telnetd: we were having telnetd with is ONLY inetd or ONLY standalone.

What if I need to have both?? This patch introduces
CONFIG_FEATURE_TELNETD_STANDALONE: y - both, n - only inetd.

7 files changed, 344 insertions, 386 deletions

diff --git a/include/libbb.h b/include/libbb.h
index bec3ce11c..1c82cbbba 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -204,6 +204,7 @@ extern off_t bb_copyfd_size(int fd1, int fd2, off_t size);
 extern off_t bb_copyfd_eof(int fd1, int fd2);
 extern char bb_process_escape_sequence(const char **ptr);
 extern char *bb_get_last_path_component(char *path);
+extern int ndelay_on(int fd);
 
 
 extern DIR *xopendir(const char *path);
diff --git a/include/usage.h b/include/usage.h
index 2a6e335ba..69e958d68 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -3034,22 +3034,24 @@ USE_FEATURE_START_STOP_DAEMON_FANCY( \
 	"computer over a network using the TELNET protocol."
 #endif
 
-#ifdef CONFIG_FEATURE_TELNETD_INETD
+#ifdef CONFIG_FEATURE_TELNETD_STANDALONE
 #define telnetd_trivial_usage \
-	"(inetd mode) [OPTION]"
+	"[OPTION]"
 #define telnetd_full_usage \
-	"Telnetd uses incoming TELNET connections via inetd.\n" \
+	"Telnetd listens for incoming TELNET connections on PORT.\n" \
 	"Options:\n" \
-	"\t-l LOGIN\texec LOGIN on connect (default /bin/sh)\n" \
-	"\t-f issue_file\tDisplay issue_file instead of /etc/issue"
+	"\t-p PORT\t\tlisten for connections on PORT (default 23)\n" \
+	"\t-l LOGIN\texec LOGIN on connect\n" \
+	"\t-f issue_file\tDisplay issue_file instead of /etc/issue\n" \
+	"\t-F\t\tForeground mode\n" \
+	"\t-i\t\tInetd mode"
 #else
 #define telnetd_trivial_usage \
 	"[OPTION]"
 #define telnetd_full_usage \
-	"Telnetd listens for incoming TELNET connections on PORT.\n" \
+	"Telnetd uses incoming TELNET connections via inetd.\n" \
 	"Options:\n" \
-	"\t-p PORT\tlisten for connections on PORT (default 23)\n" \
-	"\t-l LOGIN\texec LOGIN on connect (default /bin/sh)\n" \
+	"\t-l LOGIN\texec LOGIN on connect\n" \
 	"\t-f issue_file\tDisplay issue_file instead of /etc/issue"
 #endif
 
diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index 44a551639..e6f4e3a48 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -110,6 +110,18 @@ int xopen3(const char *pathname, int flags, int mode)
 	return ret;
 }
 
+/*
+int ndelay_off(int fd)
+{
+	return fcntl(fd,F_SETFL,fcntl(fd,F_GETFL,0) & ~O_NONBLOCK);
+}
+*/
+// Turn on nonblocking I/O on a fd
+int ndelay_on(int fd)
+{
+	return fcntl(fd,F_SETFL,fcntl(fd,F_GETFL,0) | O_NONBLOCK);
+}
+
 // Die with an error message if we can't write the entire buffer.
 void xwrite(int fd, void *buf, size_t count)
 {
diff --git a/networking/Config.in b/networking/Config.in
index ba41ab119..e9694af67 100644
--- a/networking/Config.in
+++ b/networking/Config.in
@@ -586,13 +586,12 @@ config TELNETD
 	  with all that done, telnetd _should_ work....
 
 
-config FEATURE_TELNETD_INETD
-	bool "Support call from inetd only"
+config FEATURE_TELNETD_STANDALONE
+	bool "Support standalone telnetd (not inetd only)"
 	default n
 	depends on TELNETD
 	help
-	  Selecting this will make telnetd only callable from inetd,
-	  removing the standalone support.
+	  Selecting this will make telnetd able to run standalone.
 
 config TFTP
 	bool "tftp"
diff --git a/networking/telnetd.c b/networking/telnetd.c
index da7911fcc..549488507 100644
--- a/networking/telnetd.c
+++ b/networking/telnetd.c
@@ -22,11 +22,11 @@
  */
 
 /*#define DEBUG 1 */
-#undef DEBUG
+#define DEBUG 0
 
 #include "busybox.h"
 
