A working DNS resolver (not yet tied in to anything)
This commit is contained in:
Michael Brown
parent
df0397f334
commit
9af12d5fba
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@ -137,6 +137,7 @@
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#define EINVAL 0xdd /**< Invalid argument */
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#define EIO 0xde /**< Input/output error */
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#define EISCONN 0xdf /**< Transport endpoint is already connected */
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#define ELOOP 0xf8 /**< Too many symbolic links */
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#define EMFILE 0xe0 /**< Too many open files */
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#define EMSGSIZE 0xe1 /**< Message too long */
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#define ENAMETOOLONG 0xe2 /**< File name too long */
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@ -1,10 +1,16 @@
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#ifndef DNS_RESOLVER_H
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#define DNS_RESOLVER_H
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#ifndef _GPXE_DNS_H
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#define _GPXE_DNS_H
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#include "stdint.h"
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/** @file
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*
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* DNS protocol
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*
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*/
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#include <stdint.h>
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#include <gpxe/in.h>
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#include "ip.h"
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#include "udp.h"
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#include <gpxe/async.h>
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#include <gpxe/retry.h>
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/*
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* Constants
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@ -33,7 +39,7 @@
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#define DNS_FLAG_RCODE_NX ( 0x03 << 0 )
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#define DNS_FLAG_RCODE(flags) ( (flags) & ( 0x0f << 0 ) )
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#define DNS_UDP_PORT 53
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#define DNS_PORT 53
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#define DNS_MAX_RETRIES 3
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#define DNS_MAX_CNAME_RECURSION 0x30
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@ -56,13 +62,11 @@ struct dns_query_info {
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} __attribute__ (( packed ));
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struct dns_query {
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struct iphdr ip;
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struct udphdr udp;
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struct dns_header dns;
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char payload[ 256 + sizeof ( struct dns_query_info ) ];
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} __attribute__ (( packed ));
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struct dns_rr_info {
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struct dns_rr_info_common {
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uint16_t type;
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uint16_t class;
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uint32_t ttl;
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@ -70,23 +74,36 @@ struct dns_rr_info {
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} __attribute__ (( packed ));
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struct dns_rr_info_a {
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struct dns_rr_info info;
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struct dns_rr_info_common common;
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struct in_addr in_addr;
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} __attribute__ (( packed ));
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struct dns_rr_info_cname {
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struct dns_rr_info info;
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char cname[0];
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struct dns_rr_info_common common;
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char cname[0];
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} __attribute__ (( packed ));
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/*
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* Functions in dns.c (used by nmb.c)
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*
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*/
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extern struct dns_header * dns_query ( struct dns_query *query,
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unsigned int query_len,
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struct sockaddr_in *nameserver );
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extern struct dns_rr_info * dns_find_rr ( struct dns_query *query,
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struct dns_header *reply );
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union dns_rr_info {
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struct dns_rr_info_common common;
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struct dns_rr_info_a a;
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struct dns_rr_info_cname cname;
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};
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#endif /* DNS_RESOLVER_H */
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struct dns_request {
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struct sockaddr_tcpip *st;
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struct async async;
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struct dns_query query;
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struct dns_query_info *qinfo;
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unsigned int recursion;
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struct udp_connection udp;
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struct retry_timer timer;
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};
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extern int dns_resolv ( const char *name, struct sockaddr_tcpip *st,
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struct async *parent );
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#endif /* _GPXE_DNS_H */
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@ -1,7 +1,7 @@
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#ifndef NMB_H
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#define NMB_H
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#include "dns.h"
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#include <gpxe/dns.h>
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/*
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* NetBIOS name query packets are basically the same as DNS packets,
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@ -0,0 +1,463 @@
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/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* Portions copyright (C) 2004 Anselm M. Hoffmeister
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* <stockholm@users.sourceforge.net>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <byteswap.h>
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#include <gpxe/async.h>
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#include <gpxe/udp.h>
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#include <gpxe/dhcp.h>
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#include <gpxe/dns.h>
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/** @file
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*
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* DNS protocol
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*
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*/
