recvfrom设置超时

struct timeval tv;
int ret;
tv.tv_sec = 10;
tv.tv_usec = 0;
if (setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) {
	printf("socket option  SO_RCVTIMEO not support\n");
	return;
}
if ((ret = recvfrom(s, buf, sizeof buf, 0, NULL, NULL)) < 0) {
	if (ret == EWOULDBLOCK || ret == EAGAIN)
		printf("recvfrom timeout\n");
	else
		printf("recvfrom err:%d\n", ret);
}