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-rw-r--r--libc/netbsd/resolv/res_cache.c1461
1 files changed, 0 insertions, 1461 deletions
diff --git a/libc/netbsd/resolv/res_cache.c b/libc/netbsd/resolv/res_cache.c
deleted file mode 100644
index 2c912de..0000000
--- a/libc/netbsd/resolv/res_cache.c
+++ /dev/null
@@ -1,1461 +0,0 @@
-/*
- * Copyright (C) 2008 The Android Open Source Project
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * * Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include "resolv_cache.h"
-#include <stdlib.h>
-#include <string.h>
-#include <time.h>
-#include "pthread.h"
-
-/* This code implements a small and *simple* DNS resolver cache.
- *
- * It is only used to cache DNS answers for a maximum of CONFIG_SECONDS seconds
- * in order to reduce DNS traffic. It is not supposed to be a full DNS cache,
- * since we plan to implement that in the future in a dedicated process running
- * on the system.
- *
- * Note that its design is kept simple very intentionally, i.e.:
- *
- * - it takes raw DNS query packet data as input, and returns raw DNS
- * answer packet data as output
- *
- * (this means that two similar queries that encode the DNS name
- * differently will be treated distinctly).
- *
- * - the TTLs of answer RRs are ignored. our DNS resolver library does not use
- * them anyway, but it means that records with a TTL smaller than
- * CONFIG_SECONDS will be kept in the cache anyway.
- *
- * this is bad, but we absolutely want to avoid parsing the answer packets
- * (and should be solved by the later full DNS cache process).
- *
- * - the implementation is just a (query-data) => (answer-data) hash table
- * with a trivial least-recently-used expiration policy.
- *
- * Doing this keeps the code simple and avoids to deal with a lot of things
- * that a full DNS cache is expected to do.
- *
- * The API is also very simple:
- *
- * - the client calls _resolv_cache_get() to obtain a handle to the cache.
- * this will initialize the cache on first usage. the result can be NULL
- * if the cache is disabled.
- *
- * - the client calls _resolv_cache_lookup() before performing a query
- *
- * if the function returns RESOLV_CACHE_FOUND, a copy of the answer data
- * has been copied into the client-provided answer buffer.
- *
- * if the function returns RESOLV_CACHE_NOTFOUND, the client should perform
- * a request normally, *then* call _resolv_cache_add() to add the received
- * answer to the cache.
- *
- * if the function returns RESOLV_CACHE_UNSUPPORTED, the client should
- * perform a request normally, and *not* call _resolv_cache_add()
- *
- * note that RESOLV_CACHE_UNSUPPORTED is also returned if the answer buffer
- * is too short to accomodate the cached result.
- *
- * - when network settings change, the cache must be flushed since the list
- * of DNS servers probably changed. this is done by calling
- * _resolv_cache_reset()
- *
- * the parameter to this function must be an ever-increasing generation
- * number corresponding to the current network settings state.
- *
- * This is done because several threads could detect the same network
- * settings change (but at different times) and will all end up calling the
- * same function. Comparing with the last used generation number ensures
- * that the cache is only flushed once per network change.
- */
-
-/* the name of an environment variable that will be checked the first time
- * this code is called if its value is "0", then the resolver cache is
- * disabled.
- */
-#define CONFIG_ENV "BIONIC_DNSCACHE"
-
-/* entries older than CONFIG_SECONDS seconds are always discarded.
- */
-#define CONFIG_SECONDS (60*10) /* 10 minutes */
-
-/* maximum number of entries kept in the cache. This value has been
- * determined by browsing through various sites and counting the number
- * of corresponding requests. Keep in mind that our framework is currently
- * performing two requests per name lookup (one for IPv4, the other for IPv6)
- *
- * www.google.com 4
- * www.ysearch.com 6
- * www.amazon.com 8
- * www.nytimes.com 22
- * www.espn.com 28
- * www.msn.com 28
- * www.lemonde.fr 35
- *
- * (determined in 2009-2-17 from Paris, France, results may vary depending
- * on location)
- *
- * most high-level websites use lots of media/ad servers with different names
- * but these are generally reused when browsing through the site.