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/**
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* Compare DNS reply name against the query name from the original request
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*
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* @v dns DNS request
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* @v reply DNS reply
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* @v rname Reply name
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* @ret zero Names match
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* @ret non-zero Names do not match
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*/
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static int dns_name_cmp ( struct dns_request *dns, struct dns_header *reply,
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const char *rname ) {
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const char *qname = dns->query.payload;
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int i;
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while ( 1 ) {
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/* Obtain next section of rname */
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while ( ( *rname ) & 0xc0 ) {
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rname = ( ( ( char * ) reply ) +
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( ntohs( *((uint16_t *)rname) ) & ~0xc000 ));
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}
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/* Check that lengths match */
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if ( *rname != *qname )
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return -1;
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/* If length is zero, we have reached the end */
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if ( ! *qname )
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return 0;
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/* Check that data matches */
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for ( i = *qname + 1; i > 0 ; i-- ) {
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if ( *(rname++) != *(qname++) )
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return -1;
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}
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}
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}
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/**
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* Skip over a (possibly compressed) DNS name
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*
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* @v name DNS name
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* @ret name Next DNS name
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*/
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static const char * dns_skip_name ( const char *name ) {
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while ( 1 ) {
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if ( ! *name ) {
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/* End of name */
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return ( name + 1);
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}
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if ( *name & 0xc0 ) {
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/* Start of a compressed name */
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return ( name + 2 );
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}
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/* Uncompressed name portion */
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name += *name + 1;
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}
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}
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/**
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* Find an RR in a reply packet corresponding to our query
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*
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* @v dns DNS request
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* @v reply DNS reply
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* @ret rr DNS RR, or NULL if not found
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*/
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static union dns_rr_info * dns_find_rr ( struct dns_request *dns,
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struct dns_header *reply ) {
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int i, cmp;
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const char *p = ( ( char * ) reply ) + sizeof ( struct dns_header );
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union dns_rr_info *rr_info;
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/* Skip over the questions section */
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for ( i = ntohs ( reply->qdcount ) ; i > 0 ; i-- ) {
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p = dns_skip_name ( p ) + sizeof ( struct dns_query_info );
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}
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/* Process the answers section */
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for ( i = ntohs ( reply->ancount ) ; i > 0 ; i-- ) {
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cmp = dns_name_cmp ( dns, reply, p );
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p = dns_skip_name ( p );
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rr_info = ( ( union dns_rr_info * ) p );
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if ( cmp == 0 )
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return rr_info;
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p += ( sizeof ( rr_info->common ) +
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ntohs ( rr_info->common.rdlength ) );
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}
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return NULL;
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}
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/**
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* Convert a standard NUL-terminated string to a DNS name
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*
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* @v string Name as a NUL-terminated string
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* @v buf Buffer in which to place DNS name
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* @ret next Byte following constructed DNS name
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*
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* DNS names consist of "<length>element" pairs.
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*/
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static char * dns_make_name ( const char *string, char *buf ) {
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char *length_byte = buf++;
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char c;
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while ( ( c = *(string++) ) ) {
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if ( c == '.' ) {
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*length_byte = buf - length_byte - 1;
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length_byte = buf;
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}
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*(buf++) = c;
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}
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*length_byte = buf - length_byte - 1;
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*(buf++) = '\0';
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return buf;
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}
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/**
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* Convert an uncompressed DNS name to a NUL-terminated string
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*
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* @v name DNS name
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* @ret string NUL-terminated string
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*
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* Produce a printable version of a DNS name. Used only for debugging.
