1462 lines
39 KiB
C
1462 lines
39 KiB
C
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/*
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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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#include "resolv_cache.h"
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include "pthread.h"
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/* This code implements a small and *simple* DNS resolver cache.
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*
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* It is only used to cache DNS answers for a maximum of CONFIG_SECONDS seconds
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* in order to reduce DNS traffic. It is not supposed to be a full DNS cache,
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* since we plan to implement that in the future in a dedicated process running
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* on the system.
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*
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* Note that its design is kept simple very intentionally, i.e.:
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*
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* - it takes raw DNS query packet data as input, and returns raw DNS
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* answer packet data as output
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*
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* (this means that two similar queries that encode the DNS name
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* differently will be treated distinctly).
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*
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* - the TTLs of answer RRs are ignored. our DNS resolver library does not use
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* them anyway, but it means that records with a TTL smaller than
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* CONFIG_SECONDS will be kept in the cache anyway.
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*
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* this is bad, but we absolutely want to avoid parsing the answer packets
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* (and should be solved by the later full DNS cache process).
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*
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* - the implementation is just a (query-data) => (answer-data) hash table
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* with a trivial least-recently-used expiration policy.
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*
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* Doing this keeps the code simple and avoids to deal with a lot of things
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* that a full DNS cache is expected to do.
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*
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* The API is also very simple:
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*
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* - the client calls _resolv_cache_get() to obtain a handle to the cache.
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* this will initialize the cache on first usage. the result can be NULL
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* if the cache is disabled.
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*
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* - the client calls _resolv_cache_lookup() before performing a query
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*
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* if the function returns RESOLV_CACHE_FOUND, a copy of the answer data
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* has been copied into the client-provided answer buffer.
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*
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* if the function returns RESOLV_CACHE_NOTFOUND, the client should perform
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* a request normally, *then* call _resolv_cache_add() to add the received
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* answer to the cache.
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*
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* if the function returns RESOLV_CACHE_UNSUPPORTED, the client should
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* perform a request normally, and *not* call _resolv_cache_add()
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*
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* note that RESOLV_CACHE_UNSUPPORTED is also returned if the answer buffer
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* is too short to accomodate the cached result.
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*
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* - when network settings change, the cache must be flushed since the list
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* of DNS servers probably changed. this is done by calling
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* _resolv_cache_reset()
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*
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* the parameter to this function must be an ever-increasing generation
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* number corresponding to the current network settings state.
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*
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* This is done because several threads could detect the same network
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* settings change (but at different times) and will all end up calling the
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* same function. Comparing with the last used generation number ensures
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* that the cache is only flushed once per network change.
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*/
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/* the name of an environment variable that will be checked the first time
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* this code is called if its value is "0", then the resolver cache is
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* disabled.
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*/
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#define CONFIG_ENV "BIONIC_DNSCACHE"
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/* entries older than CONFIG_SECONDS seconds are always discarded.
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*/
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#define CONFIG_SECONDS (60*10) /* 10 minutes */
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/* maximum number of entries kept in the cache. This value has been
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* determined by browsing through various sites and counting the number
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* of corresponding requests. Keep in mind that our framework is currently
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* performing two requests per name lookup (one for IPv4, the other for IPv6)
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*
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* www.google.com 4
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* www.ysearch.com 6
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* www.amazon.com 8
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* www.nytimes.com 22
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* www.espn.com 28
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* www.msn.com 28
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* www.lemonde.fr 35
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*
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* (determined in 2009-2-17 from Paris, France, results may vary depending
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* on location)
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*
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* most high-level websites use lots of media/ad servers with different names
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* but these are generally reused when browsing through the site.
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*
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* As such, a valud of 64 should be relatively conformtable at the moment.
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*/
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#define CONFIG_MAX_ENTRIES 64
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/****************************************************************************/
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/****************************************************************************/
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/***** *****/
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/***** *****/
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/***** *****/
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/****************************************************************************/
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/****************************************************************************/
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/* set to 1 to debug cache operations */
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#define DEBUG 0
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/* set to 1 to debug query data */
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#define DEBUG_DATA 0
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#if DEBUG
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# include <logd.h>
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# define XLOG(...) \
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__libc_android_log_print(ANDROID_LOG_DEBUG,"libc",__VA_ARGS__)
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#include <stdio.h>
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#include <stdarg.h>
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/** BOUNDED BUFFER FORMATTING
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**/
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/* technical note:
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*
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* the following debugging routines are used to append data to a bounded
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* buffer they take two parameters that are:
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*
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* - p : a pointer to the current cursor position in the buffer
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* this value is initially set to the buffer's address.
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*
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* - end : the address of the buffer's limit, i.e. of the first byte
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* after the buffer. this address should never be touched.
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*
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* IMPORTANT: it is assumed that end > buffer_address, i.e.
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* that the buffer is at least one byte.
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*
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* the _bprint_() functions return the new value of 'p' after the data
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* has been appended, and also ensure the following:
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*
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* - the returned value will never be strictly greater than 'end'
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*
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* - a return value equal to 'end' means that truncation occured
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* (in which case, end[-1] will be set to 0)
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*
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* - after returning from a _bprint_() function, the content of the buffer
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* is always 0-terminated, even in the event of truncation.
