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 -option
 * option:
 *	-t: do traffic monitoring test, the program will continuously
 * print out network traffic happens after program started A sample
 * output 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
 *
 *	-s: do getsockopt SO_COOKIE test, the program will set up a pair of
 * UDP sockets and send packets between them. And read out the traffic data
 * directly from the ebpf map based on the socket cookie.
 *
 * 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 <net/if.h>
#include <signal.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 "bpf_insn.h"

#define PORT 8888

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

static int map_fd, prog_fd;

static bool test_finish;

static void maps_create(void)
{
	map_fd = bpf_map_create(BPF_MAP_TYPE_HASH, NULL, sizeof(uint32_t),
				sizeof(struct stats), 100, NULL);
	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 + (__s16)offsetof(struct stats, uid)),
		BPF_ST_MEM(BPF_DW, BPF_REG_10,
			   -32 + (__s16)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 + (__s16)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_ATOMIC_OP(BPF_DW, BPF_ADD, 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_ATOMIC_OP(BPF_DW, BPF_ADD, 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(),
	};
	LIBBPF_OPTS(bpf_prog_load_opts, opts,
		.log_buf = log_buf,
		.log_size = sizeof(log_buf),
	);

	prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL",
				prog, ARRAY_SIZE(prog), &opts);
	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[256];

	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);
	}
	ret = snprintf(rules, sizeof(rules),
		       "iptables -A OUTPUT -m bpf --object-pinned %s -j ACCEPT",
		       file);
	if (ret < 0 || ret >= sizeof(rules)) {
		printf("error constructing iptables command\n");
		exit(1);
	}
	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;
	int 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);
		}
	}
}

static void udp_client(void)
{
	struct sockaddr_in si_other = {0};
	struct sockaddr_in si_me = {0};
	struct stats dataEntry;
	int s_rcv, s_send, i, recv_len;
	char message = 'a';
	char buf;
	uint64_t cookie;
	int res;
	socklen_t cookie_len = sizeof(cookie);
	socklen_t slen = sizeof(si_other);

	s_rcv = socket(PF_INET, SOCK_DGRAM, 0);
	if (s_rcv < 0)
		error(1, errno, "rcv socket creat failed!\n");
	si_other.sin_family = AF_INET;
	si_other.sin_port = htons(PORT);
	if (inet_aton("127.0.0.1", &si_other.sin_addr) == 0)
		error(1, errno, "inet_aton\n");
	if (bind(s_rcv, (struct sockaddr *)&si_other, sizeof(si_other)) == -1)
		error(1, errno, "bind\n");
	s_send = socket(PF_INET, SOCK_DGRAM, 0);
	if (s_send < 0)
		error(1, errno, "send socket creat failed!\n");
	res = getsockopt(s_send, SOL_SOCKET, SO_COOKIE, &cookie, &cookie_len);
	if (res < 0)
		printf("get cookie failed: %s\n", strerror(errno));
	res = bpf_map_lookup_elem(map_fd, &cookie, &dataEntry);
	if (res != -1)
		error(1, errno, "socket stat found while flow not active\n");
	for (i = 0; i < 10; i++) {
		res = sendto(s_send, &message, sizeof(message), 0,
			     (struct sockaddr *)&si_other, slen);
		if (res == -1)
			error(1, errno, "send\n");
		if (res != sizeof(message))
			error(1, 0, "%uB != %luB\n", res, sizeof(message));
		recv_len = recvfrom(s_rcv, &buf, sizeof(buf), 0,
			     (struct sockaddr *)&si_me, &slen);
		if (recv_len < 0)
			error(1, errno, "receive\n");
		res = memcmp(&(si_other.sin_addr), &(si_me.sin_addr),
			   sizeof(si_me.sin_addr));
		if (res != 0)
			error(1, EFAULT, "sender addr error: %d\n", res);
		printf("Message received: %c\n", buf);
		res = bpf_map_lookup_elem(map_fd, &cookie, &dataEntry);
		if (res < 0)
			error(1, errno, "lookup sk stat failed, cookie: %lu\n",
			      cookie);
		printf("cookie: %lu, uid: 0x%x, Packet Count: %lu,"
			" Bytes Count: %lu\n\n", cookie, dataEntry.uid,
			dataEntry.packets, dataEntry.bytes);
	}
	close(s_send);
	close(s_rcv);
}

static int usage(void)
{
	printf("Usage: ./run_cookie_uid_helper_example.sh"
		" bpfObjName -option\n"
		"	-t	traffic monitor test\n"
		"	-s	getsockopt cookie test\n");
	return 1;
}

static void finish(int ret)
{
	test_finish = true;
}

int main(int argc, char *argv[])
{
	int opt;
	bool cfg_test_traffic = false;
	bool cfg_test_cookie = false;

	if (argc != 3)
		return usage();
	while ((opt = getopt(argc, argv, "ts")) != -1) {
		switch (opt) {
		case 't':
			cfg_test_traffic = true;
			break;
		case 's':
			cfg_test_cookie = true;
			break;

		default:
			printf("unknown option %c\n", opt);
			usage();
			return -1;
		}
	}
	maps_create();
	prog_load();
	prog_attach_iptables(argv[2]);
	if (cfg_test_traffic) {
		if (signal(SIGINT, finish) == SIG_ERR)
			error(1, errno, "register SIGINT handler failed");
		if (signal(SIGTERM, finish) == SIG_ERR)
			error(1, errno, "register SIGTERM handler failed");
		while (!test_finish) {
			print_table();
			printf("\n");
			sleep(1);
		}
	} else if (cfg_test_cookie) {
		udp_client();
	}
	close(prog_fd);
	close(map_fd);
	return 0;
}