't create client process"); |
| 111 | return -1; |
| 112 | } |
| 113 | |
| 114 | /* child process: run nbd-client in non-fork mode */ |
| 115 | if (pid == 0) { |
Jeremy Kerr | 09295f2 | 2018-07-27 16:29:38 +0800 | [diff] [blame^] | 116 | char timeout_str[10]; |
Jeremy Kerr | f403c42 | 2018-07-26 12:14:56 +0800 | [diff] [blame] | 117 | int fd; |
| 118 | |
Jeremy Kerr | 09295f2 | 2018-07-27 16:29:38 +0800 | [diff] [blame^] | 119 | snprintf(timeout_str, sizeof(timeout_str), "%d", nbd_timeout); |
| 120 | |
Jeremy Kerr | f403c42 | 2018-07-26 12:14:56 +0800 | [diff] [blame] | 121 | fd = open("/dev/null", O_RDWR); |
| 122 | if (fd < 0) |
| 123 | err(EXIT_FAILURE, "can't open /dev/null"); |
| 124 | |
| 125 | dup2(fd, STDIN_FILENO); |
| 126 | dup2(fd, STDOUT_FILENO); |
| 127 | dup2(fd, STDERR_FILENO); |
| 128 | close(fd); |
| 129 | close(ctx->sock); |
| 130 | |
| 131 | execlp("nbd-client", "nbd-client", |
| 132 | "-u", ctx->sock_path, |
| 133 | "-n", |
Jeremy Kerr | 09295f2 | 2018-07-27 16:29:38 +0800 | [diff] [blame^] | 134 | "-t", timeout_str, |
Jeremy Kerr | f403c42 | 2018-07-26 12:14:56 +0800 | [diff] [blame] | 135 | dev_path, |
| 136 | NULL); |
| 137 | err(EXIT_FAILURE, "can't start ndb client"); |
| 138 | } |
| 139 | |
| 140 | ctx->nbd_client_pid = pid; |
| 141 | return 0; |
| 142 | } |
| 143 | |
| 144 | static void stop_nbd_client(struct ctx *ctx) |
| 145 | { |
| 146 | int rc; |
| 147 | |
| 148 | if (!ctx->nbd_client_pid) |
| 149 | return; |
| 150 | |
| 151 | rc = kill(ctx->nbd_client_pid, SIGTERM); |
| 152 | if (rc) |
| 153 | return; |
| 154 | |
| 155 | waitpid(ctx->nbd_client_pid, NULL, 0); |
| 156 | ctx->nbd_client_pid = 0; |
| 157 | } |
| 158 | |
| 159 | static int copy_fd(struct ctx *ctx, int fd_in, int fd_out) |
| 160 | { |
| 161 | #ifdef HAVE_SPLICE |
| 162 | int rc; |
| 163 | |
| 164 | rc = splice(fd_in, NULL, fd_out, NULL, ctx->bufsize, 0); |
| 165 | if (rc < 0) |
| 166 | warn("splice"); |
| 167 | |
| 168 | return rc; |
| 169 | #else |
| 170 | size_t len, pos; |
| 171 | ssize_t rc; |
| 172 | |
| 173 | for (;;) { |
| 174 | errno = 0; |
| 175 | rc = read(fd_in, ctx->buf, ctx->bufsize); |
| 176 | if (rc < 0) { |
| 177 | if (errno == EINTR) |
| 178 | continue; |
| 179 | warn("read failure"); |
| 180 | return -1; |
| 181 | } |
| 182 | if (rc == 0) |
| 183 | return 0; |
| 184 | break; |
| 185 | } |
| 186 | |
| 187 | len = rc; |
| 188 | |
| 189 | for (pos = 0; pos < len;) { |
| 190 | errno = 0; |
| 191 | rc = write(fd_out, ctx->buf + pos, len - pos); |
| 192 | if (rc < 0) { |
| 193 | if (errno == EINTR) |
| 194 | continue; |
| 195 | warn("write failure"); |
| 196 | return -1; |
| 197 | } |
| 198 | if (rc == 0) |
| 199 | break; |
| 200 | pos += rc; |
| 201 | } |
| 202 | |
| 203 | return pos; |
| 204 | #endif |
| 205 | } |
| 206 | |
| 207 | static int signal_pipe_fd = -1; |
| 208 | |
