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/*
* The MIT License (MIT)
*
* Copyright (c) 2015 by Sergey Fetisov <fsenok@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
/*
* version: 1.0 demo (7.02.2015)
* brief: tiny dns ipv4 server using lwip (pcb)
*/
#include "dnserver.h"
#define DNS_MAX_HOST_NAME_LEN 128
static struct udp_pcb *pcb = NULL;
dns_query_proc_t query_proc = NULL;
#pragma pack(push, 1)
typedef struct
{
#if BYTE_ORDER == LITTLE_ENDIAN
uint8_t rd: 1, /* Recursion Desired */
tc: 1, /* Truncation Flag */
aa: 1, /* Authoritative Answer Flag */
opcode: 4, /* Operation code */
qr: 1; /* Query/Response Flag */
uint8_t rcode: 4, /* Response Code */
z: 3, /* Zero */
ra: 1; /* Recursion Available */
#else
uint8_t qr: 1, /* Query/Response Flag */
opcode: 4, /* Operation code */
aa: 1, /* Authoritative Answer Flag */
tc: 1, /* Truncation Flag */
rd: 1; /* Recursion Desired */
uint8_t ra: 1, /* Recursion Available */
z: 3, /* Zero */
rcode: 4; /* Response Code */
#endif
} dns_header_flags_t;
typedef struct
{
uint16_t id;
dns_header_flags_t flags;
uint16_t n_record[4];
} dns_header_t;
typedef struct dns_answer
{
uint16_t name;
uint16_t type;
uint16_t Class;
uint32_t ttl;
uint16_t len;
uint32_t addr;
} dns_answer_t;
#pragma pack(pop)
typedef struct dns_query
{
char name[DNS_MAX_HOST_NAME_LEN];
uint16_t type;
uint16_t Class;
} dns_query_t;
static uint16_t get_uint16(const uint8_t *pnt)
{
uint16_t result;
memcpy(&result, pnt, sizeof(result));
return result;
}
static int parse_next_query(void *data, int size, dns_query_t *query)
{
int len;
int lables;
uint8_t *ptr;
len = 0;
lables = 0;
ptr = (uint8_t *)data;
while (true)
{
uint8_t lable_len;
if (size <= 0) return -1;
lable_len = *ptr++;
size--;
if (lable_len == 0) break;
if (lables > 0)
{
if (len == DNS_MAX_HOST_NAME_LEN) return -2;
query->name[len++] = '.';
}
if (lable_len > size) return -1;
if (len + lable_len >= DNS_MAX_HOST_NAME_LEN) return -2;
memcpy(&query->name[len], ptr, lable_len);
len += lable_len;
ptr += lable_len;
size -= lable_len;
lables++;
}
if (size < 4) return -1;
query->name[len] = 0;
query->type = get_uint16(ptr);
ptr += 2;
query->Class = get_uint16(ptr);
ptr += 2;
return ptr - (uint8_t *)data;
}
static void udp_recv_proc(void *arg, struct udp_pcb *upcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
int len;
dns_header_t *header;
static dns_query_t query;
struct pbuf *out;
ip_addr_t host_addr;
dns_answer_t *answer;
(void)arg;
if (p->len <= sizeof(dns_header_t)) goto error;
header = (dns_header_t *)p->payload;
if (header->flags.qr != 0) goto error;
if (ntohs(header->n_record[0]) != 1) goto error;
len = parse_next_query(header + 1, p->len - sizeof(dns_header_t), &query);
if (len < 0) goto error;
if (!query_proc(query.name, &host_addr)) goto error;
len += sizeof(dns_header_t);
out = pbuf_alloc(PBUF_TRANSPORT, len + 16, PBUF_POOL);
if (out == NULL) goto error;
memcpy(out->payload, p->payload, len);
header = (dns_header_t *)out->payload;
header->flags.qr = 1;
header->n_record[1] = htons(1);
answer = (struct dns_answer *)((uint8_t *)out->payload + len);
answer->name = htons(0xC00C);
answer->type = htons(1);
answer->Class = htons(1);
answer->ttl = htonl(32);
answer->len = htons(4);
answer->addr = host_addr.addr;
udp_sendto(upcb, out, addr, port);
pbuf_free(out);
error:
pbuf_free(p);
}
err_t dnserv_init(const ip_addr_t *bind, uint16_t port, dns_query_proc_t qp)
{
err_t err;
udp_init();
dnserv_free();
pcb = udp_new();
if (pcb == NULL)
return ERR_MEM;
err = udp_bind(pcb, bind, port);
if (err != ERR_OK)
{
dnserv_free();
return err;
}
udp_recv(pcb, udp_recv_proc, NULL);
query_proc = qp;
return ERR_OK;
}
void dnserv_free()
{
if (pcb == NULL) return;
udp_remove(pcb);
pcb = NULL;
}
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