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*
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* these conventions allow you to call _bprint_ functions multiple times and
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* only check for truncation at the end of the sequence, as in:
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*
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* char buff[1000], *p = buff, *end = p + sizeof(buff);
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*
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* p = _bprint_c(p, end, '"');
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* p = _bprint_s(p, end, my_string);
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* p = _bprint_c(p, end, '"');
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*
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* if (p >= end) {
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* // buffer was too small
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* }
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*
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* printf( "%s", buff );
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*/
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/* add a char to a bounded buffer */
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static char*
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_bprint_c( char* p, char* end, int c )
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{
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if (p < end) {
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if (p+1 == end)
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*p++ = 0;
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else {
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*p++ = (char) c;
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*p = 0;
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}
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}
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return p;
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}
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/* add a sequence of bytes to a bounded buffer */
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static char*
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_bprint_b( char* p, char* end, const char* buf, int len )
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{
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int avail = end - p;
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if (avail <= 0 || len <= 0)
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return p;
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if (avail > len)
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avail = len;
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memcpy( p, buf, avail );
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p += avail;
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if (p < end)
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p[0] = 0;
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else
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end[-1] = 0;
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return p;
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}
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/* add a string to a bounded buffer */
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static char*
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_bprint_s( char* p, char* end, const char* str )
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{
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return _bprint_b(p, end, str, strlen(str));
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}
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/* add a formatted string to a bounded buffer */
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static char*
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_bprint( char* p, char* end, const char* format, ... )
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{
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int avail, n;
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va_list args;
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avail = end - p;
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if (avail <= 0)
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return p;
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va_start(args, format);
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n = snprintf( p, avail, format, args);
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va_end(args);
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/* certain C libraries return -1 in case of truncation */
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if (n < 0 || n > avail)
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n = avail;
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p += n;
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/* certain C libraries do not zero-terminate in case of truncation */
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if (p == end)
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p[-1] = 0;
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return p;
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}
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/* add a hex value to a bounded buffer, up to 8 digits */
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static char*
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_bprint_hex( char* p, char* end, unsigned value, int numDigits )
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{
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char text[sizeof(unsigned)*2];
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int nn = 0;
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while (numDigits-- > 0) {
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text[nn++] = "0123456789abcdef"[(value >> (numDigits*4)) & 15];
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}
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return _bprint_b(p, end, text, nn);
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}
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/* add the hexadecimal dump of some memory area to a bounded buffer */
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static char*
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_bprint_hexdump( char* p, char* end, const uint8_t* data, int datalen )
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{
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int lineSize = 16;
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while (datalen > 0) {
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int avail = datalen;
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int nn;
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if (avail > lineSize)
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avail = lineSize;
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for (nn = 0; nn < avail; nn++) {
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if (nn > 0)
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p = _bprint_c(p, end, ' ');
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p = _bprint_hex(p, end, data[nn], 2);
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}
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for ( ; nn < lineSize; nn++ ) {
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p = _bprint_s(p, end, " ");
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}
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p = _bprint_s(p, end, " ");
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for (nn = 0; nn < avail; nn++) {
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int c = data[nn];
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if (c < 32 || c > 127)
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c = '.';
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p = _bprint_c(p, end, c);
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}
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p = _bprint_c(p, end, '\n');
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data += avail;
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datalen -= avail;
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}
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return p;
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}
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/* dump the content of a query of packet to the log */
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static void
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XLOG_BYTES( const void* base, int len )
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{
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char buff[1024];
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char* p = buff, *end = p + sizeof(buff);
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p = _bprint_hexdump(p, end, base, len);
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XLOG("%s",buff);
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}
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#else /* !DEBUG */
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# define XLOG(...) ((void)0)
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# define XLOG_BYTES(a,b) ((void)0)
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#endif
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static time_t
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_time_now( void )
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{
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struct timeval tv;
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gettimeofday( &tv, NULL );
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return tv.tv_sec;
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}
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/* reminder: the general format of a DNS packet is the following:
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*
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* HEADER (12 bytes)
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* QUESTION (variable)
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* ANSWER (variable)
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* AUTHORITY (variable)
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* ADDITIONNAL (variable)
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*
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* the HEADER is made of:
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*
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* ID : 16 : 16-bit unique query identification field
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*
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* QR : 1 : set to 0 for queries, and 1 for responses
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* Opcode : 4 : set to 0 for queries
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* AA : 1 : set to 0 for queries
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* TC : 1 : truncation flag, will be set to 0 in queries
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* RD : 1 : recursion desired
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*
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* RA : 1 : recursion available (0 in queries)
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* Z : 3 : three reserved zero bits
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* RCODE : 4 : response code (always 0=NOERROR in queries)
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|
*
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* QDCount: 16 : question count
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||
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* ANCount: 16 : Answer count (0 in queries)
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||
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* NSCount: 16: Authority Record count (0 in queries)
|
||
|
* ARCount: 16: Additionnal Record count (0 in queries)
|
||
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*
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* the QUESTION is made of QDCount Question Record (QRs)
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* the ANSWER is made of ANCount RRs
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* the AUTHORITY is made of NSCount RRs
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* the ADDITIONNAL is made of ARCount RRs
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*
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* Each Question Record (QR) is made of:
|
||
|
*
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||
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* QNAME : variable : Query DNS NAME
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* TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255)
|
||
|
* CLASS : 16 : class of query (IN=1)
|
||
|
*
|
||
|
* Each Resource Record (RR) is made of:
|
||
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*
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* NAME : variable : DNS NAME
|
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* TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255)
|
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* CLASS : 16 : class of query (IN=1)
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|
* TTL : 32 : seconds to cache this RR (0=none)
|
||
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* RDLENGTH: 16 : size of RDDATA in bytes
|
||
|
* RDDATA : variable : RR data (depends on TYPE)
|
||
|
*
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||
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* Each QNAME contains a domain name encoded as a sequence of 'labels'
|
||
|
* terminated by a zero. Each label has the following format:
|
||
|
*
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||
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* LEN : 8 : lenght of label (MUST be < 64)
|
||
|
* NAME : 8*LEN : label length (must exclude dots)
|
||
|
*
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||
|
* A value of 0 in the encoding is interpreted as the 'root' domain and
|
||
|
* terminates the encoding. So 'www.android.com' will be encoded as:
|
||
|
*
|
||
|
* <3>www<7>android<3>com<0>
|
||
|
*
|
||
|
* Where <n> represents the byte with value 'n'
|
||
|
*
|
||
|
* Each NAME reflects the QNAME of the question, but has a slightly more
|
||
|
* complex encoding in order to provide message compression. This is achieved
|
||
|
* by using a 2-byte pointer, with format:
|
||
|
*
|
||
|
* TYPE : 2 : 0b11 to indicate a pointer, 0b01 and 0b10 are reserved
|
||
|
* OFFSET : 14 : offset to another part of the DNS packet
|
||
|
*
|
||
|
* The offset is relative to the start of the DNS packet and must point
|
||
|
* A pointer terminates the encoding.
|
||
|
*
|
||
|
* The NAME can be encoded in one of the following formats:
|
||
|
*
|
||
|
* - a sequence of simple labels terminated by 0 (like QNAMEs)
|
||
|
* - a single pointer
|
||
|
* - a sequence of simple labels terminated by a pointer
|
||
|
*
|
||
|
* A pointer shall always point to either a pointer of a sequence of
|
||
|
* labels (which can themselves be terminated by either a 0 or a pointer)
|
||
|
*
|
||
|
* The expanded length of a given domain name should not exceed 255 bytes.
|
||
|
*
|
||
|
* NOTE: we don't parse the answer packets, so don't need to deal with NAME
|
||
|
* records, only QNAMEs.
