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4dd3f50af4
Follow-up to kernel commit 6c9059817432 ("bpf: pre-allocate hash map
elements"). Add flags support, so that we can pass in BPF_F_NO_PREALLOC
flag for disallowing preallocation. Update examples accordingly and also
remove the BPF_* map helper macros from them as they were not very useful.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
117 lines
2.8 KiB
C
117 lines
2.8 KiB
C
#include "../../include/bpf_api.h"
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#define ENTRY_INIT 3
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#define ENTRY_0 0
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#define ENTRY_1 1
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#define MAX_JMP_SIZE 2
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#define FOO 42
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#define BAR 43
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/* This example doesn't really do anything useful, but it's purpose is to
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* demonstrate eBPF tail calls on a very simple example.
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*
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* cls_entry() is our classifier entry point, from there we jump based on
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* skb->hash into cls_case1() or cls_case2(). They are both part of the
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* program array jmp_tc. Indicated via __section_tail(), the tc loader
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* populates the program arrays with the loaded file descriptors already.
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*
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* To demonstrate nested jumps, cls_case2() jumps within the same jmp_tc
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* array to cls_case1(). And whenever we arrive at cls_case1(), we jump
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* into cls_exit(), part of the jump array jmp_ex.
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*
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* Also, to show it's possible, all programs share map_sh and dump the value
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* that the entry point incremented. The sections that are loaded into a
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* program array can be atomically replaced during run-time, e.g. to change
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* classifier behaviour.
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*/
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struct bpf_elf_map __section_maps jmp_tc = {
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.type = BPF_MAP_TYPE_PROG_ARRAY,
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.id = FOO,
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.size_key = sizeof(uint32_t),
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.size_value = sizeof(uint32_t),
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.pinning = PIN_OBJECT_NS,
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.max_elem = MAX_JMP_SIZE,
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};
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struct bpf_elf_map __section_maps jmp_ex = {
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.type = BPF_MAP_TYPE_PROG_ARRAY,
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.id = BAR,
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.size_key = sizeof(uint32_t),
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.size_value = sizeof(uint32_t),
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.pinning = PIN_OBJECT_NS,
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.max_elem = 1,
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};
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struct bpf_elf_map __section_maps map_sh = {
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.type = BPF_MAP_TYPE_ARRAY,
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.size_key = sizeof(uint32_t),
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.size_value = sizeof(uint32_t),
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.pinning = PIN_OBJECT_NS,
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.max_elem = 1,
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};
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__section_tail(FOO, ENTRY_0)
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int cls_case1(struct __sk_buff *skb)
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{
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int key = 0, *val;
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val = map_lookup_elem(&map_sh, &key);
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if (val)
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printt("case1: map-val: %d from:%u\n", *val, skb->cb[0]);
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skb->cb[0] = ENTRY_0;
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tail_call(skb, &jmp_ex, ENTRY_0);
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return BPF_H_DEFAULT;
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}
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__section_tail(FOO, ENTRY_1)
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int cls_case2(struct __sk_buff *skb)
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{
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int key = 0, *val;
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val = map_lookup_elem(&map_sh, &key);
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if (val)
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printt("case2: map-val: %d from:%u\n", *val, skb->cb[0]);
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skb->cb[0] = ENTRY_1;
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tail_call(skb, &jmp_tc, ENTRY_0);
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return BPF_H_DEFAULT;
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}
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__section_tail(BAR, ENTRY_0)
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int cls_exit(struct __sk_buff *skb)
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{
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int key = 0, *val;
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val = map_lookup_elem(&map_sh, &key);
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if (val)
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printt("exit: map-val: %d from:%u\n", *val, skb->cb[0]);
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/* Termination point. */
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return BPF_H_DEFAULT;
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}
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__section_cls_entry
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int cls_entry(struct __sk_buff *skb)
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{
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int key = 0, *val;
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/* For transferring state, we can use skb->cb[0] ... skb->cb[4]. */
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val = map_lookup_elem(&map_sh, &key);
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if (val) {
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lock_xadd(val, 1);
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skb->cb[0] = ENTRY_INIT;
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tail_call(skb, &jmp_tc, skb->hash & (MAX_JMP_SIZE - 1));
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}
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printt("fallthrough\n");
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return BPF_H_DEFAULT;
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}
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BPF_LICENSE("GPL");
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