src/shared/ptyfwd.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010-2013 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <sys/epoll.h>
  23 #include <sys/ioctl.h>
  24 #include <limits.h>
  25 #include <termios.h>
  26
  27 #include "util.h"
  28 #include "ptyfwd.h"
  29
  30 struct PTYForward {
  31         sd_event *event;
  32
  33         int master;
  34
  35         sd_event_source *stdin_event_source;
  36         sd_event_source *stdout_event_source;
  37         sd_event_source *master_event_source;
  38
  39         sd_event_source *sigwinch_event_source;
  40
  41         struct termios saved_stdin_attr;
  42         struct termios saved_stdout_attr;
  43
  44         bool read_only:1;
  45
  46         bool saved_stdin:1;
  47         bool saved_stdout:1;
  48
  49         bool stdin_readable:1;
  50         bool stdin_hangup:1;
  51         bool stdout_writable:1;
  52         bool stdout_hangup:1;
  53         bool master_readable:1;
  54         bool master_writable:1;
  55         bool master_hangup:1;
  56
  57         /* Continue reading after hangup? */
  58         bool ignore_vhangup:1;
  59
  60         bool last_char_set:1;
  61         char last_char;
  62
  63         char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
  64         size_t in_buffer_full, out_buffer_full;
  65
  66         usec_t escape_timestamp;
  67         unsigned escape_counter;
  68 };
  69
  70 #define ESCAPE_USEC (1*USEC_PER_SEC)
  71
  72 static bool look_for_escape(PTYForward *f, const char *buffer, size_t n) {
  73         const char *p;
  74
  75         assert(f);
  76         assert(buffer);
  77         assert(n > 0);
  78
  79         for (p = buffer; p < buffer + n; p++) {
  80
  81                 /* Check for ^] */
  82                 if (*p == 0x1D) {
  83                         usec_t nw = now(CLOCK_MONOTONIC);
  84
  85                         if (f->escape_counter == 0 || nw > f->escape_timestamp + ESCAPE_USEC)  {
  86                                 f->escape_timestamp = nw;
  87                                 f->escape_counter = 1;
  88                         } else {
  89                                 (f->escape_counter)++;
  90
  91                                 if (f->escape_counter >= 3)
  92                                         return true;
  93                         }
  94                 } else {
  95                         f->escape_timestamp = 0;
  96                         f->escape_counter = 0;
  97                 }
  98         }
  99
 100         return false;
 101 }
 102
 103 static int shovel(PTYForward *f) {
 104         ssize_t k;
 105
 106         assert(f);
 107
 108         while ((f->stdin_readable && f->in_buffer_full <= 0) ||
 109                (f->master_writable && f->in_buffer_full > 0) ||
 110                (f->master_readable && f->out_buffer_full <= 0) ||
 111                (f->stdout_writable && f->out_buffer_full > 0)) {
 112
 113                 if (f->stdin_readable && f->in_buffer_full < LINE_MAX) {
 114
 115                         k = read(STDIN_FILENO, f->in_buffer + f->in_buffer_full, LINE_MAX - f->in_buffer_full);
 116                         if (k < 0) {
 117
 118                                 if (errno == EAGAIN)
 119                                         f->stdin_readable = false;
 120                                 else if (errno == EIO || errno == EPIPE || errno == ECONNRESET) {
 121                                         f->stdin_readable = false;
 122                                         f->stdin_hangup = true;
 123
 124                                         f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 125                                 } else {
 126                                         log_error_errno(errno, "read(): %m");
 127                                         return sd_event_exit(f->event, EXIT_FAILURE);
 128                                 }
 129                         } else if (k == 0) {
 130                                 /* EOF on stdin */
 131                                 f->stdin_readable = false;
 132                                 f->stdin_hangup = true;
 133
 134                                 f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 135                         } else  {
