ash: fix for read $IFS splitting. Closes bug 235
[oweals/busybox.git] / networking / telnetd.c
index 5188edbab97cfb3f0cbbc21b8dffddbb003404fe..b0a1cc4d8632a71d6713aa967f98b411827b4c9c 100644 (file)
  *
  * The telnetd manpage says it all:
  *
- *   Telnetd operates by allocating a pseudo-terminal device (see pty(4))  for
- *   a client, then creating a login process which has the slave side of the
- *   pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
- *   master side of the pseudo-terminal, implementing the telnet protocol and
- *   passing characters between the remote client and the login process.
+ * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for
+ * a client, then creating a login process which has the slave side of the
+ * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
+ * master side of the pseudo-terminal, implementing the telnet protocol and
+ * passing characters between the remote client and the login process.
  *
  * Vladimir Oleynik <dzo@simtreas.ru> 2001
- *     Set process group corrections, initial busybox port
+ * Set process group corrections, initial busybox port
  */
 
 #define DEBUG 0
 #endif
 #include <arpa/telnet.h>
 
-/* Structure that describes a session */
 struct tsession {
        struct tsession *next;
-       int sockfd_read, sockfd_write, ptyfd;
-       int shell_pid;
+       pid_t shell_pid;
+       int sockfd_read;
+       int sockfd_write;
+       int ptyfd;
 
        /* two circular buffers */
        /*char *buf1, *buf2;*/
-/*#define TS_BUF1 ts->buf1*/
-/*#define TS_BUF2 TS_BUF2*/
-#define TS_BUF1 ((unsigned char*)(ts + 1))
-#define TS_BUF2 (((unsigned char*)(ts + 1)) + BUFSIZE)
+/*#define TS_BUF1(ts) ts->buf1*/
+/*#define TS_BUF2(ts) TS_BUF2(ts)*/
+#define TS_BUF1(ts) ((unsigned char*)(ts + 1))
+#define TS_BUF2(ts) (((unsigned char*)(ts + 1)) + BUFSIZE)
        int rdidx1, wridx1, size1;
        int rdidx2, wridx2, size2;
 };
@@ -54,10 +55,17 @@ enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 };
 
 
 /* Globals */
-static int maxfd;
-static struct tsession *sessions;
-static const char *loginpath = "/bin/login";
-static const char *issuefile = "/etc/issue.net";
+struct globals {
+       struct tsession *sessions;
+       const char *loginpath;
+       const char *issuefile;
+       int maxfd;
+};
+#define G (*(struct globals*)&bb_common_bufsiz1)
+#define INIT_G() do { \
+       G.loginpath = "/bin/login"; \
+       G.issuefile = "/etc/issue.net"; \
+} while (0)
 
 
 /*
@@ -74,9 +82,6 @@ static const char *issuefile = "/etc/issue.net";
    past (bf + len) then that IAC will be left unprocessed and *processed
    will be less than len.
 
-   FIXME - if we mean to send 0xFF to the terminal then it will be escaped,
-   what is the escape character?  We aren't handling that situation here.
-
    CR-LF ->'s CR mapping is also done here, for convenience.
 
    NB: may fail to remove iacs which wrap around buffer!
@@ -84,7 +89,7 @@ static const char *issuefile = "/etc/issue.net";
 static unsigned char *
 remove_iacs(struct tsession *ts, int *pnum_totty)
 {
-       unsigned char *ptr0 = TS_BUF1 + ts->wridx1;
+       unsigned char *ptr0 = TS_BUF1(ts) + ts->wridx1;
        unsigned char *ptr = ptr0;
        unsigned char *totty = ptr;
        unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
@@ -96,63 +101,126 @@ remove_iacs(struct tsession *ts, int *pnum_totty)
 
                        *totty++ = c;
                        ptr++;
-                       /* We now map \r\n ==> \r for pragmatic reasons.
+                       /* We map \r\n ==> \r for pragmatic reasons.
                         * Many client implementations send \r\n when
                         * the user hits the CarriageReturn key.
                         */
                        if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0'))
                                ptr++;
-               } else {
-                       /*
-                        * TELOPT_NAWS support!
-                        */
-                       if ((ptr+2) >= end) {
-                               /* only the beginning of the IAC is in the
-                               buffer we were asked to process, we can't
-                               process this char. */
-                               break;
-                       }
+                       continue;
+               }
 