|
||
|
*/
|
||
|
|
||
|
#define DNS_HEADER_SIZE 12
|
||
|
|
||
|
#define DNS_TYPE_A "\00\01" /* big-endian decimal 1 */
|
||
|
#define DNS_TYPE_PTR "\00\014" /* big-endian decimal 12 */
|
||
|
#define DNS_TYPE_MX "\00\017" /* big-endian decimal 15 */
|
||
|
#define DNS_TYPE_AAAA "\00\034" /* big-endian decimal 28 */
|
||
|
#define DNS_TYPE_ALL "\00\0377" /* big-endian decimal 255 */
|
||
|
|
||
|
#define DNS_CLASS_IN "\00\01" /* big-endian decimal 1 */
|
||
|
|
||
|
typedef struct {
|
||
|
const uint8_t* base;
|
||
|
const uint8_t* end;
|
||
|
const uint8_t* cursor;
|
||
|
} DnsPacket;
|
||
|
|
||
|
static void
|
||
|
_dnsPacket_init( DnsPacket* packet, const uint8_t* buff, int bufflen )
|
||
|
{
|
||
|
packet->base = buff;
|
||
|
packet->end = buff + bufflen;
|
||
|
packet->cursor = buff;
|
||
|
}
|
||
|
|
||
|
static void
|
||
|
_dnsPacket_rewind( DnsPacket* packet )
|
||
|
{
|
||
|
packet->cursor = packet->base;
|
||
|
}
|
||
|
|
||
|
static void
|
||
|
_dnsPacket_skip( DnsPacket* packet, int count )
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor + count;
|
||
|
|
||
|
if (p > packet->end)
|
||
|
p = packet->end;
|
||
|
|
||
|
packet->cursor = p;
|
||
|
}
|
||
|
|
||
|
static int
|
||
|
_dnsPacket_readInt16( DnsPacket* packet )
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor;
|
||
|
|
||
|
if (p+2 > packet->end)
|
||
|
return -1;
|
||
|
|
||
|
packet->cursor = p+2;
|
||
|
return (p[0]<< 8) | p[1];
|
||
|
}
|
||
|
|
||
|
/** QUERY CHECKING
|
||
|
**/
|
||
|
|
||
|
/* check bytes in a dns packet. returns 1 on success, 0 on failure.
|
||
|
* the cursor is only advanced in the case of success
|
||
|
*/
|
||
|
static int
|
||
|
_dnsPacket_checkBytes( DnsPacket* packet, int numBytes, const void* bytes )
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor;
|
||
|
|
||
|
if (p + numBytes > packet->end)
|
||
|
return 0;
|
||
|
|
||
|
if (memcmp(p, bytes, numBytes) != 0)
|
||
|
return 0;
|
||
|
|
||
|
packet->cursor = p + numBytes;
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
/* parse and skip a given QNAME stored in a query packet,
|
||
|
* from the current cursor position. returns 1 on success,
|
||
|
* or 0 for malformed data.
|
||
|
*/
|
||
|
static int
|
||
|
_dnsPacket_checkQName( DnsPacket* packet )
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor;
|
||
|
const uint8_t* end = packet->end;
|
||
|
|
||
|
for (;;) {
|
||
|
int c;
|
||
|
|
||
|
if (p >= end)
|
||
|
break;
|
||
|
|
||
|
c = *p++;
|
||
|
|
||
|
if (c == 0) {
|
||
|
packet->cursor = p;
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
/* we don't expect label compression in QNAMEs */
|
||
|
if (c >= 64)
|
||
|
break;
|
||
|
|
||
|
p += c;
|
||
|
/* we rely on the bound check at the start
|
||
|
* of the loop here */
|
||
|
}
|
||
|
/* malformed data */
|
||
|
XLOG("malformed QNAME");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* parse and skip a given QR stored in a packet.
|
||
|
* returns 1 on success, and 0 on failure
|
||
|
*/
|
||
|
static int
|
||
|
_dnsPacket_checkQR( DnsPacket* packet )
|
||
|
{
|
||
|
int len;
|
||
|
|
||
|
if (!_dnsPacket_checkQName(packet))
|
||
|
return 0;
|
||
|
|
||
|
/* TYPE must be one of the things we support */
|
||
|
if (!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_A) &&
|
||
|
!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_PTR) &&
|
||
|
!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_MX) &&
|
||
|
!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_AAAA) &&
|
||
|
!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_ALL))
|
||
|
{
|
||
|
XLOG("unsupported TYPE");
|
||
|
return 0;
|
||
|
}
|
||
|
/* CLASS must be IN */
|
||
|
if (!_dnsPacket_checkBytes(packet, 2, DNS_CLASS_IN)) {
|
||
|
XLOG("unsupported CLASS");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
/* check the header of a DNS Query packet, return 1 if it is one
|
||
|
* type of query we can cache, or 0 otherwise
|
||
|
*/
|
||
|
static int
|
||
|
_dnsPacket_checkQuery( DnsPacket* packet )
|
||
|
{
|
||
|
const uint8_t* p = packet->base;
|
||
|
int qdCount, anCount, dnCount, arCount;
|
||
|
|
||
|
if (p + DNS_HEADER_SIZE > packet->end) {
|
||
|
XLOG("query packet too small");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* QR must be set to 0, opcode must be 0 and AA must be 0 */
|
||
|
/* RA, Z, and RCODE must be 0 */
|
||
|
if ((p[2] & 0xFC) != 0 || p[3] != 0) {
|
||
|
XLOG("query packet flags unsupported");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* Note that we ignore the TC and RD bits here for the
|
||
|
* following reasons:
|
||
|
*
|
||
|
* - there is no point for a query packet sent to a server
|
||
|
* to have the TC bit set, but the implementation might
|
||
|
* set the bit in the query buffer for its own needs
|
||
|
* between a _resolv_cache_lookup and a
|
||
|
* _resolv_cache_add. We should not freak out if this
|
||
|
* is the case.
|
||
|
*
|
||
|
* - we consider that the result from a RD=0 or a RD=1
|
||
|
* query might be different, hence that the RD bit
|
||
|
* should be used to differentiate cached result.