| 209 | static void signal_handler(int signal) |
| 210 | { |
| 211 | int rc; |
| 212 | |
| 213 | rc = write(signal_pipe_fd, &signal, sizeof(signal)); |
| 214 | |
| 215 | /* not a lot we can do here but exit... */ |
| 216 | if (rc != sizeof(signal)) |
| 217 | exit(EXIT_FAILURE); |
| 218 | } |
| 219 | |
| 220 | static int setup_signals(struct ctx *ctx) |
| 221 | { |
| 222 | struct sigaction sa; |
| 223 | int rc; |
| 224 | |
| 225 | rc = pipe(ctx->signal_pipe); |
| 226 | if (rc) { |
| 227 | warn("cant setup signal pipe"); |
| 228 | return -1; |
| 229 | } |
| 230 | |
| 231 | signal_pipe_fd = ctx->signal_pipe[1]; |
| 232 | |
| 233 | memset(&sa, 0, sizeof(sa)); |
| 234 | sa.sa_handler = signal_handler; |
| 235 | |
| 236 | sigaction(SIGINT, &sa, NULL); |
| 237 | sigaction(SIGTERM, &sa, NULL); |
| 238 | sigaction(SIGCHLD, &sa, NULL); |
| 239 | |
| 240 | return 0; |
| 241 | } |
| 242 | |
| 243 | static void cleanup_signals(struct ctx *ctx) |
| 244 | { |
| 245 | struct sigaction sa; |
| 246 | memset(&sa, 0, sizeof(sa)); |
| 247 | sa.sa_handler = SIG_DFL; |
| 248 | |
| 249 | sigaction(SIGINT, &sa, NULL); |
| 250 | sigaction(SIGTERM, &sa, NULL); |
| 251 | sigaction(SIGCHLD, &sa, NULL); |
| 252 | |
| 253 | close(ctx->signal_pipe[0]); |
| 254 | close(ctx->signal_pipe[1]); |
| 255 | } |
| 256 | |
| 257 | static int process_signal_pipe(struct ctx *ctx, bool *exit) |
| 258 | { |
| 259 | int buf, rc, status; |
| 260 | |
| 261 | rc = read(ctx->signal_pipe[0], &buf, sizeof(buf)); |
| 262 | if (rc != sizeof(buf)) |
| 263 | return -1; |
| 264 | |
| 265 | *exit = false; |
| 266 | |
| 267 | switch (buf) { |
| 268 | case SIGCHLD: |
| 269 | rc = waitpid(ctx->nbd_client_pid, &status, WNOHANG); |
| 270 | if (rc > 0) { |
| 271 | warnx("nbd client stopped (%s: %d); exiting", |
| 272 | WIFEXITED(status) ? "rc" : "sig", |
| 273 | WIFEXITED(status) ? |
| 274 | WEXITSTATUS(status) : |
| 275 | WTERMSIG(status)); |
| 276 | ctx->nbd_client_pid = 0; |
| 277 | } |
| 278 | break; |
| 279 | case SIGINT: |
| 280 | case SIGTERM: |
| 281 | *exit = true; |
| 282 | break; |
| 283 | } |
| 284 | |
| 285 | return 0; |
| 286 | } |
| 287 | |
| 288 | static int wait_for_nbd_client(struct ctx *ctx) |
| 289 | { |
| 290 | struct pollfd pollfds[2]; |
| 291 | int rc; |
| 292 | |
| 293 | pollfds[0].fd = ctx->sock; |
| 294 | pollfds[0].events = POLLIN; |
| 295 | pollfds[1].fd = ctx->signal_pipe[0]; |
| 296 | pollfds[1].events = POLLIN; |
| 297 | |
| 298 | for (;;) { |
| 299 | errno = 0; |
| 300 | rc = poll(pollfds, 2, -1); |
| 301 | if (rc < 0) { |
| 302 | if (errno == EINTR) |
| 303 | continue; |
| 304 | warn("poll failed"); |
| 305 | return -1; |
| 306 | } |
| 307 | |
| 308 | if (pollfds[0].revents) { |
| 309 | rc = accept(ctx->sock, NULL, NULL); |
| 310 | if (rc < 0) { |
| 311 | warn("can't create connection"); |
| 312 | return -1; |
| 313 | } |
| 314 | ctx->sock_client = rc; |
