samples: bpf: add userspace example for attaching eBPF programs to cgroups (d8c5b17f) · Commits · 戴 / test

samples/bpf/Makefile

+2 −0

Original line number	Diff line number	Diff line
		@@ -22,6 +22,7 @@ hostprogs-y += spintest
		hostprogs-y += map_perf_test
		hostprogs-y += test_overhead
		hostprogs-y += test_cgrp2_array_pin
		hostprogs-y += test_cgrp2_attach
		hostprogs-y += xdp1
		hostprogs-y += xdp2
		hostprogs-y += test_current_task_under_cgroup
		@@ -49,6 +50,7 @@ spintest-objs := bpf_load.o libbpf.o spintest_user.o
		map_perf_test-objs := bpf_load.o libbpf.o map_perf_test_user.o
		test_overhead-objs := bpf_load.o libbpf.o test_overhead_user.o
		test_cgrp2_array_pin-objs := libbpf.o test_cgrp2_array_pin.o
		test_cgrp2_attach-objs := libbpf.o test_cgrp2_attach.o
		xdp1-objs := bpf_load.o libbpf.o xdp1_user.o
		# reuse xdp1 source intentionally
		xdp2-objs := bpf_load.o libbpf.o xdp1_user.o

samples/bpf/libbpf.c

+21 −0

Original line number	Diff line number	Diff line
		@@ -104,6 +104,27 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
		return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
		}

		int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type)
		{
		union bpf_attr attr = {
		.target_fd = target_fd,
		.attach_bpf_fd = prog_fd,
		.attach_type = type,
		};

		return syscall(__NR_bpf, BPF_PROG_ATTACH, &attr, sizeof(attr));
		}

		int bpf_prog_detach(int target_fd, enum bpf_attach_type type)
		{
		union bpf_attr attr = {
		.target_fd = target_fd,
		.attach_type = type,
		};

		return syscall(__NR_bpf, BPF_PROG_DETACH, &attr, sizeof(attr));
		}

		int bpf_obj_pin(int fd, const char *pathname)
		{
		union bpf_attr attr = {

samples/bpf/libbpf.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -15,6 +15,9 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
		const struct bpf_insn *insns, int insn_len,
		const char *license, int kern_version);

		int bpf_prog_attach(int prog_fd, int attachable_fd, enum bpf_attach_type type);
		int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type);

		int bpf_obj_pin(int fd, const char *pathname);
		int bpf_obj_get(const char *pathname);

samples/bpf/test_cgrp2_attach.c

0 → 100644

+147 −0

Original line number	Diff line number	Diff line
		/* eBPF example program:
		*
		* - Creates arraymap in kernel with 4 bytes keys and 8 byte values
		*
		* - Loads eBPF program
		*
		* The eBPF program accesses the map passed in to store two pieces of
		* information. The number of invocations of the program, which maps
		* to the number of packets received, is stored to key 0. Key 1 is
		* incremented on each iteration by the number of bytes stored in
		* the skb.
		*
		* - Detaches any eBPF program previously attached to the cgroup
		*
		* - Attaches the new program to a cgroup using BPF_PROG_ATTACH
		*
		* - Every second, reads map[0] and map[1] to see how many bytes and
		* packets were seen on any socket of tasks in the given cgroup.
		*/

		#define _GNU_SOURCE

		#include <stdio.h>
		#include <stdlib.h>
		#include <stddef.h>
		#include <string.h>
		#include <unistd.h>
		#include <assert.h>
		#include <errno.h>
		#include <fcntl.h>

		#include <linux/bpf.h>

		#include "libbpf.h"

		enum {
		MAP_KEY_PACKETS,
		MAP_KEY_BYTES,
		};

		static int prog_load(int map_fd, int verdict)
		{
		struct bpf_insn prog[] = {
		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */

		/* Count packets */
		BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* (u32 )(fp - 4) = r0 */
		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
		BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
		BPF_RAW_INSN(BPF_JMP \| BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
		BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
		BPF_RAW_INSN(BPF_STX \| BPF_XADD \| BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */

		/* Count bytes */
		BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* (u32 )(fp - 4) = r0 */
		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
		BPF_RAW_INSN(BPF_JMP \| BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
		BPF_RAW_INSN(BPF_STX \| BPF_XADD \| BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */

		BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
		BPF_EXIT_INSN(),
		};

		return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB,
		prog, sizeof(prog), "GPL", 0);
		}

		static int usage(const char *argv0)
		{
		printf("Usage: %s <cg-path> <egress\|ingress> [drop]\n", argv0);
		return EXIT_FAILURE;
		}

		int main(int argc, char **argv)
		{
		int cg_fd, map_fd, prog_fd, key, ret;
		long long pkt_cnt, byte_cnt;
		enum bpf_attach_type type;
		int verdict = 1;

		if (argc < 3)
		return usage(argv[0]);

		if (strcmp(argv[2], "ingress") == 0)
		type = BPF_CGROUP_INET_INGRESS;
		else if (strcmp(argv[2], "egress") == 0)
		type = BPF_CGROUP_INET_EGRESS;
		else
		return usage(argv[0]);

		if (argc > 3 && strcmp(argv[3], "drop") == 0)
		verdict = 0;

		cg_fd = open(argv[1], O_DIRECTORY \| O_RDONLY);
		if (cg_fd < 0) {
		printf("Failed to open cgroup path: '%s'\n", strerror(errno));
		return EXIT_FAILURE;
		}

		map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY,
		sizeof(key), sizeof(byte_cnt),
		256, 0);
		if (map_fd < 0) {
		printf("Failed to create map: '%s'\n", strerror(errno));
		return EXIT_FAILURE;
		}

		prog_fd = prog_load(map_fd, verdict);
		printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);

		if (prog_fd < 0) {
		printf("Failed to load prog: '%s'\n", strerror(errno));
		return EXIT_FAILURE;
		}

		ret = bpf_prog_detach(cg_fd, type);
		printf("bpf_prog_detach() returned '%s' (%d)\n", strerror(errno), errno);

		ret = bpf_prog_attach(prog_fd, cg_fd, type);
		if (ret < 0) {
		printf("Failed to attach prog to cgroup: '%s'\n",
		strerror(errno));
		return EXIT_FAILURE;
		}

		while (1) {
		key = MAP_KEY_PACKETS;
		assert(bpf_lookup_elem(map_fd, &key, &pkt_cnt) == 0);

		key = MAP_KEY_BYTES;
		assert(bpf_lookup_elem(map_fd, &key, &byte_cnt) == 0);

		printf("cgroup received %lld packets, %lld bytes\n",
		pkt_cnt, byte_cnt);
		sleep(1);
		}

		return EXIT_SUCCESS;
		}

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