| title | description |
|---|---|
Helper Function 'bpf_timer_start' |
This page documents the 'bpf_timer_start' eBPF helper function, including its defintion, usage, program types that can use it, and examples. |
This helper starts a timer.
Copyright (c) 2015 The Libbpf Authors. All rights reserved.
Set timer expiration N nanoseconds from the current time. The configured callback will be invoked in soft irq context on some cpu and will not repeat unless another bpf_timer_start() is made. In such case the next invocation can migrate to a different cpu. Since struct bpf_timer is a field inside map element the map owns the timer. The bpf_timer_set_callback() will increment refcnt of BPF program to make sure that callback_fn code stays valid. When user space reference to a map reaches zero all timers in a map are cancelled and corresponding program's refcnts are decremented. This is done to make sure that Ctrl-C of a user process doesn't leave any timers running. If map is pinned in bpffs the callback_fn can re-arm itself indefinitely. bpf_map_update/delete_elem() helpers and user space sys_bpf commands cancel and free the timer in the given map element. The map can contain timers that invoke callback_fn-s from different programs. The same callback_fn can serve different timers from different maps if key/value layout matches across maps. Every bpf_timer_set_callback() can have different callback_fn.
flags can be one of:
BPF_F_TIMER_ABS
Start the timer in absolute expire value instead of the default relative one.
BPF_F_TIMER_CPU_PIN
Timer will be pinned to the CPU of the caller.
0 on success. -EINVAL if timer was not initialized with bpf_timer_init() earlier or invalid flags are passed.
#!c static long (* const bpf_timer_start)(struct bpf_timer *timer, __u64 nsecs, __u64 flags) = (void *) 171;
!!! example "Docs could be improved" This part of the docs is incomplete, contributions are very welcome
This helper call can be used in the following program types:
- BPF_PROG_TYPE_CGROUP_DEVICE
- BPF_PROG_TYPE_CGROUP_SKB
- BPF_PROG_TYPE_CGROUP_SOCK
- BPF_PROG_TYPE_CGROUP_SOCKOPT
- BPF_PROG_TYPE_CGROUP_SOCK_ADDR
- BPF_PROG_TYPE_CGROUP_SYSCTL
- BPF_PROG_TYPE_FLOW_DISSECTOR
- BPF_PROG_TYPE_LSM
- BPF_PROG_TYPE_LWT_IN
- BPF_PROG_TYPE_LWT_OUT
- BPF_PROG_TYPE_LWT_SEG6LOCAL
- BPF_PROG_TYPE_LWT_XMIT
- BPF_PROG_TYPE_SCHED_ACT
- BPF_PROG_TYPE_SCHED_CLS
- BPF_PROG_TYPE_SK_LOOKUP
- BPF_PROG_TYPE_SK_MSG
- BPF_PROG_TYPE_SK_REUSEPORT
- BPF_PROG_TYPE_SK_SKB
- BPF_PROG_TYPE_SOCKET_FILTER
- BPF_PROG_TYPE_SOCK_OPS
- BPF_PROG_TYPE_SYSCALL
- BPF_PROG_TYPE_TRACING
- BPF_PROG_TYPE_XDP
!!! example "Docs could be improved" This part of the docs is incomplete, contributions are very welcome