Re: replace microtime with getmicrouptime in ip_mroute.c
OK florian@ On Thu, Sep 08, 2016 at 11:54:01AM +1000, David Gwynne wrote: > it uses the time to rate limit the sending of assertion messages. > > there are two reasons for this change. > > firstly, using uptime instead of wall time means the intervals will > be measured against a a monotonic clock that isnt skewed by clock > changes. it should therefore always be rate limited to 30 seconds, > even if the clock jumps in the middle of that interval. > > secondly, using the get variant of the api means it can use a cached clock > time at the expense of accuracy. accuracy between 30s intervals isnt > necessary in this use case, but making it use the faster clock read is good > cos this path is in response to packets, so it will mitigate a DoS. > > ok? > > after this i intend to tweak the code to use ratecheck(). > > Index: ip_mroute.c > === > RCS file: /cvs/src/sys/netinet/ip_mroute.c,v > retrieving revision 1.90 > diff -u -p -r1.90 ip_mroute.c > --- ip_mroute.c 7 Mar 2016 18:44:00 - 1.90 > +++ ip_mroute.c 8 Sep 2016 01:49:05 - > @@ -1482,7 +1482,7 @@ ip_mdq(struct mbuf *m, struct ifnet *ifp > return (0); > } > > - microtime(); > + getmicrouptime(); > > TV_DELTA(rt->mfc_last_assert, now, delta); > > -- I'm not entirely sure you are real.
Re: replace microtime with getmicrouptime in ip_mroute.c
On Thu, Sep 08, 2016 at 11:54:01AM +1000, David Gwynne wrote: > it uses the time to rate limit the sending of assertion messages. > > there are two reasons for this change. > > firstly, using uptime instead of wall time means the intervals will > be measured against a a monotonic clock that isnt skewed by clock > changes. it should therefore always be rate limited to 30 seconds, > even if the clock jumps in the middle of that interval. > > secondly, using the get variant of the api means it can use a cached clock > time at the expense of accuracy. accuracy between 30s intervals isnt > necessary in this use case, but making it use the faster clock read is good > cos this path is in response to packets, so it will mitigate a DoS. > > ok? OK claudio@ > after this i intend to tweak the code to use ratecheck(). > > Index: ip_mroute.c > === > RCS file: /cvs/src/sys/netinet/ip_mroute.c,v > retrieving revision 1.90 > diff -u -p -r1.90 ip_mroute.c > --- ip_mroute.c 7 Mar 2016 18:44:00 - 1.90 > +++ ip_mroute.c 8 Sep 2016 01:49:05 - > @@ -1482,7 +1482,7 @@ ip_mdq(struct mbuf *m, struct ifnet *ifp > return (0); > } > > - microtime(); > + getmicrouptime(); > > TV_DELTA(rt->mfc_last_assert, now, delta); > > -- :wq Claudio
