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, 8 insertions, 13 deletions

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();