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*/
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static inline char * dns_unmake_name ( char *name ) {
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char *p;
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unsigned int len;
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p = name;
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while ( ( len = *p ) ) {
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*(p++) = '.';
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p += len;
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}
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return name + 1;
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}
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/**
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* Decompress a DNS name
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*
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* @v reply DNS replay
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* @v name DNS name
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* @v buf Buffer into which to decompress DNS name
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* @ret next Byte following decompressed DNS name
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*/
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static char * dns_decompress_name ( struct dns_header *reply,
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const char *name, char *buf ) {
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int i, len;
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do {
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/* Obtain next section of name */
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while ( ( *name ) & 0xc0 ) {
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name = ( ( char * ) reply +
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( ntohs ( *((uint16_t *)name) ) & ~0xc000 ) );
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}
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/* Copy data */
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len = *name;
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for ( i = len + 1 ; i > 0 ; i-- ) {
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*(buf++) = *(name++);
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}
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} while ( len );
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return buf;
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}
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/**
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* Mark DNS request as complete
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*
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* @v dns DNS request
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* @v rc Return status code
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*/
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static void dns_done ( struct dns_request *dns, int rc ) {
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/* Stop the retry timer */
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stop_timer ( &dns->timer );
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/* Close UDP connection */
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udp_close ( &dns->udp );
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/* Mark async operation as complete */
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async_done ( &dns->async, rc );
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}
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/**
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* Send next packet in DNS request
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*
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* @v dns DNS request
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*/
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static void dns_send_packet ( struct dns_request *dns ) {
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static unsigned int qid = 0;
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/* Increment query ID */
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dns->query.dns.id = htons ( ++qid );
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DBGC ( dns, "DNS %p sending query ID %d\n", dns, qid );
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/* Start retransmission timer */
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start_timer ( &dns->timer );
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/* Send the data */
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udp_send ( &dns->udp, &dns->query,
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( ( ( void * ) dns->qinfo ) - ( ( void * ) &dns->query )
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+ sizeof ( dns->qinfo ) ) );
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}
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/**
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* Handle DNS retransmission timer expiry
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*
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* @v timer Retry timer
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* @v fail Failure indicator
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*/
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static void dns_timer_expired ( struct retry_timer *timer, int fail ) {
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struct dns_request *dns =
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container_of ( timer, struct dns_request, timer );
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if ( fail ) {
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dns_done ( dns, -ETIMEDOUT );
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} else {
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dns_send_packet ( dns );
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}
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}
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/**
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* Receive new data
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*
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* @v udp UDP connection
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* @v data Received data
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* @v len Length of received data
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* @v st_src Partially-filled source address
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* @v st_dest Partially-filled destination address
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*/
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static int dns_newdata ( struct udp_connection *conn, void *data, size_t len,
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struct sockaddr_tcpip *st_src __unused,
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struct sockaddr_tcpip *st_dest __unused ) {
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struct dns_request *dns =
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container_of ( conn, struct dns_request, udp );
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struct dns_header *reply = data;
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union dns_rr_info *rr_info;
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struct sockaddr_in *sin;
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unsigned int qtype = dns->qinfo->qtype;
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/* Sanity check */
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if ( len < sizeof ( *reply ) ) {
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DBGC ( dns, "DNS %p received underlength packet length %zd\n",
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dns, len );
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return -EINVAL;
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}
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/* Check reply ID matches query ID */
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if ( reply->id != dns->query.dns.id ) {
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DBGC ( dns, "DNS %p received unexpected reply ID %d "
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"(wanted %d)\n", dns, ntohs ( reply->id ),
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ntohs ( dns->query.dns.id ) );
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return -EINVAL;
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}
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DBGC ( dns, "DNS %p received reply ID %d\n", dns, ntohs ( reply->id ));
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/* Stop the retry timer. After this point, each code path
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* must either restart the timer by calling dns_send_packet(),
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* or mark the DNS operation as complete by calling
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* dns_done()
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*/
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stop_timer ( &dns->timer );
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/* Search through response for useful answers. Do this
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* multiple times, to take advantage of useful nameservers
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* which send us e.g. the CNAME *and* the A record for the
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* pointed-to name.
