auto import from //depot/cupcake/@135843
diff --git a/libc/netbsd/resolv/res_cache.c b/libc/netbsd/resolv/res_cache.c
new file mode 100644
index 0000000..2c912de
--- /dev/null
+++ b/libc/netbsd/resolv/res_cache.c
@@ -0,0 +1,1461 @@
+/*
+ * 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 );
+}