RT_TIMER(9)

💖 NAME 💖

okay bestie, welcome to RT_TIMER(9) from the Kernel Developer's Manual — this is the page for route callout functions, and the whole crew is rt_timer, rt_timer_add, rt_timer_queue_create, rt_timer_queue_change, rt_timer_queue_destroy, and rt_timer_remove_all. Their whole thing is route callout functions. 💅

✨ SYNOPSIS ✨

bestie, start with this header, no cap:

#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 give you generic route callout functionality. They let a function 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) — creates a new timer queue with the specified timeout period timeout, expressed in seconds. 🎀
• rt_timer_queue_change(rttimer_queue *q, time_t timeout) — 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) — 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) — 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) — 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) — go read those too, bestie. 🫶

💜 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. 🚀

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okay that's the whole page, bestie 💖 — this one came from Debian, dated June 1, 2016, and it's RT_TIMER(9). mwah ✨