- *
- * As such, a valud of 64 should be relatively conformtable at the moment.
- */
-#define CONFIG_MAX_ENTRIES 64
-
-/****************************************************************************/
-/****************************************************************************/
-/***** *****/
-/***** *****/
-/***** *****/
-/****************************************************************************/
-/****************************************************************************/
-
-/* set to 1 to debug cache operations */
-#define DEBUG 0
-
-/* set to 1 to debug query data */
-#define DEBUG_DATA 0
-
-#if DEBUG
-# include <logd.h>
-# define XLOG(...) \
- __libc_android_log_print(ANDROID_LOG_DEBUG,"libc",__VA_ARGS__)
-
-#include <stdio.h>
-#include <stdarg.h>
-
-/** BOUNDED BUFFER FORMATTING
- **/
-
-/* technical note:
- *
- * the following debugging routines are used to append data to a bounded
- * buffer they take two parameters that are:
- *
- * - p : a pointer to the current cursor position in the buffer
- * this value is initially set to the buffer's address.
- *
- * - end : the address of the buffer's limit, i.e. of the first byte
- * after the buffer. this address should never be touched.
- *
- * IMPORTANT: it is assumed that end > buffer_address, i.e.
- * that the buffer is at least one byte.
- *
- * the _bprint_() functions return the new value of 'p' after the data
- * has been appended, and also ensure the following:
- *
- * - the returned value will never be strictly greater than 'end'
- *
- * - a return value equal to 'end' means that truncation occured
- * (in which case, end[-1] will be set to 0)
- *
- * - after returning from a _bprint_() function, the content of the buffer
- * is always 0-terminated, even in the event of truncation.
- *
- * these conventions allow you to call _bprint_ functions multiple times and
- * only check for truncation at the end of the sequence, as in:
- *
- * char buff[1000], *p = buff, *end = p + sizeof(buff);
- *
- * p = _bprint_c(p, end, '"');
- * p = _bprint_s(p, end, my_string);
- * p = _bprint_c(p, end, '"');
- *
- * if (p >= end) {
- * // buffer was too small
- * }
- *
- * printf( "%s", buff );
- */
-
-/* add a char to a bounded buffer */
-static char*
-_bprint_c( char* p, char* end, int c )
-{
- if (p < end) {
- if (p+1 == end)
- *p++ = 0;
- else {
- *p++ = (char) c;
- *p = 0;
- }
- }
- return p;
-}
-
-/* add a sequence of bytes to a bounded buffer */
-static char*
-_bprint_b( char* p, char* end, const char* buf, int len )
-{
- int avail = end - p;
-
- if (avail <= 0 || len <= 0)
- return p;
-
- if (avail > len)
- avail = len;
-
- memcpy( p, buf, avail );
- p += avail;
-
- if (p < end)
- p[0] = 0;
- else
- end[-1] = 0;
-
- return p;
-}
-
-/* add a string to a bounded buffer */
-static char*
-_bprint_s( char* p, char* end, const char* str )
-{
- return _bprint_b(p, end, str, strlen(str));
-}
-
-/* add a formatted string to a bounded buffer */
-static char*
-_bprint( char* p, char* end, const char* format, ... )
-{
- int avail, n;
- va_list args;
-
- avail = end - p;
-
- if (avail <= 0)
- return p;
-
- va_start(args, format);
- n = snprintf( p, avail, format, args);
- va_end(args);
-
- /* certain C libraries return -1 in case of truncation */
- if (n < 0 || n > avail)
- n = avail;
-
- p += n;
- /* certain C libraries do not zero-terminate in case of truncation */
