DNS resolver rewritten, moved to proto/dns.c

src/core/dns_resolver.c

@@ -1,419 +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
-*    
-*    $Revision$
-*    $Author$
-*    $Date$
-*
-*    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
-***************************************************************************/
-
-#ifdef DNS_RESOLVER
-#include "etherboot.h"
-#include "nic.h"
-#include "dns_resolver.h"
-
-#define	MAX_DNS_RETRIES	3
-#define	MAX_CNAME_RECURSION 0x30
-#undef DNSDEBUG
-
-int	donameresolution ( char * hostname, int hnlength, char * deststring );
-
-/*
- *	dns_resolver
- *	Function: Main function for name resolution - will be called by other
- *		parts of etherboot
- *	Param:	string filename (not containing proto prefix like "tftp://")
- *	Return:	string filename, with hostname replaced by IP in dotted quad
- *		or NULL for resolver error
- *		In case no substitution is necessary, return will be = param
- *		The returned string, if not == input, will be temporary and
- *		probably be overwritten during the next call to dns_resolver
- *		The returned string may (or may not) only contain an IP
- *		address, or an IP followed by a ":" or "/", or be NULL(=error)
- */
-char *	dns_resolver ( char * filename ) {
-	int	i = 0, j, k;
-	static char ipaddr[16] = { 0 };
-	// Search for "end of hostname" (which might be either ":" or "/")
-	for ( j = i; (filename[j] != ':') && (filename[j] != '/'); ++j ) {
-		// If no hostname delimiter was found, assume no name present
-		if ( filename[j] == 0 )	return	filename;
-	}
-	// Check if the filename is an IP, in which case, leave unchanged
-	k = j - i - 1;
-	while ( ( '.' == filename[i+k] ) ||
-		( ( '0' <= filename[i+k] ) && ( '9' >= filename[i+k] ) ) ) {
-		--k;
-		if ( k < 0 ) return filename; // Only had nums and dots->IP
-	}
-	// Now that we know it's a full hostname, attempt to resolve
-	if ( donameresolution ( filename + i, j - i, ipaddr ) ) {
-		return	NULL;	// Error in resolving - Fatal.
-	}
-	// Return the dotted-quad IP which resulted
-	return	ipaddr;
-}
-
-/*
- *	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
- *	Return:	see dns_resolver.h for constant return values + descriptions
- */
-static int await_dns (int ival, void *ptr,
-	unsigned short ptype __unused, struct iphdr *ip __unused,
-	struct udphdr *udp, struct tcphdr *tcp __unused) {
-	int	i, j, k;
-	unsigned char *p = (unsigned char *)udp + sizeof(struct udphdr);
-	// p is set to the beginning of the payload
-	unsigned char *q;
-	unsigned int querytype = QUERYTYPE_A;
-	if (  0 == udp  )	// Parser couldn't find UDP header
-		return RET_PACK_GARBAG;	// Not a UDP packet
-	if (( UDP_PORT_DNS != ntohs (udp->src )) ||
-	    ( UDP_PORT_DNS != ntohs (udp->dest)) )
-		// Neither source nor destination port is "53"
-		return RET_PACK_GARBAG;	// UDP port wrong
-	if (( p[QINDEX_ID  ] != 0) ||
-	    ( p[QINDEX_ID+1] != (ival & 0xff)))
-		// Checking if this packet has set (inside payload)
-		// the sequence identifier that we expect
-		return RET_PACK_GARBAG;	// Not matching our request ID
-	if (( p[QINDEX_FLAGS  ] & QUERYFLAGS_MASK ) != QUERYFLAGS_WANT )
-		// We only accept responses to the query(ies) we sent
-		return	RET_PACK_GARBAG;	// Is not response=opcode <0>
-	querytype = (ival & 0xff00) >> 8;
-	if (((p[QINDEX_NUMANSW+1] + (p[QINDEX_NUMANSW+1]<<8)) == 0 ) ||
-	     ( ERR_NOSUCHNAME == (p[QINDEX_FLAGS+1] & 0x0f) ) ) {
-		// Answer section has 0 entries, or "no such name" returned
-		if ( QUERYTYPE_A == querytype) {
-			// It was an A type query, so we should try if there's
-			// an alternative "CNAME" record available
-			return	RET_RUN_CNAME_Q; // So try CNAME query next
-		} else if ( QUERYTYPE_CNAME == querytype) {
-			// There's no CNAME either, so give up
-			return	RET_NOSUCHNAME;
-		} else {
-			// Anything else? No idea what. Should not happen.
