Minimal changes to bring the resolver into the C++ era
It took surprisingly few changes, considering the leap from C with some
K&R constructs to C++17; most of the diffs are adding explicit pointer
casts and renaming variables called 'class' or 'try'.
As a result of building as C++, some of the names are now mangled,
making clashes with bionic harder. However, some names remain C due to
the __BEGIN_DECLS / __END_DECLS macros, scheduled to be removed in a
later cleanup pass.
Test: atest netd_integration_test
Change-Id: I3aefb9078421ec42f98f97d917785b365545feba
diff --git a/resolv/res_cache.cpp b/resolv/res_cache.cpp
new file mode 100644
index 0000000..4d13126
--- /dev/null
+++ b/resolv/res_cache.cpp
@@ -0,0 +1,2092 @@
+/*
+ * 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 <pthread.h>
+#include <resolv.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include <arpa/nameser.h>
+#include <errno.h>
+#include <linux/if.h>
+#include <net/if.h>
+#include <netdb.h>
+
+#include <arpa/inet.h>
+
+#include "res_private.h"
+#include "resolv_cache.h"
+#include "resolv_netid.h"
+#include "resolv_private.h"
+
+#include <async_safe/log.h>
+
+/* This code implements a small and *simple* DNS resolver cache.
+ *
+ * It is only used to cache DNS answers for a time defined by the smallest TTL
+ * among the answer records 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 smallest TTL value among the answer records are used as the time
+ * to keep an answer in the cache.
+ *
+ * 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.
+ */
+
+/* default 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 value of 64 should be relatively comfortable at the moment.
+ *
+ * ******************************************
+ * * NOTE - this has changed.
+ * * 1) we've added IPv6 support so each dns query results in 2 responses
+ * * 2) we've made this a system-wide cache, so the cost is less (it's not
+ * * duplicated in each process) and the need is greater (more processes
+ * * making different requests).
+ * * Upping by 2x for IPv6
+ * * Upping by another 5x for the centralized nature
+ * *****************************************
+ */
+#define CONFIG_MAX_ENTRIES 64 * 2 * 5
+
+/* set to 1 to debug cache operations */
+#define DEBUG 0
+
+/* set to 1 to debug query data */
+#define DEBUG_DATA 0
+
+#undef XLOG
+
+#define XLOG(...) \
+ ({ \
+ if (DEBUG) { \
+ async_safe_format_log(ANDROID_LOG_DEBUG, "libc", __VA_ARGS__); \
+ } else { \
+ ((void) 0); \
+ } \
+ })
+
+/** 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 */
+[[maybe_unused]] 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 = vsnprintf(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 */
+[[maybe_unused]] static void XLOG_BYTES(const uint8_t* base, int len) {
+ if (DEBUG_DATA) {
+ char buff[1024];
+ char *p = buff, *end = p + sizeof(buff);
+
+ p = _bprint_hexdump(p, end, base, len);
+ XLOG("%s", buff);
+ }
+}
+
+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) {
+ 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] & 0xCF) != 0) {
+ XLOG("query packet flags unsupported");
+ return 0;
+ }
+
+ /* Note that we ignore the TC, RD, CD, and AD 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 query might depend on
+ * the RD, AD, and CD bits, so these bits
+ * should be used to differentiate cached result.
+ *
+ * this implies that these bits are 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 > 1) {
+ 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) {
+ hash = _dnsPacket_hashQName(packet, hash);
+ hash = _dnsPacket_hashBytes(packet, 4, hash); /* TYPE and CLASS */
+ return hash;
+}
+
+static unsigned _dnsPacket_hashRR(DnsPacket* packet, unsigned hash) {
+ int rdlength;
+ hash = _dnsPacket_hashQR(packet, hash);
+ hash = _dnsPacket_hashBytes(packet, 4, hash); /* TTL */
+ rdlength = _dnsPacket_readInt16(packet);
+ hash = _dnsPacket_hashBytes(packet, rdlength, hash); /* RDATA */
+ return hash;
+}
+
+static unsigned _dnsPacket_hashQuery(DnsPacket* packet) {
+ unsigned hash = FNV_BASIS;
+ int count, arcount;
+ _dnsPacket_rewind(packet);
+
+ /* ignore the ID */
+ _dnsPacket_skip(packet, 2);
+
+ /* 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);
+
+ /* mark the first header byte as processed */
+ _dnsPacket_skip(packet, 1);