|
||
|
*
|
||
|
* this implies that RD is checked when hashing or
|
||
|
* comparing query packets, but not TC
|
||
|
*/
|
||
|
|
||
|
/* ANCOUNT, DNCOUNT and ARCOUNT must be 0 */
|
||
|
qdCount = (p[4] << 8) | p[5];
|
||
|
anCount = (p[6] << 8) | p[7];
|
||
|
dnCount = (p[8] << 8) | p[9];
|
||
|
arCount = (p[10]<< 8) | p[11];
|
||
|
|
||
|
if (anCount != 0 || dnCount != 0 || arCount != 0) {
|
||
|
XLOG("query packet contains non-query records");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
if (qdCount == 0) {
|
||
|
XLOG("query packet doesn't contain query record");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* Check QDCOUNT QRs */
|
||
|
packet->cursor = p + DNS_HEADER_SIZE;
|
||
|
|
||
|
for (;qdCount > 0; qdCount--)
|
||
|
if (!_dnsPacket_checkQR(packet))
|
||
|
return 0;
|
||
|
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
/** QUERY DEBUGGING
|
||
|
**/
|
||
|
#if DEBUG
|
||
|
static char*
|
||
|
_dnsPacket_bprintQName(DnsPacket* packet, char* bp, char* bend)
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor;
|
||
|
const uint8_t* end = packet->end;
|
||
|
int first = 1;
|
||
|
|
||
|
for (;;) {
|
||
|
int c;
|
||
|
|
||
|
if (p >= end)
|
||
|
break;
|
||
|
|
||
|
c = *p++;
|
||
|
|
||
|
if (c == 0) {
|
||
|
packet->cursor = p;
|
||
|
return bp;
|
||
|
}
|
||
|
|
||
|
/* we don't expect label compression in QNAMEs */
|
||
|
if (c >= 64)
|
||
|
break;
|
||
|
|
||
|
if (first)
|
||
|
first = 0;
|
||
|
else
|
||
|
bp = _bprint_c(bp, bend, '.');
|
||
|
|
||
|
bp = _bprint_b(bp, bend, (const char*)p, c);
|
||
|
|
||
|
p += c;
|
||
|
/* we rely on the bound check at the start
|
||
|
* of the loop here */
|
||
|
}
|
||
|
/* malformed data */
|
||
|
bp = _bprint_s(bp, bend, "<MALFORMED>");
|
||
|
return bp;
|
||
|
}
|
||
|
|
||
|
static char*
|
||
|
_dnsPacket_bprintQR(DnsPacket* packet, char* p, char* end)
|
||
|
{
|
||
|
#define QQ(x) { DNS_TYPE_##x, #x }
|
||
|
static const struct {
|
||
|
const char* typeBytes;
|
||
|
const char* typeString;
|
||
|
} qTypes[] =
|
||
|
{
|
||
|
QQ(A), QQ(PTR), QQ(MX), QQ(AAAA), QQ(ALL),
|
||
|
{ NULL, NULL }
|
||
|
};
|
||
|
int nn;
|
||
|
const char* typeString = NULL;
|
||
|
|
||
|
/* dump QNAME */
|
||
|
p = _dnsPacket_bprintQName(packet, p, end);
|
||
|
|
||
|
/* dump TYPE */
|
||
|
p = _bprint_s(p, end, " (");
|
||
|
|
||
|
for (nn = 0; qTypes[nn].typeBytes != NULL; nn++) {
|
||
|
if (_dnsPacket_checkBytes(packet, 2, qTypes[nn].typeBytes)) {
|
||
|
typeString = qTypes[nn].typeString;
|
||
|
break;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if (typeString != NULL)
|
||
|
p = _bprint_s(p, end, typeString);
|
||
|
else {
|
||
|
int typeCode = _dnsPacket_readInt16(packet);
|
||
|
p = _bprint(p, end, "UNKNOWN-%d", typeCode);
|
||
|
}
|
||
|
|
||
|
p = _bprint_c(p, end, ')');
|
||
|
|
||
|
/* skip CLASS */
|
||
|
_dnsPacket_skip(packet, 2);
|
||
|
return p;
|
||
|
}
|
||
|
|
||
|
/* this function assumes the packet has already been checked */
|
||
|
static char*
|
||
|
_dnsPacket_bprintQuery( DnsPacket* packet, char* p, char* end )
|
||
|
{
|
||
|
int qdCount;
|
||
|
|
||
|
if (packet->base[2] & 0x1) {
|
||
|
p = _bprint_s(p, end, "RECURSIVE ");
|
||
|
}
|
||
|
|
||
|
_dnsPacket_skip(packet, 4);
|
||
|
qdCount = _dnsPacket_readInt16(packet);
|
||
|
_dnsPacket_skip(packet, 6);
|
||
|
|
||
|
for ( ; qdCount > 0; qdCount-- ) {
|
||
|
p = _dnsPacket_bprintQR(packet, p, end);
|
||
|
}
|
||
|
return p;
|
||
|
}
|
||
|
#endif
|
||
|
|
||
|
|
||
|
/** QUERY HASHING SUPPORT
|
||
|
**
|
||
|
** THE FOLLOWING CODE ASSUMES THAT THE INPUT PACKET HAS ALREADY
|
||
|
** BEEN SUCCESFULLY CHECKED.
|
||
|
**/
|
||
|
|
||
|
/* use 32-bit FNV hash function */
|
||
|
#define FNV_MULT 16777619U
|
||
|
#define FNV_BASIS 2166136261U
|
||
|
|
||
|
static unsigned
|
||
|
_dnsPacket_hashBytes( DnsPacket* packet, int numBytes, unsigned hash )
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor;
|
||
|
const uint8_t* end = packet->end;
|
||
|
|
||
|
while (numBytes > 0 && p < end) {
|
||
|
hash = hash*FNV_MULT ^ *p++;
|
||
|
}
|
||
|
packet->cursor = p;
|
||
|
return hash;
|
||
|
}
|
||
|
|
||
|
|
||
|
static unsigned
|
||
|
_dnsPacket_hashQName( DnsPacket* packet, unsigned hash )
|
||
|
{
|
||
|
const uint8_t* p = packet->cursor;
|
||
|
const uint8_t* end = packet->end;
|
||
|
|
||
|
for (;;) {
|
||
|
int c;
|
||
|
|
||
|
if (p >= end) { /* should not happen */
|
||
|
XLOG("%s: INTERNAL_ERROR: read-overflow !!\n", __FUNCTION__);
|
||
|
break;
|
||
|
}
|
||
|
|
||
|
c = *p++;
|
||
|
|
||
|
if (c == 0)
|
||
|
break;
|
||
|
|
||
|
if (c >= 64) {
|
||
|
XLOG("%s: INTERNAL_ERROR: malformed domain !!\n", __FUNCTION__);
|
||
|
break;
|
||
|
}
|
||
|
if (p + c >= end) {
|
||
|
XLOG("%s: INTERNAL_ERROR: simple label read-overflow !!\n",
|
||
|
__FUNCTION__);
|
||
|
break;
|
||
|
}
|
||
|
while (c > 0) {
|
||
|
hash = hash*FNV_MULT ^ *p++;
|
||
|
c -= 1;
|
||
|
}
|
||
|
}
|
||
|
packet->cursor = p;
|
||
|
return hash;
|
||
|
}
|
||
|
|
||
|
static unsigned
|
||
|
_dnsPacket_hashQR( DnsPacket* packet, unsigned hash )
|
||
|
{
|
||
|
int len;
|
||
|
|
||
|
hash = _dnsPacket_hashQName(packet, hash);
|
||
|
hash = _dnsPacket_hashBytes(packet, 4, hash); /* TYPE and CLASS */
|
||
|
return hash;
|
||
|
}
|
||
|
|
||
|
static unsigned
|
||
|
_dnsPacket_hashQuery( DnsPacket* packet )
|
||
|
{
|
||
|
unsigned hash = FNV_BASIS;
|
||
|
int count;
|
||
|
_dnsPacket_rewind(packet);
|
||
|
|
||
|
/* we ignore the TC bit for reasons explained in
|
||
|
* _dnsPacket_checkQuery().
