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Commit a8085782 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

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: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 249b812d

samples/bpf/Makefile

+14 −0
Original line number Diff line number Diff line
@@ -4,12 +4,26 @@ obj- := dummy.o 
# List of programs to build

hostprogs-y := test_verifier test_maps

hostprogs-y += sock_example

hostprogs-y += sockex1



test_verifier-objs := test_verifier.o libbpf.o

test_maps-objs := test_maps.o libbpf.o

sock_example-objs := sock_example.o libbpf.o

sockex1-objs := bpf_load.o libbpf.o sockex1_user.o



# Tell kbuild to always build the programs

always := $(hostprogs-y)

always += sockex1_kern.o



HOSTCFLAGS += -I$(objtree)/usr/include



HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable

HOSTLOADLIBES_sockex1 += -lelf



# point this to your LLVM backend with bpf support

LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc



%.o: %.c

	clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \

		-D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \

		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@

samples/bpf/libbpf.h

+1 −1
Original line number Diff line number Diff line
@@ -15,7 +15,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type, 
		  const struct bpf_insn *insns, int insn_len,

		  const char *license);



#define LOG_BUF_SIZE 8192

#define LOG_BUF_SIZE 65536

extern char bpf_log_buf[LOG_BUF_SIZE];



/* ALU ops on registers, bpf_add|sub|...: dst_reg += src_reg */

samples/bpf/sockex1_kern.c

0 → 100644
+25 −0
Original line number Diff line number Diff line 
#include <uapi/linux/bpf.h>

#include <uapi/linux/if_ether.h>

#include <uapi/linux/ip.h>

#include "bpf_helpers.h"



struct bpf_map_def SEC("maps") my_map = {

	.type = BPF_MAP_TYPE_ARRAY,

	.key_size = sizeof(u32),

	.value_size = sizeof(long),

	.max_entries = 256,

};



SEC("socket1")

int bpf_prog1(struct sk_buff *skb)

{

	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);



	return 0;

}

char _license[] SEC("license") = "GPL";

samples/bpf/sockex1_user.c

0 → 100644
+49 −0
Original line number Diff line number Diff line 
#include <stdio.h>

#include <assert.h>

#include <linux/bpf.h>

#include "libbpf.h"

#include "bpf_load.h"

#include <unistd.h>

#include <arpa/inet.h>



int main(int ac, char **argv)

{

	char filename[256];

	FILE *f;

	int i, sock;



	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);



	if (load_bpf_file(filename)) {

		printf("%s", bpf_log_buf);

		return 1;

	}



	sock = open_raw_sock("lo");



	assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, prog_fd,

			  sizeof(prog_fd[0])) == 0);



	f = popen("ping -c5 localhost", "r");

	(void) f;



	for (i = 0; i < 5; i++) {

		long long tcp_cnt, udp_cnt, icmp_cnt;

		int key;



		key = IPPROTO_TCP;

		assert(bpf_lookup_elem(map_fd[0], &key, &tcp_cnt) == 0);



		key = IPPROTO_UDP;

		assert(bpf_lookup_elem(map_fd[0], &key, &udp_cnt) == 0);



		key = IPPROTO_ICMP;

		assert(bpf_lookup_elem(map_fd[0], &key, &icmp_cnt) == 0);



		printf("TCP %lld UDP %lld ICMP %lld packets\n",

		       tcp_cnt, udp_cnt, icmp_cnt);

		sleep(1);

	}



	return 0;

}