+
+ /* process the second header byte */
+ hash = _dnsPacket_hashBytes(packet, 1, hash);
+
+ /* read QDCOUNT */
+ count = _dnsPacket_readInt16(packet);
+
+ /* assume: ANcount and NScount are 0 */
+ _dnsPacket_skip(packet, 4);
+
+ /* read ARCOUNT */
+ arcount = _dnsPacket_readInt16(packet);
+
+ /* hash QDCOUNT QRs */
+ for (; count > 0; count--) hash = _dnsPacket_hashQR(packet, hash);
+
+ /* hash ARCOUNT RRs */
+ for (; arcount > 0; arcount--) hash = _dnsPacket_hashRR(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_isEqualRR(DnsPacket* pack1, DnsPacket* pack2) {
+ int rdlength1, rdlength2;
+ /* compare query + TTL */
+ if (!_dnsPacket_isEqualQR(pack1, pack2) || !_dnsPacket_isEqualBytes(pack1, pack2, 4)) return 0;
+
+ /* compare RDATA */
+ rdlength1 = _dnsPacket_readInt16(pack1);
+ rdlength2 = _dnsPacket_readInt16(pack2);
+ if (rdlength1 != rdlength2 || !_dnsPacket_isEqualBytes(pack1, pack2, rdlength1)) return 0;
+
+ return 1;
+}
+
+static int _dnsPacket_isEqualQuery(DnsPacket* pack1, DnsPacket* pack2) {
+ int count1, count2, arcount1, arcount2;
+
+ /* 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;
+ }
+
+ if (pack1->base[3] != pack2->base[3]) {
+ XLOG("different CD or AD");
+ return 0;
+ }
+
+ /* mark ID and header bytes as compared */
+ _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 and NScount are 0 */
+ _dnsPacket_skip(pack1, 4);
+ _dnsPacket_skip(pack2, 4);
+
+ /* compare ARCOUNT */
+ arcount1 = _dnsPacket_readInt16(pack1);
+ arcount2 = _dnsPacket_readInt16(pack2);
+ if (arcount1 != arcount2 || arcount1 < 0) {
+ XLOG("different ARCOUNT");
+ return 0;
+ }
+
+ /* compare the QDCOUNT QRs */
+ for (; count1 > 0; count1--) {
+ if (!_dnsPacket_isEqualQR(pack1, pack2)) {
+ XLOG("different QR");
+ return 0;
+ }
+ }
+
+ /* compare the ARCOUNT RRs */
+ for (; arcount1 > 0; arcount1--) {
+ if (!_dnsPacket_isEqualRR(pack1, pack2)) {
+ XLOG("different additional RR");
+ 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 expires; /* time_t when the entry isn't valid any more */
+ int id; /* for debugging purpose */
+} Entry;
+
+/*
+ * Find the TTL for a negative DNS result. This is defined as the minimum
+ * of the SOA records TTL and the MINIMUM-TTL field (RFC-2308).
+ *
+ * Return 0 if not found.
+ */
+static u_long answer_getNegativeTTL(ns_msg handle) {
+ int n, nscount;
+ u_long result = 0;
+ ns_rr rr;
+
+ nscount = ns_msg_count(handle, ns_s_ns);
+ for (n = 0; n < nscount; n++) {
+ if ((ns_parserr(&handle, ns_s_ns, n, &rr) == 0) && (ns_rr_type(rr) == ns_t_soa)) {
+ const u_char* rdata = ns_rr_rdata(rr); // find the data
+ const u_char* edata = rdata + ns_rr_rdlen(rr); // add the len to find the end
+ int len;
+ u_long ttl, rec_result = ns_rr_ttl(rr);
+
+ // find the MINIMUM-TTL field from the blob of binary data for this record
+ // skip the server name
+ len = dn_skipname(rdata, edata);
+ if (len == -1) continue; // error skipping
+ rdata += len;
+
+ // skip the admin name
+ len = dn_skipname(rdata, edata);
+ if (len == -1) continue; // error skipping
+ rdata += len;
+
+ if (edata - rdata != 5 * NS_INT32SZ) continue;
+ // skip: serial number + refresh interval + retry interval + expiry
+ rdata += NS_INT32SZ * 4;
+ // finally read the MINIMUM TTL
+ ttl = ns_get32(rdata);
+ if (ttl < rec_result) {
+ rec_result = ttl;
+ }
+ // Now that the record is read successfully, apply the new min TTL
+ if (n == 0 || rec_result < result) {
+ result = rec_result;
+ }
+ }
+ }
+ return result;
+}
+
+/*
+ * Parse the answer records and find the appropriate
+ * smallest TTL among the records. This might be from
+ * the answer records if found or from the SOA record
+ * if it's a negative result.
+ *
+ * The returned TTL is the number of seconds to
+ * keep the answer in the cache.
+ *
+ * In case of parse error zero (0) is returned which
+ * indicates that the answer shall not be cached.
+ */
+static u_long answer_getTTL(const void* answer, int answerlen) {
+ ns_msg handle;
+ int ancount, n;
+ u_long result, ttl;
+ ns_rr rr;
+
+ result = 0;
+ if (ns_initparse((const uint8_t*) answer, answerlen, &handle) >= 0) {
+ // get number of answer records
+ ancount = ns_msg_count(handle, ns_s_an);
+
+ if (ancount == 0) {
+ // a response with no answers? Cache this negative result.
