samples/bpf/cookie_uid_helper_example.c

/* This test is a demo of using get_socket_uid and get_socket_cookie
 * helper function to do per socket based network traffic monitoring.
 * It requires iptables version higher then 1.6.1. to load pinned eBPF
 * program into the xt_bpf match.
 *
 * TEST:
 * ./run_cookie_uid_helper_example.sh
 * Then generate some traffic in variate ways. ping 0 -c 10 would work
 * but the cookie and uid in this case could both be 0. A sample output
 * with some traffic generated by web browser is shown below:
 *
 * cookie: 877, uid: 0x3e8, Pakcet Count: 20, Bytes Count: 11058
 * cookie: 132, uid: 0x0, Pakcet Count: 2, Bytes Count: 286
 * cookie: 812, uid: 0x3e8, Pakcet Count: 3, Bytes Count: 1726
 * cookie: 802, uid: 0x3e8, Pakcet Count: 2, Bytes Count: 104
 * cookie: 877, uid: 0x3e8, Pakcet Count: 20, Bytes Count: 11058
 * cookie: 831, uid: 0x3e8, Pakcet Count: 2, Bytes Count: 104
 * cookie: 0, uid: 0x0, Pakcet Count: 6, Bytes Count: 712
 * cookie: 880, uid: 0xfffe, Pakcet Count: 1, Bytes Count: 70
 *
 * Clean up: if using shell script, the script file will delete the iptables
 * rule and unmount the bpf program when exit. Else the iptables rule need
 * to be deleted by hand, see run_cookie_uid_helper_example.sh for detail.
 */

#define _GNU_SOURCE

#define offsetof(type, member)	__builtin_offsetof(type, member)
#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))

#include <arpa/inet.h>
#include <errno.h>
#include <error.h>
#include <limits.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <bpf/bpf.h>
#include "libbpf.h"

struct stats {
	uint32_t uid;
	uint64_t packets;
	uint64_t bytes;
};

static int map_fd, prog_fd;

static void maps_create(void)
{
	map_fd = bpf_create_map(BPF_MAP_TYPE_HASH, sizeof(uint32_t),
				sizeof(struct stats), 100, 0);
	if (map_fd < 0)
		error(1, errno, "map create failed!\n");
}

static void prog_load(void)
{
	static char log_buf[1 << 16];

	struct bpf_insn prog[] = {
		/*
		 * Save sk_buff for future usage. value stored in R6 to R10 will
		 * not be reset after a bpf helper function call.
		 */
		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
		/*
		 * pc1: BPF_FUNC_get_socket_cookie takes one parameter,
		 * R1: sk_buff
		 */
		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
				BPF_FUNC_get_socket_cookie),
		/* pc2-4: save &socketCookie to r7 for future usage*/
		BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
		BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
		BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
		/*
		 * pc5-8: set up the registers for BPF_FUNC_map_lookup_elem,
		 * it takes two parameters (R1: map_fd,  R2: &socket_cookie)
		 */
		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
		BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
				BPF_FUNC_map_lookup_elem),
		/*
		 * pc9. if r0 != 0x0, go to pc+14, since we have the cookie
		 * stored already
		 * Otherwise do pc10-22 to setup a new data entry.
		 */
		BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 14),
		BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
				BPF_FUNC_get_socket_uid),
		/*
		 * Place a struct stats in the R10 stack and sequentially
		 * place the member value into the memory. Packets value
		 * is set by directly place a IMM value 1 into the stack.
		 */
		BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0,
				-32 + offsetof(struct stats, uid)),
		BPF_ST_MEM(BPF_DW, BPF_REG_10,
				-32 + offsetof(struct stats, packets), 1),
		/*
		 * __sk_buff is a special struct used for eBPF program to
		 * directly access some sk_buff field.
		 */
		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6,
				offsetof(struct __sk_buff, len)),
		BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_1,
				-32 + offsetof(struct stats, bytes)),
		/*
		 * add new map entry using BPF_FUNC_map_update_elem, it takes
		 * 4 parameters (R1: map_fd, R2: &socket_cookie, R3: &stats,
		 * R4: flags)
		 */
		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
		BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
		BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
		BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -32),
		BPF_MOV64_IMM(BPF_REG_4, 0),
		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
				BPF_FUNC_map_update_elem),
		BPF_JMP_IMM(BPF_JA, 0, 0, 5),
		/*
		 * pc24-30 update the packet info to a exist data entry, it can
		 * be done by directly write to pointers instead of using
		 * BPF_FUNC_map_update_elem helper function
		 */
		BPF_MOV64_REG(BPF_REG_9, BPF_REG_0),
		BPF_MOV64_IMM(BPF_REG_1, 1),
		BPF_STX_XADD(BPF_DW, BPF_REG_9, BPF_REG_1,
				offsetof(struct stats, packets)),
		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6,
				offsetof(struct __sk_buff, len)),
		BPF_STX_XADD(BPF_DW, BPF_REG_9, BPF_REG_1,
				offsetof(struct stats, bytes)),
		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_6,
				offsetof(struct __sk_buff, len)),
		BPF_EXIT_INSN(),
	};
	prog_fd = bpf_load_program(BPF_PROG_TYPE_SOCKET_FILTER, prog,
					ARRAY_SIZE(prog), "GPL", 0,
					log_buf, sizeof(log_buf));
	if (prog_fd < 0)
		error(1, errno, "failed to load prog\n%s\n", log_buf);
}

static void prog_attach_iptables(char *file)
{
	int ret;
	char rules[100];

	if (bpf_obj_pin(prog_fd, file))
		error(1, errno, "bpf_obj_pin");
	if (strlen(file) > 50) {
		printf("file path too long: %s\n", file);
		exit(1);
	}
	sprintf(rules, "iptables -A INPUT -m bpf --object-pinned %s -j ACCEPT",
		file);
	ret = system(rules);
	if (ret < 0) {
		printf("iptables rule update failed: %d/n", WEXITSTATUS(ret));
		exit(1);
	}
}

static void print_table(void)
{
	struct stats curEntry;
	uint32_t curN = UINT32_MAX;
	uint32_t nextN, res;

	while (bpf_map_get_next_key(map_fd, &curN, &nextN) > -1) {
		curN = nextN;
		res = bpf_map_lookup_elem(map_fd, &curN, &curEntry);
		if (res < 0) {
			error(1, errno, "fail to get entry value of Key: %u\n",
				curN);
		} else {
			printf("cookie: %u, uid: 0x%x, Packet Count: %lu,"
				" Bytes Count: %lu\n", curN, curEntry.uid,
				curEntry.packets, curEntry.bytes);
		}
	}
}

int main(int argc, char *argv[])
{
	if (argc > 2) {
		printf("Too many argument provided\n");
		return 1;
	} else if (argc < 2) {
		printf("Usage: %s bpfObjName\n", argv[0]);
		return 1;
	}

	maps_create();
	prog_load();
	prog_attach_iptables(argv[1]);

	while (true) {
		print_table();
		printf("\n");
		sleep(1);
	};

	return 0;
}