|
||
|
*
|
||
|
* however we hash the RD bit to differentiate
|
||
|
* between answers for recursive and non-recursive
|
||
|
* queries.
|
||
|
*/
|
||
|
hash = hash*FNV_MULT ^ (packet->base[2] & 1);
|
||
|
|
||
|
/* assume: other flags are 0 */
|
||
|
_dnsPacket_skip(packet, 4);
|
||
|
|
||
|
/* read QDCOUNT */
|
||
|
count = _dnsPacket_readInt16(packet);
|
||
|
|
||
|
/* assume: ANcount, NScount, ARcount are 0 */
|
||
|
_dnsPacket_skip(packet, 6);
|
||
|
|
||
|
/* hash QDCOUNT QRs */
|
||
|
for ( ; count > 0; count-- )
|
||
|
hash = _dnsPacket_hashQR(packet, hash);
|
||
|
|
||
|
return hash;
|
||
|
}
|
||
|
|
||
|
|
||
|
/** QUERY COMPARISON
|
||
|
**
|
||
|
** THE FOLLOWING CODE ASSUMES THAT THE INPUT PACKETS HAVE ALREADY
|
||
|
** BEEN SUCCESFULLY CHECKED.
|
||
|
**/
|
||
|
|
||
|
static int
|
||
|
_dnsPacket_isEqualDomainName( DnsPacket* pack1, DnsPacket* pack2 )
|
||
|
{
|
||
|
const uint8_t* p1 = pack1->cursor;
|
||
|
const uint8_t* end1 = pack1->end;
|
||
|
const uint8_t* p2 = pack2->cursor;
|
||
|
const uint8_t* end2 = pack2->end;
|
||
|
|
||
|
for (;;) {
|
||
|
int c1, c2;
|
||
|
|
||
|
if (p1 >= end1 || p2 >= end2) {
|
||
|
XLOG("%s: INTERNAL_ERROR: read-overflow !!\n", __FUNCTION__);
|
||
|
break;
|
||
|
}
|
||
|
c1 = *p1++;
|
||
|
c2 = *p2++;
|
||
|
if (c1 != c2)
|
||
|
break;
|
||
|
|
||
|
if (c1 == 0) {
|
||
|
pack1->cursor = p1;
|
||
|
pack2->cursor = p2;
|
||
|
return 1;
|
||
|
}
|
||
|
if (c1 >= 64) {
|
||
|
XLOG("%s: INTERNAL_ERROR: malformed domain !!\n", __FUNCTION__);
|
||
|
break;
|
||
|
}
|
||
|
if ((p1+c1 > end1) || (p2+c1 > end2)) {
|
||
|
XLOG("%s: INTERNAL_ERROR: simple label read-overflow !!\n",
|
||
|
__FUNCTION__);
|
||
|
break;
|
||
|
}
|
||
|
if (memcmp(p1, p2, c1) != 0)
|
||
|
break;
|
||
|
p1 += c1;
|
||
|
p2 += c1;
|
||
|
/* we rely on the bound checks at the start of the loop */
|
||
|
}
|
||
|
/* not the same, or one is malformed */
|
||
|
XLOG("different DN");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static int
|
||
|
_dnsPacket_isEqualBytes( DnsPacket* pack1, DnsPacket* pack2, int numBytes )
|
||
|
{
|
||
|
const uint8_t* p1 = pack1->cursor;
|
||
|
const uint8_t* p2 = pack2->cursor;
|
||
|
|
||
|
if ( p1 + numBytes > pack1->end || p2 + numBytes > pack2->end )
|
||
|
return 0;
|
||
|
|
||
|
if ( memcmp(p1, p2, numBytes) != 0 )
|
||
|
return 0;
|
||
|
|
||
|
pack1->cursor += numBytes;
|
||
|
pack2->cursor += numBytes;
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
static int
|
||
|
_dnsPacket_isEqualQR( DnsPacket* pack1, DnsPacket* pack2 )
|
||
|
{
|
||
|
/* compare domain name encoding + TYPE + CLASS */
|
||
|
if ( !_dnsPacket_isEqualDomainName(pack1, pack2) ||
|
||
|
!_dnsPacket_isEqualBytes(pack1, pack2, 2+2) )
|
||
|
return 0;
|
||
|
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
static int
|
||
|
_dnsPacket_isEqualQuery( DnsPacket* pack1, DnsPacket* pack2 )
|
||
|
{
|
||
|
int count1, count2;
|
||
|
|
||
|
/* compare the headers, ignore most fields */
|
||
|
_dnsPacket_rewind(pack1);
|
||
|
_dnsPacket_rewind(pack2);
|
||
|
|
||
|
/* compare RD, ignore TC, see comment in _dnsPacket_checkQuery */
|
||
|
if ((pack1->base[2] & 1) != (pack2->base[2] & 1)) {
|
||
|
XLOG("different RD");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* assume: other flags are all 0 */
|
||
|
_dnsPacket_skip(pack1, 4);
|
||
|
_dnsPacket_skip(pack2, 4);
|
||
|
|
||
|
/* compare QDCOUNT */
|
||
|
count1 = _dnsPacket_readInt16(pack1);
|
||
|
count2 = _dnsPacket_readInt16(pack2);
|
||
|
if (count1 != count2 || count1 < 0) {
|
||
|
XLOG("different QDCOUNT");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* assume: ANcount, NScount and ARcount are all 0 */
|
||
|
_dnsPacket_skip(pack1, 6);
|
||
|
_dnsPacket_skip(pack2, 6);
|
||
|
|
||
|
/* compare the QDCOUNT QRs */
|
||
|
for ( ; count1 > 0; count1-- ) {
|
||
|
if (!_dnsPacket_isEqualQR(pack1, pack2)) {
|
||
|
XLOG("different QR");
|
||
|
return 0;
|
||
|
}
|
||
|
}
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
/****************************************************************************/
|
||
|
/****************************************************************************/
|
||
|
/***** *****/
|
||
|
/***** *****/
|
||
|
/***** *****/
|
||
|
/****************************************************************************/
|
||
|
/****************************************************************************/
|
||
|
|
||
|
/* cache entry. for simplicity, 'hash' and 'hlink' are inlined in this
|
||
|
* structure though they are conceptually part of the hash table.
