Major addition to support DNS SRV resolution in PJSIP:

- added DNS asynchronous/caching resolver engine in
  PJLIB-UTIL (resolver.[hc])
- modified SIP resolver (sip_resolve.c) to properly
  perform DNS SRV/A resolution when DNS resolution is
  enabled.
- added dns_test.c in PJSIP-TEST for testing the SIP
  resolver.
- added nameserver configuration in PJSUA-LIB
- added "--nameserver" option in PJSUA.
- updated project/Makefiles and doxygen documentation.



git-svn-id: http://svn.pjsip.org/repos/pjproject/trunk@753 74dad513-b988-da41-8d7b-12977e46ad98

4 files changed, 1732 insertions, 52 deletions

diff --git a/pjlib-util/src/pjlib-util/dns.c b/pjlib-util/src/pjlib-util/dns.c
index 2afd6a22..e2d3b9f4 100644
--- a/pjlib-util/src/pjlib-util/dns.c
+++ b/pjlib-util/src/pjlib-util/dns.c
@@ -25,13 +25,29 @@
 #include <pj/string.h>
 
 
+PJ_DEF(const char *) pj_dns_get_type_name(int type)
+{
+    switch (type) {
+    case PJ_DNS_TYPE_A:	    return "A";
+    case PJ_DNS_TYPE_SRV:   return "SRV";
+    case PJ_DNS_TYPE_NS:    return "NS";
+    case PJ_DNS_TYPE_CNAME: return "CNAME";
+    case PJ_DNS_TYPE_PTR:   return "PTR";
+    case PJ_DNS_TYPE_MX:    return "MX";
+    case PJ_DNS_TYPE_TXT:   return "TXT";
+    case PJ_DNS_TYPE_NAPTR: return "NAPTR";
+    }
+    return "(Unknown)";
+}
+
+
 /**
  * Initialize a DNS query transaction.
  */
 PJ_DEF(pj_status_t) pj_dns_make_query( void *packet,
 				       unsigned *size,
 				       pj_uint16_t id,
-				       pj_dns_type qtype,
+				       int qtype,
 				       const pj_str_t *name)
 {
     pj_dns_hdr *hdr;
@@ -224,17 +240,42 @@ static pj_status_t get_name(int rec_counter, const char *pkt,
 
 
 /* Skip query records. */
-static pj_status_t skip_query(const char *pkt, const char *start, 
-			      const char *max, int *skip_len)
+static pj_status_t parse_query(pj_dns_parsed_query *q, pj_pool_t *pool,
+			       const char *pkt, const char *start, 
+			       const char *max, int *parsed_len)
 {
-    int name_len = 0;
+    const char *p = start;
+    int name_len, name_part_len;
     pj_status_t status;
 
-    status = get_name_len(0, pkt, start, max, skip_len, &name_len);
+    /* Get the length of the name */
+    status = get_name_len(0, pkt, start, max, &name_part_len, &name_len);
+    if (status != PJ_SUCCESS)
+	return status;
+
+    /* Allocate memory for the name */
+    q->name.ptr = pj_pool_alloc(pool, name_len+4);
+    q->name.slen = 0;
+
+    /* Get the name */
+    status = get_name(0, pkt, start, max, &q->name);
     if (status != PJ_SUCCESS)
 	return status;
 
-    (*skip_len) += 4;
+    p = (start + name_part_len);
+
+    /* Get the type */
+    pj_memcpy(&q->type, p, 2);
+    q->type = pj_ntohs(q->type);
+    p += 2;
+
+    /* Get the class */
+    pj_memcpy(&q->dnsclass, p, 2);
+    q->dnsclass = pj_ntohs(q->dnsclass);
+    p += 2;
+
+    *parsed_len = (int)(p - start);
+
     return PJ_SUCCESS;
 }
 
@@ -275,12 +316,12 @@ static pj_status_t parse_rr(pj_dns_parsed_rr *rr, pj_pool_t *pool,
     p += 2;
     
     /* Get the class */
-    pj_memcpy(&rr->class_, p, 2);
-    rr->class_ = pj_ntohs(rr->class_);
+    pj_memcpy(&rr->dnsclass, p, 2);
+    rr->dnsclass = pj_ntohs(rr->dnsclass);
     p += 2;
 
     /* Class MUST be IN */
-    if (rr->class_ != 1)
+    if (rr->dnsclass != 1)
 	return PJLIB_UTIL_EDNSINCLASS;
 
     /* Get TTL */
@@ -297,10 +338,6 @@ static pj_status_t parse_rr(pj_dns_parsed_rr *rr, pj_pool_t *pool,
     if (p + rr->rdlength > max)
 	return PJLIB_UTIL_EDNSINSIZE;
 
-    /* Copy the raw data */
-    rr->data = pj_pool_alloc(pool, rr->rdlength);
-    pj_memcpy(rr->data, p, rr->rdlength);
-
     /* Parse some well known records */
     if (rr->type == PJ_DNS_TYPE_A) {
 	pj_in_addr ip_addr;
@@ -364,6 +401,10 @@ static pj_status_t parse_rr(pj_dns_parsed_rr *rr, pj_pool_t *pool,
 	p += name_part_len;
 
