udhcp: use poll() instead of select()

function                                             old     new   delta
udhcp_sp_read                                         65      46     -19
udhcp_sp_fd_set                                       79      54     -25
udhcpd_main                                         1530    1482     -48
udhcpc_main                                         2780    2730     -50
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/4 up/down: 0/-142)           Total: -142 bytes

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

5 files changed, 45 insertions, 53 deletions

diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index a526494d7..ee12cf91b 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -300,8 +300,8 @@ int udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
 		uint32_t dest_nip, int dest_port) FAST_FUNC;
 
 void udhcp_sp_setup(void) FAST_FUNC;
-int udhcp_sp_fd_set(fd_set *rfds, int extra_fd) FAST_FUNC;
-int udhcp_sp_read(const fd_set *rfds) FAST_FUNC;
+void udhcp_sp_fd_set(struct pollfd *pfds, int extra_fd) FAST_FUNC;
+int udhcp_sp_read(struct pollfd *pfds) FAST_FUNC;
 
 int udhcp_read_interface(const char *interface, int *ifindex, uint32_t *nip, uint8_t *mac) FAST_FUNC;
 
diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index 64339c9b5..067d35115 100644
--- a/networking/udhcp/d6_dhcpc.c
+++ b/networking/udhcp/d6_dhcpc.c
@@ -935,9 +935,7 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 	int timeout; /* must be signed */
 	unsigned already_waited_sec;
 	unsigned opt;
-	int max_fd;
 	int retval;
-	fd_set rfds;
 
 	setup_common_bufsiz();
 
@@ -1063,7 +1061,8 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 	 * "continue" statements in code below jump to the top of the loop.
 	 */
 	for (;;) {
-		struct timeval tv;
+		int tv;
+		struct pollfd pfds[2];
 		struct d6_packet packet;
 		uint8_t *packet_end;
 		/* silence "uninitialized!" warning */
@@ -1078,16 +1077,15 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 		 * to change_listen_mode(). Thus we open listen socket
 		 * BEFORE we send renew request (see "case BOUND:"). */
 
-		max_fd = udhcp_sp_fd_set(&rfds, sockfd);
+		udhcp_sp_fd_set(pfds, sockfd);
 
-		tv.tv_sec = timeout - already_waited_sec;
-		tv.tv_usec = 0;
+		tv = timeout - already_waited_sec;
 		retval = 0;
 		/* If we already timed out, fall through with retval = 0, else... */
-		if ((int)tv.tv_sec > 0) {
-			log1("waiting on select %u seconds", (int)tv.tv_sec);
+		if (tv > 0) {
+			log1("waiting on select %u seconds", tv);
 			timestamp_before_wait = (unsigned)monotonic_sec();
-			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
+			retval = poll(pfds, 2, tv * 1000);
 			if (retval < 0) {
 				/* EINTR? A signal was caught, don't panic */
 				if (errno == EINTR) {
@@ -1222,8 +1220,8 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 		/* select() didn't timeout, something happened */
 
 		/* Is it a signal? */
-		/* note: udhcp_sp_read checks FD_ISSET before reading */
-		switch (udhcp_sp_read(&rfds)) {
+		/* note: udhcp_sp_read checks poll result before reading */
+		switch (udhcp_sp_read(pfds)) {
 		case SIGUSR1:
 			client_config.first_secs = 0; /* make secs field count from 0 */
 			already_waited_sec = 0;
@@ -1258,7 +1256,7 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 		}
 
 		/* Is it a packet? */
-		if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
+		if (listen_mode == LISTEN_NONE || !pfds[1].revents)
 			continue; /* no */
 
 		{
@@ -1460,8 +1458,8 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 				if (lease_seconds < 0x10)
 					lease_seconds = 0x10;
 /// TODO: check for 0 lease time?
-				if (lease_seconds >= 0x10000000)
-					lease_seconds = 0x0fffffff;
+				if (lease_seconds > 0x7fffffff / 1000)
+					lease_seconds = 0x7fffffff / 1000;
 				/* enter bound state */
 				timeout = lease_seconds / 2;
 				bb_error_msg("lease obtained, lease time %u",
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 0e236261b..8f7f59e08 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1281,9 +1281,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 	unsigned already_waited_sec;
 	unsigned opt;
 	IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
-	int max_fd;
 	int retval;
-	fd_set rfds;
 
 	setup_common_bufsiz();
 
@@ -1432,7 +1430,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 	 * "continue" statements in code below jump to the top of the loop.
 	 */
 	for (;;) {
-		struct timeval tv;
+		int tv;
+		struct pollfd pfds[2];
 		struct dhcp_packet packet;
 		/* silence "uninitialized!" warning */
 		unsigned timestamp_before_wait = timestamp_before_wait;
@@ -1446,16 +1445,15 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		 * to change_listen_mode(). Thus we open listen socket
 		 * BEFORE we send renew request (see "case BOUND:"). */
 
-		max_fd = udhcp_sp_fd_set(&rfds, sockfd);
+		udhcp_sp_fd_set(pfds, sockfd);
 
-		tv.tv_sec = timeout - already_waited_sec;
-		tv.tv_usec = 0;
+		tv = timeout - already_waited_sec;
 		retval = 0;
 		/* If we already timed out, fall through with retval = 0, else... */
-		if ((int)tv.tv_sec > 0) {
-			log1("waiting on select %u seconds", (int)tv.tv_sec);
+		if (tv > 0) {
+			log1("waiting on select %u seconds", tv);
 			timestamp_before_wait = (unsigned)monotonic_sec();
-			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
+			retval = poll(pfds, 2, tv * 1000);
 			if (retval < 0) {
 				/* EINTR? A signal was caught, don't panic */
 				if (errno == EINTR) {
@@ -1591,8 +1589,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		/* select() didn't timeout, something happened */
 