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*/
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while ( ( rr_info = dns_find_rr ( dns, reply ) ) ) {
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switch ( rr_info->common.type ) {
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case htons ( DNS_TYPE_A ):
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/* Found the target A record */
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DBGC ( dns, "DNS %p found address %s\n",
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dns, inet_ntoa ( rr_info->a.in_addr ) );
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sin = ( struct sockaddr_in * ) dns->st;
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sin->sin_family = AF_INET;
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sin->sin_addr = rr_info->a.in_addr;
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/* Mark operation as complete */
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dns_done ( dns, 0 );
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return 0;
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case htons ( DNS_TYPE_CNAME ):
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/* Found a CNAME record; update query and recurse */
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DBGC ( dns, "DNS %p found CNAME\n", dns );
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dns->qinfo = ( void * ) dns_decompress_name ( reply,
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rr_info->cname.cname,
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dns->query.payload );
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dns->qinfo->qtype = htons ( DNS_TYPE_A );
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dns->qinfo->qclass = htons ( DNS_CLASS_IN );
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/* Terminate the operation if we recurse too far */
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if ( ++dns->recursion > DNS_MAX_CNAME_RECURSION ) {
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DBGC ( dns, "DNS %p recursion exceeded\n",
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dns );
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dns_done ( dns, -ELOOP );
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return 0;
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}
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break;
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default:
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DBGC ( dns, "DNS %p got unknown record type %d\n",
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dns, ntohs ( rr_info->common.type ) );
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break;
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}
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}
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/* Determine what to do next based on the type of query we
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* issued and the reponse we received
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*/
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switch ( qtype ) {
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case htons ( DNS_TYPE_A ):
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/* We asked for an A record and got nothing;
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* try the CNAME.
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*/
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DBGC ( dns, "DNS %p found no A record; trying CNAME\n", dns );
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dns->qinfo->qtype = htons ( DNS_TYPE_CNAME );
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dns_send_packet ( dns );
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return 0;
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case htons ( DNS_TYPE_CNAME ):
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/* We asked for a CNAME record. If we got a response
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* (i.e. if the next A query is already set up), then
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* issue it, otherwise abort.
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*/
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if ( dns->qinfo->qtype == htons ( DNS_TYPE_A ) ) {
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dns_send_packet ( dns );
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return 0;
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} else {
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DBGC ( dns, "DNS %p found no CNAME record\n", dns );
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dns_done ( dns, -ENXIO );
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return 0;
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}
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default:
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assert ( 0 );
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dns_done ( dns, -EINVAL );
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return 0;
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}
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}