+ result = answer_getNegativeTTL(handle);
+ } else {
+ for (n = 0; n < ancount; n++) {
+ if (ns_parserr(&handle, ns_s_an, n, &rr) == 0) {
+ ttl = ns_rr_ttl(rr);
+ if (n == 0 || ttl < result) {
+ result = ttl;
+ }
+ } else {
+ XLOG("ns_parserr failed ancount no = %d. errno = %s\n", n, strerror(errno));
+ }
+ }
+ }
+ } else {
+ XLOG("ns_parserr failed. %s\n", strerror(errno));
+ }
+
+ XLOG("TTL = %lu\n", result);
+
+ return result;
+}
+
+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 = (const uint8_t*) query;
+ e->querylen = querylen;
+ e->hash = entry_hash(e);
+
+ _dnsPacket_init(pack, e->query, e->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 = (Entry*) 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);
+
+ 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.
+ */
+
+/* Maximum time for a thread to wait for an pending request */
+#define PENDING_REQUEST_TIMEOUT 20;
+
+typedef struct pending_req_info {
+ unsigned int hash;
+ pthread_cond_t cond;
+ struct pending_req_info* next;
+} PendingReqInfo;
+
+typedef struct resolv_cache {
+ int max_entries;
+ int num_entries;
+ Entry mru_list;
+ int last_id;
+ Entry* entries;
+ PendingReqInfo pending_requests;
+} Cache;
+
+struct resolv_cache_info {
+ unsigned netid;
+ Cache* cache;
+ struct resolv_cache_info* next;
+ int nscount;
+ char* nameservers[MAXNS];
+ struct addrinfo* nsaddrinfo[MAXNS];
+ int revision_id; // # times the nameservers have been replaced
+ struct __res_params params;
+ struct __res_stats nsstats[MAXNS];
+ char defdname[MAXDNSRCHPATH];
+ int dnsrch_offset[MAXDNSRCH + 1]; // offsets into defdname
+};
+
+#define HTABLE_VALID(x) ((x) != NULL && (x) != HTABLE_DELETED)
+
+static pthread_once_t _res_cache_once = PTHREAD_ONCE_INIT;
+static void _res_cache_init(void);
+
+// lock protecting everything in the _resolve_cache_info structs (next ptr, etc)
+static pthread_mutex_t _res_cache_list_lock;
+
+/* gets cache associated with a network, or NULL if none exists */
+static struct resolv_cache* _find_named_cache_locked(unsigned netid);
+
+static void _cache_flush_pending_requests_locked(struct resolv_cache* cache) {
+ struct pending_req_info *ri, *tmp;
+ if (cache) {
+ ri = cache->pending_requests.next;
+
+ while (ri) {
+ tmp = ri;
+ ri = ri->next;
+ pthread_cond_broadcast(&tmp->cond);
+
+ pthread_cond_destroy(&tmp->cond);
+ free(tmp);
+ }
+
+ cache->pending_requests.next = NULL;
+ }
+}
+
+/* Return 0 if no pending request is found matching the key.
+ * If a matching request is found the calling thread will wait until
+ * the matching request completes, then update *cache and return 1. */
+static int _cache_check_pending_request_locked(struct resolv_cache** cache, Entry* key,
+ unsigned netid) {
+ struct pending_req_info *ri, *prev;
+ int exist = 0;
+
+ if (*cache && key) {
+ ri = (*cache)->pending_requests.next;
+ prev = &(*cache)->pending_requests;
+ while (ri) {
+ if (ri->hash == key->hash) {
+ exist = 1;
+ break;
+ }
+ prev = ri;
+ ri = ri->next;
+ }
+
+ if (!exist) {
+ ri = (struct pending_req_info*) calloc(1, sizeof(struct pending_req_info));
+ if (ri) {
+ ri->hash = key->hash;
+ pthread_cond_init(&ri->cond, NULL);
+ prev->next = ri;
+ }
+ } else {
+ struct timespec ts = {0, 0};
+ XLOG("Waiting for previous request");
+ ts.tv_sec = _time_now() + PENDING_REQUEST_TIMEOUT;
+ pthread_cond_timedwait(&ri->cond, &_res_cache_list_lock, &ts);
+ /* Must update *cache as it could have been deleted. */
+ *cache = _find_named_cache_locked(netid);
+ }
+ }
+
+ return exist;
+}
+
+/* notify any waiting thread that waiting on a request
+ * matching the key has been added to the cache */
+static void _cache_notify_waiting_tid_locked(struct resolv_cache* cache, Entry* key) {
+ struct pending_req_info *ri, *prev;
+
+ if (cache && key) {
+ ri = cache->pending_requests.next;
+ prev = &cache->pending_requests;
+ while (ri) {
+ if (ri->hash == key->hash) {
+ pthread_cond_broadcast(&ri->cond);
+ break;
+ }
+ prev = ri;
+ ri = ri->next;
+ }
+
+ // remove item from list and destroy
+ if (ri) {
+ prev->next = ri->next;
+ pthread_cond_destroy(&ri->cond);
+ free(ri);
+ }
+ }
+}
+
+/* notify the cache that the query failed */
+void _resolv_cache_query_failed(unsigned netid, const void* query, int querylen) {
+ Entry key[1];
+ Cache* cache;
+
+ if (!entry_init_key(key, query, querylen)) return;
+
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ cache = _find_named_cache_locked(netid);
+
+ if (cache) {
+ _cache_notify_waiting_tid_locked(cache, key);
+ }
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+}
+
+static struct resolv_cache_info* _find_cache_info_locked(unsigned netid);
+
+static void _cache_flush_locked(Cache* cache) {
+ int nn;
+
+ for (nn = 0; nn < cache->max_entries; nn++) {
+ Entry** pnode = (Entry**) &cache->entries[nn];
+
+ while (*pnode != NULL) {
+ Entry* node = *pnode;
+ *pnode = node->hlink;
+ entry_free(node);
+ }
+ }
+
+ // flush pending request
+ _cache_flush_pending_requests_locked(cache);
+
+ 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"
+ "*************************");
+}
+
+static int _res_cache_get_max_entries(void) {
+ int cache_size = CONFIG_MAX_ENTRIES;
+
+ const char* cache_mode = getenv("ANDROID_DNS_MODE");
+ if (cache_mode == NULL || strcmp(cache_mode, "local") != 0) {
+ // Don't use the cache in local mode. This is used by the proxy itself.
