expire_callout
callout_reset_sbt(&rnh->expire_callout, SBT_1S * seconds,
SBT_1MS * 500, expire_callout, rnh, 0);
if (callout_pending(&rnh->expire_callout) == 0)
callout_reset_sbt(&rnh->expire_callout, SBT_1S * seconds,
SBT_1MS * 500, expire_callout, rnh, 0);
callout_init(&rh->expire_callout, 1);
callout_drain(&rh->expire_callout);
struct callout expire_callout; /* Callout for expiring dynamic routes */