prefork-interp.c

   1 /*
   2  * "Interpreter" that you can put in #! like this
   3  *   #!/usr/bin/prefork-interp [<options>] <interpreter>
   4  */
   5
   6 /*
   7  * Process structure:
   8  *  client (C wrapper)        connects to server
   9  *                            if fails or garbage
  10  *                            === acquire lock ===
  11  *                               makes new listening socket
  12  *                               makes first-instance socketpair
  13  *                            forks setup (script, sock fds indicated in env)
  14  *                            fd0, fd1, fd2: from-outer-caller
  15  *                            other fd: call(client-end)(fake)
  16  *                            reaps setup (and reports error)
  17  *                            (implicitly releases lock)
  18  *
  19  *     setup (pre-exec)       fd0: null,
  20  *                            fd[12: fd2-from-outer-caller
  21  *                            env fds: orig-fd[01], listener,
  22  *                            env fds: call(server-end)(fake)
  23  *                            close fd: lockfile
  24  *
  25  *     setup (script)         runs initialisation parts of the script
  26  *                            at prefork establishment point:
  27  *                            forks to logger(1)
  28  *                            forks for server, now becomes like monitor below
  29  *                            exits
  30  *
  31  *         server (script)    fd0: null, fd[12]: syslog
  32  *                            other fds: orig-fd[01], listener,
  33  *                            other fds: call(server-end)(fake)
  34  *
  35  *                            right away, forks one fake-accepted monitor:
  36  *          f-a monitor       [fd0: null, fd[12]: syslgo]
  37  *                            other fds: call(server-end)(fake)
  38  *                            runs as monitor, below
  39  *
  40  *         [server (script)]  fd0: null, fd[12]: syslog
  41  *                            other fds: listener
  42  *                            closes fds: orig-fd[01], call(server-end)fake)
  43  *                            runs in loop accepting and forking,
  44  *                            reaping and limiting children
  45  *                            reports failures of monitors to syslog
  46  *
  47  *  [client (C wrapper)]      if client connect succeeds:
  48  *                            now fd: call(client-end)
  49  *                               sends message with: cmdline, env
  50  *                               sends fds
  51  *
  52  *        [server (script)]   accepts, forks monitor
  53  *
  54  *          monitor           [fd0: null, fd[12]: syslgo]
  55  *                            other fds: call(server-end)
  56  *                            receives args, env, fds
  57  *                            forks executor
  58  *
  59  *            executor        sorts out fds:
  60  *                            fd0, fd1, fd2: from-outer-caller
  61  *                            close fds: call(server-end)
  62  *                            implicitly closed fds: syslog
  63  *
  64  *                            sets cmdline, env
  65  *                            runs main part of script
  66  *                            exits normally
  67  *
  68  *          [monitor]         [fd0: null, fd[12]: syslgo]
  69  *                            [other fds: call(server-end)]
  70  *                            reaps executor
  71  *                            reports status via socket
  72  *
  73  *    [client (C wrapper)]    [fd0, fd1, fd2: from-outer-caller]
  74  *                            [other fd: call(client-end)]
  75  *                            receives status, exits appropriately
  76  *                            (if was bad signal, reports to stderr, exits 127)
  77  */
  78
  79 struct sockaddr_un sun;
  80
  81 int main(int argc, const char *const *argv) {
  82   script = process_opts(argc, argv);
  83
  84   find_socket_path();
  85   FILLZERO(sun);
  86   sun.sun_family = AF_UNIX;
  87   assert(strlen(socket_path) <= sizeof(sun.sun_path));
  88   strncpy(sun.sun_path, socket_path, sizeof(sun.sun_path));
  89
  90   bool isgarbage = check_garbage();
  91
  92   int client_fd = socket(AF_UNIX, SOCK_STREAM, 0);
  93   if (client_fd==-1) diee("socket() for client");
  94
  95   salen_t salen = sizeof(sun);
  96   r = connect(client, (const struct sockaddr*)sun, salen);
  97   if (r==-1) {
  98     if (errno==ECONNREFUSED || errno==ENOENT) {
  99
 100 }