#include <stdnoreturn.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <getopt.h>
#include <signal.h>
#include <sys/types.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include <net/if.h>
#include <linux/if_link.h>
#include <linux/limits.h>
static unsigned int ifindex;
static __u32 attached_prog_id;
static bool attached_tc;
static void noreturn cleanup(int sig)
{
LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
int prog_fd;
int err;
if (attached_prog_id == 0)
exit(0);
if (attached_tc) {
LIBBPF_OPTS(bpf_tc_hook, hook,
.ifindex = ifindex,
.attach_point = BPF_TC_INGRESS);
err = bpf_tc_hook_destroy(&hook);
if (err < 0) {
fprintf(stderr, "Error: bpf_tc_hook_destroy: %s\n", strerror(-err));
fprintf(stderr, "Failed to destroy the TC hook\n");
exit(1);
}
exit(0);
}
prog_fd = bpf_prog_get_fd_by_id(attached_prog_id);
if (prog_fd < 0) {
fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
err = bpf_xdp_attach(ifindex, -1, 0, NULL);
if (err < 0) {
fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n", strerror(-err));
fprintf(stderr, "Failed to detach XDP program\n");
exit(1);
}
} else {
opts.old_prog_fd = prog_fd;
err = bpf_xdp_attach(ifindex, -1, XDP_FLAGS_REPLACE, &opts);
close(prog_fd);
if (err < 0) {
fprintf(stderr, "Error: bpf_set_link_xdp_fd_opts: %s\n", strerror(-err));
if (err != -EEXIST) {
fprintf(stderr, "Failed to detach XDP program\n");
exit(1);
}
}
}
exit(0);
}
static noreturn void usage(const char *progname)
{
fprintf(stderr, "Usage: %s [--iface <iface>|--prog <prog_id>] [--mss4 <mss ipv4> --mss6 <mss ipv6> --wscale <wscale> --ttl <ttl>] [--ports <port1>,<port2>,...] [--single] [--tc]\n",
progname);
exit(1);
}
static unsigned long parse_arg_ul(const char *progname, const char *arg, unsigned long limit)
{
unsigned long res;
char *endptr;
errno = 0;
res = strtoul(arg, &endptr, 10);
if (errno != 0 || *endptr != '\0' || arg[0] == '\0' || res > limit)
usage(progname);
return res;
}
static void parse_options(int argc, char *argv[], unsigned int *ifindex, __u32 *prog_id,
__u64 *tcpipopts, char **ports, bool *single, bool *tc)
{
static struct option long_options[] = {
{ "help", no_argument, NULL, 'h' },
{ "iface", required_argument, NULL, 'i' },
{ "prog", required_argument, NULL, 'x' },
{ "mss4", required_argument, NULL, 4 },
{ "mss6", required_argument, NULL, 6 },
{ "wscale", required_argument, NULL, 'w' },
{ "ttl", required_argument, NULL, 't' },
{ "ports", required_argument, NULL, 'p' },
{ "single", no_argument, NULL, 's' },
{ "tc", no_argument, NULL, 'c' },
{ NULL, 0, NULL, 0 },
};
unsigned long mss4, wscale, ttl;
unsigned long long mss6;
unsigned int tcpipopts_mask = 0;
if (argc < 2)
usage(argv[0]);
*ifindex = 0;
*prog_id = 0;
*tcpipopts = 0;
*ports = NULL;
*single = false;
*tc = false;
while (true) {
int opt;
opt = getopt_long(argc, argv, "", long_options, NULL);
if (opt == -1)
break;
switch (opt) {
case 'h':
usage(argv[0]);
break;
case 'i':
*ifindex = if_nametoindex(optarg);
if (*ifindex == 0)
usage(argv[0]);
break;
case 'x':
*prog_id = parse_arg_ul(argv[0], optarg, UINT32_MAX);
if (*prog_id == 0)
usage(argv[0]);
break;
case 4:
mss4 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
tcpipopts_mask |= 1 << 0;
break;
case 6:
mss6 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
tcpipopts_mask |= 1 << 1;
