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// MIT License, Copyright (c) 2020 Marvin Borner
// TODO: Less magic, auto xld splitting
// TODO: DNS cache
#include <def.h>
#include <mem.h>
#include <net.h>
#include <print.h>
#include <random.h>
#include <socket.h>
#include <str.h>
static u32 dns_ip_addr = ip(1, 1, 1, 1);
struct dns_packet {
u16 qid;
u16 flags;
u16 questions;
u16 answers;
u16 authorities;
u16 additional;
u8 data[];
} __attribute__((packed));
static void dns_make_packet(struct dns_packet *packet, const char *name, const char *tld)
{
packet->qid = htons(rand());
packet->flags = htons(0x0100); // Standard query
packet->questions = htons(1);
packet->answers = htons(0);
packet->authorities = htons(0);
packet->additional = htons(0);
packet->data[0] = (u8)strlen(name);
memcpy(&packet->data[1], name, (u8)strlen(name));
packet->data[(u8)strlen(name) + 1] = (u8)strlen(tld);
memcpy(&packet->data[(u8)strlen(name) + 2], tld, (u8)strlen(tld));
packet->data[(u8)strlen(name) + (u8)strlen(tld) + 2] = 0x00; // Name end
packet->data[(u8)strlen(name) + (u8)strlen(tld) + 4] = 0x01; // A
packet->data[(u8)strlen(name) + (u8)strlen(tld) + 6] = 0x01; // IN
}
static u32 dns_handle_packet(struct dns_packet *packet)
{
u16 flags = htons(packet->flags);
u8 reply_code = flags & 0xf;
if (reply_code != DNS_NOERROR) {
printf("DNS error: %d\n", reply_code);
return 0;
}
u8 *start = &packet->data[1] + strlen((char *)&packet->data[1]);
printf("TTL of %s: %ds\n", &packet->data[1], (u32)start[14]);
u8 *ip = &start[17];
printf("IP: %d.%d.%d.%d\n", ip[0], ip[1], ip[2], ip[3]);
return ip(ip[0], ip[1], ip[2], ip[3]);
}
u32 dns_request(const char *name, const char *tld)
{
struct socket *socket = net_open(S_UDP);
/* if (socket) */
/* socket->src_port = 50053; */
if (!socket || !net_connect(socket, dns_ip_addr, 53))
return 0;
u32 length = sizeof(struct dns_packet) + strlen(name) + strlen(tld) + 7; // TODO: 7 :)
struct dns_packet *packet = malloc(length);
memset(packet, 0, length);
dns_make_packet(packet, name, tld);
net_send(socket, packet, length);
free(packet);
u8 buf[128] = { 0 };
int l = net_receive(socket, buf, 128);
if (l > 0)
return dns_handle_packet((void *)buf);
else
return 0;
}
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