- NetBSD Manual Pages
RT_TIMER(9) NetBSD Kernel Developer's Manual RT_TIMER(9)
Powered by man-cgi (2021-06-01).
Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
rt_timer, rt_timer_add, rt_timer_queue_create, rt_timer_queue_change,
rt_timer_queue_destroy, rt_timer_remove_all -- route callout functions
struct rttimer_queue *
rt_timer_queue_change(struct rttimer_queue *q, time_t timeout);
rt_timer_queue_destroy(struct rttimer_queue *q, int destroy);
rt_timer_add(struct rtentry *rt,
void(*f)(struct rtentry *, struct rttimer *),
struct rttimer_queue *q);
rt_timer_remove_all(struct rtentry *rt);
The rt_timer functions provide a generic route callout functionality.
They allow a function to be called for a route at any time. This was
originally intended to be used to remove routes added by path MTU discov-
For maximum efficiency, a separate queue should be defined for each time-
out period. For example, one queue should be created for the 10 minute
path MTU discovery timeouts, another for 20 minute ARP timeouts after 20
minutes, and so on. This permits extremely fast queue manipulations so
that the timeout functions remain scalable, even in the face of thousands
of route manipulations per minute.
It is possible to create only a single timeout queue for all possible
timeout values, but doing so is not scalable as queue manipulations
become quite expensive if the timeout deltas are not roughly constant.
The rt_timer interface provides the following functions:
This function creates a new timer queue with the specified time-
out period timeout, expressed in seconds.
rt_timer_queue_change(rttimer_queue *q, time_t timeout)
This function modifies the timeout period for a timer queue.
Any value, including 0, is valid. The next time the timer
queue's timeout expires (based on the previous timeout value),
all entries which are valid to execute based on the new timeout
will be executed, and the new timeout period scheduled.
rt_timer_queue_destroy(rttimer_queue *q, int destroy)
This function destroys a timeout queue. All entries are
removed, and if the destroy argument is non-zero, the timeout
action is performed for each entry.
rt_timer_add(struct rtentry *rt, void(*f)(struct rtentry *, struct
rttimer *), struct rttimer_queue *q)
This function adds an entry to a timeout queue. The function f
will be called after the timeout period for queue q has elapsed.
If f is NULL the route will be deleted when the timeout expires.
rt_timer_remove_all(struct rtentry *rt)
This function removes all references to the given route from the
rt_timer subsystem. This is used when a route is deleted to
ensure that no dangling references remain.
The rt_timer interface is implemented in sys/net/route.h and
The rt_timer interface appeared in NetBSD 1.4.
This interface is roughly based on (but, alas, not compatible with) one
designed by David Borman of BSDI. This implementation is by Kevin Lahey
of the Numerical Aerospace Simulation Facility, NASA Ames Research Cen-
NetBSD 9.99 June 1, 2016 NetBSD 9.99