break;
case 'w':
wscale = parse_arg_ul(argv[0], optarg, 14);
tcpipopts_mask |= 1 << 2;
break;
case 't':
ttl = parse_arg_ul(argv[0], optarg, UINT8_MAX);
tcpipopts_mask |= 1 << 3;
break;
case 'p':
*ports = optarg;
break;
case 's':
*single = true;
break;
case 'c':
*tc = true;
break;
default:
usage(argv[0]);
}
}
if (optind < argc)
usage(argv[0]);
if (tcpipopts_mask == 0xf) {
if (mss4 == 0 || mss6 == 0 || wscale == 0 || ttl == 0)
usage(argv[0]);
*tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
} else if (tcpipopts_mask != 0) {
usage(argv[0]);
}
if (*ifindex != 0 && *prog_id != 0)
usage(argv[0]);
if (*ifindex == 0 && *prog_id == 0)
usage(argv[0]);
}
static int syncookie_attach(const char *argv0, unsigned int ifindex, bool tc)
{
struct bpf_prog_info info = {};
__u32 info_len = sizeof(info);
char xdp_filename[PATH_MAX];
struct bpf_program *prog;
struct bpf_object *obj;
int prog_fd;
int err;
snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.bpf.o", argv0);
obj = bpf_object__open_file(xdp_filename, NULL);
err = libbpf_get_error(obj);
if (err < 0) {
fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
return err;
}
err = bpf_object__load(obj);
if (err < 0) {
fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
return err;
}
prog = bpf_object__find_program_by_name(obj, tc ? "syncookie_tc" : "syncookie_xdp");
if (!prog) {
fprintf(stderr, "Error: bpf_object__find_program_by_name: program was not found\n");
return -ENOENT;
}
prog_fd = bpf_program__fd(prog);
err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len);
if (err < 0) {
fprintf(stderr, "Error: bpf_prog_get_info_by_fd: %s\n",
strerror(-err));
goto out;
}
attached_tc = tc;
attached_prog_id = info.id;
signal(SIGINT, cleanup);
signal(SIGTERM, cleanup);
if (tc) {
LIBBPF_OPTS(bpf_tc_hook, hook,
.ifindex = ifindex,
.attach_point = BPF_TC_INGRESS);
LIBBPF_OPTS(bpf_tc_opts, opts,
.handle = 1,
.priority = 1,
.prog_fd = prog_fd);
err = bpf_tc_hook_create(&hook);
if (err < 0) {
fprintf(stderr, "Error: bpf_tc_hook_create: %s\n",
strerror(-err));
goto fail;
}
err = bpf_tc_attach(&hook, &opts);
if (err < 0) {
fprintf(stderr, "Error: bpf_tc_attach: %s\n",
strerror(-err));
goto fail;
}
} else {
err = bpf_xdp_attach(ifindex, prog_fd,
XDP_FLAGS_UPDATE_IF_NOEXIST, NULL);
if (err < 0) {
fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n",
strerror(-err));
goto fail;
}
}
err = 0;
out:
bpf_object__close(obj);
return err;
fail:
signal(SIGINT, SIG_DFL);
signal(SIGTERM, SIG_DFL);
attached_prog_id = 0;
goto out;
}
static int syncookie_open_bpf_maps(__u32 prog_id, int *values_map_fd, int *ports_map_fd)
{
struct bpf_prog_info prog_info;
__u32 map_ids[8];
__u32 info_len;
int prog_fd;
int err;
int i;
*values_map_fd = -1;
*ports_map_fd = -1;
prog_fd = bpf_prog_get_fd_by_id(prog_id);
if (prog_fd < 0) {
fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
return prog_fd;
}
prog_info = (struct bpf_prog_info) {
.nr_map_ids = 8,
.map_ids = (__u64)(unsigned long)map_ids,
};
info_len = sizeof(prog_info);
err = bpf_prog_get_info_by_fd(prog_fd, &prog_info, &info_len);
if (err != 0) {
fprintf(stderr, "Error: bpf_prog_get_info_by_fd: %s\n",
strerror(-err));
goto out;
}
if (prog_info.nr_map_ids < 2) {
fprintf(stderr, "Error: Found %u BPF maps, expected at least 2\n",
prog_info.nr_map_ids);
