server.c

   1 #define FD_SET_MAX(fd, set, maxfd) do { \
   2                 FD_SET(fd, set);        \
   3                 if (fd > maxfd)         \
   4                         maxfd = fd;     \
   5         } while (0)
   6
   7 static Client *client_malloc(int socket) {
   8         Client *c = calloc(1, sizeof(Client));
   9         if (!c)
  10                 return NULL;
  11         c->socket = socket;
  12         return c;
  13 }
  14
  15 static void client_free(Client *c) {
  16         if (c && c->socket > 0)
  17                 close(c->socket);
  18         free(c);
  19 }
  20
  21 static void server_sink_client() {
  22         if (!server.clients || !server.clients->next)
  23                 return;
  24         Client *target = server.clients;
  25         server.clients = target->next;
  26         Client *dst = server.clients;
  27         while (dst->next)
  28                 dst = dst->next;
  29         target->next = NULL;
  30         dst->next = target;
  31 }
  32
  33 static void server_mark_socket_exec(bool exec, bool usr) {
  34         struct stat sb;
  35         if (stat(sockaddr.sun_path, &sb) == -1)
  36                 return;
  37         mode_t mode = sb.st_mode;
  38         mode_t flag = usr ? S_IXUSR : S_IXGRP;
  39         if (exec)
  40                 mode |= flag;
  41         else
  42                 mode &= ~flag;
  43         chmod(sockaddr.sun_path, mode);
  44 }
  45
  46 static int server_create_socket(const char *name) {
  47         if (!set_socket_name(&sockaddr, name))
  48                 return -1;
  49         int fd = socket(AF_UNIX, SOCK_STREAM, 0);
  50         if (fd == -1)
  51                 return -1;
  52         socklen_t socklen = offsetof(struct sockaddr_un, sun_path) + strlen(sockaddr.sun_path) + 1;
  53         mode_t mask = umask(S_IXUSR|S_IRWXG|S_IRWXO);
  54         int r = bind(fd, (struct sockaddr*)&sockaddr, socklen);
  55         umask(mask);
  56
  57         if (r == -1 || chmod(sockaddr.sun_path, S_ISVTX|S_IRUSR|S_IWUSR) == -1) {
  58                 close(fd);
  59                 return -1;
  60         }
  61
  62         if (listen(fd, 5) == -1) {
  63                 unlink(sockaddr.sun_path);
  64                 close(fd);
  65                 return -1;
  66         }
  67
  68         return fd;
  69 }
  70
  71 static int server_set_socket_non_blocking(int sock) {
  72         int flags;
  73         if ((flags = fcntl(sock, F_GETFL, 0)) == -1)
  74                 flags = 0;
  75         return fcntl(sock, F_SETFL, flags | O_NONBLOCK);
  76 }
  77
  78 static Client *server_accept_client(void) {
  79         int newfd = accept(server.socket, NULL, NULL);
  80         if (newfd == -1 || server_set_socket_non_blocking(newfd) == -1)
  81                 goto error;
  82         Client *c = client_malloc(newfd);
  83         if (!c)
  84                 goto error;
  85         if (!server.clients)
  86                 server_mark_socket_exec(true, true);
  87         c->socket = newfd;
  88         c->state = STATE_CONNECTED;
  89         c->next = server.clients;
  90         server.clients = c;
  91         server.read_pty = true;
  92         return c;
  93 error:
  94         if (newfd != -1)
  95                 close(newfd);
  96         return NULL;
  97 }
  98
  99 static bool server_read_pty(Packet *pkt) {
 100         pkt->type = MSG_CONTENT;
 101         ssize_t len = read(server.pty, pkt->u.msg, sizeof(pkt->u.msg));
 102         if (len != -1)
 103                 pkt->len = len;
 104         else if (errno != EAGAIN && errno != EINTR)
 105                 server.running = false;
 106         print_packet("server-read-pty:", pkt);
 107         return len > 0;
 108 }
 109
 110 static bool server_write_pty(Packet *pkt) {
 111         print_packet("server-write-pty:", pkt);
 112         size_t size = pkt->len;
 113         if (write_all(server.pty, pkt->u.msg, size) == size)
 114                 return true;
 115         debug("FAILED\n");
 116         server.running = false;
 117         return false;
 118 }
 119
 120 static bool server_recv_packet(Client *c, Packet *pkt) {
 121         if (recv_packet(c->socket, pkt)) {
 122                 print_packet("server-recv:", pkt);
 123                 return true;
 124         }
 125         debug("server-recv: FAILED\n");
 126         c->state = STATE_DISCONNECTED;
 127         return false;
 128 }
 129
 130 static bool server_send_packet(Client *c, Packet *pkt) {
 131         print_packet("server-send:", pkt);
 132         if (send_packet(c->socket, pkt))
 133                 return true;
 134         debug("FAILED\n");
 135         c->state = STATE_DISCONNECTED;
 136         return false;
 137 }
 138
 139 static void server_pty_died_handler(int sig) {
 140         int errsv = errno;
 141         pid_t pid;
 142
 143         while ((pid = waitpid(-1, &server.exit_status, WNOHANG)) != 0) {
 144                 if (pid == -1)
 145                         break;
 146                 server.exit_status = WEXITSTATUS(server.exit_status);
 147                 server_mark_socket_exec(true, false);
 148         }
 149
 150         debug("server pty died: %d\n", server.exit_status);
 151         errno = errsv;
 152 }
 153
 154 static void server_sigterm_handler(int sig) {
 155         exit(EXIT_FAILURE); /* invoke atexit handler */
 156 }
 157
 158 static void server_sigusr1_handler(int sig) {
 159         int socket = server_create_socket(server.session_name);
 160         if (socket != -1) {
 161                 if (server.socket)
 162                         close(server.socket);
 163                 server.socket = socket;
 164         }
 165 }
 166
 167 static void server_atexit_handler(void) {
 168         unlink(sockaddr.sun_path);
 169 }
 170
 171 static void server_mainloop(void) {
