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>

1 files changed, 12 insertions, 14 deletions

diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index 64339c9..067d351 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",