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100 lines
2.6 KiB
Plaintext
100 lines
2.6 KiB
Plaintext
Copyright (C) 1999, 2000 Internet Software Consortium.
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See COPYRIGHT in the source root or http://www.isc.org/copyright for terms.
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Name Decompression
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$Id: decompression,v 1.5 2000/08/01 01:18:09 tale Exp $
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Overview.
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There are 4 type of compression: global 14 bit, global 16 bit,
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local 14 bit and local 16 bit.
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In general the resolver / nameserver should accept any compression
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method at any time regardless of whether it was legal to
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send it. This fits with the priciple of being liberal with
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what you accept and strict with what you send.
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There are a few cases where it does not make sence to accept
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compression pointers of a given type. i.e. the first domain name
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in a message, local compression pointers in the ownername of a RR
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or in a question.
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When performing regression testing however we should be as strict
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as possible. Hence we need to be able modifiy the behaviour of the
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decompression routines.
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To be able to decompress a domain name we need some or all of the
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following pieces of information.
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1. where the message starts.
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2. where the current rdata starts in the message (local compression).
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3. what the current owner name is (local compression).
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4. where the domainname we are decompressing starts.
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5. what are allowable decompression method. These vary across type
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and edn version.
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Implementation:
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dns_rdata_fromwire will set the allowed decompression methods allowed
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by looking at edns, strict and the type values.
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Types:
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struct dns_decompress {
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unsigned int magic;
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unsigned int allowed;
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int edns;
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dns_name_t owner_name;
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unsigned int rdata;
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isc_boolean_t strict;
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}
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Functions:
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void
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dns_decompress_init(dns_decompress_t *dctx, int edns,
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isc_boolean_t strict);
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initalise dctx
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dctx->ownername is invalidated
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void
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dns_decompress_localinit(dns_decompress_t *dctx, dns_name_t *name,
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isc_buffer_t *source);
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initalise dctx->ownername
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record source->current to dctx->rdata
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void
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dns_decompress_invalidate(dns_decompress_t *dctx);
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invalidate dctx
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void
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dns_decompress_localinvalidate(dns_decompress_t *dctx);
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invalidate dctx->ownername
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void
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dns_decompress_setmethods(dns_decompress_t *dctx, unsigned int allowed);
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sets dctx->allowed
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unsigned int
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dns_decompress_getmethods(dns_decompress_t *dctx);
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returns dctx->allowed
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int
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dns_decompress_edns(dns_decompress_t *dctx);
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returns dctx->edns
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isc_boolean_t
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dns_decompress_strict(dns_decompress_t *dctx);
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returns dctx->strict
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dns_result_t
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dns_name_fromwire(dns_name_t *name, isc_buffer_t *source,
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dns_decompress_t *dctx, isc_boolean_t downcase,
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isc_buffer_t *target)
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