-			return	RET_NOSUCHNAME; // Bail out with error
-		}
-	}
-	if ( 0 != ( p[QINDEX_FLAGS+1] & 0x0f ) )
-		// The response packet's flag section tells us:
-		return	RET_NOSUCHNAME;	// Another (unspecific) error occured
-	// Now we have an answer packet in response to our query. Next thing
-	// to do is to search the payload for the "answer section", as there is
-	// a question section first usually that needs to be skipped
-	// If question section was not repeated, that saves a lot of work :
-	if ( 0 >= (i = ((p[QINDEX_NUMQUEST] << 8) + p[QINDEX_NUMQUEST+1]))) {
-		q = p+ QINDEX_QUESTION;	// No question section, just continue;
-	} else if ( i >= 2 ) {		// More than one query section? Error!
-		return	RET_NOSUCHNAME;	// That's invalid for us anyway - 
-					// We only place one query at a time
-	} else {
-		// We have to skip through the question section first to
-		// find the beginning of the answer section
-		q = p + QINDEX_QUESTION;
-		while ( 0 != q[0] )
-			q += q[0] + 1; // Skip through
-		q += 5; // Skip over end-\0 and query type section
-	}
-	// Now our pointer shows the beginning of the answer section
-	// So now move it past the (repeated) query string, we only
-	// want the answer
-	while ( 0 != q[0] ) {
-		if ( 0xc0 == ( q[0] & 0xc0 ) ) { // Pointer
-			++q;
-			break;
-		}
-		q += q[0] + 1;
-	}
-	++q;
-	// Now check wether it's an INET host address (resp. CNAME)?
-	// There seem to be nameservers out there (Bind 9, for example),
-	// that return CNAMEs when no As are there, e.g. in
-	//   testname.test.   IN CNAME othername.test.
-	// case, bind 9 would return the CNAME record on an A query.
-	// Accept this case as it saves a lot of work (an extra query)
-	if (( QUERYTYPE_CNAME == q[1] ) &&
-	    ( QUERYTYPE_A     == querytype )) {
-		// A query, but CNAME response.
-		// Do simulate having done a CNAME query now and just assume
-		// the answer we are working on here is that of a CNAME query
-		// This works for single-depth CNAMEs fine.
-		// For deeper recursion, we won't parse the answer
-		// packet deeper but rely on a separate CNAME query
-		querytype = QUERYTYPE_CNAME;
-	}
-	// Now check wether the answer packet is of the expected type
-	// (remember, we just tweaked CNAME answers to A queries already)
-	if ( (q[0] != 0) ||
-	     (q[1] !=   querytype) ||   // query type matches?
-	     (q[2] != ((QUERYCLASS_INET & 0xff00) >> 8)) ||
-	     (q[3] !=  (QUERYCLASS_INET & 0x00ff))) { // class IN response?
-		return	RET_DNSERROR;	// Should not happen. DNS server bad?
-	}
-	q += 8;	// skip querytype/-class/ttl which are uninteresting now
-	if ( querytype == QUERYTYPE_A ) {
-		// So what we sent was an A query - expect an IPv4 address
-		// Check if datalength looks satisfactory
-		if ( ( 0 != q[0] ) || ( 4 != q[1] ) ) {
-			// Data length is not 4 bytes
-			return	RET_DNSERROR;
-		}
-		// Go to the IP address and copy it to the response buffer
-		p = ptr + QINDEX_STORE_A;
-		for ( i = 0; i < 4; ++i ) {
-			p[i] = q[i+2];
-		}
-		return	RET_GOT_ADDR; // OK! Address RETURNED! VERY FINE!
-	} else if ( querytype == QUERYTYPE_CNAME ) { // CNAME QUERY
-		// The pointer "q" now stands on the "payload length" of the
-		// CNAME data [2 byte field]. We will have to check wether this
-		// name is referenced in a following response, which would save
-		// us further queries, or if it is standalone, which calls for
-		// making a separate query
-		// This statement above probably needs clarification. To help
-		// the reader understand what's going on, imagine the DNS
-		// answer to be 4-section: query(repeating what we sent to the
-		// DNS server), answer(like the CNAME record we wanted),
-		// additional (which might hold the A for the CNAME - esp.
