NAME
rt_timer,
rt_timer_add,
rt_timer_queue_create,
rt_timer_queue_change,
rt_timer_queue_destroy,
rt_timer_remove_all —
route callout
functions
SYNOPSIS
#include <net/route.h>
struct rttimer_queue *
rt_timer_queue_create(
time_t
timeout);
void
rt_timer_queue_change(
struct
rttimer_queue *q,
time_t
timeout);
void
rt_timer_queue_destroy(
struct
rttimer_queue *q,
int
destroy);
int
rt_timer_add(
struct
rtentry *rt,
void(*f)(struct rtentry *, struct
rttimer *),
struct
rttimer_queue *q);
void
rt_timer_remove_all(
struct
rtentry *rt);
DESCRIPTION
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
discovery code.
For maximum efficiency, a separate queue should be defined for each timeout
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:
-
-
- rt_timer_queue_create(time_t
timeout)
- This function creates a new timer queue with the specified
timeout 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.
CODE REFERENCES
The
rt_timer interface is implemented in
sys/net/route.h and
sys/net/route.c.
SEE ALSO
netstat(1),
arp(9)
HISTORY
The
rt_timer interface appeared in
NetBSD
1.4.
AUTHORS
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 Center.