samples: bpf: trivial eBPF program in C
this example does the same task as previous socket example in assembler, but this one does it in C. eBPF program in kernel does: /* assume that packet is IPv4, load one byte of IP->proto */ int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)); long *value; value = bpf_map_lookup_elem(&my_map, &index); if (value) __sync_fetch_and_add(value, 1); Corresponding user space reads map[tcp], map[udp], map[icmp] and prints protocol stats every second Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -4,12 +4,26 @@ obj- := dummy.o
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# List of programs to build
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hostprogs-y := test_verifier test_maps
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hostprogs-y += sock_example
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hostprogs-y += sockex1
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test_verifier-objs := test_verifier.o libbpf.o
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test_maps-objs := test_maps.o libbpf.o
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sock_example-objs := sock_example.o libbpf.o
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sockex1-objs := bpf_load.o libbpf.o sockex1_user.o
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# Tell kbuild to always build the programs
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always := $(hostprogs-y)
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always += sockex1_kern.o
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HOSTCFLAGS += -I$(objtree)/usr/include
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HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
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HOSTLOADLIBES_sockex1 += -lelf
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# point this to your LLVM backend with bpf support
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LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
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%.o: %.c
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clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
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-D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
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-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@
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@ -15,7 +15,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
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const struct bpf_insn *insns, int insn_len,
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const char *license);
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#define LOG_BUF_SIZE 8192
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#define LOG_BUF_SIZE 65536
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extern char bpf_log_buf[LOG_BUF_SIZE];
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/* ALU ops on registers, bpf_add|sub|...: dst_reg += src_reg */
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@ -0,0 +1,25 @@
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#include <uapi/linux/bpf.h>
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#include <uapi/linux/if_ether.h>
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#include <uapi/linux/ip.h>
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#include "bpf_helpers.h"
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struct bpf_map_def SEC("maps") my_map = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(u32),
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.value_size = sizeof(long),
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.max_entries = 256,
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};
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SEC("socket1")
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int bpf_prog1(struct sk_buff *skb)
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{
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int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
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long *value;
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value = bpf_map_lookup_elem(&my_map, &index);
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if (value)
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__sync_fetch_and_add(value, 1);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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@ -0,0 +1,49 @@
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#include <stdio.h>
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#include <assert.h>
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#include <linux/bpf.h>
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#include "libbpf.h"
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#include "bpf_load.h"
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#include <unistd.h>
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#include <arpa/inet.h>
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int main(int ac, char **argv)
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{
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char filename[256];
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FILE *f;
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int i, sock;
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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if (load_bpf_file(filename)) {
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printf("%s", bpf_log_buf);
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return 1;
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}
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sock = open_raw_sock("lo");
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assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, prog_fd,
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sizeof(prog_fd[0])) == 0);
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f = popen("ping -c5 localhost", "r");
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(void) f;
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for (i = 0; i < 5; i++) {
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long long tcp_cnt, udp_cnt, icmp_cnt;
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int key;
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key = IPPROTO_TCP;
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assert(bpf_lookup_elem(map_fd[0], &key, &tcp_cnt) == 0);
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key = IPPROTO_UDP;
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assert(bpf_lookup_elem(map_fd[0], &key, &udp_cnt) == 0);
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key = IPPROTO_ICMP;
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assert(bpf_lookup_elem(map_fd[0], &key, &icmp_cnt) == 0);
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printf("TCP %lld UDP %lld ICMP %lld packets\n",
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tcp_cnt, udp_cnt, icmp_cnt);
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sleep(1);
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}
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return 0;
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}
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