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/** DNS UDP operations */
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struct udp_operations dns_udp_operations = {
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.newdata = dns_newdata,
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};
|
||||
|
||||
/**
|
||||
* Reap asynchronous operation
|
||||
*
|
||||
* @v async Asynchronous operation
|
||||
*/
|
||||
static void dns_reap ( struct async *async ) {
|
||||
struct dns_request *dns =
|
||||
container_of ( async, struct dns_request, async );
|
||||
|
||||
free ( dns );
|
||||
}
|
||||
|
||||
/** DNS asynchronous operations */
|
||||
static struct async_operations dns_async_operations = {
|
||||
.reap = dns_reap,
|
||||
};
|
||||
|
||||
/**
|
||||
* Resolve name using DNS
|
||||
*
|
||||
*/
|
||||
int dns_resolv ( const char *name, struct sockaddr_tcpip *st,
|
||||
struct async *parent ) {
|
||||
struct dns_request *dns;
|
||||
union {
|
||||
struct sockaddr_tcpip st;
|
||||
struct sockaddr_in sin;
|
||||
} nameserver;
|
||||
int rc;
|
||||
|
||||
/* Allocate DNS structure */
|
||||
dns = malloc ( sizeof ( *dns ) );
|
||||
if ( ! dns ) {
|
||||
rc = -ENOMEM;
|
||||
goto err;
|
||||
}
|
||||
memset ( dns, 0, sizeof ( *dns ) );
|
||||
dns->st = st;
|
||||
dns->timer.expired = dns_timer_expired;
|
||||
dns->udp.udp_op = &dns_udp_operations;
|
||||
|
||||
/* Create query */
|
||||
dns->query.dns.flags = htons ( DNS_FLAG_QUERY | DNS_FLAG_OPCODE_QUERY |
|
||||
DNS_FLAG_RD );
|
||||
dns->query.dns.qdcount = htons ( 1 );
|
||||
dns->qinfo = ( void * ) dns_make_name ( name, dns->query.payload );
|
||||
dns->qinfo->qtype = htons ( DNS_TYPE_A );
|
||||
dns->qinfo->qclass = htons ( DNS_CLASS_IN );
|
||||
|
||||
/* Open UDP connection */
|
||||
memset ( &nameserver, 0, sizeof ( nameserver ) );
|
||||
nameserver.sin.sin_family = AF_INET;
|
||||
nameserver.sin.sin_port = htons ( DNS_PORT );
|
||||
#warning "DHCP-DNS hack"
|
||||
struct dhcp_option *option =
|
||||
find_global_dhcp_option ( DHCP_DNS_SERVERS );
|
||||
if ( ! option ) {
|
||||
DBGC ( dns, "DNS %p no name servers\n", dns );
|
||||
rc = -ENXIO;
|
||||
goto err;
|
||||
}
|
||||
dhcp_ipv4_option ( option, &nameserver.sin.sin_addr );
|
||||
DBGC ( dns, "DNS %p using nameserver %s\n", dns,
|
||||
inet_ntoa ( nameserver.sin.sin_addr ) );
|
||||
udp_connect ( &dns->udp, &nameserver.st );
|
||||
if ( ( rc = udp_open ( &dns->udp, 0 ) ) != 0 )
|
||||
goto err;
|
||||
|
||||
dns_send_packet ( dns );
|
||||
|
||||
async_init ( &dns->async, &dns_async_operations, parent );
|
||||
return 0;
|
||||
|
||||
err:
|
||||
DBGC ( dns, "DNS %p could not create request: %s\n",
|
||||
dns, strerror ( rc ) );
|
||||
free ( dns );
|
||||
return rc;
|
||||
}
|
||||
361
src/proto/dns.c
361
src/proto/dns.c
|
|
@ -1,361 +0,0 @@
|
|||
/**************************************************************************
|
||||
*
|
||||
* dns_resolver.c: Etherboot support for resolution of host/domain
|
||||
* names in filename parameters
|
||||
* Written 2004 by Anselm M. Hoffmeister
|
||||
* <stockholm@users.sourceforge.net>
|
||||
*
|
||||
* This program is free software; you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License as published by
|
||||
* the Free Software Foundation; either version 2 of the License, or
|
||||
* (at your option) any later version.
|
||||
*
|
||||
* This program is distributed in the hope that it will be useful,
|
||||
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
* GNU General Public License for more details.
|
||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with this program; if not, write to the Free Software
|
||||
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
||||
*
|
||||
* This code is using nuts and bolts from throughout etherboot.
|
||||
* It is a fresh implementation according to the DNS RFC, #1035
|
||||
*
|
||||
* REVISION HISTORY:
|
||||
* ================
|
||||
* 2004-05-10 File created
|
||||
* 2004-05-19 First release to CVS
|
||||
* 2004-05-22 CNAME support first stage finished
|
||||
* 2004-05-24 First "stable" release to CVS
|
||||
* 2004-08-28 Improve readability, set recursion flag
|
||||
* 2005-04-30 Tidied up to the point of being a complete rewrite (mcb30)
|
||||
***************************************************************************/
|
||||
|
||||
#include "etherboot.h"
|
||||
#include "nic.h"
|
||||
#include "resolv.h"
|
||||
#include "dns.h"
|
||||
|
||||
/*
|
||||
* await_dns
|
||||
* Shall be called on any incoming packet during the resolution process
|
||||
* (as is the case with all the other await_ functions in etherboot)
|
||||
* Param: as any await functions
|
||||
*
|
||||
*/
|
||||
static int await_dns ( int ival, void *ptr,
|
||||
unsigned short ptype __unused,
|
||||
struct iphdr *ip __unused,
|
||||
struct udphdr *udp, struct tcphdr *tcp __unused ) {
|
||||
struct dns_header **header = ptr;
|
||||
|
||||
if ( ! udp )
|
||||
return 0;
|
||||
if ( ntohs ( udp->dest ) != ival )
|
||||
return 0;
|
||||
*header = ( struct dns_header * ) ( udp + 1 );
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Send a name server query and wait for a response. Query is retried
|
||||
* up to DNS_MAX_RETRIES times. Returns a pointer to the answer
|
||||
* packet, or NULL if no answer was received.
