229N/A

229N/A Name Decompression

229N/A

229N/A $Id: decompression,v 1.3 1999/02/24 06:31:31 marka Exp $

229N/A

229N/AOverview.

229N/A

229N/A There are 4 type of compression: global 14 bit, global 16 bit,

229N/A local 14 bit and local 16 bit.

229N/A

229N/A In general the resolver / nameserver should accept any compression

229N/A method at any time regardless of whether it was legal to

229N/A send it. This fits with the priciple of being liberal with

229N/A what you accept and strict with what you send.

229N/A

229N/A There are a few cases where it does not make sence to accept

229N/A compression pointers of a given type. i.e. the first domain name

229N/A in a message, local compression pointers in the ownername of a RR

229N/A or in a question.

229N/A

229N/A When performing regression testing however we should be as strict

229N/A as possible. Hence we need to be able modifiy the behaviour of the

229N/A decompression routines.

229N/A

229N/A To be able to decompress a domain name we need some or all of the

229N/A following pieces of information.

229N/A

229N/A 1. where the message starts.

229N/A 2. where the current rdata starts in the message (local compression).

229N/A 3. what the current owner name is (local compression).

229N/A 4. where the domainname we are decompressing starts.

229N/A 5. what are allowable decompression method. These vary across type

229N/A and edn version.

229N/A

229N/AImplementation:

229N/A

229N/A dns_rdata_fromwire will set the allowed decompression methods allowed

229N/A by looking at edns, strict and the type values.

229N/A

229N/ATypes:

229N/A struct dns_decompress {

229N/A unsigned int magic;

229N/A unsigned int allowed;

229N/A int edns;

229N/A dns_name_t owner_name;

229N/A unsigned int rdata;

229N/A isc_boolean_t strict;

229N/A }

229N/A

229N/AFunctions:

229N/A

229N/A void

229N/A dns_decompress_init(dns_decompress_t *dctx, int edns,

229N/A isc_boolean_t strict);

229N/A initalise dctx

229N/A dctx->ownername is invalidated

229N/A

229N/A void

229N/A dns_decompress_localinit(dns_decompress_t *dctx, dns_name_t *name,

229N/A isc_buffer_t *source);

229N/A initalise dctx->ownername

229N/A record source->current to dctx->rdata

229N/A

229N/A void

229N/A dns_decompress_invalidate(dns_decompress_t *dctx);

229N/A

229N/A invalidate dctx

229N/A

229N/A void

229N/A dns_decompress_localinvalidate(dns_decompress_t *dctx);

invalidate dctx->ownername

void

dns_decompress_setmethods(dns_decompress_t *dctx, unsigned int allowed);

sets dctx->allowed

unsigned int

dns_decompress_getmethods(dns_decompress_t *dctx);

returns dctx->allowed

int

dns_decompress_edns(dns_decompress_t *dctx);

returns dctx->edns

isc_boolean_t

dns_decompress_strict(dns_decompress_t *dctx);

returns dctx->strict

dns_result_t

dns_name_fromwire(dns_name_t *name, isc_buffer_t *source,

dns_decompress_t *dctx, isc_boolean_t downcase,

isc_buffer_t *target)