auto import from //branches/cupcake/...@132276
diff --git a/libc/netbsd/resolv/res_cache.c b/libc/netbsd/resolv/res_cache.c
index 210dfdd..2c912de 100644
--- a/libc/netbsd/resolv/res_cache.c
+++ b/libc/netbsd/resolv/res_cache.c
@@ -28,30 +28,104 @@
#include "resolv_cache.h"
#include <stdlib.h>
+#include <string.h>
#include <time.h>
#include "pthread.h"
-/* this code implements a small DNS resolver cache for all gethostbyname* functions
+/* This code implements a small and *simple* DNS resolver cache.
*
- * the cache is shared between all threads of the current process, but the result of
- * a succesful lookup is always copied to a thread-local variable to honor the persistence
- * rules of the gethostbyname*() APIs.
+ * 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.
+/* 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. otherwise we could keep
- * stale addresses in the cache and be oblivious to DNS server changes
+/* entries older than CONFIG_SECONDS seconds are always discarded.
*/
#define CONFIG_SECONDS (60*10) /* 10 minutes */
-/* maximum number of entries kept in the cache. be frugal, this is the C library
- * this MUST BE A POWER OF 2
+/* 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 128
+#define CONFIG_MAX_ENTRIES 64
/****************************************************************************/
/****************************************************************************/
@@ -61,42 +135,204 @@
/****************************************************************************/
/****************************************************************************/
-#define DEBUG 0
+/* set to 1 to debug cache operations */
+#define DEBUG 0
+
+/* set to 1 to debug query data */
+#define DEBUG_DATA 0
#if DEBUG
-#include <fcntl.h>
-#include <errno.h>
-#include <stdarg.h>
+# include <logd.h>
+# define XLOG(...) \
+ __libc_android_log_print(ANDROID_LOG_DEBUG,"libc",__VA_ARGS__)
+
#include <stdio.h>
-static void
-xlog( const char* fmt, ... )
+#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 )
{
- static int fd = -2;
- int ret;
-
- if (fd == -2) {
- do {
- fd = open( "/data/dns.log", O_CREAT | O_APPEND | O_WRONLY, 0666 );
- } while (fd < 0 && errno == EINTR);
+ if (p < end) {
+ if (p+1 == end)
+ *p++ = 0;
+ else {
+ *p++ = (char) c;
+ *p = 0;
+ }
}
-
- if (fd >= 0) {
- char temp[128];
- va_list args;
- va_start(args, fmt);
- vsnprintf( temp, sizeof(temp), fmt, args);
- va_end(args);
-
- do {
- ret = write( fd, temp, strlen(temp) );
- } while (ret == -1 && errno == EINTR);
- }
+ return p;
}
-#define XLOG(...) xlog(__VA_ARGS__)
-#else
-#define XLOG(...) ((void)0)
-#endif
+/* 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 )
@@ -107,96 +343,625 @@
return tv.tv_sec;
}
-/****************************************************************************/
-/****************************************************************************/
-/***** *****/
-/***** *****/
-/***** *****/
-/****************************************************************************/
-/****************************************************************************/
-
-/* used to define the content of _RESOLV_HOSTENT_NONE
+/* 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.