-		// Bind9 seems to provide us with this info when we didn't
-		// query for it yet) and authoritative (the DNS server's info
-		// on who is responsible for that data). For compression's
-		// sake, instead of specifying the full hostname string all
-		// the time, one can instead specify something like "same as on
-		// payload offset 0x123" - if this happens here, we can check
-		// if that payload offset given here by coincidence is that of
-		// an additional "A" record which saves us sending a separate
-		// query.
-		// We will look if there's  a/ two or more answer sections
-		// AND  b/ the next is a reference to us.
-		p = (unsigned char *)udp + sizeof(struct udphdr);
-		i = q + 2 - p;
-		if ( p[7] > 1 ) { // More than one answer section
-			// Check the next if it's a ref
-			// For that, we have to locate the next. Do this with "q".
-			p = q + (q[0] * 0x100) + q[1] + 2;
-			if ( (p[0] == (0xc0 + ((i & 0xf00)/256))) &&
-			     (p[1] == (i & 0xff) ) &&
-			     (p[2] == ((QUERYTYPE_A     & 0xff00) >> 8)) &&
-			     (p[3] ==  (QUERYTYPE_A     & 0x00ff)) &&
-			     (p[4] == ((QUERYCLASS_INET & 0xff00) >> 8 )) &&
-			     (p[5] ==  (QUERYCLASS_INET & 0x00ff)) &&
-			     (p[10]== 0) &&		// Data length expected
-			     (p[11]== 4)) {		// to be <4> (IP-addr)
-				// Behind that sections: TTL, data length(4)
-				for ( i = 0; i < 4; ++i ) {
-				    ((unsigned char*)ptr)[QINDEX_STORE_A+i] =
-					    p[12+i];
-				}
-				return	RET_GOT_ADDR;
-			}
-		}
-		// Reference not found, next query (A) needed (because CNAME
-		// queries usually return another hostname, not an IP address
-		// as we need it - that's the point in CNAME, anyway :-)
-		p = (unsigned char *)udp + sizeof(struct udphdr);
-#ifdef DNSDEBUG
-		printf ( " ->[");
-#endif
-		k = QINDEX_QUESTION;
-		i = (q-p) + 2;
-		// Compose the hostname that needs to be queried for
-		// This looks complicated (and is a little bit) because
-		// we might not be able to copy verbatim, but need to
-		// check wether the CNAME looks like
-		// "servername" "plus what offset 0x123 of the payload says"
-		// (this saves transfer bandwidth, which is why DNS allows
-		// this, but it makes programmers' lives more difficult)
-		while (p[i] != 0) {
-			if ( (((unsigned char *)p)[i] & 0xc0) != 0 ) {
-				i = ((p[i] & 0x3f) * 0x100) + p[i+1];
-				continue;
-			}
-			((unsigned char *)ptr)[k] = p[i];
-			for ( j = i + 1; j <= i + p[i]; ++j ) {
-				((unsigned char *)ptr)[k+j-i] = p[j];
-#ifdef DNSDEBUG
-				printf ( "%c", p[j] );
-#endif
-			}
-			k += ((unsigned char *)ptr)[k] + 1;
-			i += p[i] + 1;
-#ifdef DNSDEBUG
-			printf ( (p[i] ? ".": "") );
-#endif
-		}
-		((unsigned char *)ptr)[k] = 0;
-#ifdef DNSDEBUG
-		printf ( "].." );
-#endif
-		// So we need to run another query, this time try to
-		// get an "A" record for the hostname that the last CNAME
-		// query pointed to
-		return	RET_RUN_NEXT_A;
-	}
-	// We only accept CNAME or A replies from the nameserver, every-
-	// thing else is of no use for us.
-	// Must be an invalid packet that the nameserver sent.