-#ifdef DEBUG
+#if DEBUG
 #define TELCMDS
 #define TELOPTS
 #endif
@@ -36,7 +36,7 @@
 
 #define BUFSIZE 4000
 
-#ifdef CONFIG_FEATURE_IPV6
+#if ENABLE_FEATURE_IPV6
 #define SOCKET_TYPE	AF_INET6
 typedef struct sockaddr_in6 sockaddr_type;
 #else
@@ -44,27 +44,23 @@ typedef struct sockaddr_in6 sockaddr_type;
 typedef struct sockaddr_in sockaddr_type;
 #endif
 
-
-#ifdef CONFIG_LOGIN
+#if ENABLE_LOGIN
 static const char *loginpath = "/bin/login";
 #else
-static const char *loginpath;
+static const char *loginpath = DEFAULT_SHELL;
 #endif
+
 static const char *issuefile = "/etc/issue.net";
 
 /* shell name and arguments */
 
-static const char *argv_init[] = {NULL, NULL};
+static const char *argv_init[2];
 
 /* structure that describes a session */
 
 struct tsession {
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-	int sockfd_read, sockfd_write, ptyfd;
-#else /* CONFIG_FEATURE_TELNETD_INETD */
 	struct tsession *next;
-	int sockfd, ptyfd;
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
+	int sockfd_read, sockfd_write, ptyfd;
 	int shell_pid;
 	/* two circular buffers */
 	char *buf1, *buf2;
@@ -73,7 +69,6 @@ struct tsession {
 };
 
 /*
-
    This is how the buffers are used. The arrows indicate the movement
    of data.
 
@@ -86,7 +81,6 @@ struct tsession {
    +-------+     size2++      +------+     size2--      +----------+
 
    Each session has got two buffers.
-
 */
 
 static int maxfd;
@@ -95,7 +89,6 @@ static struct tsession *sessions;
 
 
 /*
-
    Remove all IAC's from the buffer pointed to by bf (received IACs are ignored
    and must be removed so as to not be interpreted by the terminal).  Make an
    uninterrupted string of characters fit for the terminal.  Do this by packing
@@ -113,10 +106,10 @@ static struct tsession *sessions;
    what is the escape character?  We aren't handling that situation here.
 
    CR-LF ->'s CR mapping is also done here, for convenience
-
-  */
+ */
 static char *
-remove_iacs(struct tsession *ts, int *pnum_totty) {
+remove_iacs(struct tsession *ts, int *pnum_totty)
+{
 	unsigned char *ptr0 = (unsigned char *)ts->buf1 + ts->wridx1;
 	unsigned char *ptr = ptr0;
 	unsigned char *totty = ptr;
@@ -134,8 +127,7 @@ remove_iacs(struct tsession *ts, int *pnum_totty) {
 			 */
 			if (c == '\r' && (*ptr == '\n' || *ptr == 0) && ptr < end)
 				ptr++;
-		}
-		else {
+		} else {
 			/*
 			 * TELOPT_NAWS support!
 			 */
@@ -155,14 +147,13 @@ remove_iacs(struct tsession *ts, int *pnum_totty) {
 					break;	/* incomplete, can't process */
 				ws.ws_col = (ptr[3] << 8) | ptr[4];
 				ws.ws_row = (ptr[5] << 8) | ptr[6];
-				(void) ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
+				ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
 				ptr += 9;
-			}
-			else {
+			} else {
 				/* skip 3-byte IAC non-SB cmd */
-#ifdef DEBUG
+#if DEBUG
 				fprintf(stderr, "Ignoring IAC %s,%s\n",
-					TELCMD(*(ptr+1)), TELOPT(*(ptr+2)));
+					TELCMD(ptr[1]), TELOPT(ptr[2]));
 #endif
 				ptr += 3;
 			}
@@ -184,10 +175,10 @@ remove_iacs(struct tsession *ts, int *pnum_totty) {
 