+ cache_size = 0;
+ }
+
+ XLOG("cache size: %d", cache_size);
+ return cache_size;
+}
+
+static struct resolv_cache* _resolv_cache_create(void) {
+ struct resolv_cache* cache;
+
+ cache = (struct resolv_cache*) calloc(sizeof(*cache), 1);
+ if (cache) {
+ cache->max_entries = _res_cache_get_max_entries();
+ cache->entries = (Entry*) calloc(sizeof(*cache->entries), cache->max_entries);
+ if (cache->entries) {
+ cache->mru_list.mru_prev = cache->mru_list.mru_next = &cache->mru_list;
+ XLOG("%s: cache created\n", __FUNCTION__);
+ } else {
+ free(cache);
+ cache = NULL;
+ }
+ }
+ 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);
+}
+
+static void _dump_answer(const void* answer, int answerlen) {
+ res_state statep;
+ FILE* fp;
+ char* buf;
+ int fileLen;
+
+ fp = fopen("/data/reslog.txt", "w+e");
+ if (fp != NULL) {
+ statep = __res_get_state();
+
+ res_pquery(statep, answer, answerlen, fp);
+
+ // Get file length
+ fseek(fp, 0, SEEK_END);
+ fileLen = ftell(fp);
+ fseek(fp, 0, SEEK_SET);
+ buf = (char*) malloc(fileLen + 1);
+ if (buf != NULL) {
+ // Read file contents into buffer
+ fread(buf, fileLen, 1, fp);
+ XLOG("%s\n", buf);
+ free(buf);
+ }
+ fclose(fp);
+ remove("/data/reslog.txt");
+ } else {
+ errno = 0; // else debug is introducing error signals
+ XLOG("%s: can't open file\n", __FUNCTION__);
+ }
+}
+#endif
+
+#if DEBUG
+#define XLOG_QUERY(q, len) _dump_query((q), (len))
+#define XLOG_ANSWER(a, len) _dump_answer((a), (len))
+#else
+#define XLOG_QUERY(q, len) ((void) 0)
+#define XLOG_ANSWER(a, 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 % cache->max_entries;
+ Entry** pnode = (Entry**) &cache->entries[index];
+
+ 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;
+ }
+ if (DEBUG) {
+ XLOG("Cache full - removing oldest");
+ XLOG_QUERY(oldest->query, oldest->querylen);
+ }
+ _cache_remove_p(cache, lookup);
+}
+
+/* Remove all expired entries from the hash table.
