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/* 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_populate( &zone_db, _config->zonefile ) ) {
LOGPRINTF(_LOG_ERRNO, "Failed to populate database from zonefile");
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 );
}
}
exit(0);
}
void server_handle_connection ( int _socket, database_t* _zone_db ) {
unsigned 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, 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 ( ) {
LOGPRINTF( _LOG_NOTE, "Server shutting down" );
close( sock_server );
exit(0);
}
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