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#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <signal.h>
#define PRINT_ERRNO() {printf("%s:%i %i:%s\n", __FILE__, __LINE__, errno, strerror(errno));}
#define UDP_BUFFER_LEN 512
int sock_server;
int dns_parse_packet ( int _socket,
struct sockaddr_in *sockaddr_client,
socklen_t sockaddr_client_len,
char* buffer,
int bufflen );
void signal_term ( );
void signal_term_child ( );
int main( int argc,
char* argv[] ) {
int ret;
struct sockaddr_in sock_server_addr;
char recv_buffer[ UDP_BUFFER_LEN ];
signal ( SIGTERM, signal_term );
signal ( SIGINT, signal_term );
sock_server = socket ( AF_INET, SOCK_DGRAM, 0 );
if ( sock_server == -1 ) {
PRINT_ERRNO();
return 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!
printf( "inet_aton(): Invalid IP\n" );
return 1;
}
ret = bind( sock_server,
(struct sockaddr*) &sock_server_addr,
sizeof(struct sockaddr_in) );
if ( ret == -1 ) {
PRINT_ERRNO();
return 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 ) {
PRINT_ERRNO();
return errno;
}
printf ( "recieved\n" );
if ( dns_parse_packet ( sock_server,
&sock_client_addr,
sock_client_addr_len,
recv_buffer,
ret ) ) {
PRINT_ERRNO();
return errno;
}
printf ( "forked\n" );
}
close( sock_server );
return 0;
}
int dns_parse_packet ( int _socket,
struct sockaddr_in *sockaddr_client,
socklen_t sockaddr_client_len,
char* buffer,
int bufflen ) {
pid_t pid = fork();
if ( pid > 0)
return 0;
else if ( pid < 0 )
return errno;
signal ( SIGTERM, signal_term_child);
sleep ( 999 ); //Keep child active
exit ( 0 );
}
void signal_term ( ) {
printf( "Recieved Signal. Terminating active connections and closing socket\n" );
kill ( 0, SIGTERM ); //terminate all child processes
shutdown ( sock_server, SHUT_RDWR );
close ( sock_server );
printf( "done\n" );
exit( 0 );
}
void signal_term_child ( ) {
close ( sock_server );
printf ( "%i: Active connection terminated\n", getpid() );
exit( 0 );
}
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