 
 static int
-getpty(char *line)
+getpty(char *line, int size)
 {
 	int p;
-#ifdef CONFIG_FEATURE_DEVPTS
+#if ENABLE_FEATURE_DEVPTS
 	p = open("/dev/ptmx", O_RDWR);
 	if (p > 0) {
 		const char *name;
@@ -198,7 +189,7 @@ getpty(char *line)
 			bb_perror_msg("ptsname error (is /dev/pts mounted?)");
 			return -1;
 		}
-		strcpy(line, name);
+		safe_strncpy(line, name, size);
 		return p;
 	}
 #else
@@ -216,9 +207,8 @@ getpty(char *line)
 		}
 		for (j = 0; j < 16; j++) {
 			line[9] = j < 10 ? j + '0' : j - 10 + 'a';
-#ifdef DEBUG
-			fprintf(stderr, "Trying to open device: %s\n", line);
-#endif
+			if (DEBUG)
+				fprintf(stderr, "Trying to open device: %s\n", line);
 			p = open(line, O_RDWR | O_NOCTTY);
 			if (p >= 0) {
 				line[5] = 't';
@@ -226,7 +216,7 @@ getpty(char *line)
 			}
 		}
 	}
-#endif /* CONFIG_FEATURE_DEVPTS */
+#endif /* FEATURE_DEVPTS */
 	return -1;
 }
 
@@ -234,7 +224,7 @@ getpty(char *line)
 static void
 send_iac(struct tsession *ts, unsigned char command, int option)
 {
-	/* We rely on that there is space in the buffer for now.  */
+	/* We rely on that there is space in the buffer for now. */
 	char *b = ts->buf2 + ts->rdidx2;
 	*b++ = IAC;
 	*b++ = command;
@@ -245,401 +235,376 @@ send_iac(struct tsession *ts, unsigned char command, int option)
 
 
 static struct tsession *
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-make_new_session(void)
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-make_new_session(int sockfd)
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-{
+make_new_session(
+		USE_FEATURE_TELNETD_STANDALONE(int sock_r, int sock_w)
+		SKIP_FEATURE_TELNETD_STANDALONE(void)
+) {
 	struct termios termbuf;
-	int pty, pid;
+	int fd, pid;
 	char tty_name[32];
 	struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2);
 
 	ts->buf1 = (char *)(&ts[1]);
 	ts->buf2 = ts->buf1 + BUFSIZE;
 
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-	ts->sockfd_write = 1;
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-	ts->sockfd = sockfd;
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-
-	/* Got a new connection, set up a tty and spawn a shell.  */
-
-	pty = getpty(tty_name);
-
-	if (pty < 0) {
+	/* Got a new connection, set up a tty. */
+	fd = getpty(tty_name, 32);
+	if (fd < 0) {
 		bb_error_msg("all terminals in use");
-		return 0;
+		return NULL;
 	}
-
-	if (pty > maxfd)
-		maxfd = pty;
-
-	ts->ptyfd = pty;
-
+	if (fd > maxfd) maxfd = fd;
+	ndelay_on(ts->ptyfd = fd);
+#if ENABLE_FEATURE_TELNETD_STANDALONE
+	if (sock_w > maxfd) maxfd = sock_w;
+	if (sock_r > maxfd) maxfd = sock_r;
+	ndelay_on(ts->sockfd_write = sock_w);
+	ndelay_on(ts->sockfd_read = sock_r);
+#else
+	ts->sockfd_write = 1;
+	/* xzalloc: ts->sockfd_read = 0; */
+	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
-	 * stuff that requires char-by-char support.
-	 */
-
+	 * stuff that requires char-by-char support. */
 	send_iac(ts, DO, TELOPT_ECHO);
 	send_iac(ts, DO, TELOPT_NAWS);
 	send_iac(ts, DO, TELOPT_LFLOW);
 	send_iac(ts, WILL, TELOPT_ECHO);
 	send_iac(ts, WILL, TELOPT_SGA);
 