|
||||
*
|
||||
*/
|
||||
struct dns_header * dns_query ( struct dns_query *query,
|
||||
unsigned int query_len,
|
||||
struct sockaddr_in *nameserver ) {
|
||||
long timeout;
|
||||
int retry;
|
||||
struct dns_header *reply;
|
||||
|
||||
for ( retry = 0 ; retry < DNS_MAX_RETRIES ; retry++ ) {
|
||||
udp_transmit ( nameserver->sin_addr.s_addr,
|
||||
nameserver->sin_port, nameserver->sin_port,
|
||||
query_len, query );
|
||||
timeout = rfc2131_sleep_interval ( TIMEOUT, retry );
|
||||
if ( ! await_reply ( await_dns, nameserver->sin_port,
|
||||
&reply, timeout ) )
|
||||
continue;
|
||||
if ( reply->id != query->dns.id ) {
|
||||
DBG ( "DNS received unexpected reply ID %d "
|
||||
"(wanted %d)\n",
|
||||
ntohs ( reply->id ), ntohs ( query->dns.id ) );
|
||||
continue;
|
||||
}
|
||||
/* We have a valid reply! */
|
||||
return reply;
|
||||
}
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Compare two DNS names to see if they are the same. Takes
|
||||
* compressed names in the reply into account (though the query name
|
||||
* must be uncompressed). Returns 0 for a match (for consistency with
|
||||
* strcmp et al).
|
||||
*
|
||||
*/
|
||||
static inline int dns_name_cmp ( const char *qname, const char *rname,
|
||||
struct dns_header *reply ) {
|
||||
int i;
|
||||
while ( 1 ) {
|
||||
/* Obtain next section of rname */
|
||||
while ( ( *rname ) & 0xc0 ) {
|
||||
rname = ( ( char * ) reply +
|
||||
( ntohs( *((uint16_t *)rname) ) & ~0xc000 ));
|
||||
}
|
||||
/* Check that lengths match */
|
||||
if ( *rname != *qname )
|
||||
return 1;
|
||||
/* If length is zero, we have reached the end */
|
||||
if ( ! *qname )
|
||||
return 0;
|
||||
/* Check that data matches */
|
||||
for ( i = *qname + 1; i > 0 ; i-- ) {
|
||||
if ( *(rname++) != *(qname++) )
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Skip over a DNS name, which may be compressed
|
||||
*
|
||||
*/
|
||||
static inline const char * dns_skip_name ( const char *name ) {
|
||||
while ( 1 ) {
|
||||
if ( ! *name ) {
|
||||
/* End of name */
|
||||
return ( name + 1);
|
||||
}
|
||||
if ( *name & 0xc0 ) {
|
||||
/* Start of a compressed name */
|
||||
return ( name + 2 );
|
||||
}
|
||||
/* Uncompressed name portion */
|
||||
name += *name + 1;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Find a Resource Record in a reply packet corresponding to our
|
||||
* query. Returns a pointer to the RR, or NULL if no answer found.
|
||||
*
|
||||
*/
|
||||
struct dns_rr_info * dns_find_rr ( struct dns_query *query,
|
||||
struct dns_header *reply ) {
|
||||
int i, cmp;
|
||||
const char *p = ( ( char * ) reply ) + sizeof ( struct dns_header );
|
||||
|
||||
/* Skip over the questions section */
|
||||
for ( i = ntohs ( reply->qdcount ) ; i > 0 ; i-- ) {
|
||||
p = dns_skip_name ( p ) + sizeof ( struct dns_query_info );
|
||||
}
|
||||
|
||||
/* Process the answers section */
|
||||
for ( i = ntohs ( reply->ancount ) ; i > 0 ; i-- ) {
|
||||
cmp = dns_name_cmp ( query->payload, p, reply );
|
||||
p = dns_skip_name ( p );
|
||||
if ( cmp == 0 )
|
||||
return ( ( struct dns_rr_info * ) p );
|
||||
p += ( sizeof ( struct dns_rr_info ) +
|
||||
ntohs ( ( ( struct dns_rr_info * ) p )->rdlength ) );
|
||||
}
|
||||
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Convert a standard NUL-terminated string to a DNS query name,
|
||||
* consisting of "<length>element" pairs.