*/
-const struct hostent _resolv_hostent_none_cst = {
- NULL,
- NULL,
- AF_INET,
- 4,
- NULL
-};
-struct hostent*
-_resolv_hostent_copy( struct hostent* hp )
+#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 )
{
- struct hostent* dst;
- int nn, len;
- char* p;
- int num_aliases = 0, num_addresses = 0;
+ packet->base = buff;
+ packet->end = buff + bufflen;
+ packet->cursor = buff;
+}
- if (hp == NULL)
- return NULL;
+static void
+_dnsPacket_rewind( DnsPacket* packet )
+{
+ packet->cursor = packet->base;
+}
- if (hp == _RESOLV_HOSTENT_NONE)
- return hp;
+static void
+_dnsPacket_skip( DnsPacket* packet, int count )
+{
+ const uint8_t* p = packet->cursor + count;
- len = sizeof(*hp);
- len += strlen(hp->h_name) + 1;
+ if (p > packet->end)
+ p = packet->end;
- if (hp->h_aliases != NULL) {
- for (nn = 0; hp->h_aliases[nn] != NULL; nn++)
- len += sizeof(char*) + strlen(hp->h_aliases[nn]) + 1;
- num_aliases = nn;
+ 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 */
}
- len += sizeof(char*);
+ /* malformed data */
+ XLOG("malformed QNAME");
+ return 0;
+}
- for (nn = 0; hp->h_addr_list[nn] != NULL; nn++) {
- len += sizeof(char*) + hp->h_length;
+/* 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;
}
- num_addresses = nn;
- len += sizeof(char*);
-
- dst = malloc( len );
- if (dst == NULL)
- return NULL;
-
- dst->h_aliases = (char**)(dst + 1);
- dst->h_addr_list = dst->h_aliases + num_aliases + 1;
- dst->h_length = hp->h_length;
- dst->h_addrtype = hp->h_addrtype;
-
- p = (char*)(dst->h_addr_list + num_addresses + 1);
-
- /* write the addresses first, to help with alignment issues */
- for (nn = 0; nn < num_addresses; nn++) {
- dst->h_addr_list[nn] = p;
- len = hp->h_length;
- memcpy( p, hp->h_addr_list[nn], len );
- p += len;
+ /* CLASS must be IN */
+ if (!_dnsPacket_checkBytes(packet, 2, DNS_CLASS_IN)) {
+ XLOG("unsupported CLASS");
+ return 0;
}
- dst->h_addr_list[nn] = NULL;
- for (nn = 0; nn < num_aliases; nn++) {
- dst->h_aliases[nn] = p;
- len = strlen(hp->h_aliases[nn]) + 1;
- memcpy( p, hp->h_aliases[nn], len );
- p += len;
+ 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;
}
- dst->h_aliases[nn] = NULL;
- dst->h_name = p;
- len = strlen(hp->h_name) + 1;
- memcpy(p, hp->h_name, len);
- p += len;
+ /* 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;
+ }
- return dst;
+ /* 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;
}
-void
-_resolv_hostent_free( struct hostent* hp )
+static unsigned
+_dnsPacket_hashQName( DnsPacket* packet, unsigned hash )
{
- if (hp && hp != _RESOLV_HOSTENT_NONE)
- free(hp);
+ 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;
}
/****************************************************************************/
@@ -207,15 +972,23 @@
/****************************************************************************/
/****************************************************************************/
+/* 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;
- const char* name;
- short af;
- short index;
+ unsigned int hash; /* hash value */
+ struct Entry* hlink; /* next in collision chain */
struct Entry* mru_prev;
struct Entry* mru_next;
- time_t when;
- struct hostent* hp;
+
+ 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;
@@ -224,30 +997,10 @@
{
/* everything is allocated in a single memory block */
if (e) {
- _resolv_hostent_free(e->hp);
free(e);
}
}
-static void
-entry_init_key( Entry* e, const char* name, int af )
-{
- unsigned h = 0;
- const char* p = name;
-
- /* compute hash */
- p = name;
- while (*p) {
- h = h*33 + *p++;
- }
- h += af*17;
-
- e->hash = h;
- e->name = name;
- e->af = (short) af;
-}
-
-
static __inline__ void
entry_mru_remove( Entry* e )
{
@@ -267,46 +1020,75 @@