+ */
+static void _cache_remove_expired(Cache* cache) {
+ Entry* e;
+ time_t now = _time_now();
+
+ for (e = cache->mru_list.mru_next; e != &cache->mru_list;) {
+ // Entry is old, remove
+ if (now >= e->expires) {
+ Entry** lookup = _cache_lookup_p(cache, e);
+ if (*lookup == NULL) { /* should not happen */
+ XLOG("%s: ENTRY NOT IN HTABLE ?", __FUNCTION__);
+ return;
+ }
+ e = e->mru_next;
+ _cache_remove_p(cache, lookup);
+ } else {
+ e = e->mru_next;
+ }
+ }
+}
+
+ResolvCacheStatus _resolv_cache_lookup(unsigned netid, const void* query, int querylen,
+ void* answer, int answersize, int* answerlen) {
+ Entry key[1];
+ Entry** lookup;
+ Entry* e;
+ time_t now;
+ Cache* cache;
+
+ 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_once(&_res_cache_once, _res_cache_init);
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ cache = _find_named_cache_locked(netid);
+ if (cache == NULL) {
+ result = RESOLV_CACHE_UNSUPPORTED;
+ goto Exit;
+ }
+
+ /* 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");
+ // calling thread will wait if an outstanding request is found
+ // that matching this query
+ if (!_cache_check_pending_request_locked(&cache, key, netid) || cache == NULL) {
+ goto Exit;
+ } else {
+ lookup = _cache_lookup_p(cache, key);
+ e = *lookup;
+ if (e == NULL) {
+ goto Exit;
+ }
+ }
+ }
+
+ now = _time_now();
+
+ /* remove stale entries here */
+ if (now >= e->expires) {
+ XLOG(" NOT IN CACHE (STALE ENTRY %p DISCARDED)", *lookup);
+ XLOG_QUERY(e->query, e->querylen);
+ _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(&_res_cache_list_lock);
+ return result;
+}
+
+void _resolv_cache_add(unsigned netid, const void* query, int querylen, const void* answer,
+ int answerlen) {
+ Entry key[1];
+ Entry* e;
+ Entry** lookup;
+ u_long ttl;
+ Cache* cache = NULL;
+
+ /* 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(&_res_cache_list_lock);
+
+ cache = _find_named_cache_locked(netid);
+ if (cache == NULL) {
+ goto Exit;
+ }
+
+ XLOG("%s: query:", __FUNCTION__);
+ XLOG_QUERY(query, querylen);
+ XLOG_ANSWER(answer, answerlen);
+#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 >= cache->max_entries) {
+ _cache_remove_expired(cache);
+ if (cache->num_entries >= cache->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;
+ }
+ }
+
+ ttl = answer_getTTL(answer, answerlen);
+ if (ttl > 0) {
+ e = entry_alloc(key, answer, answerlen);
+ if (e != NULL) {
+ e->expires = ttl + _time_now();
+ _cache_add_p(cache, lookup, e);
+ }
+ }
+#if DEBUG
+ _cache_dump_mru(cache);
+#endif
+Exit:
+ if (cache != NULL) {
+ _cache_notify_waiting_tid_locked(cache, key);
+ }
+ pthread_mutex_unlock(&_res_cache_list_lock);
+}
+
+// Head of the list of caches. Protected by _res_cache_list_lock.
+static struct resolv_cache_info _res_cache_list;
+
+/* insert resolv_cache_info into the list of resolv_cache_infos */
+static void _insert_cache_info_locked(struct resolv_cache_info* cache_info);
+/* creates a resolv_cache_info */
+static struct resolv_cache_info* _create_cache_info(void);
+/* gets a resolv_cache_info associated with a network, or NULL if not found */
+static struct resolv_cache_info* _find_cache_info_locked(unsigned netid);
+/* look up the named cache, and creates one if needed */
+static struct resolv_cache* _get_res_cache_for_net_locked(unsigned netid);
+/* empty the named cache */
+static void _flush_cache_for_net_locked(unsigned netid);
+/* empty the nameservers set for the named cache */
+static void _free_nameservers_locked(struct resolv_cache_info* cache_info);
+/* return 1 if the provided list of name servers differs from the list of name servers
+ * currently attached to the provided cache_info */
+static int _resolv_is_nameservers_equal_locked(struct resolv_cache_info* cache_info,
+ const char** servers, int numservers);
+/* clears the stats samples contained withing the given cache_info */
+static void _res_cache_clear_stats_locked(struct resolv_cache_info* cache_info);
+
+static void _res_cache_init(void) {
+ memset(&_res_cache_list, 0, sizeof(_res_cache_list));
+ pthread_mutex_init(&_res_cache_list_lock, NULL);
+}
+
+static struct resolv_cache* _get_res_cache_for_net_locked(unsigned netid) {
+ struct resolv_cache* cache = _find_named_cache_locked(netid);
+ if (!cache) {
+ struct resolv_cache_info* cache_info = _create_cache_info();
+ if (cache_info) {
+ cache = _resolv_cache_create();
+ if (cache) {
+ cache_info->cache = cache;
+ cache_info->netid = netid;
+ _insert_cache_info_locked(cache_info);
+ } else {
+ free(cache_info);
+ }
+ }
+ }
+ return cache;
+}
+
+void _resolv_flush_cache_for_net(unsigned netid) {
+ pthread_once(&_res_cache_once, _res_cache_init);
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ _flush_cache_for_net_locked(netid);
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+}
+
+static void _flush_cache_for_net_locked(unsigned netid) {
+ struct resolv_cache* cache = _find_named_cache_locked(netid);
+ if (cache) {
+ _cache_flush_locked(cache);
+ }
+
+ // Also clear the NS statistics.