- if (p == end)
- p[-1] = 0;
-
- return p;
-}
-
-/* add a hex value to a bounded buffer, up to 8 digits */
-static char*
-_bprint_hex( char* p, char* end, unsigned value, int numDigits )
-{
- char text[sizeof(unsigned)*2];
- int nn = 0;
-
- while (numDigits-- > 0) {
- text[nn++] = "0123456789abcdef"[(value >> (numDigits*4)) & 15];
- }
- return _bprint_b(p, end, text, nn);
-}
-
-/* add the hexadecimal dump of some memory area to a bounded buffer */
-static char*
-_bprint_hexdump( char* p, char* end, const uint8_t* data, int datalen )
-{
- int lineSize = 16;
-
- while (datalen > 0) {
- int avail = datalen;
- int nn;
-
- if (avail > lineSize)
- avail = lineSize;
-
- for (nn = 0; nn < avail; nn++) {
- if (nn > 0)
- p = _bprint_c(p, end, ' ');
- p = _bprint_hex(p, end, data[nn], 2);
- }
- for ( ; nn < lineSize; nn++ ) {
- p = _bprint_s(p, end, " ");
- }
- p = _bprint_s(p, end, " ");
-
- for (nn = 0; nn < avail; nn++) {
- int c = data[nn];
-
- if (c < 32 || c > 127)
- c = '.';
-
- p = _bprint_c(p, end, c);
- }
- p = _bprint_c(p, end, '\n');
-
- data += avail;
- datalen -= avail;
- }
- return p;
-}
-
-/* dump the content of a query of packet to the log */
-static void
-XLOG_BYTES( const void* base, int len )
-{
- char buff[1024];
- char* p = buff, *end = p + sizeof(buff);
-
- p = _bprint_hexdump(p, end, base, len);
- XLOG("%s",buff);
-}
-
-#else /* !DEBUG */
-# define XLOG(...) ((void)0)
-# define XLOG_BYTES(a,b) ((void)0)
-#endif
-
-static time_t
-_time_now( void )
-{
- struct timeval tv;
-
- gettimeofday( &tv, NULL );
- return tv.tv_sec;
-}
-
-/* reminder: the general format of a DNS packet is the following:
- *
- * HEADER (12 bytes)
- * QUESTION (variable)
- * ANSWER (variable)
- * AUTHORITY (variable)
- * ADDITIONNAL (variable)
- *
- * the HEADER is made of:
- *
- * ID : 16 : 16-bit unique query identification field
- *
- * QR : 1 : set to 0 for queries, and 1 for responses
- * Opcode : 4 : set to 0 for queries
- * AA : 1 : set to 0 for queries
- * TC : 1 : truncation flag, will be set to 0 in queries
- * RD : 1 : recursion desired
- *
- * RA : 1 : recursion available (0 in queries)
- * Z : 3 : three reserved zero bits
- * RCODE : 4 : response code (always 0=NOERROR in queries)
- *
- * QDCount: 16 : question count
- * ANCount: 16 : Answer count (0 in queries)
- * NSCount: 16: Authority Record count (0 in queries)
- * ARCount: 16: Additionnal Record count (0 in queries)
- *
- * the QUESTION is made of QDCount Question Record (QRs)
- * the ANSWER is made of ANCount RRs
- * the AUTHORITY is made of NSCount RRs
- * the ADDITIONNAL is made of ARCount RRs
- *
- * Each Question Record (QR) is made of:
- *
- * QNAME : variable : Query DNS NAME
- * 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:
- *
- * NAME : variable : DNS NAME
- * TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255)
- * CLASS : 16 : class of query (IN=1)
- * TTL : 32 : seconds to cache this RR (0=none)
- * RDLENGTH: 16 : size of RDDATA in bytes
- * RDDATA : variable : RR data (depends on TYPE)
- *
- * Each QNAME contains a domain name encoded as a sequence of 'labels'
- * terminated by a zero. Each label has the following format:
- *
- * LEN : 8 : lenght of label (MUST be < 64)
- * NAME : 8*LEN : label length (must exclude dots)
- *
- * 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 );
-}
generated by cgit v1.1 at 2025-01-26 20:25:48 +0000