-	return	RET_DNSERROR;
-}
-
-int	chars_to_next_dot ( char * countfrom, int maxnum ) {
-	// Count the number of characters of this part of a hostname
-	int i;
-	for ( i = 1; i < maxnum; ++i ) {
-		if ( countfrom[i] == '.' ) return i;
-	}
-	return	maxnum;
-}
-
-/*
- *	donameresolution
- *	Function: Compose the initial query packet, handle answers until
- *		a/ an IP address is retrieved
- *		b/ too many CNAME references occured (max. MAX_DNS_RETRIES)
- *		c/ No matching record for A or CNAME can be found
- *	Param:	string hostname, length (hostname needs no \0-end-marker),
- *		string to which dotted-quad-IP shall be written
- *	Return:	0 for success, >0 for failure
- */
-int	donameresolution ( char * hostname, int hnlength, char * deststring ) {
-	unsigned char	querybuf[260+sizeof(struct iphdr)+sizeof(struct udphdr)];
-		// 256 for the DNS query payload, +4 for the result temporary
-	unsigned char	*query = &querybuf[sizeof(struct iphdr)+sizeof(struct udphdr)];
-		// Pointer to the payload
-	int	i, h = hnlength;
-	long	timeout;
-	int	retry, recursion;
-	// Setup the query data
-	query[QINDEX_ID  ]	= (QUERYIDENTIFIER & 0xff00) >> 8;
-	query[QINDEX_ID+1]	=  QUERYIDENTIFIER & 0xff;
-	query[QINDEX_FLAGS  ]	= (QUERYFLAGS & 0xff00) >> 8;
-	query[QINDEX_FLAGS+1]	=  QUERYFLAGS & 0xff;
-	query[QINDEX_NUMQUEST  ]= 0;
-	query[QINDEX_NUMQUEST+1]= 1; // 1 standard query to be sent
-	query[QINDEX_NUMANSW  ]	= 0;
-	query[QINDEX_NUMANSW+1]	= 0;
-	query[QINDEX_NUMAUTH  ]	= 0;
-	query[QINDEX_NUMAUTH+1]	= 0;
-	query[QINDEX_NUMADDIT  ]= 0;
-	query[QINDEX_NUMADDIT+1]= 0;
-	query[QINDEX_QUESTION]	= chars_to_next_dot(hostname,h);
-	if ( h > 236 ) return 1;	// Hostnames longer than 236 chars are refused.
-					// This is an arbitrary decision, SHOULD check
-					// what the RFCs say about that
-	for ( i = 0; i < h; ++i ) {
-		// Compose the query section's hostname - replacing dots (and
-		// preceding the string) with one-byte substring-length values
-		// (for the immediately following substring) - \0 terminated
-		query[QINDEX_QUESTION+i+1] = hostname[i];
-		if ( hostname[i] == '.' )
-			query[QINDEX_QUESTION+i+1] = chars_to_next_dot(hostname + i + 1, h - i - 1);
-	}
-	query[QINDEX_QTYPE+h  ]	= (QUERYTYPE_A & 0xff00) >> 8;
-	query[QINDEX_QTYPE+h+1]	=  QUERYTYPE_A & 0xff;
-					// First try an A query, if that
-					// won't work, try CNAME
-	printf ( "Resolving hostname [" );
-	for ( i = 0; i < hnlength; ++i ) { printf ( "%c", hostname[i] ); }
-	printf ("]" );
-	for ( recursion = MAX_CNAME_RECURSION; recursion > 0; --recursion ) {
-		printf ( ".." );
-		// Try MAX_CNAME_RECURSION CNAME queries maximally, if then no
-		// A record is found, assume the hostname to not be resolvable
-		query[QINDEX_QUESTION+h+1] = 0;	// Marks the end of
-						// the query string
-		query[QINDEX_QCLASS+h  ]= (QUERYCLASS_INET & 0xff00) >> 8;
-		query[QINDEX_QCLASS+h+1]=  QUERYCLASS_INET & 0xff;
-		rx_qdrain();	// Clear NIC packet buffer -
-				// there won't be anything of interest *now*.