-	if ((pid = fork()) < 0) {
+	pid = fork();
+	if (pid < 0) {
+		free(ts);
+		close(fd);
 		bb_perror_msg("fork");
+		return NULL;
 	}
-	if (pid == 0) {
-		/* In child, open the child's side of the tty.  */
-		int i;
-
-		for(i = 0; i <= maxfd; i++)
-			close(i);
-		/* make new process group */
-		setsid();
-
-		xopen(tty_name, O_RDWR /*| O_NOCTTY*/);
-		dup(0);
-		dup(0);
-
-		tcsetpgrp(0, getpid());
-
-		/* 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);
-
-		print_login_issue(issuefile, NULL);
-
-		/* exec shell, with correct argv and env */
-		execv(loginpath, (char *const *)argv_init);
-
-		/* NOT REACHED */
-		bb_perror_msg_and_die("execv");
+	if (pid > 0) {
+		/* parent */
+		ts->shell_pid = pid;
+		return ts;
 	}
-
-	ts->shell_pid = pid;
-
-	return ts;
+	
+	/* child */
+
+	/* open the child's side of the tty. */
+	fd = xopen(tty_name, O_RDWR /*| O_NOCTTY*/);
+	dup2(fd, 0);
+	dup2(fd, 1);
+	dup2(fd, 2);
+	while (fd > 2) close(fd--);
+	/* make new process group */
+	setsid();
+	tcsetpgrp(0, getpid());
+
+	/* 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);
+
+	print_login_issue(issuefile, NULL);
+
+	/* exec shell, with correct argv and env */
+	execv(loginpath, (char *const *)argv_init);
+	bb_perror_msg_and_die("execv");
 }
 
-#ifndef CONFIG_FEATURE_TELNETD_INETD
+#if ENABLE_FEATURE_TELNETD_STANDALONE
+
 static void
 free_session(struct tsession *ts)
 {
 	struct tsession *t = sessions;
 
-	/* Unlink this telnet session from the session list.  */
+	/* unlink this telnet session from the session list */
 	if (t == ts)
 		sessions = ts->next;
 	else {
-		while(t->next != ts)
+		while (t->next != ts)
 			t = t->next;
 		t->next = ts->next;
 	}
 
 	kill(ts->shell_pid, SIGKILL);
-
 	wait4(ts->shell_pid, NULL, 0, NULL);
-
 	close(ts->ptyfd);
-	close(ts->sockfd);
-
-	if (ts->ptyfd == maxfd || ts->sockfd == maxfd)
-		maxfd--;
-	if (ts->ptyfd == maxfd || ts->sockfd == maxfd)
-		maxfd--;
-
+	close(ts->sockfd_read);
+	/* error if ts->sockfd_read == ts->sockfd_write. So what? ;) */
+	close(ts->sockfd_write);
 	free(ts);
+
+	/* scan all sessions and find new maxfd */
+        ts = sessions;
+	maxfd = 0;
+	while (ts) {
+		if (maxfd < ts->ptyfd)
+			maxfd = ts->ptyfd;
+		if (maxfd < ts->sockfd_read)
+			maxfd = ts->sockfd_read;
+		if (maxfd < ts->sockfd_write)
+			maxfd = ts->sockfd_write;
+		ts = ts->next;
+	}
 }
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
 
-int
-telnetd_main(int argc, char **argv)
+static int
+create_socket(int port, const char *opt_bindaddr)
 {
-	unsigned opt;
-	fd_set rdfdset, wrfdset;
-	int selret;
-#ifndef CONFIG_FEATURE_TELNETD_INETD
+	static const int on = 1;
+	int fd;
 	sockaddr_type sa;
-	int master_fd;
-	int on = 1;
-	unsigned portnbr = 23;
+#if !ENABLE_FEATURE_IPV6
 	struct in_addr bind_addr = { .s_addr = 0x0 };
-	char *opt_portnbr, *opt_bindaddr;
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-	int maxlen, w, r;
 
