a59cfcfd08
If two or more rapid dns requests for the same server are done from different threads it turns into separate dns reques, if the response of the request isn't found in the cache. This patch avoid multiple request for the same server by letting subsequents request wait until the first request has finished. Change-Id: Ic72ea0e7d3964a4164eddf866feb4357ec4dfe54
105 lines
4.4 KiB
C
105 lines
4.4 KiB
C
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _RESOLV_CACHE_H_
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#define _RESOLV_CACHE_H_
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struct resolv_cache; /* forward */
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/* gets the cache for the default interface. Might be NULL*/
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extern struct resolv_cache* __get_res_cache(void);
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/* get the cache for a specified interface. Can be NULL*/
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extern struct resolv_cache* __get_res_cache_for_iface(const char* ifname);
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/* this gets called everytime we detect some changes in the DNS configuration
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* and will flush the cache */
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extern void _resolv_cache_reset( unsigned generation );
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/* Gets the address of the n:th name server for the default interface
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* Return length of address on success else 0.
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* Note: The first name server is at n = 1 */
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extern int _resolv_cache_get_nameserver(int n, char* addr, int addrLen);
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/* Gets the address of the n:th name server for a certain interface
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* Return length of address on success else 0.
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* Note: The first name server is at n = 1 */
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extern int _resolv_cache_get_nameserver_for_iface(const char* ifname, int n,
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char* addr, int addrLen);
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/* Gets addrinfo of the n:th name server associated with an interface.
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* NULL is returned if no address if found.
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* Note: The first name server is at n = 1. */
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extern struct addrinfo* _resolv_cache_get_nameserver_addr_for_iface(const char* ifname, int n);
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/* Gets addrinfo of the n:th name server associated with the default interface
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* NULL is returned if no address if found.
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* Note: The first name server is at n = 1. */
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extern struct addrinfo* _resolv_cache_get_nameserver_addr(int n);
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/* gets the address associated with the default interface */
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extern struct in_addr* _resolv_get_addr_of_default_iface();
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/* gets the address associated with the specified interface */
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extern struct in_addr* _resolv_get_addr_of_iface(const char* ifname);
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/* Get name of default interface */
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extern char* _resolv_get_default_iface();
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typedef enum {
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RESOLV_CACHE_UNSUPPORTED, /* the cache can't handle that kind of queries */
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/* or the answer buffer is too small */
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RESOLV_CACHE_NOTFOUND, /* the cache doesn't know about this query */
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RESOLV_CACHE_FOUND /* the cache found the answer */
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} ResolvCacheStatus;
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extern ResolvCacheStatus
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_resolv_cache_lookup( struct resolv_cache* cache,
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const void* query,
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int querylen,
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void* answer,
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int answersize,
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int *answerlen );
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/* add a (query,answer) to the cache, only call if _resolv_cache_lookup
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* did return RESOLV_CACHE_NOTFOUND
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*/
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extern void
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_resolv_cache_add( struct resolv_cache* cache,
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const void* query,
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int querylen,
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const void* answer,
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int answerlen );
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/* Notify the cache a request failed */
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extern void
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_resolv_cache_query_failed( struct resolv_cache* cache,
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const void* query,
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int querylen);
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#endif /* _RESOLV_CACHE_H_ */
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