Collaboration diagram for IP Cache API:

Modules
	IP Cache Internals

Classes
class	ipcache_entry

Functions
void	ipcache_purgelru (void *)

void	ipcache_nbgethostbyname (const char name, IPH handler, void *handlerData)

void	ipcache_init (void)

const ipcache_addrs *	ipcache_gethostbyname (const char *name, int flags)

void	ipcacheInvalidate (const char *name)

void	ipcacheInvalidateNegative (const char *name)

static const Dns::CachedIps *	ipcacheCheckNumeric (const char *name)

void	ipcacheMarkGoodAddr (const char *name, const Ip::Address &addr)

void	ipcache_restart (void)

int	ipcacheAddEntryFromHosts (const char name, const char ipaddr)

variable_list *	snmp_netIpFn (variable_list Var, snint ErrP)

Detailed Description

Introduction

: The IP 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 IP cache usually doesn't block on a request except for special cases where this is desired (see below).

Function Documentation

◆ ipcache_gethostbyname()

const ipcache_addrs * ipcache_gethostbyname	(	const char *	name,
		int	flags
	)

Is different from ipcache_nbgethostbyname in that it only checks if an entry exists in the cache and does not by default contact the DNS, unless this is requested, by setting the flags.

Parameters

name	Host name to resolve.
flags	Default is NULL, set to IP_LOOKUP_IF_MISS to explicitly perform DNS lookups.

Return values

NULL	An error occurred during lookup
NULL	No results available in cache and no lookup specified
*	Pointer to the ipcahce_addrs structure containing the lookup results

Definition at line 728 of file ipcache.cc.

References ipcache_entry::addrs, assert, debugs, ipcache_entry::flags, _ipcache_stats::hits, IP_LOOKUP_IF_MISS, ipcache_get(), ipcache_nbgethostbyname(), ipcacheCheckNumeric(), ipcacheExpiredEntry(), ipcacheRelease(), IpcacheStats, ipcache_entry::lastref, _ipcache_stats::misses, _ipcache_stats::negative_hits, ipcache_entry::Flags::negcached, _ipcache_stats::numeric_hits, _ipcache_stats::requests, and squid_curtime.

Referenced by Acl::DestinationAsnCheck::match(), ACLDestinationIP::match(), and netdbClosestParent().

◆ ipcache_init()

void ipcache_init ( void )

Initialize the ipcache. Is called from mainInitialize() after disk initialization and prior to the reverse FQDNCache initialization

Definition at line 695 of file ipcache.cc.

References Config, debugs, hash4, hash_create(), hashPrime(), SquidConfig::high, Important, ip_table, SquidConfig::ipcache, ipcache_high, ipcache_low, ipcacheRegisterWithCacheManager(), IpcacheStats, SquidConfig::low, lru_list, and SquidConfig::size.

Referenced by mainInitialize().

◆ ipcache_nbgethostbyname()

void ipcache_nbgethostbyname	(	const char *	name,
		IPH *	handler,
		void *	handlerData
	)

Parameters

name	Host to resolve.
handler	Pointer to the function to be called when the reply from the IP cache (or the DNS if the IP cache misses)
handlerData	Information that is passed to the handler and does not affect the IP cache.

XXX: on hits and some errors, the handler is called immediately instead of scheduling an async call. This reentrant behavior means that the user job must be extra careful after calling ipcache_nbgethostbyname, especially if the handler destroys the job. Moreover, the job has no way of knowing whether the reentrant call happened. Comm::Connection setup usually protects the job by scheduling an async call, but some user code calls ipcache_nbgethostbyname directly.

Definition at line 608 of file ipcache.cc.

References debugs, handler(), and ipcache_nbgethostbyname_().

Referenced by DestinationIPLookup::checkForAsync(), ClientRequestContext::hostHeaderVerify(), icpIncomingConnectionOpened(), ipcache_gethostbyname(), netdbPingSite(), Adaptation::Icap::Xaction::openConnection(), peerAlive(), and peerRefreshDNS().