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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <poll.h>
struct stun_client {
struct addrinfo *serverinfo;
};
struct stun_response {
struct sockaddr addr;
};
struct stun_header {
uint16_t type;
uint16_t length;
uint32_t cookie;
uint32_t id[3];
} __attribute((packed));
struct stun_packet {
struct stun_header header;
uint8_t data[0];
} __attribute((packed));
#define STUN_CLASS(c0, c1) (((c0) << 4) | ((c1) << 8))
#define STUN_CLASS_REQUEST STUN_CLASS(0, 0)
#define STUN_CLASS_INDICATION STUN_CLASS(0, 1)
#define STUN_CLASS_SUCCESS STUN_CLASS(1, 0)
#define STUN_CLASS_ERROR STUN_CLASS(1, 1)
#define STUN_CLASS_MASK STUN_CLASS(1, 1)
#define STUN_MESSAGE(msg) (((msg & 0xf10) << 2) | ((msg & 0x70) << 1) | (msg & 0xf))
#define STUN_MESSAGE_BIND STUN_MESSAGE(1)
#define STUN_COOKIE 0x2112a442
enum {
STUN_ATTR_TYPE_MAPPED_ADDRESS = 0x1,
STUN_ATTR_TYPE_XOR_MAPPED_ADDRESS = 0x20,
STUN_ATTR_TYPE_XOR_MAPPED_ADDRESS2 = 0x8020,
};
static inline uint16_t get_unaligned_be16(const uint8_t *buf)
{
return (buf[0] << 8) | buf[1];
}
static inline uint16_t get_unaligned_be32(const uint8_t *buf)
{
return (buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3];
}
static int stun_parse_xor_mapped_address(struct stun_response *response,
const uint8_t *buf, int length)
{
uint8_t fam = buf[1];
uint16_t port = get_unaligned_be16(&buf[2]);
struct sockaddr_in *sin = (struct sockaddr_in *)&response->addr;
struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&response->addr;
switch (fam) {
case 0x1:
sin->sin_family = AF_INET;
sin->sin_port = htons((port ^ (uint16_t)((STUN_COOKIE & 0xffff0000) >> 16)));
memcpy(&sin->sin_addr.s_addr, buf + 4, 4);
sin->sin_addr.s_addr ^= htonl(STUN_COOKIE);
printf("xor port: %d\n", sin->sin_port);
break;
case 0x2:
sin6->sin6_family = AF_INET6;
sin->sin_port = htons((port ^ (uint16_t)((STUN_COOKIE & 0xffff0000) >> 16)));
memcpy(sin6->sin6_addr.s6_addr, buf + 4, 16);
break;
}
return 0;
}
static int stun_parse_mapped_address(struct stun_response *response,
const uint8_t *buf, int length)
{
uint8_t fam = buf[1];
uint16_t port = get_unaligned_be16(&buf[2]);
struct sockaddr_in *sin = (struct sockaddr_in *)&response->addr;
struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&response->addr;
printf("port: %d\n", port);
switch (fam) {
case 0x1:
sin->sin_family = AF_INET;
sin->sin_port = htons(port);
memcpy(&sin->sin_addr.s_addr, buf + 4, 4);
break;
case 0x2:
sin6->sin6_family = AF_INET6;
sin6->sin6_port = htons(port);
memcpy(sin6->sin6_addr.s6_addr, buf + 4, 16);
break;
}
return 0;
}
static int stun_parse_response(struct stun_response *response,
const struct stun_packet *packet)
{
uint16_t attr_type, attr_length;
const uint8_t *buf;
int length = ntohs(packet->header.length);
int ret;
int i = 0;
if (packet->header.cookie != htonl(STUN_COOKIE))
return -1;
if (packet->header.length < 4)
return 0;
buf = packet->data;
do {
attr_type = get_unaligned_be16(&buf[i]);
attr_length = get_unaligned_be16(&buf[i + 2]);
i += 4;
if (i + attr_length > length)
break;
switch (attr_type) {
case STUN_ATTR_TYPE_MAPPED_ADDRESS:
ret = stun_parse_mapped_address(response, &buf[i], attr_length);
break;
case STUN_ATTR_TYPE_XOR_MAPPED_ADDRESS:
case STUN_ATTR_TYPE_XOR_MAPPED_ADDRESS2:
ret = stun_parse_xor_mapped_address(response, &buf[i], attr_length);
break;
}
i += attr_length;
} while (i < length && ret == 0);
return 0;
}
static struct stun_packet *stun_packet_alloc(size_t data_size)
{
return malloc(sizeof(struct stun_packet) + data_size);
}
int stun_client_resolve(struct stun_client *stun, int sockfd, struct sockaddr *addr)
{
struct stun_packet *packet = stun_packet_alloc(200);
struct stun_response response;
int ret;
int retries = 4;
int timeout = 500;
struct pollfd pollfd;
pollfd.events = POLLIN;
pollfd.fd = sockfd;
packet->header.type = htons(STUN_CLASS_REQUEST | STUN_MESSAGE_BIND);
packet->header.cookie = htonl(STUN_COOKIE);
packet->header.id[0] = 0x12345678;
packet->header.id[1] = 0x12345678;
packet->header.id[2] = 0x12345678;
packet->header.length = 0;
while (retries--) {
ret = sendto(sockfd, packet, sizeof(struct stun_header) + packet->header.length,
0, stun->serverinfo->ai_addr, stun->serverinfo->ai_addrlen);
ret = poll(&pollfd, 1, timeout);
switch (ret) {
case 0:
timeout <<= 1;
case -EINTR:
printf("retry\n");
continue;
default:
retries = 0;
}
ret = recvfrom(sockfd, packet, 200, 0, NULL, NULL);
}
if (ret <= 0)
return ret ? ret : -ETIMEDOUT;
memset(&response, 0, sizeof(response));
ret = stun_parse_response(&response, packet);
*addr = response.addr;
return ret;
}
struct stun_client *stun_client_alloc(const char *hostname, uint16_t port)
{
struct addrinfo hints;
struct stun_client *stun;
int ret;
char p[6];
stun = malloc(sizeof(*stun));
if (!stun)
return NULL;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_NUMERICSERV;
snprintf(p, sizeof(p), "%d", port);
if ((ret = getaddrinfo(hostname, p, &hints, &stun->serverinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
return NULL;
}
return stun;
}
void stun_client_free(struct stun_client *stun)
{
freeaddrinfo(stun->serverinfo);
free(stun);
}
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