-                       /*
-                        * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE
-                        */
-                       else if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) {
-                               struct winsize ws;
-
-                               if ((ptr+8) >= end)
-                                       break;  /* incomplete, can't process */
-                               ws.ws_col = (ptr[3] << 8) | ptr[4];
-                               ws.ws_row = (ptr[5] << 8) | ptr[6];
-                               ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
-                               ptr += 9;
-                       } else {
-                               /* skip 3-byte IAC non-SB cmd */
+               if ((ptr+1) >= end)
+                       break;
+               if (ptr[1] == NOP) { /* Ignore? (putty keepalive, etc.) */
+                       ptr += 2;
+                       continue;
+               }
+               if (ptr[1] == IAC) { /* Literal IAC? (emacs M-DEL) */
+                       *totty++ = ptr[1];
+                       ptr += 2;
+                       continue;
+               }
+
+               /*
+                * TELOPT_NAWS support!
+                */
+               if ((ptr+2) >= end) {
+                       /* Only the beginning of the IAC is in the
+                       buffer we were asked to process, we can't
+                       process this char */
+                       break;
+               }
+               /*
+                * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE
+                */
+               if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) {
+                       struct winsize ws;
+                       if ((ptr+8) >= end)
+                               break;  /* incomplete, can't process */
+                       ws.ws_col = (ptr[3] << 8) | ptr[4];
+                       ws.ws_row = (ptr[5] << 8) | ptr[6];
+                       ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
+                       ptr += 9;
+                       continue;
+               }
+               /* skip 3-byte IAC non-SB cmd */
 #if DEBUG
-                               fprintf(stderr, "Ignoring IAC %s,%s\n",
-                                       TELCMD(ptr[1]), TELOPT(ptr[2]));
+               fprintf(stderr, "Ignoring IAC %s,%s\n",
+                               TELCMD(ptr[1]), TELOPT(ptr[2]));
 #endif
-                               ptr += 3;
-                       }
-               }
+               ptr += 3;
        }
 
        num_totty = totty - ptr0;
        *pnum_totty = num_totty;
-       /* the difference between ptr and totty is number of iacs
-          we removed from the stream. Adjust buf1 accordingly. */
+       /* The difference between ptr and totty is number of iacs
+          we removed from the stream. Adjust buf1 accordingly */
        if ((ptr - totty) == 0) /* 99.999% of cases */
                return ptr0;
        ts->wridx1 += ptr - totty;
        ts->size1 -= ptr - totty;
-       /* move chars meant for the terminal towards the end of the buffer */
+       /* Move chars meant for the terminal towards the end of the buffer */
        return memmove(ptr - num_totty, ptr0, num_totty);
 }
 
+/*
+ * Converting single IAC into double on output
+ */
+static size_t iac_safe_write(int fd, const char *buf, size_t count)
+{
+       const char *IACptr;
+       size_t wr, rc, total;
+
+       total = 0;
+       while (1) {
+               if (count == 0)
+                       return total;
+               if (*buf == (char)IAC) {
+                       static const char IACIAC[] ALIGN1 = { IAC, IAC };
+                       rc = safe_write(fd, IACIAC, 2);
+                       if (rc != 2)
+                               break;
+                       buf++;
+                       total++;
+                       count--;
+                       continue;
+               }
+               /* count != 0, *buf != IAC */
+               IACptr = memchr(buf, IAC, count);
+               wr = count;
+               if (IACptr)
+                       wr = IACptr - buf;
+               rc = safe_write(fd, buf, wr);
+               if (rc != wr)
+                       break;
+               buf += rc;
+               total += rc;
+               count -= rc;
+       }
+       /* here: rc - result of last short write */
+       if ((ssize_t)rc < 0) { /* error? */
+               if (total == 0)
+                       return rc;
+               rc = 0;
+       }
+       return total + rc;
+}
+
+/* Must match getopt32 string */
+enum {
+       OPT_WATCHCHILD = (1 << 2), /* -K */
+       OPT_INETD      = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */
+       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 *
 make_new_session(
-               USE_FEATURE_TELNETD_STANDALONE(int sock)
-               SKIP_FEATURE_TELNETD_STANDALONE(void)
+               IF_FEATURE_TELNETD_STANDALONE(int sock)
+               IF_NOT_FEATURE_TELNETD_STANDALONE(void)
 ) {
        const char *login_argv[2];
        struct termios termbuf;
@@ -163,32 +231,35 @@ make_new_session(
        /*ts->buf1 = (char *)(ts + 1);*/
        /*ts->buf2 = ts->buf1 + BUFSIZE;*/
 
