Hello all,
I did not see any comments on my patch so I wanted to check in. Any
thoughts on including it in BusyBox?
--John Schroeder
Hello all,
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!
I patched dhcpc.c in my build using the following patch below. I used
the existing variable already_waited_sec to calculate the number of
seconds it took to complete running the scripts. If the delay was not
greater than the timeout (i.e. half the lease time), then the code
would simply send the renew using the already_waited_sec (e.g. 30 sec
- 18 sec = 12 sec to send the renew). If the delay was greater than
the timeout but less than the lease time, the code subtracts the time
out from the already_waited_sec, halves the time out, and continues as
before. (E.g. already_waited_sec is 40 sec, then the timeout would be
15 sec and already_waited_sec would be changed to 10 sec. This would
cause the renew to be sent out 5 seconds later at the 45 second mark.)
This happens in a while loop while the timeout is greater than 0.
(Note that if a renew event is missed, it is simply skipped. E.g. In a
60 sec lease, the 30 sec mark could be skipped and the next renew sent
at 45 seconds.) If the already_waited_sec ends up being greater than
the timeout, the code will not send a renew and re-enter the
requesting state.
Some improvements: If a renew event is missed, the code waits until
the next timeout. An improvement could be to send a renew immediately.
Another possible improvement would be to goto the renew event using a
goto rather than continuing. Both of these issues I did not see as a
big issue since I think both of these are unlikely events and are
handled well enough. I mostly saw issues with the scripts taking a few
seconds to run and wanted to account for the delay. I also did not
want to send a renew after the lease had expired.
I also put in some comments but I am not sure if they are up to par
for busybox. I would appreciate any feedback. Thank you.
--John Schroeder
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1752,6 +1752,7 @@
#endif
/* enter bound state */
timeout = lease_seconds / 2;
+ timestamp_before_wait = (unsigned)monotonic_sec();
temp_addr.s_addr = packet.yiaddr;
bb_info_msg("Lease of %s obtained, lease time %u",
inet_ntoa(temp_addr), (unsigned)lease_seconds);
@@ -1774,7 +1775,21 @@
#endif
/* make future renew packets use different xid */
/* xid = random_xid(); ...but why bother? */
- already_waited_sec = 0;
+ already_waited_sec = (unsigned)monotonic_sec() -
timestamp_before_wait;
+ /* If already beyond timeout, skip the next renew
+ * event. Continue skipping renews and halving the
+ * timeout until the next timeout is less that the
+ * already waited time or the timeout is 0.
+ */
+ while ((already_waited_sec > timeout) && (timeout >
0)) {
+ already_waited_sec -= timeout;
+ timeout >>= 1;
+ }
+ /* If timeout is 0, then the lease has expired. Set
+ * already_waited_sec to 0.
+ */
+ if (timeout == 0)
+ already_waited_sec = 0;
continue; /* back to main loop */
}
if (*message == DHCPNAK) {
_______________________________________________
busybox mailing list
[email protected]
http://lists.busybox.net/mailman/listinfo/busybox