| 315 | break; |
| 316 | } |
| 317 | |
| 318 | if (pollfds[1].revents) { |
| 319 | bool exit; |
| 320 | rc = process_signal_pipe(ctx, &exit); |
| 321 | if (rc || exit) |
| 322 | return -1; |
| 323 | } |
| 324 | } |
| 325 | |
| 326 | return 0; |
| 327 | } |
| 328 | |
| 329 | |
| 330 | static int run_proxy(struct ctx *ctx) |
| 331 | { |
| 332 | struct pollfd pollfds[3]; |
| 333 | bool exit = false; |
| 334 | int rc; |
| 335 | |
| 336 | /* main proxy: forward data between stdio & socket */ |
| 337 | pollfds[0].fd = ctx->sock_client; |
| 338 | pollfds[0].events = POLLIN; |
| 339 | pollfds[1].fd = STDIN_FILENO; |
| 340 | pollfds[1].events = POLLIN; |
| 341 | pollfds[2].fd = ctx->signal_pipe[0]; |
| 342 | pollfds[2].events = POLLIN; |
| 343 | |
| 344 | for (;;) { |
| 345 | errno = 0; |
| 346 | rc = poll(pollfds, 3, -1); |
| 347 | if (rc < 0) { |
| 348 | if (errno == EINTR) |
| 349 | continue; |
| 350 | warn("poll failed"); |
| 351 | break; |
| 352 | } |
| 353 | |
| 354 | if (pollfds[0].revents) { |
| 355 | rc = copy_fd(ctx, ctx->sock_client, STDOUT_FILENO); |
| 356 | if (rc <= 0) |
| 357 | break; |
| 358 | } |
| 359 | |
| 360 | if (pollfds[1].revents) { |
| 361 | rc = copy_fd(ctx, STDIN_FILENO, ctx->sock_client); |
| 362 | if (rc <= 0) |
| 363 | break; |
| 364 | } |
| 365 | |
| 366 | if (pollfds[2].revents) { |
| 367 | rc = process_signal_pipe(ctx, &exit); |
| 368 | if (rc || exit) |
| 369 | break; |
| 370 | } |
| 371 | } |
| 372 | |
| 373 | return rc ? -1 : 0; |
| 374 | } |
| 375 | |
| 376 | int main(void) |
| 377 | { |
| 378 | struct ctx _ctx, *ctx; |
| 379 | int rc; |
| 380 | |
| 381 | ctx = &_ctx; |
| 382 | ctx->bufsize = bufsize; |
| 383 | ctx->buf = malloc(ctx->bufsize); |
| 384 | ctx->sock_path = NULL; |
| 385 | ctx->nbd_client_pid = 0; |
| 386 | |
| 387 | rc = open_nbd_socket(ctx); |
| 388 | if (rc) |
| 389 | goto out_free; |
| 390 | |
| 391 | rc = setup_signals(ctx); |
| 392 | if (rc) |
| 393 | goto out_close; |
| 394 | |
| 395 | rc = start_nbd_client(ctx); |
| 396 | if (rc) |
| 397 | goto out_stop_client; |
| 398 | |
| 399 | rc = wait_for_nbd_client(ctx); |
| 400 | if (rc) |
| 401 | goto out_stop_client; |
| 402 | |
| 403 | rc = run_proxy(ctx); |
| 404 | |
| 405 | out_stop_client: |
| 406 | /* we cleanup signals before stopping the client, because we |
| 407 | * no longer care about SIGCHLD from the stopping nbd-client |
| 408 | * process. stop_nbd_client will be a no-op if the client hasn't |
| 409 | * been started. */ |
| 410 | cleanup_signals(ctx); |
| 411 | |
| 412 | stop_nbd_client(ctx); |
| 413 | close(ctx->sock_client); |
| 414 | |
| 415 | out_close: |
| 416 | if (ctx->sock_path) { |
| 417 | unlink(ctx->sock_path); |
| 418 | free(ctx->sock_path); |
| 419 | } |
| 420 | close(ctx->sock); |
| 421 | out_free: |
| 422 | free(ctx->buf); |
| 423 | return rc ? EXIT_FAILURE : EXIT_SUCCESS; |
| 424 | } |