-       /* Got a new connection, set up a tty. */
-       fd = getpty(tty_name);
-       if (fd < 0) {
-               bb_error_msg("can't create pty");
-               return NULL;
-       }
-       if (fd > maxfd)
-               maxfd = fd;
+       /* Got a new connection, set up a tty */
+       fd = xgetpty(tty_name);
+       if (fd > G.maxfd)
+               G.maxfd = fd;
        ts->ptyfd = fd;
        ndelay_on(fd);
+       close_on_exec_on(fd);
+
 #if ENABLE_FEATURE_TELNETD_STANDALONE
+       /* SO_KEEPALIVE by popular demand */
+       setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
        ts->sockfd_read = sock;
        ndelay_on(sock);
-       if (!sock) { /* We are called with fd 0 - we are in inetd mode */
+       if (sock == 0) { /* We are called with fd 0 - we are in inetd mode */
                sock++; /* so use fd 1 for output */
                ndelay_on(sock);
        }
        ts->sockfd_write = sock;
-       if (sock > maxfd)
-               maxfd = sock;
+       if (sock > G.maxfd)
+               G.maxfd = sock;
 #else
+       /* SO_KEEPALIVE by popular demand */
+       setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
        /* ts->sockfd_read = 0; - done by xzalloc */
        ts->sockfd_write = 1;
        ndelay_on(0);
        ndelay_on(1);
 #endif
+
        /* Make the telnet client understand we will echo characters so it
         * should not do it locally. We don't tell the client to run linemode,
         * because we want to handle line editing and tab completion and other
@@ -197,16 +268,27 @@ make_new_session(
                static const char iacs_to_send[] ALIGN1 = {
                        IAC, DO, TELOPT_ECHO,
                        IAC, DO, TELOPT_NAWS,
-                       IAC, DO, TELOPT_LFLOW,
+               /* This requires telnetd.ctrlSQ.patch (incomplete) */
+               /*      IAC, DO, TELOPT_LFLOW, */
                        IAC, WILL, TELOPT_ECHO,
                        IAC, WILL, TELOPT_SGA
                };
-               memcpy(TS_BUF2, iacs_to_send, sizeof(iacs_to_send));
-               ts->rdidx2 = sizeof(iacs_to_send);
-               ts->size2 = sizeof(iacs_to_send);
+               /* This confuses iac_safe_write(), it will try to duplicate
+                * each IAC... */
+               //memcpy(TS_BUF2(ts), iacs_to_send, sizeof(iacs_to_send));
+               //ts->rdidx2 = sizeof(iacs_to_send);
+               //ts->size2 = sizeof(iacs_to_send);
+               /* So just stuff it into TCP stream! (no error check...) */
+#if ENABLE_FEATURE_TELNETD_STANDALONE
+               safe_write(sock, iacs_to_send, sizeof(iacs_to_send));
+#else
+               safe_write(1, iacs_to_send, sizeof(iacs_to_send));
+#endif
+               /*ts->rdidx2 = 0; - xzalloc did it */
+               /*ts->size2 = 0;*/
        }
 
-       fflush(NULL); /* flush all streams */
+       fflush_all();
        pid = vfork(); /* NOMMU-friendly */
        if (pid < 0) {
                free(ts);
@@ -224,72 +306,66 @@ make_new_session(
        /* Child */
        /* Careful - we are after vfork! */
 
-       /* make new session and process group */
-       setsid();
-
-       /* Restore default signal handling */
+       /* Restore default signal handling ASAP */
        bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
 
