/* 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;
}