Helper function bpf_ringbuf_reserve
Definition
Copyright (c) 2015 The Libbpf Authors. All rights reserved.
Reserve size bytes of payload in a ring buffer ringbuf. flags must be 0.
Returns
Valid pointer with size bytes of memory available; NULL, otherwise.
static void *(* const bpf_ringbuf_reserve)(void *ringbuf, __u64 size, __u64 flags) = (void *) 131;
Usage
The rinfbuf
argument must be a pointer to a ring buffer definition. The size
argument specifies the number of bytes to be reserved in the ring buffer. And the flags
argument must be set to 0.
This function is generally used in combination with a struct
that defines the structure of the data stored in the ring buffer. Hence, in this case, the size
argument would be set to the size of the struct. The function returns a pointer to the reserved memory, which can be used to write data to the ring buffer. See the example below for more details.
Also check bpf_ringbuf_submit
and bpf_ringbuf_discard
for more information on how to handle the reserved memory in the ring buffer.
Program types
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_KPROBE
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_NETFILTER
BPF_PROG_TYPE_PERF_EVENT
BPF_PROG_TYPE_RAW_TRACEPOINT
BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE
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_STRUCT_OPS
BPF_PROG_TYPE_SYSCALL
BPF_PROG_TYPE_TRACEPOINT
BPF_PROG_TYPE_TRACING
BPF_PROG_TYPE_XDP
Example
struct ringbuf_data *rb_data = bpf_ringbuf_reserve(&my_ringbuf, sizeof(struct ringbuf_data), 0);
if (! rb_data) {
// if bpf_ringbuf_reserve fails, print an error message and return
bpf_printk("bpf_ringbuf_reserve failed\n");
return 1;
}
Where my_ringbuf
is the pointer to the ring buffer, and ringbuf_data
is a struct that defines the structure of the data to be stored in the ring buffer.