|
||
|
*
|
||
|
* similarly, mru_next and mru_prev are part of the global MRU list
|
||
|
*/
|
||
|
typedef struct Entry {
|
||
|
unsigned int hash; /* hash value */
|
||
|
struct Entry* hlink; /* next in collision chain */
|
||
|
struct Entry* mru_prev;
|
||
|
struct Entry* mru_next;
|
||
|
|
||
|
const uint8_t* query;
|
||
|
int querylen;
|
||
|
const uint8_t* answer;
|
||
|
int answerlen;
|
||
|
time_t when; /* time_t when entry was added to table */
|
||
|
int id; /* for debugging purpose */
|
||
|
} Entry;
|
||
|
|
||
|
|
||
|
static void
|
||
|
entry_free( Entry* e )
|
||
|
{
|
||
|
/* everything is allocated in a single memory block */
|
||
|
if (e) {
|
||
|
free(e);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static __inline__ void
|
||
|
entry_mru_remove( Entry* e )
|
||
|
{
|
||
|
e->mru_prev->mru_next = e->mru_next;
|
||
|
e->mru_next->mru_prev = e->mru_prev;
|
||
|
}
|
||
|
|
||
|
static __inline__ void
|
||
|
entry_mru_add( Entry* e, Entry* list )
|
||
|
{
|
||
|
Entry* first = list->mru_next;
|
||
|
|
||
|
e->mru_next = first;
|
||
|
e->mru_prev = list;
|
||
|
|
||
|
list->mru_next = e;
|
||
|
first->mru_prev = e;
|
||
|
}
|
||
|
|
||
|
/* compute the hash of a given entry, this is a hash of most
|
||
|
* data in the query (key) */
|
||
|
static unsigned
|
||
|
entry_hash( const Entry* e )
|
||
|
{
|
||
|
DnsPacket pack[1];
|
||
|
|
||
|
_dnsPacket_init(pack, e->query, e->querylen);
|
||
|
return _dnsPacket_hashQuery(pack);
|
||
|
}
|
||
|
|
||
|
/* initialize an Entry as a search key, this also checks the input query packet
|
||
|
* returns 1 on success, or 0 in case of unsupported/malformed data */
|
||
|
static int
|
||
|
entry_init_key( Entry* e, const void* query, int querylen )
|
||
|
{
|
||
|
DnsPacket pack[1];
|
||
|
|
||
|
memset(e, 0, sizeof(*e));
|
||
|
|
||
|
e->query = query;
|
||
|
e->querylen = querylen;
|
||
|
e->hash = entry_hash(e);
|
||
|
|
||
|
_dnsPacket_init(pack, query, querylen);
|
||
|
|
||
|
return _dnsPacket_checkQuery(pack);
|
||
|
}
|
||
|
|
||
|
/* allocate a new entry as a cache node */
|
||
|
static Entry*
|
||
|
entry_alloc( const Entry* init, const void* answer, int answerlen )
|
||
|
{
|
||
|
Entry* e;
|
||
|
int size;
|
||
|
|
||
|
size = sizeof(*e) + init->querylen + answerlen;
|
||
|
e = calloc(size, 1);
|
||
|
if (e == NULL)
|
||
|
return e;
|
||
|
|
||
|
e->hash = init->hash;
|
||
|
e->query = (const uint8_t*)(e+1);
|
||
|
e->querylen = init->querylen;
|
||
|
|
||
|
memcpy( (char*)e->query, init->query, e->querylen );
|
||
|
|
||
|
e->answer = e->query + e->querylen;
|
||
|
e->answerlen = answerlen;
|
||
|
|
||
|
memcpy( (char*)e->answer, answer, e->answerlen );
|
||
|
|
||
|
e->when = _time_now();
|
||
|
|
||
|
return e;
|
||
|
}
|
||
|
|
||
|
static int
|
||
|
entry_equals( const Entry* e1, const Entry* e2 )
|
||
|
{
|
||
|
DnsPacket pack1[1], pack2[1];
|
||
|
|
||
|
if (e1->querylen != e2->querylen) {
|
||
|
return 0;
|
||
|
}
|
||
|
_dnsPacket_init(pack1, e1->query, e1->querylen);
|
||
|
_dnsPacket_init(pack2, e2->query, e2->querylen);
|
||
|
|
||
|
return _dnsPacket_isEqualQuery(pack1, pack2);
|
||
|
}
|
||
|
|
||
|
/****************************************************************************/
|
||
|
/****************************************************************************/
|
||
|
/***** *****/
|
||
|
/***** *****/
|
||
|
/***** *****/
|
||
|
/****************************************************************************/
|
||
|
/****************************************************************************/
|
||
|
|
||
|
/* We use a simple hash table with external collision lists
|
||
|
* for simplicity, the hash-table fields 'hash' and 'hlink' are
|
||
|
* inlined in the Entry structure.
