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

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
......@@ -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 $@
......@@ -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 */
......
#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";
#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;
}
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