99 lines
2.5 KiB
C
99 lines
2.5 KiB
C
#include "../../include/bpf_api.h"
|
|
|
|
#define ENTRY_INIT 3
|
|
#define ENTRY_0 0
|
|
#define ENTRY_1 1
|
|
#define MAX_JMP_SIZE 2
|
|
|
|
#define FOO 42
|
|
#define BAR 43
|
|
|
|
/* This example doesn't really do anything useful, but it's purpose is to
|
|
* demonstrate eBPF tail calls on a very simple example.
|
|
*
|
|
* cls_entry() is our classifier entry point, from there we jump based on
|
|
* skb->hash into cls_case1() or cls_case2(). They are both part of the
|
|
* program array jmp_tc. Indicated via __section_tail(), the tc loader
|
|
* populates the program arrays with the loaded file descriptors already.
|
|
*
|
|
* To demonstrate nested jumps, cls_case2() jumps within the same jmp_tc
|
|
* array to cls_case1(). And whenever we arrive at cls_case1(), we jump
|
|
* into cls_exit(), part of the jump array jmp_ex.
|
|
*
|
|
* Also, to show it's possible, all programs share map_sh and dump the value
|
|
* that the entry point incremented. The sections that are loaded into a
|
|
* program array can be atomically replaced during run-time, e.g. to change
|
|
* classifier behaviour.
|
|
*/
|
|
|
|
BPF_PROG_ARRAY(jmp_tc, FOO, PIN_OBJECT_NS, MAX_JMP_SIZE);
|
|
BPF_PROG_ARRAY(jmp_ex, BAR, PIN_OBJECT_NS, 1);
|
|
|
|
BPF_ARRAY4(map_sh, 0, PIN_OBJECT_NS, 1);
|
|
|
|
__section_tail(FOO, ENTRY_0)
|
|
int cls_case1(struct __sk_buff *skb)
|
|
{
|
|
char fmt[] = "case1: map-val: %d from:%u\n";
|
|
int key = 0, *val;
|
|
|
|
val = map_lookup_elem(&map_sh, &key);
|
|
if (val)
|
|
trace_printk(fmt, sizeof(fmt), *val, skb->cb[0]);
|
|
|
|
skb->cb[0] = ENTRY_0;
|
|
tail_call(skb, &jmp_ex, ENTRY_0);
|
|
|
|
return BPF_H_DEFAULT;
|
|
}
|
|
|
|
__section_tail(FOO, ENTRY_1)
|
|
int cls_case2(struct __sk_buff *skb)
|
|
{
|
|
char fmt[] = "case2: map-val: %d from:%u\n";
|
|
int key = 0, *val;
|
|
|
|
val = map_lookup_elem(&map_sh, &key);
|
|
if (val)
|
|
trace_printk(fmt, sizeof(fmt), *val, skb->cb[0]);
|
|
|
|
skb->cb[0] = ENTRY_1;
|
|
tail_call(skb, &jmp_tc, ENTRY_0);
|
|
|
|
return BPF_H_DEFAULT;
|
|
}
|
|
|
|
__section_tail(BAR, ENTRY_0)
|
|
int cls_exit(struct __sk_buff *skb)
|
|
{
|
|
char fmt[] = "exit: map-val: %d from:%u\n";
|
|
int key = 0, *val;
|
|
|
|
val = map_lookup_elem(&map_sh, &key);
|
|
if (val)
|
|
trace_printk(fmt, sizeof(fmt), *val, skb->cb[0]);
|
|
|
|
/* Termination point. */
|
|
return BPF_H_DEFAULT;
|
|
}
|
|
|
|
__section_cls_entry
|
|
int cls_entry(struct __sk_buff *skb)
|
|
{
|
|
char fmt[] = "fallthrough\n";
|
|
int key = 0, *val;
|
|
|
|
/* For transferring state, we can use skb->cb[0] ... skb->cb[4]. */
|
|
val = map_lookup_elem(&map_sh, &key);
|
|
if (val) {
|
|
lock_xadd(val, 1);
|
|
|
|
skb->cb[0] = ENTRY_INIT;
|
|
tail_call(skb, &jmp_tc, skb->hash & (MAX_JMP_SIZE - 1));
|
|
}
|
|
|
|
trace_printk(fmt, sizeof(fmt));
|
|
return BPF_H_DEFAULT;
|
|
}
|
|
|
|
BPF_LICENSE("GPL");
|