-       /* open the child's side of the tty. */
+       /* Make new session and process group */
+       setsid();
+
+       /* Open the child's side of the tty */
        /* NB: setsid() disconnects from any previous ctty's. Therefore
         * we must open child's side of the tty AFTER setsid! */
-       fd = xopen(tty_name, O_RDWR); /* becomes our ctty */
-       dup2(fd, 0);
-       dup2(fd, 1);
-       dup2(fd, 2);
-       while (fd > 2) close(fd--);
+       close(0);
+       xopen(tty_name, O_RDWR); /* becomes our ctty */
+       xdup2(0, 1);
+       xdup2(0, 2);
        tcsetpgrp(0, getpid()); /* switch this tty's process group to us */
 
-       /* The pseudo-terminal allocated to the client is configured to operate in
-        * cooked mode, and with XTABS CRMOD enabled (see tty(4)). */
+       /* The pseudo-terminal allocated to the client is configured to operate
+        * in cooked mode, and with XTABS CRMOD enabled (see tty(4)) */
        tcgetattr(0, &termbuf);
        termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */
        termbuf.c_oflag |= ONLCR | XTABS;
        termbuf.c_iflag |= ICRNL;
        termbuf.c_iflag &= ~IXOFF;
        /*termbuf.c_lflag &= ~ICANON;*/
-       tcsetattr(0, TCSANOW, &termbuf);
+       tcsetattr_stdin_TCSANOW(&termbuf);
 
-       /* Uses FILE-based I/O to stdout, but does fflush(stdout),
+       /* Uses FILE-based I/O to stdout, but does fflush_all(),
         * so should be safe with vfork.
         * I fear, though, that some users will have ridiculously big
         * issue files, and they may block writing to fd 1,
         * (parent is supposed to read it, but parent waits
         * for vforked child to exec!) */
-       print_login_issue(issuefile, NULL);
+       print_login_issue(G.issuefile, tty_name);
 
        /* Exec shell / login / whatever */
-       login_argv[0] = loginpath;
+       login_argv[0] = G.loginpath;
        login_argv[1] = NULL;
        /* exec busybox applet (if PREFER_APPLETS=y), if that fails,
-        * exec external program */
-       BB_EXECVP(loginpath, (char **)login_argv);
+        * exec external program.
+        * NB: sock is either 0 or has CLOEXEC set on it.
+        * fd has CLOEXEC set on it too. These two fds will be closed here.
+        */
+       BB_EXECVP(G.loginpath, (char **)login_argv);
        /* _exit is safer with vfork, and we shouldn't send message
         * to remote clients anyway */
-       _exit(1); /*bb_perror_msg_and_die("execv %s", loginpath);*/
+       _exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", G.loginpath);*/
 }
 
-/* Must match getopt32 string */
-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_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
-};
-
 #if ENABLE_FEATURE_TELNETD_STANDALONE
 
 static void
 free_session(struct tsession *ts)
 {
-       struct tsession *t = sessions;
+       struct tsession *t = G.sessions;
 
        if (option_mask32 & OPT_INETD)
-               exit(0);
+               exit(EXIT_SUCCESS);
 
        /* Unlink this telnet session from the session list */
        if (t == ts)
-               sessions = ts->next;
+               G.sessions = ts->next;
        else {
                while (t->next != ts)
                        t = t->next;
@@ -301,7 +377,7 @@ free_session(struct tsession *ts)
         * doesn't send SIGKILL. When we close ptyfd,
         * kernel sends SIGHUP to processes having slave side opened. */
        kill(ts->shell_pid, SIGKILL);
-       wait4(ts->shell_pid, NULL, 0, NULL);
+       waitpid(ts->shell_pid, NULL, 0);
 #endif
        close(ts->ptyfd);
        close(ts->sockfd_read);
@@ -311,17 +387,17 @@ free_session(struct tsession *ts)
        free(ts);
 