 		/* Is it a signal? */
-		/* note: udhcp_sp_read checks FD_ISSET before reading */
-		switch (udhcp_sp_read(&rfds)) {
+		/* note: udhcp_sp_read checks poll result before reading */
+		switch (udhcp_sp_read(pfds)) {
 		case SIGUSR1:
 			client_config.first_secs = 0; /* make secs field count from 0 */
 			already_waited_sec = 0;
@@ -1627,7 +1625,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		}
 
 		/* Is it a packet? */
-		if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
+		if (listen_mode == LISTEN_NONE || !pfds[1].revents)
 			continue; /* no */
 
 		{
@@ -1742,8 +1740,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 					/* paranoia: must not be too small and not prone to overflows */
 					if (lease_seconds < 0x10)
 						lease_seconds = 0x10;
-					if (lease_seconds >= 0x10000000)
-						lease_seconds = 0x0fffffff;
+					if (lease_seconds > 0x7fffffff / 1000)
+						lease_seconds = 0x7fffffff / 1000;
 				}
 #if ENABLE_FEATURE_UDHCPC_ARPING
 				if (opt & OPT_a) {
diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index e116ba3af..5eff026bc 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -794,7 +794,7 @@ static NOINLINE void send_inform(struct dhcp_packet *oldpacket)
 int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 {
-	int server_socket = -1, retval, max_sock;
+	int server_socket = -1, retval;
 	uint8_t *state;
 	unsigned timeout_end;
 	unsigned num_ips;
@@ -891,10 +891,10 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
  continue_with_autotime:
 	timeout_end = monotonic_sec() + server_config.auto_time;
 	while (1) { /* loop until universe collapses */
-		fd_set rfds;
+		struct pollfd pfds[2];
 		struct dhcp_packet packet;
 		int bytes;
-		struct timeval tv;
+		int tv;
 		uint8_t *server_id_opt;
 		uint8_t *requested_ip_opt;
 		uint32_t requested_nip = requested_nip; /* for compiler */
@@ -906,16 +906,11 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 					server_config.interface);
 		}
 
-		max_sock = udhcp_sp_fd_set(&rfds, server_socket);
-		if (server_config.auto_time) {
-			/* cast to signed is essential if tv_sec is wider than int */
-			tv.tv_sec = (int)(timeout_end - monotonic_sec());
-			tv.tv_usec = 0;
-		}
+		udhcp_sp_fd_set(pfds, server_socket);
+		tv = timeout_end - monotonic_sec();
 		retval = 0;
-		if (!server_config.auto_time || tv.tv_sec > 0) {
-			retval = select(max_sock + 1, &rfds, NULL, NULL,
-					server_config.auto_time ? &tv : NULL);
+		if (!server_config.auto_time || tv > 0) {
+			retval = poll(pfds, 2, server_config.auto_time ? tv * 1000 : -1);
 		}
 		if (retval == 0) {
 			write_leases();
@@ -926,7 +921,7 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 			continue;
 		}
 
-		switch (udhcp_sp_read(&rfds)) {
+		switch (udhcp_sp_read(pfds)) {
 		case SIGUSR1:
 			bb_error_msg("received %s", "SIGUSR1");
 			write_leases();
diff --git a/networking/udhcp/signalpipe.c b/networking/udhcp/signalpipe.c
index 30bccd6bf..b101b4ce4 100644
--- a/networking/udhcp/signalpipe.c
+++ b/networking/udhcp/signalpipe.c
@@ -48,28 +48,29 @@ void FAST_FUNC udhcp_sp_setup(void)
 		, signal_handler);
 }
 
-/* Quick little function to setup the rfds. Will return the
- * max_fd for use with select. Limited in that you can only pass
- * one extra fd */
-int FAST_FUNC udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
+/* Quick little function to setup the pfds.
+ * Limited in that you can only pass one extra fd.
+ */
+void FAST_FUNC udhcp_sp_fd_set(struct pollfd pfds[2], int extra_fd)
 {
-	FD_ZERO(rfds);
-	FD_SET(signal_pipe.rd, rfds);
+	pfds[0].fd = signal_pipe.rd;
+	pfds[0].events = POLLIN;
+	pfds[1].fd = -1;
 	if (extra_fd >= 0) {
 		close_on_exec_on(extra_fd);
-		FD_SET(extra_fd, rfds);
+		pfds[1].fd = extra_fd;
+		pfds[1].events = POLLIN;
 	}
-	return signal_pipe.rd > extra_fd ? signal_pipe.rd : extra_fd;
 }
 
 /* Read a signal from the signal pipe. Returns 0 if there is
  * no signal, -1 on error (and sets errno appropriately), and
  * your signal on success */
-int FAST_FUNC udhcp_sp_read(const fd_set *rfds)
+int FAST_FUNC udhcp_sp_read(struct pollfd pfds[2])
 {
 	unsigned char sig;
 
-	if (!FD_ISSET(signal_pipe.rd, rfds))
+	if (!pfds[0].revents)
 		return 0;
 
 	if (safe_read(signal_pipe.rd, &sig, 1) != 1)