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 char* name, int af, int index, struct hostent* hp )
+entry_alloc( const Entry* init, const void* answer, int answerlen )
{
Entry* e;
- int num_aliases = 0;
- int num_addresses = 0;
- char** aliases;
- char** addresses;
+ int size;
- /* compute the length of the memory block that will contain everything */
- int len = sizeof(*e) + strlen(name)+1;
-
- e = malloc(len);
+ size = sizeof(*e) + init->querylen + answerlen;
+ e = calloc(size, 1);
if (e == NULL)
return e;
- entry_init_key(e, name, af);
+ e->hash = init->hash;
+ e->query = (const uint8_t*)(e+1);
+ e->querylen = init->querylen;
- e->mru_next = e->mru_prev = e;
- e->index = (short) index;
- e->when = _time_now();
- e->hp = _resolv_hostent_copy(hp);
+ memcpy( (char*)e->query, init->query, e->querylen );
- if (e->hp == NULL) {
- free(e);
- return NULL;
- }
+ e->answer = e->query + e->querylen;
+ e->answerlen = answerlen;
- e->name = (char*)(e+1);
- len = strlen(name)+1;
- memcpy( (char*)e->name, name, len );
+ memcpy( (char*)e->answer, answer, e->answerlen );
+
+ e->when = _time_now();
+
return e;
}
-
-static __inline__ int
+static int
entry_equals( const Entry* e1, const Entry* e2 )
{
- return e1->hash == e2->hash && e1->af == e2->af && !strcmp( e1->name, e2->name );
+ 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);
}
/****************************************************************************/
@@ -317,30 +1099,49 @@
/****************************************************************************/
/****************************************************************************/
+/* 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;
- int disabled;
- Entry* entries[ MAX_HASH_ENTRIES ]; /* hash-table of pointers to entries */
+ int num_entries;
+ Entry mru_list;
+ pthread_mutex_t lock;
+ unsigned generation;
+ int last_id;
+ Entry* entries[ MAX_HASH_ENTRIES ];
} Cache;
-void
-_resolv_cache_destroy( struct resolv_cache* cache )
-{
- if (cache != NULL) {
- int nn;
- for (nn = 0; nn < MAX_HASH_ENTRIES; nn++) {
- entry_free(cache->entries[nn]);
- }
- pthread_mutex_destroy(&cache->lock);
- free(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 )
@@ -349,116 +1150,203 @@
cache = calloc(sizeof(*cache), 1);
if (cache) {
- const char* env = getenv(CONFIG_ENV);
-
- if (env && atoi(env) == 0)
- cache->disabled = 1;
-
+ 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=%p %s\n", __FUNCTION__, cache, cache->disabled ? "disabled" : "enabled" );
+ XLOG("%s: cache created\n", __FUNCTION__);
}
return cache;
}
-static int
-_resolv_cache_find_index( Cache* cache,
- const char* name,
- int af )
+#if DEBUG
+static void
+_dump_query( const uint8_t* query, int querylen )
{
- Entry key;
- int nn, step, tries;
+ char temp[256], *p=temp, *end=p+sizeof(temp);
+ DnsPacket pack[1];
- entry_init_key( &key, name, af );
-
- tries = MAX_HASH_ENTRIES;
- nn = key.hash % MAX_HASH_ENTRIES;
- step = 5;
-
- while (tries > 0) {
- Entry* key2 = cache->entries[nn];
-
- if (key2 == NULL) {
- return -(nn + 1);
- }
-
- if (entry_equals( &key, key2 ) ) {
- return nn;
- }
-
- nn = (nn + step) % MAX_HASH_ENTRIES;
- tries -= 1;
- }
- return -(MAX_HASH_ENTRIES+1);
+ _dnsPacket_init(pack, query, querylen);
+ p = _dnsPacket_bprintQuery(pack, p, end);
+ XLOG("QUERY: %s", temp);
}
-
static void
-_resolv_cache_remove( struct resolv_cache* cache,
- Entry* e )
+_cache_dump_mru( Cache* cache )
{
- XLOG("%s: name='%s' af=%d\n", __FUNCTION__, e->name, e->af);
- cache->entries[ e->index ] = NULL; /* remove from hash table */
- entry_mru_remove( e );
- entry_free( e );
+ 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;
}
-
-struct hostent*
-_resolv_cache_lookup( struct resolv_cache* cache,
- const char* name,
- int af )
+/* Remove the oldest entry from the hash table.