|
||||
*
|
||||
* Returns a pointer to the character following the constructed DNS
|
||||
* query name.
|
||||
*
|
||||
*/
|
||||
static inline char * dns_make_name ( char *dest, const char *name ) {
|
||||
char *length_byte = dest++;
|
||||
char c;
|
||||
|
||||
while ( ( c = *(name++) ) ) {
|
||||
if ( c == '.' ) {
|
||||
*length_byte = dest - length_byte - 1;
|
||||
length_byte = dest;
|
||||
}
|
||||
*(dest++) = c;
|
||||
}
|
||||
*length_byte = dest - length_byte - 1;
|
||||
*(dest++) = '\0';
|
||||
return dest;
|
||||
}
|
||||
|
||||
/*
|
||||
* Produce a printable version of a DNS name. Used only for debugging.
|
||||
*
|
||||
*/
|
||||
static inline char * dns_unmake_name ( char *name ) {
|
||||
char *p;
|
||||
unsigned int len;
|
||||
|
||||
p = name;
|
||||
while ( ( len = *p ) ) {
|
||||
*(p++) = '.';
|
||||
p += len;
|
||||
}
|
||||
|
||||
return name + 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Decompress a DNS name.
|
||||
*
|
||||
* Returns a pointer to the character following the decompressed DNS
|
||||
* name.
|
||||
*
|
||||
*/
|
||||
static inline char * dns_decompress_name ( char *dest, const char *name,
|
||||
struct dns_header *header ) {
|
||||
int i, len;
|
||||
|
||||
do {
|
||||
/* Obtain next section of name */
|
||||
while ( ( *name ) & 0xc0 ) {
|
||||
name = ( ( char * ) header +
|
||||
( ntohs ( *((uint16_t *)name) ) & ~0xc000 ) );
|
||||
}
|
||||
/* Copy data */
|
||||
len = *name;
|
||||
for ( i = len + 1 ; i > 0 ; i-- ) {
|
||||
*(dest++) = *(name++);
|
||||
}
|
||||
} while ( len );
|
||||
return dest;
|
||||
}
|
||||
|
||||
/*
|
||||
* Resolve a name using DNS
|
||||
*
|
||||
*/
|
||||
static int dns_resolv ( struct in_addr *addr, const char *name ) {
|
||||
struct dns_query query;
|
||||
struct dns_query_info *query_info;
|
||||
struct dns_header *reply;
|
||||
struct dns_rr_info *rr_info;
|
||||
struct sockaddr_in nameserver;
|
||||
uint16_t qtype;
|
||||
unsigned int recursion = 0;
|
||||
unsigned int id = 1;
|
||||
|
||||
/* Fail immediately if we have no name server */
|
||||
if ( ! arptable[ARP_NAMESERVER].ipaddr.s_addr ) {
|
||||
DBG ( "DNS has no nameserver\n" );
|
||||
return 0;
|
||||
}
|
||||
|
||||
DBG ( "DNS resolving %s\n", name );
|
||||
|
||||
/* Set up the query data */
|
||||
nameserver.sin_addr = arptable[ARP_NAMESERVER].ipaddr;
|
||||
nameserver.sin_port = DNS_UDP_PORT;
|
||||
memset ( &query, 0, sizeof ( query ) );
|
||||
query.dns.flags = htons ( DNS_FLAG_QUERY | DNS_FLAG_OPCODE_QUERY |
|
||||
DNS_FLAG_RD );
|
||||
query.dns.qdcount = htons ( 1 );
|
||||
query_info = ( void * ) dns_make_name ( query.payload, name );
|
||||
query_info->qtype = htons ( DNS_TYPE_A );
|
||||
query_info->qclass = htons ( DNS_CLASS_IN );
|
||||
|
||||
while ( 1 ) {
|
||||
/* Transmit current query, wait for reply */
|
||||
query.dns.id = htons ( id++ );
|
||||
qtype = ntohs ( query_info->qtype );
|
||||
reply = dns_query ( &query,
|
||||
( ( ( char * ) query_info )
|
||||
+ sizeof ( *query_info )
|
||||
- ( ( char * ) &query ) ),
|
||||
&nameserver );
|
||||
if ( ! reply ) {
|
||||
DBG ( "DNS got no response from server %@ (port %d)\n",
|
||||
nameserver.sin_addr.s_addr,
|
||||
nameserver.sin_port );
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Search through response for useful answers. Do
|
||||
* this multiple times, to take advantage of useful
|
||||
* nameservers which send us e.g. the CNAME *and* the
|
||||
* A record for the pointed-to name.