 136                                 /* Check if ^] has been
 137                                  * pressed three times within
 138                                  * one second. If we get this
 139                                  * we quite immediately. */
 140                                 if (look_for_escape(f, f->in_buffer + f->in_buffer_full, k))
 141                                         return sd_event_exit(f->event, EXIT_FAILURE);
 142
 143                                 f->in_buffer_full += (size_t) k;
 144                         }
 145                 }
 146
 147                 if (f->master_writable && f->in_buffer_full > 0) {
 148
 149                         k = write(f->master, f->in_buffer, f->in_buffer_full);
 150                         if (k < 0) {
 151
 152                                 if (errno == EAGAIN || errno == EIO)
 153                                         f->master_writable = false;
 154                                 else if (errno == EPIPE || errno == ECONNRESET) {
 155                                         f->master_writable = f->master_readable = false;
 156                                         f->master_hangup = true;
 157
 158                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 159                                 } else {
 160                                         log_error_errno(errno, "write(): %m");
 161                                         return sd_event_exit(f->event, EXIT_FAILURE);
 162                                 }
 163                         } else {
 164                                 assert(f->in_buffer_full >= (size_t) k);
 165                                 memmove(f->in_buffer, f->in_buffer + k, f->in_buffer_full - k);
 166                                 f->in_buffer_full -= k;
 167                         }
 168                 }
 169
 170                 if (f->master_readable && f->out_buffer_full < LINE_MAX) {
 171
 172                         k = read(f->master, f->out_buffer + f->out_buffer_full, LINE_MAX - f->out_buffer_full);
 173                         if (k < 0) {
 174
 175                                 /* Note that EIO on the master device
 176                                  * might be caused by vhangup() or
 177                                  * temporary closing of everything on
 178                                  * the other side, we treat it like
 179                                  * EAGAIN here and try again, unless
 180                                  * ignore_vhangup is off. */
 181
 182                                 if (errno == EAGAIN || (errno == EIO && f->ignore_vhangup))
 183                                         f->master_readable = false;
 184                                 else if (errno == EPIPE || errno == ECONNRESET || errno == EIO) {
 185                                         f->master_readable = f->master_writable = false;
 186                                         f->master_hangup = true;
 187
 188                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 189                                 } else {
 190                                         log_error_errno(errno, "read(): %m");
 191                                         return sd_event_exit(f->event, EXIT_FAILURE);
 192                                 }
 193                         }  else
 194                                 f->out_buffer_full += (size_t) k;
 195                 }
 196
 197                 if (f->stdout_writable && f->out_buffer_full > 0) {
 198
 199                         k = write(STDOUT_FILENO, f->out_buffer, f->out_buffer_full);
 200                         if (k < 0) {
 201
 202                                 if (errno == EAGAIN)
 203                                         f->stdout_writable = false;
 204                                 else if (errno == EIO || errno == EPIPE || errno == ECONNRESET) {
 205                                         f->stdout_writable = false;
 206                                         f->stdout_hangup = true;
 207                                         f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
 208                                 } else {
 209                                         log_error_errno(errno, "write(): %m");
 210                                         return sd_event_exit(f->event, EXIT_FAILURE);