|
||
|
*/
|
||
|
#define MAX_HASH_ENTRIES (2*CONFIG_MAX_ENTRIES)
|
||
|
|
||
|
typedef struct resolv_cache {
|
||
|
int num_entries;
|
||
|
Entry mru_list;
|
||
|
pthread_mutex_t lock;
|
||
|
unsigned generation;
|
||
|
int last_id;
|
||
|
Entry* entries[ MAX_HASH_ENTRIES ];
|
||
|
} Cache;
|
||
|
|
||
|
|
||
|
#define HTABLE_VALID(x) ((x) != NULL && (x) != HTABLE_DELETED)
|
||
|
|
||
|
static void
|
||
|
_cache_flush_locked( Cache* cache )
|
||
|
{
|
||
|
int nn;
|
||
|
time_t now = _time_now();
|
||
|
|
||
|
for (nn = 0; nn < MAX_HASH_ENTRIES; nn++)
|
||
|
{
|
||
|
Entry** pnode = &cache->entries[nn];
|
||
|
|
||
|
while (*pnode != NULL) {
|
||
|
Entry* node = *pnode;
|
||
|
*pnode = node->hlink;
|
||
|
entry_free(node);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
cache->mru_list.mru_next = cache->mru_list.mru_prev = &cache->mru_list;
|
||
|
cache->num_entries = 0;
|
||
|
cache->last_id = 0;
|
||
|
|
||
|
XLOG("*************************\n"
|
||
|
"*** DNS CACHE FLUSHED ***\n"
|
||
|
"*************************");
|
||
|
}
|
||
|
|
||
|
struct resolv_cache*
|
||
|
_resolv_cache_create( void )
|
||
|
{
|
||
|
struct resolv_cache* cache;
|
||
|
|
||
|
cache = calloc(sizeof(*cache), 1);
|
||
|
if (cache) {
|
||
|
cache->generation = ~0U;
|
||
|
pthread_mutex_init( &cache->lock, NULL );
|
||
|
cache->mru_list.mru_prev = cache->mru_list.mru_next = &cache->mru_list;
|
||
|
XLOG("%s: cache created\n", __FUNCTION__);
|
||
|
}
|
||
|
return cache;
|
||
|
}
|
||
|
|
||
|
|
||
|
#if DEBUG
|
||
|
static void
|
||
|
_dump_query( const uint8_t* query, int querylen )
|
||
|
{
|
||
|
char temp[256], *p=temp, *end=p+sizeof(temp);
|
||
|
DnsPacket pack[1];
|
||
|
|
||
|
_dnsPacket_init(pack, query, querylen);
|
||
|
p = _dnsPacket_bprintQuery(pack, p, end);
|
||
|
XLOG("QUERY: %s", temp);
|
||
|
}
|
||
|
|
||
|
static void
|
||
|
_cache_dump_mru( Cache* cache )
|
||
|
{
|
||
|
char temp[512], *p=temp, *end=p+sizeof(temp);
|
||
|
Entry* e;
|
||
|
|
||
|
p = _bprint(temp, end, "MRU LIST (%2d): ", cache->num_entries);
|
||
|
for (e = cache->mru_list.mru_next; e != &cache->mru_list; e = e->mru_next)
|
||
|
p = _bprint(p, end, " %d", e->id);
|
||
|
|
||
|
XLOG("%s", temp);
|
||
|
}
|
||
|
#endif
|
||
|
|
||
|
#if DEBUG
|
||
|
# define XLOG_QUERY(q,len) _dump_query((q), (len))
|
||
|
#else
|
||
|
# define XLOG_QUERY(q,len) ((void)0)
|
||
|
#endif
|
||
|
|
||
|
/* This function tries to find a key within the hash table
|
||
|
* In case of success, it will return a *pointer* to the hashed key.
|
||
|
* In case of failure, it will return a *pointer* to NULL
|
||
|
*
|
||
|
* So, the caller must check '*result' to check for success/failure.
|
||
|
*
|
||
|
* The main idea is that the result can later be used directly in
|
||
|
* calls to _resolv_cache_add or _resolv_cache_remove as the 'lookup'
|
||
|
* parameter. This makes the code simpler and avoids re-searching
|
||
|
* for the key position in the htable.
|
||
|
*
|
||
|
* The result of a lookup_p is only valid until you alter the hash
|
||
|
* table.
|
||
|
*/
|
||
|
static Entry**
|
||
|
_cache_lookup_p( Cache* cache,
|
||
|
Entry* key )
|
||
|
{
|
||
|
int index = key->hash % MAX_HASH_ENTRIES;
|
||
|
Entry** pnode = &cache->entries[ key->hash % MAX_HASH_ENTRIES ];
|
||
|
|
||
|
while (*pnode != NULL) {
|
||
|
Entry* node = *pnode;
|
||
|
|
||
|
if (node == NULL)
|
||
|
break;
|
||
|
|
||
|
if (node->hash == key->hash && entry_equals(node, key))
|
||
|
break;
|
||
|
|
||
|
pnode = &node->hlink;
|
||
|
}
|
||
|
return pnode;
|
||
|
}
|
||
|
|
||
|
/* Add a new entry to the hash table. 'lookup' must be the
|
||
|
* result of an immediate previous failed _lookup_p() call
|
||
|
* (i.e. with *lookup == NULL), and 'e' is the pointer to the
|
||
|
* newly created entry
|
||
|
*/
|
||
|
static void
|
||
|
_cache_add_p( Cache* cache,
|
||
|
Entry** lookup,
|
||
|
Entry* e )
|
||
|
{
|
||
|
*lookup = e;
|
||
|
e->id = ++cache->last_id;
|
||
|
entry_mru_add(e, &cache->mru_list);
|
||
|
cache->num_entries += 1;
|
||
|
|
||
|
XLOG("%s: entry %d added (count=%d)", __FUNCTION__,
|
||
|
e->id, cache->num_entries);
|
||
|
}
|
||
|
|
||
|
/* Remove an existing entry from the hash table,
|
||
|
* 'lookup' must be the result of an immediate previous
|
||
|
* and succesful _lookup_p() call.
|
||
|
*/
|
||
|
static void
|
||
|
_cache_remove_p( Cache* cache,
|
||
|
Entry** lookup )
|
||
|
{
|
||
|
Entry* e = *lookup;
|
||
|
|
||
|
XLOG("%s: entry %d removed (count=%d)", __FUNCTION__,
|
||
|
e->id, cache->num_entries-1);
|
||
|
|
||
|
entry_mru_remove(e);
|
||
|
*lookup = e->hlink;
|
||
|
entry_free(e);
|
||
|
cache->num_entries -= 1;
|
||
|
}
|
||
|
|
||
|
/* Remove the oldest entry from the hash table.
|
||
|
*/
|
||
|
static void
|
||
|
_cache_remove_oldest( Cache* cache )
|
||
|
{
|
||
|
Entry* oldest = cache->mru_list.mru_prev;
|
||
|
Entry** lookup = _cache_lookup_p(cache, oldest);
|
||
|
|
||
|
if (*lookup == NULL) { /* should not happen */
|
||
|
XLOG("%s: OLDEST NOT IN HTABLE ?", __FUNCTION__);
|
||
|
return;
|
||
|
}
|
||
|
_cache_remove_p(cache, lookup);
|
||
|
}
|
||
|
|
||
|
|
||
|
ResolvCacheStatus
|
||
|
_resolv_cache_lookup( struct resolv_cache* cache,
|
||
|
const void* query,
|
||
|
int querylen,
|
||
|
void* answer,
|
||
|
int answersize,
|
||
|
int *answerlen )
|
||
|
{
|
||
|
DnsPacket pack[1];
|
||
|
Entry key[1];
|
||
|
int index;
|
||
|
Entry** lookup;
|
||
|
Entry* e;
|
||
|
time_t now;
|
||
|
|
||
|
ResolvCacheStatus result = RESOLV_CACHE_NOTFOUND;
|
||
|
|
||
|
XLOG("%s: lookup", __FUNCTION__);
|
||
|
XLOG_QUERY(query, querylen);
|
||
|
|
||
|
/* we don't cache malformed queries */
|
||
|
if (!entry_init_key(key, query, querylen)) {
|
||
|
XLOG("%s: unsupported query", __FUNCTION__);
|
||
|
return RESOLV_CACHE_UNSUPPORTED;
|
||
|
}
|
||
|
/* lookup cache */
|
||
|
pthread_mutex_lock( &cache->lock );
|
||
|
|
||
|
/* see the description of _lookup_p to understand this.