+ struct resolv_cache_info* cache_info = _find_cache_info_locked(netid);
+ _res_cache_clear_stats_locked(cache_info);
+}
+
+void _resolv_delete_cache_for_net(unsigned netid) {
+ pthread_once(&_res_cache_once, _res_cache_init);
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ struct resolv_cache_info* prev_cache_info = &_res_cache_list;
+
+ while (prev_cache_info->next) {
+ struct resolv_cache_info* cache_info = prev_cache_info->next;
+
+ if (cache_info->netid == netid) {
+ prev_cache_info->next = cache_info->next;
+ _cache_flush_locked(cache_info->cache);
+ free(cache_info->cache->entries);
+ free(cache_info->cache);
+ _free_nameservers_locked(cache_info);
+ free(cache_info);
+ break;
+ }
+
+ prev_cache_info = prev_cache_info->next;
+ }
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+}
+
+static struct resolv_cache_info* _create_cache_info(void) {
+ return (struct resolv_cache_info*) calloc(sizeof(struct resolv_cache_info), 1);
+}
+
+static void _insert_cache_info_locked(struct resolv_cache_info* cache_info) {
+ struct resolv_cache_info* last;
+ for (last = &_res_cache_list; last->next; last = last->next) {}
+ last->next = cache_info;
+}
+
+static struct resolv_cache* _find_named_cache_locked(unsigned netid) {
+ struct resolv_cache_info* info = _find_cache_info_locked(netid);
+ if (info != NULL) return info->cache;
+ return NULL;
+}
+
+static struct resolv_cache_info* _find_cache_info_locked(unsigned netid) {
+ struct resolv_cache_info* cache_info = _res_cache_list.next;
+
+ while (cache_info) {
+ if (cache_info->netid == netid) {
+ break;
+ }
+
+ cache_info = cache_info->next;
+ }
+ return cache_info;
+}
+
+void _resolv_set_default_params(struct __res_params* params) {
+ params->sample_validity = NSSAMPLE_VALIDITY;
+ params->success_threshold = SUCCESS_THRESHOLD;
+ params->min_samples = 0;
+ params->max_samples = 0;
+ params->base_timeout_msec = 0; // 0 = legacy algorithm
+}
+
+int _resolv_set_nameservers_for_net(unsigned netid, const char** servers, unsigned numservers,
+ const char* domains, const struct __res_params* params) {
+ char sbuf[NI_MAXSERV];
+ char* cp;
+ int* offset;
+ struct addrinfo* nsaddrinfo[MAXNS];
+
+ if (numservers > MAXNS) {
+ XLOG("%s: numservers=%u, MAXNS=%u", __FUNCTION__, numservers, MAXNS);
+ return E2BIG;
+ }
+
+ // Parse the addresses before actually locking or changing any state, in case there is an error.
+ // As a side effect this also reduces the time the lock is kept.
+ struct addrinfo hints = {
+ .ai_family = AF_UNSPEC, .ai_socktype = SOCK_DGRAM, .ai_flags = AI_NUMERICHOST};
+ snprintf(sbuf, sizeof(sbuf), "%u", NAMESERVER_PORT);
+ for (unsigned i = 0; i < numservers; i++) {
+ // The addrinfo structures allocated here are freed in _free_nameservers_locked().
+ int rt = getaddrinfo(servers[i], sbuf, &hints, &nsaddrinfo[i]);
+ if (rt != 0) {
+ for (unsigned j = 0; j < i; j++) {
+ freeaddrinfo(nsaddrinfo[j]);
+ nsaddrinfo[j] = NULL;
+ }
+ XLOG("%s: getaddrinfo(%s)=%s", __FUNCTION__, servers[i], gai_strerror(rt));
+ return EINVAL;
+ }
+ }
+
+ pthread_once(&_res_cache_once, _res_cache_init);
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ // creates the cache if not created
+ _get_res_cache_for_net_locked(netid);
+
+ struct resolv_cache_info* cache_info = _find_cache_info_locked(netid);
+
+ if (cache_info != NULL) {
+ uint8_t old_max_samples = cache_info->params.max_samples;
+ if (params != NULL) {
+ cache_info->params = *params;
+ } else {
+ _resolv_set_default_params(&cache_info->params);
+ }
+
+ if (!_resolv_is_nameservers_equal_locked(cache_info, servers, numservers)) {
+ // free current before adding new
+ _free_nameservers_locked(cache_info);
+ unsigned i;
+ for (i = 0; i < numservers; i++) {
+ cache_info->nsaddrinfo[i] = nsaddrinfo[i];
+ cache_info->nameservers[i] = strdup(servers[i]);
+ XLOG("%s: netid = %u, addr = %s\n", __FUNCTION__, netid, servers[i]);
+ }
+ cache_info->nscount = numservers;
+
+ // Clear the NS statistics because the mapping to nameservers might have changed.
+ _res_cache_clear_stats_locked(cache_info);
+
+ // increment the revision id to ensure that sample state is not written back if the
+ // servers change; in theory it would suffice to do so only if the servers or
+ // max_samples actually change, in practice the overhead of checking is higher than the
+ // cost, and overflows are unlikely
+ ++cache_info->revision_id;
+ } else if (cache_info->params.max_samples != old_max_samples) {
+ // If the maximum number of samples changes, the overhead of keeping the most recent
+ // samples around is not considered worth the effort, so they are cleared instead. All
+ // other parameters do not affect shared state: Changing these parameters does not
+ // invalidate the samples, as they only affect aggregation and the conditions under
+ // which servers are considered usable.