 211                                 }
 212
 213                         } else {
 214
 215                                 if (k > 0) {
 216                                         f->last_char = f->out_buffer[k-1];
 217                                         f->last_char_set = true;
 218                                 }
 219
 220                                 assert(f->out_buffer_full >= (size_t) k);
 221                                 memmove(f->out_buffer, f->out_buffer + k, f->out_buffer_full - k);
 222                                 f->out_buffer_full -= k;
 223                         }
 224                 }
 225         }
 226
 227         if (f->stdin_hangup || f->stdout_hangup || f->master_hangup) {
 228                 /* Exit the loop if any side hung up and if there's
 229                  * nothing more to write or nothing we could write. */
 230
 231                 if ((f->out_buffer_full <= 0 || f->stdout_hangup) &&
 232                     (f->in_buffer_full <= 0 || f->master_hangup))
 233                         return sd_event_exit(f->event, EXIT_SUCCESS);
 234         }
 235
 236         return 0;
 237 }
 238
 239 static int on_master_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 240         PTYForward *f = userdata;
 241
 242         assert(f);
 243         assert(e);
 244         assert(e == f->master_event_source);
 245         assert(fd >= 0);
 246         assert(fd == f->master);
 247
 248         if (revents & (EPOLLIN|EPOLLHUP))
 249                 f->master_readable = true;
 250
 251         if (revents & (EPOLLOUT|EPOLLHUP))
 252                 f->master_writable = true;
 253
 254         return shovel(f);
 255 }
 256
 257 static int on_stdin_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 258         PTYForward *f = userdata;
 259
 260         assert(f);
 261         assert(e);
 262         assert(e == f->stdin_event_source);
 263         assert(fd >= 0);
 264         assert(fd == STDIN_FILENO);
 265
 266         if (revents & (EPOLLIN|EPOLLHUP))
 267                 f->stdin_readable = true;
 268
 269         return shovel(f);
 270 }
 271
 272 static int on_stdout_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 273         PTYForward *f = userdata;
 274
 275         assert(f);
 276         assert(e);
 277         assert(e == f->stdout_event_source);
 278         assert(fd >= 0);
 279         assert(fd == STDOUT_FILENO);
 280
 281         if (revents & (EPOLLOUT|EPOLLHUP))
 282                 f->stdout_writable = true;
 283
 284         return shovel(f);
 285 }
 286
 287 static int on_sigwinch_event(sd_event_source *e, const struct signalfd_siginfo *si, void *userdata) {
 288         PTYForward *f = userdata;
 289         struct winsize ws;
 290
 291         assert(f);
 292         assert(e);
 293         assert(e == f->sigwinch_event_source);
 294
 295         /* The window size changed, let's forward that. */
 296         if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) >= 0)
 297                 (void) ioctl(f->master, TIOCSWINSZ, &ws);
 298
 299         return 0;
 300 }
 301
 302 int pty_forward_new(
 303                 sd_event *event,
 304                 int master,
 305                 bool ignore_vhangup,
 306                 bool read_only,
 307                 PTYForward **ret) {
 308
 309         _cleanup_(pty_forward_freep) PTYForward *f = NULL;
 310         struct winsize ws;
 311         int r;
 312
 313         f = new0(PTYForward, 1);
 314         if (!f)
 315                 return -ENOMEM;
 316
 317         f->read_only = read_only;
 318         f->ignore_vhangup = ignore_vhangup;
 319
 320         if (event)
 321                 f->event = sd_event_ref(event);
 322         else {
 323                 r = sd_event_default(&f->event);
 324                 if (r < 0)
 325                         return r;
 326         }
 327
 328         if (!read_only) {
 329                 r = fd_nonblock(STDIN_FILENO, true);
 330                 if (r < 0)
 331                         return r;
 332
 333                 r = fd_nonblock(STDOUT_FILENO, true);
 334                 if (r < 0)
 335                         return r;
 336         }
 337
 338         r = fd_nonblock(master, true);
 339         if (r < 0)
 340                 return r;
