Please review the function below, forkoff(), meant to be used in
clientloop.c instead of daemon() and the code in process_escapes().
The intention is to make ~D ( like ~& but also detach) possible and to
make it possible for ssh -f (or ssh -f -f - see other thread on this)
to detach, not just forkoff().
I also intend to use the same detach technique in a feature patch for
the hang-on-exit behaviour that's been hashed to death. I.e., I might
like to add an option to control ssh's behaviour when the remote session
exits, the behaviours being: wait for the channel to be closed [current,
default], close all channels and exit, background, detach and force
exit.
To make detaching and some of the hang-on-exit options work correctly I
need a way to force a channel closed and to do it in way that is
correct wrt to the SSHv2 protocol. The forkoff() function below does
that, I think, but it would be nice to have confirmation.
Comments?
Nico
static
void
forkoff(int stop_listening, int detach)
{
pid_t pid;
int fd;
Channel *c;
/* Restore tty modes. */
leave_raw_mode();
/* Stop listening for new connections. */
if (stop_listening)
channel_stop_listening();
fprintf(stderr, "Forking off into the background - %s",
stop_listening ? "no longer listening" : "still
listening");
/* Fork into background. */
pid = fork();
if (pid < 0) {
error("fork: %.100s", strerror(errno));
return;
}
if (pid != 0) { /* This is the parent. */
/* The parent just exits. */
exit(0);
}
c = channel_lookup(session_ident);
if (c == NULL)
error("couldn't lookup session channel");
/* The child continues serving connections. */
/* fake EOF on stdin */
if (compat20) {
buffer_append(&stdin_buffer, "\004", 1);
} else if (!stdin_eof) {
/*
* Sending SSH_CMSG_EOF alone does not always appear
* to be enough. So we try to send an EOF character
* first.
*/
packet_start(SSH_CMSG_STDIN_DATA);
packet_put_string("\004", 1);
packet_send();
/* Close stdin. */
stdin_eof = 1;
if (buffer_len(&stdin_buffer) == 0) {
packet_start(SSH_CMSG_EOF);
packet_send();
}
}
if (detach) {
/*
* There should be a chan_wont_read()/chan_wont_write()
* API, differing only in the debug messages used.
*/
chan_read_failed(c);
chan_write_failed(c);
channel_close_fds(c);
fd = open(_PATH_DEVNULL, O_RDWR, 0);
if (fd < 0)
return;
(void) dup2(fd, STDIN_FILENO);
(void) dup2(fd, STDOUT_FILENO);
(void) dup2(fd, STDERR_FILENO);
if (fd > 2)
(void) close(fd);
(void) setsid();
}
}
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