err = -ENOENT;
goto out;
}
for (i = 0; i < prog_info.nr_map_ids; i++) {
struct bpf_map_info map_info = {};
int map_fd;
err = bpf_map_get_fd_by_id(map_ids[i]);
if (err < 0) {
fprintf(stderr, "Error: bpf_map_get_fd_by_id: %s\n", strerror(-err));
goto err_close_map_fds;
}
map_fd = err;
info_len = sizeof(map_info);
err = bpf_map_get_info_by_fd(map_fd, &map_info, &info_len);
if (err != 0) {
fprintf(stderr, "Error: bpf_map_get_info_by_fd: %s\n",
strerror(-err));
close(map_fd);
goto err_close_map_fds;
}
if (strcmp(map_info.name, "values") == 0) {
*values_map_fd = map_fd;
continue;
}
if (strcmp(map_info.name, "allowed_ports") == 0) {
*ports_map_fd = map_fd;
continue;
}
close(map_fd);
}
if (*values_map_fd != -1 && *ports_map_fd != -1) {
err = 0;
goto out;
}
err = -ENOENT;
err_close_map_fds:
if (*values_map_fd != -1)
close(*values_map_fd);
if (*ports_map_fd != -1)
close(*ports_map_fd);
*values_map_fd = -1;
*ports_map_fd = -1;
out:
close(prog_fd);
return err;
}
int main(int argc, char *argv[])
{
int values_map_fd, ports_map_fd;
__u64 tcpipopts;
bool firstiter;
__u64 prevcnt;
__u32 prog_id;
char *ports;
bool single;
int err = 0;
bool tc;
parse_options(argc, argv, &ifindex, &prog_id, &tcpipopts, &ports,
&single, &tc);
if (prog_id == 0) {
if (!tc) {
err = bpf_xdp_query_id(ifindex, 0, &prog_id);
if (err < 0) {
fprintf(stderr, "Error: bpf_get_link_xdp_id: %s\n",
strerror(-err));
goto out;
}
}
if (prog_id == 0) {
err = syncookie_attach(argv[0], ifindex, tc);
if (err < 0)
goto out;
prog_id = attached_prog_id;
}
}
err = syncookie_open_bpf_maps(prog_id, &values_map_fd, &ports_map_fd);
if (err < 0)
goto out;
if (ports) {
__u16 port_last = 0;
__u32 port_idx = 0;
char *p = ports;
fprintf(stderr, "Replacing allowed ports\n");
while (p && *p != '\0') {
char *token = strsep(&p, ",");
__u16 port;
port = parse_arg_ul(argv[0], token, UINT16_MAX);
err = bpf_map_update_elem(ports_map_fd, &port_idx, &port, BPF_ANY);
if (err != 0) {
fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
fprintf(stderr, "Failed to add port %u (index %u)\n",
port, port_idx);
goto out_close_maps;
}
fprintf(stderr, "Added port %u\n", port);
port_idx++;
}
err = bpf_map_update_elem(ports_map_fd, &port_idx, &port_last, BPF_ANY);
if (err != 0) {
fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
fprintf(stderr, "Failed to add the terminator value 0 (index %u)\n",
port_idx);
goto out_close_maps;
}
}
if (tcpipopts) {
__u32 key = 0;
fprintf(stderr, "Replacing TCP/IP options\n");
err = bpf_map_update_elem(values_map_fd, &key, &tcpipopts, BPF_ANY);
if (err != 0) {
fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
goto out_close_maps;
}
}
if ((ports || tcpipopts) && attached_prog_id == 0 && !single)
goto out_close_maps;
prevcnt = 0;
firstiter = true;
while (true) {
__u32 key = 1;
__u64 value;
err = bpf_map_lookup_elem(values_map_fd, &key, &value);
if (err != 0) {
fprintf(stderr, "Error: bpf_map_lookup_elem: %s\n", strerror(-err));
goto out_close_maps;
}
if (firstiter) {
prevcnt = value;
firstiter = false;
}
if (single) {
printf("Total SYNACKs generated: %llu\n", value);
break;
}
printf("SYNACKs generated: %llu (total %llu)\n", value - prevcnt, value);
prevcnt = value;
sleep(1);
}
out_close_maps:
close(values_map_fd);
close(ports_map_fd);
out:
return err == 0 ? 0 : 1;
}