|
||||
*/
|
||||
while ( ( rr_info = dns_find_rr ( &query, reply ) ) ) {
|
||||
switch ( ntohs ( rr_info->type ) ) {
|
||||
case DNS_TYPE_A: {
|
||||
/* Found the target A record */
|
||||
struct dns_rr_info_a *rr_info_a =
|
||||
( struct dns_rr_info_a * ) rr_info;
|
||||
*addr = rr_info_a->in_addr;
|
||||
DBG ( "DNS found address %@\n", addr->s_addr );
|
||||
return 1; }
|
||||
case DNS_TYPE_CNAME: {
|
||||
/* Found a CNAME record - update the query */
|
||||
struct dns_rr_info_cname *rr_info_cname =
|
||||
( struct dns_rr_info_cname * ) rr_info;
|
||||
char *cname = rr_info_cname->cname;
|
||||
|
||||
query_info = ( void * )
|
||||
dns_decompress_name ( query.payload,
|
||||
cname, reply );
|
||||
DBG ( "DNS found CNAME %s\n",
|
||||
dns_unmake_name ( query.payload ) );
|
||||
DBG ( "", /* Reconstruct name */
|
||||
dns_make_name ( query.payload,
|
||||
query.payload + 1 ) );
|
||||
|
||||
query_info->qtype = htons ( DNS_TYPE_A );
|
||||
query_info->qclass = htons ( DNS_CLASS_IN );
|
||||
|
||||
if ( ++recursion > DNS_MAX_CNAME_RECURSION ) {
|
||||
DBG ( "DNS recursion exceeded\n" );
|
||||
return 0;
|
||||
}
|
||||
break; }
|
||||
default:
|
||||
DBG ( "DNS got unknown record type %d\n",
|
||||
ntohs ( rr_info->type ) );
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
|
||||
/* Determine what to do next based on the type of
|
||||
* query we issued and the reponse we received
|
||||
*/
|
||||
switch ( qtype ) {
|
||||
case DNS_TYPE_A :
|
||||
/* We asked for an A record and got nothing;
|
||||
* try the CNAME.
|
||||
*/
|
||||
DBG ( "DNS found no A record; trying CNAME\n" );
|
||||
query_info->qtype = htons ( DNS_TYPE_CNAME );
|
||||
break;
|
||||
case DNS_TYPE_CNAME :
|
||||
/* We asked for a CNAME record. If we didn't
|
||||
* get any response (i.e. the next A query
|
||||
* isn't already set up), then abort.
|
||||
*/
|
||||
if ( query_info->qtype != htons ( DNS_TYPE_A ) ) {
|
||||
DBG ( "DNS found no CNAME record\n" );
|
||||
return 0;
|
||||
}
|
||||
break;
|
||||
default:
|
||||
DBG ( "DNS internal error - inconsistent state\n" );
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
struct resolver dns_resolver __resolver = {
|
||||
.name = "DNS",
|
||||
.resolv = dns_resolv,
|
||||
};
|
||||
|
|
@ -1,6 +1,8 @@
|
|||
#if 0
|
||||
|
||||
#include "resolv.h"
|
||||
#include "string.h"
|
||||
#include "dns.h"
|
||||
#include <gpxe/dns.h>
|
||||
#include "nic.h"
|
||||
#include "nmb.h"
|
||||
|
||||
|
|
@ -104,3 +106,5 @@ struct resolver nmb_resolver __resolver = {
|
|||
.name = "NMB",
|
||||
.resolv = nmb_resolv,
|
||||
};
|
||||
|
||||
#endif
|
||||
|
|
|
|||
Reference in New Issue