     } else {
+	/* Copy the raw data */
+	rr->data = pj_pool_alloc(pool, rr->rdlength);
+	pj_memcpy(rr->data, p, rr->rdlength);
+
 	p += rr->rdlength;
     }
 
@@ -373,14 +414,14 @@ static pj_status_t parse_rr(pj_dns_parsed_rr *rr, pj_pool_t *pool,
 
 
 /*
- * Parse raw DNS response packet into DNS response structure.
+ * Parse raw DNS packet into DNS packet structure.
  */
-PJ_DEF(pj_status_t) pj_dns_parse_response( pj_pool_t *pool,
-					   const void *packet,
-					   unsigned size,
-					   pj_dns_parsed_response **p_res)
+PJ_DEF(pj_status_t) pj_dns_parse_packet( pj_pool_t *pool,
+				  	 const void *packet,
+					 unsigned size,
+					 pj_dns_parsed_packet **p_res)
 {
-    pj_dns_parsed_response *res;
+    pj_dns_parsed_packet *res;
     char *start, *end;
     pj_status_t status;
     unsigned i;
@@ -392,8 +433,8 @@ PJ_DEF(pj_status_t) pj_dns_parse_response( pj_pool_t *pool,
     if (size < sizeof(pj_dns_hdr))
 	return PJLIB_UTIL_EDNSINSIZE;
 
-    /* Create the response */
-    res = pj_pool_zalloc(pool, sizeof(pj_dns_parsed_response));
+    /* Create the structure */
+    res = pj_pool_zalloc(pool, sizeof(pj_dns_parsed_packet));
 
     /* Copy the DNS header, and convert endianness to host byte order */
     pj_memcpy(&res->hdr, packet, sizeof(pj_dns_hdr));
@@ -408,17 +449,21 @@ PJ_DEF(pj_status_t) pj_dns_parse_response( pj_pool_t *pool,
     start = ((char*)packet) + sizeof(pj_dns_hdr);
     end = ((char*)packet) + size;
 
-    /* If we have query records (some DNS servers do send them), skip
-     * the records.
+    /* Parse query records (if any).
      */
-    for (i=0; i<res->hdr.qdcount; ++i) {
-	int skip_len;
-
-	status = skip_query(packet, start, end, &skip_len);
-	if (status != PJ_SUCCESS)
-	    return status;
+    if (res->hdr.qdcount) {
+	res->q = pj_pool_zalloc(pool, res->hdr.qdcount *
+				      sizeof(pj_dns_parsed_query));
+	for (i=0; i<res->hdr.qdcount; ++i) {
+	    int parsed_len;
+	    
+	    status = parse_query(&res->q[i], pool, packet, start, end,
+				 &parsed_len);
+	    if (status != PJ_SUCCESS)
+		return status;
 
-	start += skip_len;
+	    start += parsed_len;
+	}
     }
 
     /* Parse answer, if any */
@@ -477,3 +522,155 @@ PJ_DEF(pj_status_t) pj_dns_parse_response( pj_pool_t *pool,
 
