test/smtp-dummy: add --background option and functionality

When shell executes background process using '&' the scheduling of
that new process is arbitrary. It could be that smtp-dummy doesn't
get execution time to listen() it's server socket until some other
process attempts to connect() to it. The --background option in
smtp-dummy makes it to go background *after* it started to listen
its server socket.

When --background option is used, the line "smtp_dummy_pid='<pid>'"
is printed to stdout from where shell can eval it.

diff --git a/test/smtp-dummy.c b/test/smtp-dummy.c
index 86d43162d9750e029b134477ff3ec1f05e101317..bb136687b2fd31a29775d3a25550c1f795ec034a 100644 (file)
--- a/test/smtp-dummy.c
+++ b/test/smtp-dummy.c
@@ -119,6 +119,7 @@ do_smtp_to_file (FILE *peer, FILE *output)
 int
 main (int argc, char *argv[])
 {
+       const char * progname;
        char *output_filename;
        FILE *peer_file, *output;
        int sock, peer, err;
@@ -126,9 +127,31 @@ main (int argc, char *argv[])
        struct hostent *hostinfo;
        socklen_t peer_addr_len;
        int reuse;
+       int background;
+
+       progname = argv[0];
+
+       background = 0;
+       for (; argc >= 2; argc--, argv++) {
+               if (argv[1][0] != '-')
+                       break;
+               if (strcmp (argv[1], "--") == 0) {
+                       argc--;
+                       argv++;
+                       break;
+               }
+               if (strcmp (argv[1], "--background") == 0) {
+                       background = 1;
+                       continue;
+               }
+               fprintf(stderr, "%s: unregognized option '%s'\n",
+                       progname, argv[1]);
+               return 1;
+       }
 
        if (argc != 2) {
-               fprintf (stderr, "Usage: %s <output-file>\n", argv[0]);
+               fprintf (stderr,
+                        "Usage: %s [--background] <output-file>\n", progname);
                return 1;
        }
 
@@ -181,6 +204,36 @@ main (int argc, char *argv[])
                return 1;
        }
 
+       if (background) {
+               int pid = fork ();
+               if (pid > 0) {
+                       printf ("smtp_dummy_pid='%d'\n", pid);
+                       fflush (stdout);
+                       close (sock);
+                       return 0;
+               }
+               if (pid < 0) {
+                       fprintf (stderr, "Error: fork() failed: %s\n",
+                                strerror (errno));
+                       close (sock);
+                       return 1;
+               }
+               /* Reached if pid == 0 (the child process). */
+               /* Close stdout so that the one interested in pid value will
+                  also get EOF. */
+               close (STDOUT_FILENO);
+               /* dup2() will re-reserve fd of stdout (1) (opportunistically),
+                  in case fd of stderr (2) is open. If that was not open we
+                  don't care fd of stdout (1) either. */
+               dup2 (STDERR_FILENO, STDOUT_FILENO);
+
+               /* This process is now out of reach of shell's job control.
+                  To resolve the rare but possible condition where this
+                  "daemon" is started but never connected this process will
+                  (only) have 30 seconds to exist. */
+               alarm (30);
+       }
+
        peer_addr_len = sizeof (peer_addr);
        peer = accept (sock, (struct sockaddr *) &peer_addr, &peer_addr_len);
        if (peer == -1) {