dhcpv6-ia: add some noise to the T1 and T2 periods

Without this, all the clients get the same timeouts and try to renew
addresses at the same time.  Reduce the T1 & T2 by a pseudo random 0 to
127 seconds, thus the renew attempts are likely to be spread out a bit
in time.

Signed-off-by: Kevin Darbyshire-Bryant <[email protected]>

diff --git a/src/dhcpv6-ia.c b/src/dhcpv6-ia.c
index 5af952d1bcfad770fe1e597ac84183d7559a3ed8..edd7823cc71cf6e0eb5ab5308f6f7fa3d4a5beee 100644 (file)
--- a/src/dhcpv6-ia.c
+++ b/src/dhcpv6-ia.c
@@ -721,8 +721,11 @@ static size_t build_ia(uint8_t *buf, size_t buflen, uint16_t status,
                        /* UINT32_MAX is RFC defined as infinite lease-time */
                        a->preferred_until = (floor_preferred_lifetime == UINT32_MAX) ? 0 : floor_preferred_lifetime + now;
 
-               o_ia.t1 = htonl((floor_preferred_lifetime == UINT32_MAX) ? floor_preferred_lifetime : floor_preferred_lifetime * 5 / 10);
-               o_ia.t2 = htonl((floor_preferred_lifetime == UINT32_MAX) ? floor_preferred_lifetime : floor_preferred_lifetime * 8 / 10);
+               /* if there's sufficient time left, subtract a pseudo random 127 seconds from the refresh timers */
+               o_ia.t1 = htonl((floor_preferred_lifetime == UINT32_MAX) ? floor_preferred_liftime : (floor_preferred_liftime > 256) ?
+                               floor_preferred_lifetime * 5 / 10 - ((rand() >> 8) & 0x7f) : floor_preferred_lifetime * 5 / 10);
+               o_ia.t2 = htonl((floor_preferred_lifetime == UINT32_MAX) ? floor_preferred_lifetime : (floor_preferred_lifetime > 256) ?
+                               floor_preferred_lifetime * 8 / 10 - ((rand() >> 8) & 0x7f) : floor_preferred_lifetime * 8 / 10);
 
                if (!o_ia.t1)
                        o_ia.t1 = htonl(1);