+ _res_cache_clear_stats_locked(cache_info);
+ ++cache_info->revision_id;
+ }
+
+ // Always update the search paths, since determining whether they actually changed is
+ // complex due to the zero-padding, and probably not worth the effort. Cache-flushing
+ // however is not // necessary, since the stored cache entries do contain the domain, not
+ // just the host name.
+ // code moved from res_init.c, load_domain_search_list
+ strlcpy(cache_info->defdname, domains, sizeof(cache_info->defdname));
+ if ((cp = strchr(cache_info->defdname, '\n')) != NULL) *cp = '\0';
+
+ cp = cache_info->defdname;
+ offset = cache_info->dnsrch_offset;
+ while (offset < cache_info->dnsrch_offset + MAXDNSRCH) {
+ while (*cp == ' ' || *cp == '\t') /* skip leading white space */
+ cp++;
+ if (*cp == '\0') /* stop if nothing more to do */
+ break;
+ *offset++ = cp - cache_info->defdname; /* record this search domain */
+ while (*cp) { /* zero-terminate it */
+ if (*cp == ' ' || *cp == '\t') {
+ *cp++ = '\0';
+ break;
+ }
+ cp++;
+ }
+ }
+ *offset = -1; /* cache_info->dnsrch_offset has MAXDNSRCH+1 items */
+ }
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ return 0;
+}
+
+static int _resolv_is_nameservers_equal_locked(struct resolv_cache_info* cache_info,
+ const char** servers, int numservers) {
+ if (cache_info->nscount != numservers) {
+ return 0;
+ }
+
+ // Compare each name server against current name servers.
+ // TODO: this is incorrect if the list of current or previous nameservers
+ // contains duplicates. This does not really matter because the framework
+ // filters out duplicates, but we should probably fix it. It's also
+ // insensitive to the order of the nameservers; we should probably fix that
+ // too.
+ for (int i = 0; i < numservers; i++) {
+ for (int j = 0;; j++) {
+ if (j >= numservers) {
+ return 0;
+ }
+ if (strcmp(cache_info->nameservers[i], servers[j]) == 0) {
+ break;
+ }
+ }
+ }
+
+ return 1;
+}
+
+static void _free_nameservers_locked(struct resolv_cache_info* cache_info) {
+ int i;
+ for (i = 0; i < cache_info->nscount; i++) {
+ free(cache_info->nameservers[i]);
+ cache_info->nameservers[i] = NULL;
+ if (cache_info->nsaddrinfo[i] != NULL) {
+ freeaddrinfo(cache_info->nsaddrinfo[i]);
+ cache_info->nsaddrinfo[i] = NULL;
+ }
+ cache_info->nsstats[i].sample_count = cache_info->nsstats[i].sample_next = 0;
+ }
+ cache_info->nscount = 0;
+ _res_cache_clear_stats_locked(cache_info);
+ ++cache_info->revision_id;
+}
+
+void _resolv_populate_res_for_net(res_state statp) {
+ if (statp == NULL) {
+ return;
+ }
+
+ pthread_once(&_res_cache_once, _res_cache_init);
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ struct resolv_cache_info* info = _find_cache_info_locked(statp->netid);
+ if (info != NULL) {
+ int nserv;
+ struct addrinfo* ai;
+ XLOG("%s: %u\n", __FUNCTION__, statp->netid);
+ for (nserv = 0; nserv < MAXNS; nserv++) {
+ ai = info->nsaddrinfo[nserv];
+ if (ai == NULL) {
+ break;
+ }
+
+ if ((size_t) ai->ai_addrlen <= sizeof(statp->_u._ext.ext->nsaddrs[0])) {
+ if (statp->_u._ext.ext != NULL) {
+ memcpy(&statp->_u._ext.ext->nsaddrs[nserv], ai->ai_addr, ai->ai_addrlen);
+ statp->nsaddr_list[nserv].sin_family = AF_UNSPEC;
+ } else {
+ if ((size_t) ai->ai_addrlen <= sizeof(statp->nsaddr_list[0])) {
+ memcpy(&statp->nsaddr_list[nserv], ai->ai_addr, ai->ai_addrlen);
+ } else {
+ statp->nsaddr_list[nserv].sin_family = AF_UNSPEC;
+ }
+ }
+ } else {
+ XLOG("%s: found too long addrlen", __FUNCTION__);
+ }
+ }
+ statp->nscount = nserv;
+ // now do search domains. Note that we cache the offsets as this code runs alot
+ // but the setting/offset-computer only runs when set/changed
+ // WARNING: Don't use str*cpy() here, this string contains zeroes.
