udhcpc: account for script run time

Based on the following user report:

I ran into an issue where I was seeing a long delay in the scripts called
in udhcp_run_script. I was using an old version of OpenWrt (kamikaze)
and a satellite modem. An NTP script was being called and the modem
would sometimes take a long time to respond to the DNS lookup when
it was offline.

This delay started affecting my lease time. The lease that I would
get from my satellite modem before it was online would be short:
only 60 seconds. The delay with NTP and the modem would typically
be about 18 seconds. This would cause the first DHCP renew request
from dhcpc to be a little late. Under certain circumstances,
I could even see the first DHCP renew to occur after the lease
had expired!

function                                             old     new   delta
udhcpc_main                                         2816    2837     +21

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

1 files changed, 5 insertions, 1 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 35e7c2070..a34829c3a 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1697,6 +1697,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                 case RENEW_REQUESTED:
                 case REBINDING:
                         if (*message == DHCPACK) {
+                                unsigned start;
                                 uint32_t lease_seconds;
                                 struct in_addr temp_addr;
                                 uint8_t *temp;
@@ -1756,7 +1757,10 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                 bb_info_msg("Lease of %s obtained, lease time %u",
                                         inet_ntoa(temp_addr), (unsigned)lease_seconds);
                                 requested_ip = packet.yiaddr;
+
+                                start = monotonic_sec();
                                 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
+                                already_waited_sec = (unsigned)monotonic_sec() - start;
 
                                 state = BOUND;
                                 change_listen_mode(LISTEN_NONE);
@@ -1774,7 +1778,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 #endif
                                 /* make future renew packets use different xid */
                                 /* xid = random_xid(); ...but why bother? */
-                                already_waited_sec = 0;
+
                                 continue; /* back to main loop */
                         }
                         if (*message == DHCPNAK) {