+ */
+static void
+_cache_remove_oldest( Cache* cache )
{
- int index;
- struct hostent* result = NULL;
+ Entry* oldest = cache->mru_list.mru_prev;
+ Entry** lookup = _cache_lookup_p(cache, oldest);
- if (cache->disabled)
- return NULL;
+ 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 );
- XLOG( "%s: cache=%p name='%s' af=%d ", __FUNCTION__, cache, name, af );
- index = _resolv_cache_find_index( cache, name, af );
- if (index >= 0) {
- Entry* e = cache->entries[index];
- time_t now = _time_now();
- struct hostent** pht;
+ /* 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;
- /* ignore stale entries, they will be discarded in _resolv_cache_add */
- if ( (unsigned)(now - e->when) >= CONFIG_SECONDS ) {
- XLOG( " OLD\n" );
- goto Exit;
- }
-
- /* 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 );
- }
-
- /* now copy the result into a thread-local variable */
- pht = __get_res_cache_hostent_p();
- if (pht == NULL) {
- XLOG( " NOTLS\n" ); /* shouldn't happen */
- goto Exit;
- }
-
- if (pht[0]) {
- _resolv_hostent_free( pht[0] ); /* clear previous value */
- pht[0] = NULL;
- }
- result = _resolv_hostent_copy( e->hp );
- if (result == NULL) {
- XLOG( " NOMEM\n" ); /* bummer */
- goto Exit;
- }
- XLOG( " OK\n" );
- pht[0] = result;
+ if (e == NULL) {
+ XLOG( "NOT IN CACHE");
goto Exit;
}
- XLOG( " KO\n" );
+
+ 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;
@@ -467,42 +1355,59 @@
void
_resolv_cache_add( struct resolv_cache* cache,
- const char* name,
- int af,
- struct hostent* hp )
+ const void* query,
+ int querylen,
+ const void* answer,
+ int answerlen )
{
+ Entry key[1];
Entry* e;
- int index;
+ Entry** lookup;
- if (cache->disabled)
+ /* 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: cache=%p name='%s' af=%d\n", __FUNCTION__, cache, name, af);
+ XLOG( "%s: query:", __FUNCTION__ );
+ XLOG_QUERY(query,querylen);
+#if DEBUG_DATA
+ XLOG( "answer:");
+ XLOG_BYTES(answer,answerlen);
+#endif
- /* get rid of the oldest entry if needed */
+ 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) {
- Entry* oldest = cache->mru_list.mru_prev;
- _resolv_cache_remove( cache, oldest );
+ _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;
+ }
}
- index = _resolv_cache_find_index( cache, name, af );
- if (index >= 0) {
- /* discard stale entry */
- _resolv_cache_remove( cache, cache->entries[index] );
- } else {
- index = -(index+1);
- if (index >= MAX_HASH_ENTRIES)
- goto Exit; /* should not happen */
- }
-
- e = entry_alloc( name, af, index, hp );
+ e = entry_alloc( key, answer, answerlen );
if (e != NULL) {
- entry_mru_add( e, &cache->mru_list );
- cache->entries[index] = e;
- cache->num_entries += 1;
+ _cache_add_p(cache, lookup, e);
}
+#if DEBUG
+ _cache_dump_mru(cache);
+#endif
Exit:
pthread_mutex_unlock( &cache->lock );
}
@@ -521,6 +1426,13 @@
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();
}
@@ -531,3 +1443,19 @@
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 );
+}
diff --git a/libc/netbsd/resolv/res_send.c b/libc/netbsd/resolv/res_send.c
index 24b740a..3aca760 100644
--- a/libc/netbsd/resolv/res_send.c
+++ b/libc/netbsd/resolv/res_send.c
@@ -81,6 +81,9 @@
#endif
#endif /* LIBC_SCCS and not lint */
+/* set to 1 to use our small/simple/limited DNS cache */
+#define USE_RESOLV_CACHE 1
+
/*
* Send query to name server and wait for reply.