-		udp_transmit ( arptable[ARP_NAMESERVER].ipaddr.s_addr,
-				UDP_PORT_DNS, UDP_PORT_DNS,
-				hnlength + 18 + sizeof(struct iphdr) +
-				sizeof(struct udphdr), querybuf );
-		// If no answer comes in in a certain period of time, retry
-		for (retry = 1; retry <= MAX_DNS_RETRIES; retry++) {
-			timeout = rfc2131_sleep_interval(TIMEOUT, retry);
-			i = await_reply ( await_dns,
-				(query[QINDEX_QTYPE+h+1] << 8) +
-				((unsigned char *)query)[QINDEX_ID+1],
-				query, timeout);
-			// The parameters given are
-			//	bits 15...8 of integer = Query type  (low bits)
-			//	bits  7...0 of integer = Query index (low bits)
-			//	query + QINDEX_STORE_A points to the place
-			//	where A records	shall be stored (4 bytes);
-			//	query + 12(QINDEX_QUESTION) points to where
-			//	a CNAME should go in case one is received
-			if (i) break;
-		}
-		switch ( i ) {
-		  case	RET_GOT_ADDR:	// Address successfully retrieved
-			sprintf( deststring, "%@",
-				  (long)query[QINDEX_STORE_A  ]           +
-				( (long)query[QINDEX_STORE_A+1] * 256 ) +
-				( (long)query[QINDEX_STORE_A+2] * 65536 )+
-				( (long)query[QINDEX_STORE_A+3] * 16777216 ));
-			printf ( " -> IP [%s]\n", deststring );
-			return	RET_DNS_OK;
-		  case	RET_RUN_CNAME_Q: // No A record found, try CNAME
-			query[QINDEX_QTYPE+h  ]=(QUERYTYPE_CNAME & 0xff00)>> 8;
-			query[QINDEX_QTYPE+h+1]= QUERYTYPE_CNAME & 0xff;
-			break;
-		  case	RET_RUN_NEXT_A:
-			// Found a CNAME, now try A for the name it pointed to
-			for ( i = 0; query[QINDEX_QUESTION+i] != 0;
-					i += query[QINDEX_QUESTION+i] + 1 ) {;}
-			h = i - 1;
-			query[QINDEX_QTYPE+h  ]=(QUERYTYPE_A & 0xff00)>> 8;
-			query[QINDEX_QTYPE+h+1]= QUERYTYPE_A & 0xff;
-			break;
-		  case	RET_CNAME_FAIL:
-			// Neither A nor CNAME gave a usable result
-			printf ("Host name cannot be resolved\n");
-			return	RET_DNS_FAIL;
-		  case	RET_NOSUCHNAME:
-		  default:
-			printf ( "Name resolution failed\n" );
-			return	RET_DNS_FAIL;
-		}
-		query[QINDEX_ID  ] = 0;	// We will probably never have more
-					// than 256 queries in one run
-		query[QINDEX_ID+1]++;
-	}
-	// To deep recursion
-	printf ( "CNAME recursion to deep - abort name resolver\n" );
-	return	RET_DNS_FAIL;
-}
-#endif				/* DNS_RESOLVER */

src/include/dns.h

@@ -0,0 +1,81 @@
+#ifndef DNS_RESOLVER_H
+#define DNS_RESOLVER_H
+
+#include "stdint.h"
+#include "nic.h"
+#include "in.h"
+
+/*
+ * Constants
+ *
+ */
+
+#define DNS_TYPE_A		1
+#define DNS_TYPE_CNAME		5
+#define DNS_TYPE_ANY		255
+
+#define DNS_CLASS_IN		1
+#define DNS_CLASS_CS		2
+#define DNS_CLASS_CH		3
+#define DNS_CLASS_HS		4
+
+#define DNS_FLAG_QUERY		( 0x00 << 15 )
+#define DNS_FLAG_RESPONSE	( 0x01 << 15 )
+#define DNS_FLAG_QR(flags)	( (flags) & ( 0x01 << 15 ) )
+#define DNS_FLAG_OPCODE_QUERY	( 0x00 << 11 )
+#define DNS_FLAG_OPCODE_IQUERY	( 0x01 << 11 )
+#define DNS_FLAG_OPCODE_STATUS	( 0x02 << 11 )
+#define DNS_FLAG_OPCODE(flags)	( (flags) & ( 0x0f << 11 ) )
+#define DNS_FLAG_RD		( 0x01 << 8 )
+#define DNS_FLAG_RA		( 0x01 << 7 )
+#define DNS_FLAG_RCODE_OK	( 0x00 << 0 )
+#define DNS_FLAG_RCODE_NX	( 0x03 << 0 )
+#define DNS_FLAG_RCODE(flags)	( (flags) & ( 0x0f << 0 ) )
+
+#define	DNS_UDP_PORT		53
+#define	DNS_MAX_RETRIES		3
+#define	DNS_MAX_CNAME_RECURSION	0x30
+
+/*
+ * DNS protocol structures
+ *
+ */
+struct dns_header {
+	uint16_t	id;
+	uint16_t	flags;
+	uint16_t	qdcount;
+	uint16_t	ancount;
+	uint16_t	nscount;
+	uint16_t	arcount;
+} __attribute__ (( packed ));
+
+struct dns_query_info {
+	uint16_t	qtype;
+	uint16_t	qclass;
+} __attribute__ (( packed ));
+
+struct dns_query {
+	struct iphdr	ip;
+	struct udphdr	udp;
+	struct dns_header dns;
+	char		payload[ 256 + sizeof ( struct dns_query_info ) ];
+} __attribute__ (( packed ));
+
+struct dns_rr_info {
+	uint16_t	type;
+	uint16_t	class;
+	uint16_t	ttl;
+	uint16_t	rdlength;
+} __attribute__ (( packed ));
+
+struct dns_rr_info_a {
+	struct dns_rr_info;
+	struct in_addr in_addr;
+} __attribute__ (( packed ));
+
+struct dns_rr_info_cname {
+	struct dns_rr_info;
+	char		cname[0];
+};
+
+#endif /* DNS_RESOLVER_H */

src/include/dns_resolver.h

@@ -1,58 +0,0 @@
-// dns_resolver.h - #define statements for the DNS resolver
- 
-// We only need A and CNAME queries (later possibly AAAA/A6?)
