telnetd: add -w ("inetd wait") option. Can be configured off.

gcc fils to fully optimize it out when it's off:

function                                             old     new   delta
telnetd_main                                        1527    1548     +21
packed_usage                                       26596   26587      -9

but nevertheless it's a useful (and so far single) example
how to write "inetd wait" tcp service.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 36 insertions, 20 deletions

diff --git a/networking/telnetd.c b/networking/telnetd.c
index 540387f1a..2a0ace5cb 100644
--- a/networking/telnetd.c
+++ b/networking/telnetd.c
@@ -211,8 +211,10 @@ static size_t iac_safe_write(int fd, const char *buf, size_t count)
 enum {
         OPT_WATCHCHILD = (1 << 2), /* -K */
         OPT_INETD      = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */
-        OPT_PORT       = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p */
+        OPT_PORT       = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p PORT */
         OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
+        OPT_SYSLOG     = (1 << 7) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -S */
+        OPT_WAIT       = (1 << 8) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -w SEC */
 };
 
 static struct tsession *
@@ -438,24 +440,29 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
         struct tsession *ts;
 #if ENABLE_FEATURE_TELNETD_STANDALONE
 #define IS_INETD (opt & OPT_INETD)
-        int master_fd = master_fd; /* be happy, gcc */
-        unsigned portnbr = 23;
+        int master_fd = master_fd; /* for compiler */
+        int sec_linger = sec_linger;
         char *opt_bindaddr = NULL;
         char *opt_portnbr;
 #else
         enum {
                 IS_INETD = 1,
                 master_fd = -1,
-                portnbr = 23,
         };
 #endif
         INIT_G();
 
+        /* -w NUM, and implies -F. -w and -i don't mix */
+        IF_FEATURE_TELNETD_INETD_WAIT(opt_complementary = "wF:w+:i--w:w--i";)
         /* Even if !STANDALONE, we accept (and ignore) -i, thus people
          * don't need to guess whether it's ok to pass -i to us */
-        opt = getopt32(argv, "f:l:Ki" IF_FEATURE_TELNETD_STANDALONE("p:b:F"),
+        opt = getopt32(argv, "f:l:Ki"
+                        IF_FEATURE_TELNETD_STANDALONE("p:b:F")
+                        IF_FEATURE_TELNETD_INETD_WAIT("Sw:"),
                         &G.issuefile, &G.loginpath
-                        IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr));
+                        IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr)
+                        IF_FEATURE_TELNETD_INETD_WAIT(, &sec_linger)
+        );
         if (!IS_INETD /*&& !re_execed*/) {
                 /* inform that we start in standalone mode?
                  * May be useful when people forget to give -i */
@@ -467,32 +474,30 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
                 }
         }
         /* Redirect log to syslog early, if needed */
-        if (IS_INETD || !(opt & OPT_FOREGROUND)) {
+        if (IS_INETD || (opt & OPT_SYSLOG) || !(opt & OPT_FOREGROUND)) {
                 openlog(applet_name, LOG_PID, LOG_DAEMON);
                 logmode = LOGMODE_SYSLOG;
         }
-        IF_FEATURE_TELNETD_STANDALONE(
-                if (opt & OPT_PORT)
-                        portnbr = xatou16(opt_portnbr);
-        );
-
-        /* Used to check access(G.loginpath, X_OK) here. Pointless.
-         * exec will do this for us for free later. */
-
 #if ENABLE_FEATURE_TELNETD_STANDALONE
         if (IS_INETD) {
                 G.sessions = make_new_session(0);
                 if (!G.sessions) /* pty opening or vfork problem, exit */
-                        return 1; /* make_new_session prints error message */
+                        return 1; /* make_new_session printed error message */
         } else {
-                master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr);
-                xlisten(master_fd, 1);
+                master_fd = 0;
+                if (!(opt & OPT_WAIT)) {
+                        unsigned portnbr = 23;
+                        if (opt & OPT_PORT)
+                                portnbr = xatou16(opt_portnbr);
+                        master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr);
+                        xlisten(master_fd, 1);
+                }
                 close_on_exec_on(master_fd);
         }
 #else
         G.sessions = make_new_session();
         if (!G.sessions) /* pty opening or vfork problem, exit */
-                return 1; /* make_new_session prints error message */
+                return 1; /* make_new_session printed error message */
 #endif
 
         /* We don't want to die if just one session is broken */
@@ -556,7 +561,18 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
                         G.maxfd = master_fd;
         }
 
-        count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
+        {
+                struct timeval tv;
+                struct timeval *tv_ptr = NULL;
+                if ((opt & OPT_WAIT) && !G.sessions) {
+                        tv.tv_sec = sec_linger;
+                        tv.tv_usec = 0;
+                        tv_ptr = &tv;
+                }
+                count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, tv_ptr);
+        }
+        if (count == 0) /* "telnetd -w SEC" timed out */
+                return 0;
         if (count < 0)
                 goto again; /* EINTR or ENOMEM */