 172         atexit(server_atexit_handler);
 173         fd_set new_readfds, new_writefds;
 174         FD_ZERO(&new_readfds);
 175         FD_ZERO(&new_writefds);
 176         FD_SET(server.socket, &new_readfds);
 177         int new_fdmax = server.socket;
 178         bool exit_packet_delivered = false;
 179
 180         if (server.read_pty)
 181                 FD_SET_MAX(server.pty, &new_readfds, new_fdmax);
 182
 183         while (server.clients || !exit_packet_delivered) {
 184                 int fdmax = new_fdmax;
 185                 fd_set readfds = new_readfds;
 186                 fd_set writefds = new_writefds;
 187                 FD_SET_MAX(server.socket, &readfds, fdmax);
 188
 189                 if (select(fdmax+1, &readfds, &writefds, NULL, NULL) == -1) {
 190                         if (errno == EINTR)
 191                                 continue;
 192                         die("server-mainloop");
 193                 }
 194
 195                 FD_ZERO(&new_readfds);
 196                 FD_ZERO(&new_writefds);
 197                 new_fdmax = server.socket;
 198
 199                 bool pty_data = false;
 200
 201                 Packet server_packet, client_packet;
 202
 203                 if (FD_ISSET(server.socket, &readfds))
 204                         server_accept_client();
 205
 206                 if (FD_ISSET(server.pty, &readfds))
 207                         pty_data = server_read_pty(&server_packet);
 208
 209                 for (Client **prev_next = &server.clients, *c = server.clients; c;) {
 210                         if (FD_ISSET(c->socket, &readfds) && server_recv_packet(c, &client_packet)) {
 211                                 switch (client_packet.type) {
 212                                 case MSG_CONTENT:
 213                                         server_write_pty(&client_packet);
 214                                         break;
 215                                 case MSG_ATTACH:
 216                                         c->flags = client_packet.u.i;
 217                                         if (c->flags & CLIENT_LOWPRIORITY)
 218                                                 server_sink_client();
 219                                         break;
 220                                 case MSG_RESIZE:
 221                                         c->state = STATE_ATTACHED;
 222                                 case MSG_REDRAW:
 223                                         if (!(c->flags & CLIENT_READONLY) && (client_packet.type == MSG_REDRAW || c == server.clients)) {
 224                                                 debug("server-ioct: TIOCSWINSZ\n");
 225                                                 ioctl(server.pty, TIOCSWINSZ, &client_packet.u.ws);
 226                                         }
 227                                         kill(-server.pid, SIGWINCH);
 228                                         break;
 229                                 case MSG_EXIT:
 230                                         exit_packet_delivered = true;
 231                                         /* fall through */
 232                                 case MSG_DETACH:
 233                                         c->state = STATE_DISCONNECTED;
 234                                         break;
 235                                 default: /* ignore package */
 236                                         break;
 237                                 }
 238                         }
 239
 240                         if (c->state == STATE_DISCONNECTED) {
 241                                 bool first = (c == server.clients);
 242                                 Client *t = c->next;
 243                                 client_free(c);
 244                                 *prev_next = c = t;
 245                                 if (first && server.clients) {
 246                                         Packet pkt = {
 247                                                 .type = MSG_RESIZE,
 248                                                 .len = 0,
 249                                         };
 250                                         server_send_packet(server.clients, &pkt);
 251                                 } else if (!server.clients) {
 252                                         server_mark_socket_exec(false, true);
 253                                 }
 254                                 continue;
 255                         }
 256
 257                         FD_SET_MAX(c->socket, &new_readfds, new_fdmax);
 258
 259                         if (pty_data)
 260                                 server_send_packet(c, &server_packet);
 261                         if (!server.running) {
 262                                 if (server.exit_status != -1) {
 263                                         Packet pkt = {
 264                                                 .type = MSG_EXIT,
 265                                                 .u.i = server.exit_status,
 266                                                 .len = sizeof(pkt.u.i),
 267                                         };
 268                                         if (!server_send_packet(c, &pkt))
 269                                                 FD_SET_MAX(c->socket, &new_writefds, new_fdmax);
 270                                 } else {
 271                                         FD_SET_MAX(c->socket, &new_writefds, new_fdmax);
 272                                 }
 273                         }
 274                         prev_next = &c->next;
 275                         c = c->next;
 276                 }
 277
 278                 if (server.running && server.read_pty)
 279                         FD_SET_MAX(server.pty, &new_readfds, new_fdmax);
 280         }
 281
 282         exit(EXIT_SUCCESS);
 283 }