        /* Scan all sessions and find new maxfd */
-       maxfd = 0;
-       ts = sessions;
+       G.maxfd = 0;
+       ts = G.sessions;
        while (ts) {
-               if (maxfd < ts->ptyfd)
-                       maxfd = ts->ptyfd;
-               if (maxfd < ts->sockfd_read)
-                       maxfd = ts->sockfd_read;
+               if (G.maxfd < ts->ptyfd)
+                       G.maxfd = ts->ptyfd;
+               if (G.maxfd < ts->sockfd_read)
+                       G.maxfd = ts->sockfd_read;
 #if 0
                /* Again, sockfd_write == sockfd_read here */
-               if (maxfd < ts->sockfd_write)
-                       maxfd = ts->sockfd_write;
+               if (G.maxfd < ts->sockfd_write)
+                       G.maxfd = ts->sockfd_write;
 #endif
                ts = ts->next;
        }
@@ -329,12 +405,12 @@ free_session(struct tsession *ts)
 
 #else /* !FEATURE_TELNETD_STANDALONE */
 
-/* Used in main() only, thus "return 0" actually is exit(0). */
+/* Used in main() only, thus "return 0" actually is exit(EXIT_SUCCESS). */
 #define free_session(ts) return 0
 
 #endif
 
-static void handle_sigchld(int sig ATTRIBUTE_UNUSED)
+static void handle_sigchld(int sig UNUSED_PARAM)
 {
        pid_t pid;
        struct tsession *ts;
@@ -344,7 +420,7 @@ static void handle_sigchld(int sig ATTRIBUTE_UNUSED)
                pid = wait_any_nohang(NULL);
                if (pid <= 0)
                        break;
-               ts = sessions;
+               ts = G.sessions;
                while (ts) {
                        if (ts->shell_pid == pid) {
                                ts->shell_pid = -1;
@@ -356,7 +432,7 @@ static void handle_sigchld(int sig ATTRIBUTE_UNUSED)
 }
 
 int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
+int telnetd_main(int argc UNUSED_PARAM, char **argv)
 {
        fd_set rdfdset, wrfdset;
        unsigned opt;
@@ -364,22 +440,29 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, 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" USE_FEATURE_TELNETD_STANDALONE("p:b:F"),
-                       &issuefile, &loginpath
-                       USE_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr));
+       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_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 */
@@ -391,31 +474,30 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                }
        }
        /* Redirect log to syslog early, if needed */
-       if (IS_INETD || !(opt & OPT_FOREGROUND)) {
-               openlog(applet_name, 0, LOG_USER);
+       if (IS_INETD || (opt & OPT_SYSLOG) || !(opt & OPT_FOREGROUND)) {
+               openlog(applet_name, LOG_PID, LOG_DAEMON);
                logmode = LOGMODE_SYSLOG;
        }
-       USE_FEATURE_TELNETD_STANDALONE(
-               if (opt & OPT_PORT)
-                       portnbr = xatou16(opt_portnbr);
-       );
-
-       /* Used to check access(loginpath, X_OK) here. Pointless.
-        * exec will do this for us for free later. */
-
 #if ENABLE_FEATURE_TELNETD_STANDALONE
        if (IS_INETD) {
-               sessions = make_new_session(0);
-               if (!sessions) /* pty opening or vfork problem, exit */
-                       return 1; /* make_new_session prints error message */
+               G.sessions = make_new_session(0);
+               if (!G.sessions) /* pty opening or vfork problem, exit */
+                       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
-       sessions = make_new_session();
-       if (!sessions) /* pty opening or vfork problem, exit */
-               return 1; /* make_new_session prints error message */
+       G.sessions = make_new_session();
+       if (!G.sessions) /* pty opening or vfork problem, exit */
+               return 1; /* make_new_session printed error message */
 #endif
 
        /* We don't want to die if just one session is broken */
@@ -427,8 +509,8 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                signal(SIGCHLD, SIG_IGN);
 