-#ifndef CONFIG_LOGIN
-	loginpath = DEFAULT_SHELL;
+	/* TODO: generic string -> sockaddr converter */
+	if (opt_bindaddr && inet_aton(opt_bindaddr, &bind_addr) == 0)
+		bb_show_usage();
 #endif
-
-	/* We use inetd-style operation unconditionally
-	 * (no --foreground option), user most likely will
-	 * look into syslog for all errors, even early ones.
-	 * Direct all output to syslog at once.
-	 */
-	openlog(applet_name, 0, LOG_USER);
-	logmode = LOGMODE_SYSLOG;
-
-	opt = getopt32(argc, argv, "f:l:" SKIP_FEATURE_TELNETD_INETD("p:b:"),
-			&issuefile, &loginpath
-			SKIP_FEATURE_TELNETD_INETD(, &opt_portnbr, &opt_bindaddr));
-	//if (opt & 1) // -f
-	//if (opt & 2) // -l
-#ifndef CONFIG_FEATURE_TELNETD_INETD
-	if (opt & 4) portnbr = xatou16(opt_portnbr); // -p
-	if (opt & 8) // -b
-		if (inet_aton(opt_bindaddr, &bind_addr) == 0) bb_show_usage();
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-
-	if (access(loginpath, X_OK) < 0) {
-		bb_error_msg_and_die("'%s' unavailable", loginpath);
-	}
-
-	argv_init[0] = loginpath;
-
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-	maxfd = 1;
-	sessions = make_new_session();
-#else /* CONFIG_EATURE_TELNETD_INETD */
-	sessions = 0;
-
-	/* Grab a TCP socket.  */
-
-	master_fd = xsocket(SOCKET_TYPE, SOCK_STREAM, 0);
-	(void)setsockopt(master_fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
-
-	/* Set it to listen to specified port.  */
-
+	fd = xsocket(SOCKET_TYPE, SOCK_STREAM, 0);
+	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
 	memset((void *)&sa, 0, sizeof(sa));
-#ifdef CONFIG_FEATURE_IPV6
+#if ENABLE_FEATURE_IPV6
 	sa.sin6_family = AF_INET6;
-	sa.sin6_port = htons(portnbr);
+	sa.sin6_port = htons(port);
 	/* sa.sin6_addr = bind_addr6; */
 #else
 	sa.sin_family = AF_INET;
-	sa.sin_port = htons(portnbr);
+	sa.sin_port = htons(port);
 	sa.sin_addr = bind_addr;
 #endif
+	xbind(fd, (struct sockaddr *) &sa, sizeof(sa));
+	xlisten(fd, 1);
+	return fd;
+}
 
-	xbind(master_fd, (struct sockaddr *) &sa, sizeof(sa));
-	xlisten(master_fd, 1);
-	xdaemon(0, 0);
+#else /* !FEATURE_TELNETD_STANDALONE */
 
-	maxfd = master_fd;
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
+/* Never actually called */
+void free_session(struct tsession *ts);
+int create_socket(int port, const char *opt_bindaddr);
 
-	while(1) {
-		struct tsession *ts;
+#endif
 
-		FD_ZERO(&rdfdset);
-		FD_ZERO(&wrfdset);
 
-		/* select on the master socket, all telnet sockets and their
-		 * ptys if there is room in their respective session buffers.
-		 */
+int
+telnetd_main(int argc, char **argv)
+{
+	fd_set rdfdset, wrfdset;
+	unsigned opt;
+	int selret, maxlen, w, r;
+	struct tsession *ts;
+#if ENABLE_FEATURE_TELNETD_STANDALONE
+#define IS_INETD (opt & OPT_INETD)
+	int master_fd = -1; /* be happy, gcc */
+	unsigned portnbr = 23;
+	char *opt_bindaddr = NULL;
+	char *opt_portnbr;
+#else
+	enum {
+		IS_INETD = 1,
+		master_fd = -1,
+		portnbr = 23,
+	};
+#endif
+	enum {
+		OPT_PORT = 4 * ENABLE_FEATURE_TELNETD_STANDALONE,
+		OPT_FOREGROUND = 0x10 * ENABLE_FEATURE_TELNETD_STANDALONE,
+		OPT_INETD = 0x20 * ENABLE_FEATURE_TELNETD_STANDALONE,
+	};
 
