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samples, bpf: Refactor tail call user progs with libbpf

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BPF tail call uses the BPF_MAP_TYPE_PROG_ARRAY type map for calling
into other BPF programs and this PROG_ARRAY should be filled prior to
use. Currently, samples with the PROG_ARRAY type MAP fill this program
array with bpf_load. For bpf_load to fill this map, kernel BPF program
must specify the section with specific format of <prog_type>/<array_idx>
(e.g. SEC("socket/0"))

But by using libbpf instead of bpf_load, user program can specify which
programs should be added to PROG_ARRAY. The advantage of this approach
is that you can selectively add only the programs you want, rather than
adding all of them to PROG_ARRAY, and it's much more intuitive than the
traditional approach.

This commit refactors user programs with the PROG_ARRAY type MAP with
libbpf instead of using bpf_load.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200516040608.1377876-4-danieltimlee@gmail.com
This commit is contained in:
Daniel T. Lee
2020-05-16 13:06:06 +09:00
committed by Daniel Borkmann
parent 63841bc083
commit bc1a85977b
3 changed files with 103 additions and 31 deletions
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64
samples/bpf/sockex3_user.c
View File

@@ -1,18 +1,13 @@
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <assert.h>
#include <linux/bpf.h>
#include <bpf/bpf.h>
#include "bpf_load.h"
#include <bpf/libbpf.h>
#include "sock_example.h"
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/resource.h>
#define PARSE_IP 3
#define PARSE_IP_PROG_FD (prog_fd[0])
#define PROG_ARRAY_FD (map_fd[0])
struct flow_key_record {
__be32 src;
__be32 dst;
@@ -30,31 +25,55 @@ struct pair {
int main(int argc, char **argv)
{
int i, sock, key, fd, main_prog_fd, jmp_table_fd, hash_map_fd;
struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
struct bpf_program *prog;
struct bpf_object *obj;
char filename[256];
const char *title;
FILE *f;
int i, sock, err, id, key = PARSE_IP;
struct bpf_prog_info info = {};
uint32_t info_len = sizeof(info);
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
setrlimit(RLIMIT_MEMLOCK, &r);
if (load_bpf_file(filename)) {
printf("%s", bpf_log_buf);
return 1;
obj = bpf_object__open_file(filename, NULL);
if (libbpf_get_error(obj)) {
fprintf(stderr, "ERROR: opening BPF object file failed\n");
return 0;
}
/* Test fd array lookup which returns the id of the bpf_prog */
err = bpf_obj_get_info_by_fd(PARSE_IP_PROG_FD, &info, &info_len);
assert(!err);
err = bpf_map_lookup_elem(PROG_ARRAY_FD, &key, &id);
assert(!err);
assert(id == info.id);
/* load BPF program */
if (bpf_object__load(obj)) {
fprintf(stderr, "ERROR: loading BPF object file failed\n");
goto cleanup;
}
jmp_table_fd = bpf_object__find_map_fd_by_name(obj, "jmp_table");
hash_map_fd = bpf_object__find_map_fd_by_name(obj, "hash_map");
if (jmp_table_fd < 0 || hash_map_fd < 0) {
fprintf(stderr, "ERROR: finding a map in obj file failed\n");
goto cleanup;
}
bpf_object__for_each_program(prog, obj) {
fd = bpf_program__fd(prog);
title = bpf_program__title(prog, false);
if (sscanf(title, "socket/%d", &key) != 1) {
fprintf(stderr, "ERROR: finding prog failed\n");
goto cleanup;
}
if (key == 0)
main_prog_fd = fd;
else
bpf_map_update_elem(jmp_table_fd, &key, &fd, BPF_ANY);
}
sock = open_raw_sock("lo");
assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd[4],
/* attach BPF program to socket */
assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &main_prog_fd,
sizeof(__u32)) == 0);
if (argc > 1)
@@ -69,8 +88,8 @@ int main(int argc, char **argv)
sleep(1);
printf("IP src.port -> dst.port bytes packets\n");
while (bpf_map_get_next_key(map_fd[2], &key, &next_key) == 0) {
bpf_map_lookup_elem(map_fd[2], &next_key, &value);
while (bpf_map_get_next_key(hash_map_fd, &key, &next_key) == 0) {
bpf_map_lookup_elem(hash_map_fd, &next_key, &value);
printf("%s.%05d -> %s.%05d %12lld %12lld\n",
inet_ntoa((struct in_addr){htonl(next_key.src)}),
next_key.port16[0],
@@ -80,5 +99,8 @@ int main(int argc, char **argv)
key = next_key;
}
}
cleanup:
bpf_object__close(obj);
return 0;
}