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
|
/* server.c
* (c) Jonas Gunz, 2020
* License: MIT
* */
#include "server.h"
static int sock_server;
void server_start ( server_config_t* _config )
{
fd_set sel_fds;
struct timeval sel_interval;
int sel_ret = 0;
database_t zone_db;
signal ( SIGTERM, signal_term );
signal ( SIGINT, signal_term );
if ( database_init( &zone_db ) ) {
LOGPRINTF(_LOG_ERROR, "Failed create database");
exit(1);
}
if ( zonefile_to_database( &zone_db, _config->zonefile ) ) {
LOGPRINTF(_LOG_ERROR, "Failed populate database");
exit(1);
}
sock_server = server_get_socket( _config->bind_ip, _config->bind_port );
LOGPRINTF(_LOG_NOTE, "Done!");
while( 1 ) {
FD_ZERO ( &sel_fds );
FD_SET ( sock_server, &sel_fds );
sel_interval.tv_sec = 0;
sel_interval.tv_usec = 10000;
sel_ret = select( sock_server + 1, &sel_fds, NULL, NULL, &sel_interval );
if ( sel_ret < 0 ) {
LOGPRINTF( _LOG_ERRNO, "select()" );
exit(1);
} else if ( sel_ret ) {
DEBUG("Connection");
server_handle_connection( sock_server, &zone_db );
}
}
}
void server_handle_connection ( int _socket, database_t* _zone_db ) {
int i;
char recv_buffer[ UDP_BUFFER_LEN ];
int recv_len = 0;
char answ_buffer[ UDP_BUFFER_LEN ];
int answ_len = UDP_BUFFER_LEN;
int answ_cnt = DNS_HEADER_LEN;
/* preload with header length, because it is written last. */
struct sockaddr_in sock_client_addr;
socklen_t sock_client_addr_len = sizeof( struct sockaddr_in );
dns_message_t dns_req;
dns_header_t answ_header;
memset( &sock_client_addr, 0, sock_client_addr_len );
recv_len = recvfrom ( _socket, recv_buffer, UDP_BUFFER_LEN,
0, (struct sockaddr*) &sock_client_addr,
&sock_client_addr_len );
if ( recv_len == -1 ) {
LOGPRINTF( _LOG_ERRNO, "recvfrom()");
exit ( 1 );
}
if ( dns_parse_packet( recv_buffer, recv_len, &dns_req ) ) {
DEBUG( "Malformed packet recieved. parsing failed" );
return;
}
if ( ! dns_req.question_count ) {
DEBUG( "No questions in request." );
goto end;
}
DEBUG( "Valid data with %i question(s)", dns_req.question_count );
memset( &answ_header, 0, sizeof( dns_header_t ) );
answ_header.id = dns_req.header.id;
answ_header.QR = 1; /* Response */
answ_header.AA = 1; /* Authorative answer */
/* TODO test with artificially large rdata to exceed buffer */
for (i = 0; i < dns_req.question_count; i++) {
int cnt_inc = 0;
database_rdata_t db_rdata;
dns_question_t *quest = &dns_req.question[i];
dns_answer_t dns_answ = {quest->qname, quest->qname_len, quest->qtype, quest->qclass, 0, 0, NULL };
if( database_query( &db_rdata, _zone_db, quest->qname, quest->qname_len, quest->qtype, quest->qclass ) ) {
answ_header.RCODE = RCODE_NAMEERR;
DEBUG("Could not answer question %i", i);
continue;
}
dns_answ.rdlength = db_rdata.rdlen;
dns_answ.rdata = db_rdata.rdata;
dns_answ.ttl = db_rdata.ttl;
cnt_inc += dns_construct_answer( &answ_buffer[answ_cnt], answ_len - answ_cnt, &dns_answ );
if (cnt_inc <= 0) {
LOGPRINTF(_LOG_ERROR, "dns_construct_answer() failed with %i. Buffer overrun?", cnt_inc);
goto end;
}
answ_cnt += cnt_inc;
answ_header.answer_count += 1;
}
dns_construct_header( answ_buffer, answ_len, &answ_header );
sendto( _socket, answ_buffer, (size_t)answ_cnt, 0, (struct sockaddr*) &sock_client_addr, sock_client_addr_len );
end:
dns_destroy_struct ( &dns_req );
}
int server_get_socket ( char* _bind_ip, uint16_t _bind_port ) {
struct sockaddr_in socket_addr;
int server_socket;
LOGPRINTF(_LOG_NOTE, "Binding on %s:%i", _bind_ip, _bind_port);
server_socket = socket ( AF_INET, SOCK_DGRAM, 0 );
if ( server_socket == -1 ) {
LOGPRINTF(_LOG_ERRNO, "failed to create socket");
exit ( errno );
}
memset( &socket_addr, '\0', sizeof(struct sockaddr_in) );
socket_addr.sin_family = AF_INET;
socket_addr.sin_port = htons( _bind_port );
if ( ! inet_aton ( _bind_ip, & socket_addr.sin_addr ) ) {
LOGPRINTF(_LOG_ERROR, "inet_aton(): Invalid bind IP\n" );
exit ( 1 );
}
if ( bind( server_socket, (struct sockaddr*) &socket_addr, sizeof(struct sockaddr_in) ) ) {
LOGPRINTF(_LOG_ERRNO, "bind() failed");
exit ( errno );
}
return server_socket;
}
void signal_term ( int _sig ) {
LOGPRINTF( _LOG_NOTE, "Server shutting down" );
close( sock_server );
exit(0);
}
|