|
||
|
* the function always return a non-NULL pointer.
|
||
|
*/
|
||
|
lookup = _cache_lookup_p(cache, key);
|
||
|
e = *lookup;
|
||
|
|
||
|
if (e == NULL) {
|
||
|
XLOG( "NOT IN CACHE");
|
||
|
goto Exit;
|
||
|
}
|
||
|
|
||
|
now = _time_now();
|
||
|
|
||
|
/* remove stale entries here */
|
||
|
if ( (unsigned)(now - e->when) >= CONFIG_SECONDS ) {
|
||
|
XLOG( " NOT IN CACHE (STALE ENTRY %p DISCARDED)", *lookup );
|
||
|
_cache_remove_p(cache, lookup);
|
||
|
goto Exit;
|
||
|
}
|
||
|
|
||
|
*answerlen = e->answerlen;
|
||
|
if (e->answerlen > answersize) {
|
||
|
/* NOTE: we return UNSUPPORTED if the answer buffer is too short */
|
||
|
result = RESOLV_CACHE_UNSUPPORTED;
|
||
|
XLOG(" ANSWER TOO LONG");
|
||
|
goto Exit;
|
||
|
}
|
||
|
|
||
|
memcpy( answer, e->answer, e->answerlen );
|
||
|
|
||
|
/* bump up this entry to the top of the MRU list */
|
||
|
if (e != cache->mru_list.mru_next) {
|
||
|
entry_mru_remove( e );
|
||
|
entry_mru_add( e, &cache->mru_list );
|
||
|
}
|
||
|
|
||
|
XLOG( "FOUND IN CACHE entry=%p", e );
|
||
|
result = RESOLV_CACHE_FOUND;
|
||
|
|
||
|
Exit:
|
||
|
pthread_mutex_unlock( &cache->lock );
|
||
|
return result;
|
||
|
}
|
||
|
|
||
|
|
||
|
void
|
||
|
_resolv_cache_add( struct resolv_cache* cache,
|
||
|
const void* query,
|
||
|
int querylen,
|
||
|
const void* answer,
|
||
|
int answerlen )
|
||
|
{
|
||
|
Entry key[1];
|
||
|
Entry* e;
|
||
|
Entry** lookup;
|
||
|
|
||
|
/* don't assume that the query has already been cached
|
||
|
*/
|
||
|
if (!entry_init_key( key, query, querylen )) {
|
||
|
XLOG( "%s: passed invalid query ?", __FUNCTION__);
|
||
|
return;
|
||
|
}
|
||
|
|
||
|
pthread_mutex_lock( &cache->lock );
|
||
|
|
||
|
XLOG( "%s: query:", __FUNCTION__ );
|
||
|
XLOG_QUERY(query,querylen);
|
||
|
#if DEBUG_DATA
|
||
|
XLOG( "answer:");
|
||
|
XLOG_BYTES(answer,answerlen);
|
||
|
#endif
|
||
|
|
||
|
lookup = _cache_lookup_p(cache, key);
|
||
|
e = *lookup;
|
||
|
|
||
|
if (e != NULL) { /* should not happen */
|
||
|
XLOG("%s: ALREADY IN CACHE (%p) ? IGNORING ADD",
|
||
|
__FUNCTION__, e);
|
||
|
goto Exit;
|
||
|
}
|
||
|
|
||
|
if (cache->num_entries >= CONFIG_MAX_ENTRIES) {
|
||
|
_cache_remove_oldest(cache);
|
||
|
/* need to lookup again */
|
||
|
lookup = _cache_lookup_p(cache, key);
|
||
|
e = *lookup;
|
||
|
if (e != NULL) {
|
||
|
XLOG("%s: ALREADY IN CACHE (%p) ? IGNORING ADD",
|
||
|
__FUNCTION__, e);
|
||
|
goto Exit;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
e = entry_alloc( key, answer, answerlen );
|
||
|
if (e != NULL) {
|
||
|
_cache_add_p(cache, lookup, e);
|
||
|
}
|
||
|
#if DEBUG
|
||
|
_cache_dump_mru(cache);
|
||
|
#endif
|
||
|
Exit:
|
||
|
pthread_mutex_unlock( &cache->lock );
|
||
|
}
|
||
|
|
||
|
/****************************************************************************/
|
||
|
/****************************************************************************/
|
||
|
/***** *****/
|
||
|
/***** *****/
|
||
|
/***** *****/
|
||
|
/****************************************************************************/
|
||
|
/****************************************************************************/
|
||
|
|
||
|
static struct resolv_cache* _res_cache;
|
||
|
static pthread_once_t _res_cache_once;
|
||
|
|
||
|
static void
|
||
|
_res_cache_init( void )
|
||
|
{
|
||
|
const char* env = getenv(CONFIG_ENV);
|
||
|
|
||
|
if (env && atoi(env) == 0) {
|
||
|
/* the cache is disabled */
|
||
|
return;
|
||
|
}
|
||
|
|
||
|
_res_cache = _resolv_cache_create();
|
||
|
}
|
||
|
|
||
|
|
||
|
struct resolv_cache*
|
||
|
__get_res_cache( void )
|
||
|
{
|
||
|
pthread_once( &_res_cache_once, _res_cache_init );
|
||
|
return _res_cache;
|
||
|
}
|
||
|
|
||
|
void
|
||
|
_resolv_cache_reset( unsigned generation )
|
||
|
{
|
||
|
XLOG("%s: generation=%d", __FUNCTION__, generation);
|
||
|
|
||
|
if (_res_cache == NULL)
|
||
|
return;
|
||
|
|
||
|
pthread_mutex_lock( &_res_cache->lock );
|
||
|
if (_res_cache->generation != generation) {
|
||
|
_cache_flush_locked(_res_cache);
|
||
|
_res_cache->generation = generation;
|
||
|
}
|
||
|
pthread_mutex_unlock( &_res_cache->lock );
|
||
|
}
|