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/* main.c
* (c) Jonas Gunz, 2020
* License: MIT
* */
#include "server.h"
void run_dns_server ( void )
{
int ret;
struct sockaddr_in sock_server_addr;
char recv_buffer[ UDP_BUFFER_LEN ];
signal ( SIGTERM, signal_term );
signal ( SIGINT, signal_term );
//Avoid zombie processes
//TODO currently useless, since no forking is done.
signal (SIGCHLD, SIG_IGN);
log_init_stdout ( _LOG_DEBUG );
sock_server = socket ( AF_INET, SOCK_DGRAM, 0 );
if ( sock_server == -1 ) {
LOGPRINTF(_LOG_ERROR, "socket() failed");
exit ( errno );
}
memset( &sock_server_addr, '\0', sizeof(struct sockaddr_in) );
sock_server_addr.sin_family = AF_INET;
sock_server_addr.sin_port = htons( 53 );
ret = inet_aton ( "0.0.0.0", & sock_server_addr.sin_addr );
if( ret == 0 ) { //Error on 0, no errno!
LOGPRINTF(_LOG_NOTE, "inet_aton(): Invalid bind IP\n" );
exit ( 1 );
}
ret = bind ( sock_server,
(struct sockaddr*) &sock_server_addr,
sizeof(struct sockaddr_in) );
if ( ret == -1 ) {
LOGPRINTF(_LOG_ERROR, "bind() failed");
exit ( errno );
}
while( 1 )
{
struct sockaddr_in sock_client_addr;
socklen_t sock_client_addr_len;
sock_client_addr_len = sizeof ( struct sockaddr_in );
memset ( &sock_client_addr, '\0', sock_client_addr_len );
ret = recvfrom (sock_server,
recv_buffer,
UDP_BUFFER_LEN,
0,
(struct sockaddr*) &sock_client_addr,
&sock_client_addr_len );
if ( ret == -1 ) {
LOGPRINTF( _LOG_ERROR, "recvfrom()");
exit ( errno );
}
LOGPRINTF(_LOG_DEBUG, "UDP Packet size %i", ret);
handle_connection ( sock_server,
&sock_client_addr,
sock_client_addr_len,
recv_buffer,
ret );
}
close( sock_server );
}
int handle_connection ( int _socket,
struct sockaddr_in *sockaddr_client,
socklen_t sockaddr_client_len,
char* _buffer,
int _bufflen )
{
struct dns_message msg;
if (dns_parse_packet (_buffer, _bufflen, &msg) ) {
LOGPRINTF (_LOG_DEBUG, "Malformed packet recieved. parsing failed");
return 1;
}
if(msg.question_count > 0) {
char out[128];
qname_to_fqdn( (char*) msg.question[0].qname, 100, out, 128);
printf("%s %i\n", out, msg.question[0].qtype);
}
//Always return NXDOMAIN
struct dns_header head = {msg.header.id,1,OP_Q,0,0,0,0,0,NAMEERR,0,0,0,0};
char ret[20];
int retlen = dns_construct_header ( &head, ret, 20 );
sendto (_socket, ret, retlen, 0, (struct sockaddr*) sockaddr_client, sockaddr_client_len);
dns_destroy_struct ( &msg );
return 0;
}
void signal_term ( ) {
printf( "Recieved Signal. Terminating active connections and closing socket\n" );
//terminate all children >:)
kill ( 0, SIGTERM );
shutdown ( sock_server, SHUT_RDWR );
close ( sock_server );
printf( "done\n" );
exit( 0 );
}
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