-#define	QUERYTYPE_A	1
-#define	QUERYTYPE_CNAME	5
-
-// We only query with INTERNET class (not CHAOS or whatever)
-#define	QUERYCLASS_INET	1
-
-// Our first query will have the identifier <1> (arbitrary -
-// remember however that (256 - QUERYIDENTIFIER)/2 > MAX_CNAME_RECURSION !!!
-#define	QUERYIDENTIFIER	1
-
-// Query flags are standard values here
-#define	QUERYFLAGS	0x0100
-#define	QUERYFLAGS_MASK	0xf8
-#define	QUERYFLAGS_WANT	0x80
-
-// Indices inside the byte array that holds DNS queries/answers
-#define	QINDEX_ID	0
-#define	QINDEX_FLAGS	2
-#define	QINDEX_NUMQUEST	4
-#define	QINDEX_NUMANSW	6
-#define	QINDEX_NUMAUTH	8
-#define	QINDEX_NUMADDIT	10
-#define	QINDEX_QUESTION	12
-#define	QINDEX_QTYPE	14
-#define	QINDEX_QCLASS	16
-#define	QINDEX_STORE_A	256
-
-// Constant UDP port number for DNS traffic
-#define	UDP_PORT_DNS	53
-
-// Return values that the package parser may give
-//	This packet was not for us (broadcast or whatever)
-#define	RET_PACK_GARBAG	0
-//	Retrieved an address - query finishes
-#define	RET_GOT_ADDR	1
-//	No A record for that hostname - try running a CNAME query
-#define	RET_RUN_CNAME_Q	2
-//	The CNAME query returned a valid hostname - run A query on that
-#define	RET_RUN_NEXT_A	3
-//	The CNAME query failed - stop resolving
-#define	RET_CNAME_FAIL	4
-//	We have a reliable input that claims that the hostname does not exist
-#define	RET_NOSUCHNAME	5
-//	The name server response is somehow bogus/can not be parsed -> Abort
-#define	RET_DNSERROR	6
-
-// Return values that the query engine may give
-//	DNS query succeeded, IP address delivered
-#define	RET_DNS_OK	0
-//	DNS query failed
-#define	RET_DNS_FAIL	1
-
-// Error codes the DNS server can send to us
-#define	ERR_NOSUCHNAME	3
-

src/proto/dns.c

@@ -0,0 +1,333 @@
+/**************************************************************************
+*
+*    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.
+ *
+ */
+static struct dns_rr_info * dns_find_rr ( struct dns_query *query,
+					  struct dns_header *reply ) {
+	int i;
+	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-- ) {
+		if ( dns_name_cmp ( query->payload, p, reply ) == 0 ) {
+			return ( ( struct dns_rr_info * ) p );
+		}
+		p = dns_skip_name ( 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;
+}
+
+/*
+ * 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;
+
+	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;
+
+				DBG ( "DNS found CNAME\n" );
+				query_info = ( void * )
+					dns_decompress_name ( query.payload,
+							      cname, reply );
+				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" );
+		}
+	}
+}
+
+static struct resolver dns_resolver __resolver = {
+	.name = "DNS",
+	.resolv = dns_resolv,
+};