Collaboration diagram for FQDN Cache API:

Modules
	FQDN Cache Internals

Functions
void	fqdncache_purgelru (void *)

static void	purge_entries_fromhosts (void)

static void	fqdncacheHandleReply (void data, const rfc1035_rr answers, int na, const char *error_message, const bool lastAnswer)

void	fqdncache_nbgethostbyaddr (const Ip::Address &addr, FQDNH handler, void handlerData)

const char *	fqdncache_gethostbyaddr (const Ip::Address &addr, int flags)

void	fqdncacheFreeMemory (void)

void	fqdncache_restart (void)

void	fqdncache_init (void)

variable_list *	snmp_netFqdnFn (variable_list Var, snint ErrP)

Detailed Description

Introduction

: The FQDN cache is a built-in component of squid providing Hostname to IP-Number translation functionality and managing the involved data-structures. Efficiency concerns require mechanisms that allow non-blocking access to these mappings. The FQDN cache usually doesn't block on a request except for special cases where this is desired (see below).

Function Documentation

const char* fqdncache_gethostbyaddr	(	const Ip::Address &	addr,
		int	flags
	)

Is different in that it only checks if an entry exists in it's data-structures and does not by default contact the DNS, unless this is requested, by setting the flags to FQDN_LOOKUP_IF_MISS.

Parameters

addr	address of the FQDN being resolved
flags	values are NULL or FQDN_LOOKUP_IF_MISS. default is NULL.

Definition at line 480 of file fqdncache.cc.

References fqdncache_entry::flags, FQDN_LOOKUP_IF_MISS, fqdncache_get(), fqdncache_nbgethostbyaddr(), fqdncacheExpiredEntry(), fqdncacheRelease(), FqdncacheStats, _fqdn_cache_stats::hits, Ip::Address::isAnyAddr(), Ip::Address::isNoAddr(), fqdncache_entry::lastref, MAX_IPSTRLEN, _fqdn_cache_stats::misses, fqdncache_entry::names, _fqdn_cache_stats::negative_hits, fqdncache_entry::Flags::negcached, NULL, _fqdn_cache_stats::requests, squid_curtime, and Ip::Address::toStr().

Referenced by Format::Format::assemble(), clientdbDump(), ACLSourceDomainStrategy::match(), ACLDestinationDomainStrategy::match(), Log::Format::SquidIcap(), and ConnStateData::whenClientIpKnown().

void fqdncache_init ( void )

Initialize the fqdncache. Called after IP cache initialization.

Definition at line 698 of file fqdncache.cc.

References Config, debugs, FQDN_HIGH_WATER, FQDN_LOW_WATER, SquidConfig::fqdncache, fqdncache_high, fqdncache_low, fqdncacheRegisterWithCacheManager(), FqdncacheStats, hash4, hash_create(), hashPrime(), and SquidConfig::size.

Referenced by mainInitialize().

void fqdncache_nbgethostbyaddr	(	const Ip::Address &	addr,
		FQDNH *	handler,
		void *	handlerData
	)

Parameters

addr	IP address of domain to resolve.
handler	A pointer to the function to be called when the reply from the FQDN cache (or the DNS if the FQDN cache misses)
handlerData	Information that is passed to the handler and does not affect the FQDN cache.

Definition at line 413 of file fqdncache.cc.

References cbdataReference, current_time, debugs, fqdncache_entry::flags, fqdncache_get(), fqdncacheCallback(), fqdncacheExpiredEntry(), fqdncacheHandleReply, fqdncacheRelease(), FqdncacheStats, fqdncache_entry::handler, handler(), fqdncache_entry::handlerData, _fqdn_cache_stats::hits, idnsPTRLookup(), MAX_IPSTRLEN, _fqdn_cache_stats::misses, _fqdn_cache_stats::negative_hits, fqdncache_entry::Flags::negcached, NULL, fqdncache_entry::request_time, _fqdn_cache_stats::requests, and Ip::Address::toStr().