-#ifndef CONFIG_FEATURE_TELNETD_INETD
+	opt = getopt32(argc, argv, "f:l:" USE_FEATURE_TELNETD_STANDALONE("p:b:Fi"),
+			&issuefile, &loginpath
+			USE_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr));
+	/* Redirect log to syslog early, if needed */
+	if (IS_INETD || !(opt & OPT_FOREGROUND)) {
+		openlog(applet_name, 0, LOG_USER);
+		logmode = LOGMODE_SYSLOG;
+	}
+	//if (opt & 1) // -f
+	//if (opt & 2) // -l
+	USE_FEATURE_TELNETD_STANDALONE(
+		if (opt & OPT_PORT) // -p
+			portnbr = xatou16(opt_portnbr);
+		//if (opt & 8) // -b
+		//if (opt & 0x10) // -F
+		//if (opt & 0x20) // -i
+	);
+
+	/* Used to check access(loginpath, X_OK) here. Pointless.
+	 * exec will do this for us for free later. */
+	argv_init[0] = loginpath;
+
+#if ENABLE_FEATURE_TELNETD_STANDALONE
+	if (IS_INETD) {
+		sessions = make_new_session(0, 1);
+	} else {
+		master_fd = create_socket(portnbr, opt_bindaddr);
+		if (!(opt & OPT_FOREGROUND))
+			xdaemon(0, 0);
+	}
+#else
+	sessions = make_new_session();
+#endif
+
+	/* We don't want to die if just one session is broken */
+	signal(SIGPIPE, SIG_IGN);
+
+ again:
+	FD_ZERO(&rdfdset);
+	FD_ZERO(&wrfdset);
+	if (!IS_INETD) {
 		FD_SET(master_fd, &rdfdset);
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-
-		ts = sessions;
-#ifndef CONFIG_FEATURE_TELNETD_INETD
-		while (ts) {
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-			/* buf1 is used from socket to pty
-			 * buf2 is used from pty to socket
-			 */
-			if (ts->size1 > 0) {
-				FD_SET(ts->ptyfd, &wrfdset);  /* can write to pty */
-			}
-			if (ts->size1 < BUFSIZE) {
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-				FD_SET(ts->sockfd_read, &rdfdset); /* can read from socket */
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-				FD_SET(ts->sockfd, &rdfdset); /* can read from socket */
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-			}
-			if (ts->size2 > 0) {
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-				FD_SET(ts->sockfd_write, &wrfdset); /* can write to socket */
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-				FD_SET(ts->sockfd, &wrfdset); /* can write to socket */
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-			}
-			if (ts->size2 < BUFSIZE) {
-				FD_SET(ts->ptyfd, &rdfdset);  /* can read from pty */
-			}
-#ifndef CONFIG_FEATURE_TELNETD_INETD
-			ts = ts->next;
-		}
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
+		/* This is needed because free_session() does not
+		 * take into account master_fd when it finds new
+		 * maxfd among remaining fd's: */
+		if (master_fd > maxfd)
+			maxfd = master_fd;
+	}
 
-		selret = select(maxfd + 1, &rdfdset, &wrfdset, 0, 0);
+	/* select on the master socket, all telnet sockets and their
+	 * ptys if there is room in their session buffers. */
+	ts = sessions;
+	while (ts) {
+		/* buf1 is used from socket to pty
+		 * buf2 is used from pty to socket */
+		if (ts->size1 > 0)       /* can write to pty */
+			FD_SET(ts->ptyfd, &wrfdset);
+		if (ts->size1 < BUFSIZE) /* can read from socket */
+			FD_SET(ts->sockfd_read, &rdfdset);
+		if (ts->size2 > 0)       /* can write to socket */
+			FD_SET(ts->sockfd_write, &wrfdset);
+		if (ts->size2 < BUFSIZE) /* can read from pty */
+			FD_SET(ts->ptyfd, &rdfdset);
+		ts = ts->next;
+	}
 
-		if (!selret)
-			break;
+	selret = select(maxfd + 1, &rdfdset, &wrfdset, 0, 0);
+	if (!selret)
+		return 0;
 
-#ifndef CONFIG_FEATURE_TELNETD_INETD
-		/* First check for and accept new sessions.  */
-		if (FD_ISSET(master_fd, &rdfdset)) {
-			int fd;
-			socklen_t salen;
+#if ENABLE_FEATURE_TELNETD_STANDALONE
+	/* First check for and accept new sessions. */
+	if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) {
+		sockaddr_type sa;
+		int fd;
+		socklen_t salen;
+		struct tsession *new_ts;
+
+		salen = sizeof(sa);
+		fd = accept(master_fd, (struct sockaddr *)&sa, &salen);
+		if (fd < 0)
+			goto again;
+		/* Create a new session and link it into our active list */
+		new_ts = make_new_session(fd, fd);
+		if (new_ts) {
+			new_ts->next = sessions;
+			sessions = new_ts;
+		} else {
+			close(fd);
+		}
+	}
+#endif
 
