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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>
67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
#include "../../include/bpf_api.h"
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/* This example demonstrates how classifier run-time behaviour
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* can be altered with tail calls. We start out with an empty
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* jmp_tc array, then add section aaa to the array slot 0, and
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* later on atomically replace it with section bbb. Note that
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* as shown in other examples, the tc loader can prepopulate
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* tail called sections, here we start out with an empty one
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* on purpose to show it can also be done this way.
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*
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* tc filter add dev foo parent ffff: bpf obj graft.o
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* tc exec bpf dbg
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* [...]
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* Socket Thread-20229 [001] ..s. 138993.003923: : fallthrough
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* <idle>-0 [001] ..s. 138993.202265: : fallthrough
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* Socket Thread-20229 [001] ..s. 138994.004149: : fallthrough
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* [...]
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*
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* tc exec bpf graft m:globals/jmp_tc key 0 obj graft.o sec aaa
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* tc exec bpf dbg
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* [...]
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* Socket Thread-19818 [002] ..s. 139012.053587: : aaa
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* <idle>-0 [002] ..s. 139012.172359: : aaa
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* Socket Thread-19818 [001] ..s. 139012.173556: : aaa
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* [...]
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*
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* tc exec bpf graft m:globals/jmp_tc key 0 obj graft.o sec bbb
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* tc exec bpf dbg
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* [...]
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* Socket Thread-19818 [002] ..s. 139022.102967: : bbb
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* <idle>-0 [002] ..s. 139022.155640: : bbb
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* Socket Thread-19818 [001] ..s. 139022.156730: : bbb
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* [...]
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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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.size_key = sizeof(uint32_t),
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.size_value = sizeof(uint32_t),
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.pinning = PIN_GLOBAL_NS,
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.max_elem = 1,
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};
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__section("aaa")
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int cls_aaa(struct __sk_buff *skb)
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{
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printt("aaa\n");
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return TC_H_MAKE(1, 42);
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}
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__section("bbb")
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int cls_bbb(struct __sk_buff *skb)
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{
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printt("bbb\n");
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return TC_H_MAKE(1, 43);
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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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tail_call(skb, &jmp_tc, 0);
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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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