*/
@@ -111,6 +114,10 @@
#include <isc/eventlib.h>
+#if USE_RESOLV_CACHE
+# include <resolv_cache.h>
+#endif
+
#ifndef DE_CONST
#define DE_CONST(c,v) v = ((c) ? \
strchr((const void *)(c), *(const char *)(const void *)(c)) : NULL)
@@ -344,12 +351,17 @@
return (1);
}
+
int
res_nsend(res_state statp,
const u_char *buf, int buflen, u_char *ans, int anssiz)
{
int gotsomewhere, terrno, try, v_circuit, resplen, ns, n;
char abuf[NI_MAXHOST];
+#if USE_RESOLV_CACHE
+ struct resolv_cache* cache;
+ ResolvCacheStatus cache_status = RESOLV_CACHE_UNSUPPORTED;
+#endif
if (statp->nscount == 0) {
errno = ESRCH;
@@ -365,6 +377,20 @@
gotsomewhere = 0;
terrno = ETIMEDOUT;
+#if USE_RESOLV_CACHE
+ cache = __get_res_cache();
+ if (cache != NULL) {
+ int anslen = 0;
+ cache_status = _resolv_cache_lookup(
+ cache, buf, buflen,
+ ans, anssiz, &anslen);
+
+ if (cache_status == RESOLV_CACHE_FOUND) {
+ return anslen;
+ }
+ }
+#endif
+
/*
* If the ns_addr_list in the resolver context has changed, then
* invalidate our cached copy and the associated timing data.
@@ -534,6 +560,12 @@
(stdout, "%s", ""),
ans, (resplen > anssiz) ? anssiz : resplen);
+#if USE_RESOLV_CACHE
+ if (cache_status == RESOLV_CACHE_NOTFOUND) {
+ _resolv_cache_add(cache, buf, buflen,
+ ans, resplen);
+ }
+#endif
/*
* If we have temporarily opened a virtual circuit,
* or if we haven't been asked to keep a socket open,
diff --git a/libc/netbsd/resolv/res_state.c b/libc/netbsd/resolv/res_state.c
index 8f2851a..3a2301d 100644
--- a/libc/netbsd/resolv/res_state.c
+++ b/libc/netbsd/resolv/res_state.c
@@ -46,7 +46,6 @@
struct __res_state _nres[1];
unsigned _serial;
struct prop_info* _pi;
- struct hostent* _hostent;
struct res_static _rstatic[1];
} _res_thread;
@@ -66,9 +65,9 @@
if ( res_ninit( rt->_nres ) < 0 ) {
free(rt);
rt = NULL;
+ } else {
+ memset(rt->_rstatic, 0, sizeof rt->_rstatic);
}
- rt->_hostent = NULL;
- memset(rt->_rstatic, 0, sizeof rt->_rstatic);
}
return rt;
}
@@ -93,7 +92,6 @@
_res_thread* rt = _rt;
_res_static_done(rt->_rstatic);
- _resolv_hostent_free(rt->_hostent);
res_ndestroy(rt->_nres);
free(rt);
}
@@ -132,6 +130,7 @@
rt = NULL;
pthread_setspecific( _res_key, rt );
}
+ _resolv_cache_reset(rt->_serial);
return rt;
}
@@ -177,14 +176,6 @@
res=res;
}
-struct hostent**
-__get_res_cache_hostent_p(void)
-{
- _res_thread* rt = _res_thread_get();
-
- return rt ? &rt->_hostent : NULL;
-}
-
res_static
__res_get_static(void)
{