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/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) {