 341
 342         f->master = master;
 343
 344         if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) >= 0)
 345                 (void) ioctl(master, TIOCSWINSZ, &ws);
 346
 347         if (!read_only) {
 348                 if (tcgetattr(STDIN_FILENO, &f->saved_stdin_attr) >= 0) {
 349                         struct termios raw_stdin_attr;
 350
 351                         f->saved_stdin = true;
 352
 353                         raw_stdin_attr = f->saved_stdin_attr;
 354                         cfmakeraw(&raw_stdin_attr);
 355                         raw_stdin_attr.c_oflag = f->saved_stdin_attr.c_oflag;
 356                         tcsetattr(STDIN_FILENO, TCSANOW, &raw_stdin_attr);
 357                 }
 358
 359                 if (tcgetattr(STDOUT_FILENO, &f->saved_stdout_attr) >= 0) {
 360                         struct termios raw_stdout_attr;
 361
 362                         f->saved_stdout = true;
 363
 364                         raw_stdout_attr = f->saved_stdout_attr;
 365                         cfmakeraw(&raw_stdout_attr);
 366                         raw_stdout_attr.c_iflag = f->saved_stdout_attr.c_iflag;
 367                         raw_stdout_attr.c_lflag = f->saved_stdout_attr.c_lflag;
 368                         tcsetattr(STDOUT_FILENO, TCSANOW, &raw_stdout_attr);
 369                 }
 370
 371                 r = sd_event_add_io(f->event, &f->stdin_event_source, STDIN_FILENO, EPOLLIN|EPOLLET, on_stdin_event, f);
 372                 if (r < 0 && r != -EPERM)
 373                         return r;
 374         }
 375
 376         r = sd_event_add_io(f->event, &f->stdout_event_source, STDOUT_FILENO, EPOLLOUT|EPOLLET, on_stdout_event, f);
 377         if (r == -EPERM)
 378                 /* stdout without epoll support. Likely redirected to regular file. */
 379                 f->stdout_writable = true;
 380         else if (r < 0)
 381                 return r;
 382
 383         r = sd_event_add_io(f->event, &f->master_event_source, master, EPOLLIN|EPOLLOUT|EPOLLET, on_master_event, f);
 384         if (r < 0)
 385                 return r;
 386
 387         r = sd_event_add_signal(f->event, &f->sigwinch_event_source, SIGWINCH, on_sigwinch_event, f);
 388         if (r < 0)
 389                 return r;
 390
 391         *ret = f;
 392         f = NULL;
 393
 394         return 0;
 395 }
 396
 397 PTYForward *pty_forward_free(PTYForward *f) {
 398
 399         if (f) {
 400                 sd_event_source_unref(f->stdin_event_source);
 401                 sd_event_source_unref(f->stdout_event_source);
 402                 sd_event_source_unref(f->master_event_source);
 403                 sd_event_unref(f->event);
 404
 405                 if (f->saved_stdout)
 406                         tcsetattr(STDOUT_FILENO, TCSANOW, &f->saved_stdout_attr);
 407                 if (f->saved_stdin)
 408                         tcsetattr(STDIN_FILENO, TCSANOW, &f->saved_stdin_attr);
 409
 410                 free(f);
 411         }
 412
 413         /* STDIN/STDOUT should not be nonblocking normally, so let's
 414          * unconditionally reset it */
 415         fd_nonblock(STDIN_FILENO, false);
 416         fd_nonblock(STDOUT_FILENO, false);
 417
 418         return NULL;
 419 }
 420
 421 int pty_forward_get_last_char(PTYForward *f, char *ch) {
 422         assert(f);
 423         assert(ch);
 424
 425         if (!f->last_char_set)
 426                 return -ENXIO;
 427
 428         *ch = f->last_char;
 429         return 0;
 430 }
 431
 432 int pty_forward_set_ignore_vhangup(PTYForward *f, bool ignore_vhangup) {
 433         int r;
 434
 435         assert(f);
 436
 437         if (f->ignore_vhangup == ignore_vhangup)
 438                 return 0;
 439
 440         f->ignore_vhangup = ignore_vhangup;
 441         if (!f->ignore_vhangup) {
 442
 443                 /* We shall now react to vhangup()s? Let's check
 444                  * immediately if we might be in one */
 445
 446                 f->master_readable = true;
 447                 r = shovel(f);
 448                 if (r < 0)
 449                         return r;
 450         }
 451
 452         return 0;
 453 }
 454
 455 int pty_forward_get_ignore_vhangup(PTYForward *f) {
 456         assert(f);
 457
 458         return f->ignore_vhangup;
 459 }