-			salen = sizeof(sa);
-			fd = accept(master_fd, (struct sockaddr *)&sa, &salen);
-			if (fd < 0) {
+	/* Then check for data tunneling. */
+	ts = sessions;
+	while (ts) { /* For all sessions... */
+		struct tsession *next = ts->next; /* in case we free ts. */
+
+		if (ts->size1 && FD_ISSET(ts->ptyfd, &wrfdset)) {
+			int num_totty;
+			char *ptr;
+			/* Write to pty from buffer 1. */
+			ptr = remove_iacs(ts, &num_totty);
+			w = safe_write(ts->ptyfd, ptr, num_totty);
+			/* needed? if (w < 0 && errno == EAGAIN) continue; */
+			if (w < 0) {
+				if (IS_INETD)
+					return 0;
+				free_session(ts);
+				ts = next;
 				continue;
-			} else {
-				/* Create a new session and link it into
-					our active list.  */
-				struct tsession *new_ts = make_new_session(fd);
-				if (new_ts) {
-					new_ts->next = sessions;
-					sessions = new_ts;
-					if (fd > maxfd)
-						maxfd = fd;
-				} else {
-					close(fd);
-				}
 			}
+			ts->wridx1 += w;
+			ts->size1 -= w;
+			if (ts->wridx1 == BUFSIZE)
+				ts->wridx1 = 0;
 		}
 
-		/* Then check for data tunneling.  */
-
-		ts = sessions;
-		while (ts) { /* For all sessions...  */
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-#ifndef CONFIG_FEATURE_TELNETD_INETD
-			struct tsession *next = ts->next; /* in case we free ts. */
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-
-			if (ts->size1 && FD_ISSET(ts->ptyfd, &wrfdset)) {
-				int num_totty;
-				char *ptr;
-				/* Write to pty from buffer 1.  */
-
-				ptr = remove_iacs(ts, &num_totty);
-
-				w = write(ts->ptyfd, ptr, num_totty);
-				if (w < 0) {
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-					exit(0);
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-					free_session(ts);
-					ts = next;
-					continue;
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-				}
-				ts->wridx1 += w;
-				ts->size1 -= w;
-				if (ts->wridx1 == BUFSIZE)
-					ts->wridx1 = 0;
-			}
-
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-			if (ts->size2 && FD_ISSET(ts->sockfd_write, &wrfdset)) {
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-			if (ts->size2 && FD_ISSET(ts->sockfd, &wrfdset)) {
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-				/* Write to socket from buffer 2.  */
-				maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2);
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-				w = write(ts->sockfd_write, ts->buf2 + ts->wridx2, maxlen);
-				if (w < 0)
-					exit(0);
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-				w = write(ts->sockfd, ts->buf2 + ts->wridx2, maxlen);
-				if (w < 0) {
-					free_session(ts);
-					ts = next;
-					continue;
-				}
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-				ts->wridx2 += w;
-				ts->size2 -= w;
-				if (ts->wridx2 == BUFSIZE)
-					ts->wridx2 = 0;
+		if (ts->size2 && FD_ISSET(ts->sockfd_write, &wrfdset)) {
+			/* Write to socket from buffer 2. */
+			maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2);
+			w = safe_write(ts->sockfd_write, ts->buf2 + ts->wridx2, maxlen);
+			/* needed? if (w < 0 && errno == EAGAIN) continue; */
+			if (w < 0) {
+				if (IS_INETD)
+					return 0;
+				free_session(ts);
+				ts = next;
+				continue;
 			}
+			ts->wridx2 += w;
+			ts->size2 -= w;
+			if (ts->wridx2 == BUFSIZE)
+				ts->wridx2 = 0;
+		}
 