+ memcpy(statp->defdname, info->defdname, sizeof(statp->defdname));
+ char** pp = statp->dnsrch;
+ int* p = info->dnsrch_offset;
+ while (pp < statp->dnsrch + MAXDNSRCH && *p != -1) {
+ *pp++ = &statp->defdname[0] + *p++;
+ }
+ }
+ pthread_mutex_unlock(&_res_cache_list_lock);
+}
+
+/* Resolver reachability statistics. */
+
+static void _res_cache_add_stats_sample_locked(struct __res_stats* stats,
+ const struct __res_sample* sample, int max_samples) {
+ // Note: This function expects max_samples > 0, otherwise a (harmless) modification of the
+ // allocated but supposedly unused memory for samples[0] will happen
+ XLOG("%s: adding sample to stats, next = %d, count = %d", __FUNCTION__, stats->sample_next,
+ stats->sample_count);
+ stats->samples[stats->sample_next] = *sample;
+ if (stats->sample_count < max_samples) {
+ ++stats->sample_count;
+ }
+ if (++stats->sample_next >= max_samples) {
+ stats->sample_next = 0;
+ }
+}
+
+static void _res_cache_clear_stats_locked(struct resolv_cache_info* cache_info) {
+ if (cache_info) {
+ for (int i = 0; i < MAXNS; ++i) {
+ cache_info->nsstats->sample_count = cache_info->nsstats->sample_next = 0;
+ }
+ }
+}
+
+int android_net_res_stats_get_info_for_net(unsigned netid, int* nscount,
+ struct sockaddr_storage servers[MAXNS], int* dcount,
+ char domains[MAXDNSRCH][MAXDNSRCHPATH],
+ struct __res_params* params,
+ struct __res_stats stats[MAXNS]) {
+ int revision_id = -1;
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ struct resolv_cache_info* info = _find_cache_info_locked(netid);
+ if (info) {
+ if (info->nscount > MAXNS) {
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ XLOG("%s: nscount %d > MAXNS %d", __FUNCTION__, info->nscount, MAXNS);
+ errno = EFAULT;
+ return -1;
+ }
+ int i;
+ for (i = 0; i < info->nscount; i++) {
+ // Verify that the following assumptions are held, failure indicates corruption:
+ // - getaddrinfo() may never return a sockaddr > sockaddr_storage
+ // - all addresses are valid
+ // - there is only one address per addrinfo thanks to numeric resolution
+ int addrlen = info->nsaddrinfo[i]->ai_addrlen;
+ if (addrlen < (int) sizeof(struct sockaddr) || addrlen > (int) sizeof(servers[0])) {
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ XLOG("%s: nsaddrinfo[%d].ai_addrlen == %d", __FUNCTION__, i, addrlen);
+ errno = EMSGSIZE;
+ return -1;
+ }
+ if (info->nsaddrinfo[i]->ai_addr == NULL) {
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ XLOG("%s: nsaddrinfo[%d].ai_addr == NULL", __FUNCTION__, i);
+ errno = ENOENT;
+ return -1;
+ }
+ if (info->nsaddrinfo[i]->ai_next != NULL) {
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ XLOG("%s: nsaddrinfo[%d].ai_next != NULL", __FUNCTION__, i);
+ errno = ENOTUNIQ;
+ return -1;
+ }
+ }
+ *nscount = info->nscount;
+ for (i = 0; i < info->nscount; i++) {
+ memcpy(&servers[i], info->nsaddrinfo[i]->ai_addr, info->nsaddrinfo[i]->ai_addrlen);
+ stats[i] = info->nsstats[i];
+ }
+ for (i = 0; i < MAXDNSRCH; i++) {
+ const char* cur_domain = info->defdname + info->dnsrch_offset[i];
+ // dnsrch_offset[i] can either be -1 or point to an empty string to indicate the end
+ // of the search offsets. Checking for < 0 is not strictly necessary, but safer.
+ // TODO: Pass in a search domain array instead of a string to
+ // _resolv_set_nameservers_for_net() and make this double check unnecessary.
+ if (info->dnsrch_offset[i] < 0 ||
+ ((size_t) info->dnsrch_offset[i]) >= sizeof(info->defdname) || !cur_domain[0]) {
+ break;
+ }
+ strlcpy(domains[i], cur_domain, MAXDNSRCHPATH);
+ }
+ *dcount = i;
+ *params = info->params;
+ revision_id = info->revision_id;
+ }
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ return revision_id;
+}
+
+int _resolv_cache_get_resolver_stats(unsigned netid, struct __res_params* params,
+ struct __res_stats stats[MAXNS]) {
+ int revision_id = -1;
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ struct resolv_cache_info* info = _find_cache_info_locked(netid);
+ if (info) {
+ memcpy(stats, info->nsstats, sizeof(info->nsstats));
+ *params = info->params;
+ revision_id = info->revision_id;
+ }
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+ return revision_id;
+}
+
+void _resolv_cache_add_resolver_stats_sample(unsigned netid, int revision_id, int ns,
+ const struct __res_sample* sample, int max_samples) {
+ if (max_samples <= 0) return;
+
+ pthread_mutex_lock(&_res_cache_list_lock);
+
+ struct resolv_cache_info* info = _find_cache_info_locked(netid);
+
+ if (info && info->revision_id == revision_id) {
+ _res_cache_add_stats_sample_locked(&info->nsstats[ns], sample, max_samples);
+ }
+
+ pthread_mutex_unlock(&_res_cache_list_lock);
+}