1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
|
/*
* 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 labels;
uint8_t *ptr;
len = 0;
labels = 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 (labels > 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;
labels++;
}
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;
ip4_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(void)
{
if (pcb == NULL) return;
udp_remove(pcb);
pcb = NULL;
}
|