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-			if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd_read, &rdfdset)) {
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-			if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd, &rdfdset)) {
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-				/* Read from socket to buffer 1. */
-				maxlen = MIN(BUFSIZE - ts->rdidx1,
-						BUFSIZE - ts->size1);
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-				r = read(ts->sockfd_read, ts->buf1 + ts->rdidx1, maxlen);
-				if (!r || (r < 0 && errno != EINTR))
-					exit(0);
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-				r = read(ts->sockfd, ts->buf1 + ts->rdidx1, maxlen);
-				if (!r || (r < 0 && errno != EINTR)) {
-					free_session(ts);
-					ts = next;
-					continue;
-				}
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-				if (!*(ts->buf1 + ts->rdidx1 + r - 1)) {
-					r--;
-					if (!r)
-						continue;
-				}
-				ts->rdidx1 += r;
-				ts->size1 += r;
-				if (ts->rdidx1 == BUFSIZE)
-					ts->rdidx1 = 0;
+		if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd_read, &rdfdset)) {
+			/* Read from socket to buffer 1. */
+			maxlen = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
+			r = safe_read(ts->sockfd_read, ts->buf1 + ts->rdidx1, maxlen);
+			if (r < 0 && errno == EAGAIN) continue;
+			if (r <= 0) {
+				if (IS_INETD)
+					return 0;
+				free_session(ts);
+				ts = next;
+				continue;
 			}
-
-			if (ts->size2 < BUFSIZE && FD_ISSET(ts->ptyfd, &rdfdset)) {
-				/* Read from pty to buffer 2.  */
-				maxlen = MIN(BUFSIZE - ts->rdidx2,
-						BUFSIZE - ts->size2);
-				r = read(ts->ptyfd, ts->buf2 + ts->rdidx2, maxlen);
-				if (!r || (r < 0 && errno != EINTR)) {
-#ifdef CONFIG_FEATURE_TELNETD_INETD
-					exit(0);
-#else /* CONFIG_FEATURE_TELNETD_INETD */
-					free_session(ts);
-					ts = next;
+			if (!ts->buf1[ts->rdidx1 + r - 1])
+				if (!--r)
 					continue;
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-				}
-				ts->rdidx2 += r;
-				ts->size2 += r;
-				if (ts->rdidx2 == BUFSIZE)
-					ts->rdidx2 = 0;
-			}
-
-			if (ts->size1 == 0) {
+			ts->rdidx1 += r;
+			ts->size1 += r;
+			if (ts->rdidx1 == BUFSIZE)
 				ts->rdidx1 = 0;
-				ts->wridx1 = 0;
+		}
+
+		if (ts->size2 < BUFSIZE && FD_ISSET(ts->ptyfd, &rdfdset)) {
+			/* Read from pty to buffer 2. */
+			maxlen = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
+			r = safe_read(ts->ptyfd, ts->buf2 + ts->rdidx2, maxlen);
+			if (r < 0 && errno == EAGAIN) continue;
+			if (r <= 0) {
+				if (IS_INETD)
+					return 0;
+				free_session(ts);
+				ts = next;
+				continue;
 			}
-			if (ts->size2 == 0) {
+			ts->rdidx2 += r;
+			ts->size2 += r;
+			if (ts->rdidx2 == BUFSIZE)
 				ts->rdidx2 = 0;
-				ts->wridx2 = 0;
-			}
-#ifndef CONFIG_FEATURE_TELNETD_INETD
-			ts = next;
 		}
-#endif /* CONFIG_FEATURE_TELNETD_INETD */
-
-	} /* while(1) */
 
-	return 0;
+		if (ts->size1 == 0) {
+			ts->rdidx1 = 0;
+			ts->wridx1 = 0;
+		}
+		if (ts->size2 == 0) {
+			ts->rdidx2 = 0;
+			ts->wridx2 = 0;
+		}
+		ts = next;
+	}
+	goto again;
 }
diff --git a/runit/runit_lib.c b/runit/runit_lib.c
index c95d641f1..5ebbc5840 100644
--- a/runit/runit_lib.c
+++ b/runit/runit_lib.c
@@ -34,10 +34,6 @@ ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "libbb.h"
 #include "runit_lib.h"
 
-#ifndef O_NONBLOCK
-#define O_NONBLOCK O_NDELAY
-#endif
-
 /*** buffer.c ***/
 
 void buffer_init(buffer *s,int (*op)(int fd,char *buf,unsigned len),int fd,char *buf,unsigned len)
@@ -625,22 +621,6 @@ int lock_exnb(int fd)
 }
 
 
-/*** ndelay_off.c ***/
-
-int ndelay_off(int fd)
-{
-	return fcntl(fd,F_SETFL,fcntl(fd,F_GETFL,0) & ~O_NONBLOCK);
-}
-
-
-/*** ndelay_on.c ***/
-
-int ndelay_on(int fd)
-{
-	return fcntl(fd,F_SETFL,fcntl(fd,F_GETFL,0) | O_NONBLOCK);
-}
-
-
 /*** open_append.c ***/
 
 int open_append(const char *fn)
diff --git a/scripts/defconfig b/scripts/defconfig
index 11361dc42..102c21a5f 100644
--- a/scripts/defconfig
+++ b/scripts/defconfig
@@ -560,7 +560,6 @@ CONFIG_TELNET=y
 CONFIG_FEATURE_TELNET_TTYPE=y
 CONFIG_FEATURE_TELNET_AUTOLOGIN=y
 CONFIG_TELNETD=y
-CONFIG_FEATURE_TELNETD_INETD=y
 CONFIG_TFTP=y
 CONFIG_FEATURE_TFTP_GET=y
 CONFIG_FEATURE_TFTP_PUT=y