Nicolas Williams
2002-Feb-01 18:10 UTC
FEATURE: -f -f - fork after successful open of fwd port/display/agent
Background
=========
"ssh -f ..." causes ssh to fork into the background when userauth
successfully completes.
WHAT
==
With this patch "ssh -f -f ..." causes ssh to fork into the background
when the first forwarded port/x11 display/agent is successfully opened.
WHY
==
This feature makes launching remote X11 apps more reliable: when ssh
exits it must have exited because the app exited, and you can observe
the error messages / exit status, OR because the app opened the display,
meaning it can now display any future errors.
****
ALSO, "ssh -f -f ..." actually detaches from the tty, and it closes
the
session channel correctly.
Please see the forkoff() function added to clientloop.c: it correctly
closes the channel for the SSHv2 session.
Comments?
Nico
--
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Index: 3_0_2p1.1/ssh.c
--- 3_0_2p1.1/ssh.c Wed, 21 Nov 2001 10:38:46 -0500
+++ 3_0_2p1_double_dash_f.1/ssh.c Fri, 01 Feb 2002 12:59:13 -0500
@@ -111,6 +111,7 @@
* background.
*/
int fork_after_authentication_flag = 0;
+int wait_for_port_open_before_fork = 0;
/*
* General data structure for command line options and options configurable
@@ -330,6 +331,8 @@
stdin_null_flag = 1;
break;
case 'f':
+ if (fork_after_authentication_flag)
+ wait_for_port_open_before_fork = 1;
fork_after_authentication_flag = 1;
stdin_null_flag = 1;
break;
@@ -1164,7 +1167,7 @@
id = ssh_session2_open();
/* If requested, let ssh continue in the background. */
- if (fork_after_authentication_flag)
+ if (fork_after_authentication_flag && !wait_for_port_open_before_fork)
if (daemon(1, 1) < 0)
fatal("daemon() failed: %.200s", strerror(errno));
Index: 3_0_2p1.1/clientloop.c
--- 3_0_2p1.1/clientloop.c Wed, 21 Nov 2001 10:38:46 -0500
+++ 3_0_2p1_double_dash_f.1/clientloop.c Fri, 01 Feb 2002 12:59:13 -0500
@@ -95,6 +95,9 @@
*/
extern char *host;
+extern int fork_after_authentication_flag;
+extern int wait_for_port_open_before_fork;
+
/*
* Flag to indicate that we have received a window change signal which has
* not yet been processed. This will cause a message indicating the new
@@ -1007,6 +1010,80 @@
/*********/
+/*
+ * Detach the program (continue to serve connections,
+ * but put in background and no more new connections).
+ */
+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) {
+ 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();
+ }
+}
+
static void
client_input_stdout_data(int type, int plen, void *ctxt)
{
@@ -1187,6 +1264,8 @@
packet_put_int(c->local_maxpacket);
packet_send();
}
+ if (fork_after_authentication_flag && wait_for_port_open_before_fork)
+ forkoff(0, 1);
} else {
debug("failure %s", ctype);
packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
Index: 3_0_2p1.1/channels.h
--- 3_0_2p1.1/channels.h Wed, 21 Nov 2001 10:38:46 -0500
+++ 3_0_2p1_double_dash_f.1/channels.h Fri, 01 Feb 2002 12:59:13 -0500
@@ -153,6 +153,7 @@
void channel_register_filter(int, channel_filter_fn *);
void channel_cancel_cleanup(int);
int channel_close_fd(int *);
+void channel_close_fds(Channel *);
/* protocol handler */
Index: 3_0_2p1.1/channels.c
--- 3_0_2p1.1/channels.c Wed, 21 Nov 2001 10:38:46 -0500
+++ 3_0_2p1_double_dash_f.1/channels.c Fri, 01 Feb 2002 12:59:13 -0500
@@ -301,7 +301,7 @@
/* Close all channel fd/socket. */
-static void
+void
channel_close_fds(Channel *c)
{
debug3("channel_close_fds: channel %d: r %d w %d e %d",
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Frank Cusack
2002-Feb-01 21:38 UTC
FEATURE: -f -f - fork after successful open of fwd port/display/agent
On Fri, Feb 01, 2002 at 01:10:57PM -0500, Nicolas Williams wrote:> ALSO, "ssh -f -f ..." actually detaches from the tty, and it closes the > session channel correctly. > > Please see the forkoff() function added to clientloop.c: it correctly > closes the channel for the SSHv2 session. > > Comments?"-f -f" is fairly ugly. /fc