 /*
-   This is how the buffers are used. The arrows indicate the movement
-   of data.
+   This is how the buffers are used. The arrows indicate data flow.
+
    +-------+     wridx1++     +------+     rdidx1++     +----------+
    |       | <--------------  | buf1 | <--------------  |          |
    |       |     size1--      +------+     size1++      |          |
@@ -452,9 +534,9 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
         * ptys if there is room in their session buffers.
         * NB: scalability problem: we recalculate entire bitmap
         * before each select. Can be a problem with 500+ connections. */
-       ts = sessions;
+       ts = G.sessions;
        while (ts) {
-               struct tsession *next = ts->next; /* in case we free ts. */
+               struct tsession *next = ts->next; /* in case we free ts */
                if (ts->shell_pid == -1) {
                        /* Child died and we detected that */
                        free_session(ts);
@@ -475,16 +557,29 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                /* This is needed because free_session() does not
                 * take master_fd into account when it finds new
                 * maxfd among remaining fd's */
-               if (master_fd > maxfd)
-                       maxfd = master_fd;
+               if (master_fd > G.maxfd)
+                       G.maxfd = master_fd;
        }
 
-       count = select(maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
+       {
+               struct timeval *tv_ptr = NULL;
+#if ENABLE_FEATURE_TELNETD_INETD_WAIT
+               struct timeval tv;
+               if ((opt & OPT_WAIT) && !G.sessions) {
+                       tv.tv_sec = sec_linger;
+                       tv.tv_usec = 0;
+                       tv_ptr = &tv;
+               }
+#endif
+               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 */
 
 #if ENABLE_FEATURE_TELNETD_STANDALONE
-       /* First check for and accept new sessions. */
+       /* Check for and accept new sessions */
        if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) {
                int fd;
                struct tsession *new_ts;
@@ -492,26 +587,28 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                fd = accept(master_fd, NULL, NULL);
                if (fd < 0)
                        goto again;
-               /* Create a new session and link it into our active list */
+               close_on_exec_on(fd);
+
+               /* Create a new session and link it into active list */
                new_ts = make_new_session(fd);
                if (new_ts) {
-                       new_ts->next = sessions;
-                       sessions = new_ts;
+                       new_ts->next = G.sessions;
+                       G.sessions = new_ts;
                } else {
                        close(fd);
                }
        }
 #endif
 
-       /* Then check for data tunneling. */
-       ts = sessions;
+       /* Then check for data tunneling */
+       ts = G.sessions;
        while (ts) { /* For all sessions... */
-               struct tsession *next = ts->next; /* in case we free ts. */
+               struct tsession *next = ts->next; /* in case we free ts */
 
                if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) {
                        int num_totty;
                        unsigned char *ptr;
-                       /* Write to pty from buffer 1. */
+                       /* Write to pty from buffer 1 */
                        ptr = remove_iacs(ts, &num_totty);
                        count = safe_write(ts->ptyfd, ptr, num_totty);
                        if (count < 0) {
@@ -526,9 +623,9 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                }
  skip1:
                if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
-                       /* Write to socket from buffer 2. */
+                       /* Write to socket from buffer 2 */
                        count = MIN(BUFSIZE - ts->wridx2, ts->size2);
-                       count = safe_write(ts->sockfd_write, TS_BUF2 + ts->wridx2, count);
+                       count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count);
                        if (count < 0) {
                                if (errno == EAGAIN)
                                        goto skip2;
@@ -556,16 +653,16 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                }
 
                if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) {
-                       /* Read from socket to buffer 1. */
+                       /* Read from socket to buffer 1 */
                        count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
-                       count = safe_read(ts->sockfd_read, TS_BUF1 + ts->rdidx1, count);
+                       count = safe_read(ts->sockfd_read, TS_BUF1(ts) + ts->rdidx1, count);
                        if (count <= 0) {
                                if (count < 0 && errno == EAGAIN)
                                        goto skip3;
                                goto kill_session;
                        }
                        /* Ignore trailing NUL if it is there */
-                       if (!TS_BUF1[ts->rdidx1 + count - 1]) {
+                       if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) {
                                --count;
                        }
                        ts->size1 += count;
@@ -575,9 +672,9 @@ int telnetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                }
  skip3:
                if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
-                       /* Read from pty to buffer 2. */
+                       /* Read from pty to buffer 2 */
                        count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
-                       count = safe_read(ts->ptyfd, TS_BUF2 + ts->rdidx2, count);
+                       count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
                        if (count <= 0) {
                                if (count < 0 && errno == EAGAIN)
                                        goto skip4;