     return PJ_SUCCESS;
 }
+
+
+/* Perform name compression scheme.
+ * If a name is already in the nametable, when no need to duplicate
+ * the string with the pool, but rather just use the pointer there.
+ */
+static void apply_name_table( unsigned *count,
+			      pj_str_t nametable[],
+		    	      const pj_str_t *src,
+			      pj_pool_t *pool,
+			      pj_str_t *dst)
+{
+    unsigned i;
+
+    /* Scan strings in nametable */
+    for (i=0; i<*count; ++i) {
+	if (pj_stricmp(&nametable[i], src) == 0)
+	    break;
+    }
+
+    /* If name is found in nametable, use the pointer in the nametable */
+    if (i != *count) {
+	dst->ptr = nametable[i].ptr;
+	dst->slen = nametable[i].slen;
+	return;
+    }
+
+    /* Otherwise duplicate the string, and insert new name in nametable */
+    pj_strdup(pool, dst, src);
+
+    if (*count < PJ_DNS_MAX_NAMES_IN_NAMETABLE) {
+	nametable[*count].ptr = dst->ptr;
+	nametable[*count].slen = dst->slen;
+
+	++(*count);
+    }
+}
+
+static void copy_query(pj_pool_t *pool, pj_dns_parsed_query *dst,
+		       const pj_dns_parsed_query *src,
+		       unsigned *nametable_count,
+		       pj_str_t nametable[])
+{
+    pj_memcpy(dst, src, sizeof(*src));
+    apply_name_table(nametable_count, nametable, &src->name, pool, &dst->name);
+}
+
+
+static void copy_rr(pj_pool_t *pool, pj_dns_parsed_rr *dst,
+		    const pj_dns_parsed_rr *src,
+		    unsigned *nametable_count,
+		    pj_str_t nametable[])
+{
+    pj_memcpy(dst, src, sizeof(*src));
+    apply_name_table(nametable_count, nametable, &src->name, pool, &dst->name);
+
+    if (src->data) {
+	dst->data = pj_pool_alloc(pool, src->rdlength);
+	pj_memcpy(dst->data, src->data, src->rdlength);
+    }
+
+    if (src->type == PJ_DNS_TYPE_SRV) {
+	apply_name_table(nametable_count, nametable, &src->rdata.srv.target, 
+			 pool, &dst->rdata.srv.target);
+    } else if (src->type == PJ_DNS_TYPE_A) {
+	pj_strdup(pool, &dst->rdata.a.ip_addr, &src->rdata.a.ip_addr);
+    } else if (src->type == PJ_DNS_TYPE_CNAME) {
+	pj_strdup(pool, &dst->rdata.cname.name, &src->rdata.cname.name);
+    } else if (src->type == PJ_DNS_TYPE_NS) {
+	pj_strdup(pool, &dst->rdata.ns.name, &src->rdata.ns.name);
+    } else if (src->type == PJ_DNS_TYPE_PTR) {
+	pj_strdup(pool, &dst->rdata.ptr.name, &src->rdata.ptr.name);
+    }
+}
+
+/*
+ * Duplicate DNS packet.
+ */
+PJ_DEF(void) pj_dns_packet_dup(pj_pool_t *pool,
+			       const pj_dns_parsed_packet*p,
+			       pj_dns_parsed_packet **p_dst)
+{
+    pj_dns_parsed_packet *dst;
+    unsigned nametable_count = 0;
+#if PJ_DNS_MAX_NAMES_IN_NAMETABLE
+    pj_str_t nametable[PJ_DNS_MAX_NAMES_IN_NAMETABLE];
+#else
+    pj_str_t *nametable = NULL;
+#endif
+    unsigned i;
+
+    PJ_ASSERT_ON_FAIL(pool && p && p_dst, return);
+
+    /* Create packet and copy header */
+    *p_dst = dst = pj_pool_zalloc(pool, sizeof(pj_dns_parsed_packet));
+    pj_memcpy(&dst->hdr, &p->hdr, sizeof(p->hdr));
+
+    /* Initialize section counts in the target packet to zero.
+     * If memory allocation fails during copying process, the target packet
+     * should have a correct section counts.
+     */
+    dst->hdr.qdcount = 0;
+    dst->hdr.anscount = 0;
+    dst->hdr.nscount = 0;
+    dst->hdr.arcount = 0;
+	
+
+    /* Copy query section */
+    if (p->hdr.qdcount) {
+	dst->q = pj_pool_alloc(pool, p->hdr.qdcount * 
+				     sizeof(pj_dns_parsed_query));
+	for (i=0; i<p->hdr.qdcount; ++i) {
+	    copy_query(pool, &dst->q[i], &p->q[i], 
+		       &nametable_count, nametable);
+	    ++dst->hdr.qdcount;
+	}
+    }
+
+    /* Copy answer section */
+    if (p->hdr.anscount) {
+	dst->ans = pj_pool_alloc(pool, p->hdr.anscount * 
+				       sizeof(pj_dns_parsed_rr));
+	for (i=0; i<p->hdr.anscount; ++i) {
+	    copy_rr(pool, &dst->ans[i], &p->ans[i],
+		    &nametable_count, nametable);
+	    ++dst->hdr.anscount;
+	}
+    }
+
+    /* Copy NS section */
+    if (p->hdr.nscount) {
+	dst->ns = pj_pool_alloc(pool, p->hdr.nscount * 
+				      sizeof(pj_dns_parsed_rr));
+	for (i=0; i<p->hdr.nscount; ++i) {
+	    copy_rr(pool, &dst->ns[i], &p->ns[i],
+		    &nametable_count, nametable);
+	    ++dst->hdr.nscount;
+	}
+    }
+
+    /* Copy additional info section */
+    if (p->hdr.arcount) {
+	dst->arr = pj_pool_alloc(pool, p->hdr.arcount * 
+				       sizeof(pj_dns_parsed_rr));
+	for (i=0; i<p->hdr.arcount; ++i) {
+	    copy_rr(pool, &dst->arr[i], &p->arr[i],
+		    &nametable_count, nametable);
+	    ++dst->hdr.arcount;
+	}
+    }
+}
+
diff --git a/pjlib-util/src/pjlib-util/dns_dump.c b/pjlib-util/src/pjlib-util/dns_dump.c
index 37738c96..31602163 100644
--- a/pjlib-util/src/pjlib-util/dns_dump.c
+++ b/pjlib-util/src/pjlib-util/dns_dump.c
@@ -19,43 +19,93 @@
 #include <pjlib-util/dns.h>
 #include <pj/assert.h>
 #include <pj/log.h>
+#include <pj/string.h>
 
 #define THIS_FILE   "dns_dump.c"
 #define LEVEL	    3
 
-static const char *get_rr_name(int type)
+static const char *spell_ttl(char *buf, int size, unsigned ttl)
 {
-    switch (type) {
-    case PJ_DNS_TYPE_A:	    return "A";
-    case PJ_DNS_TYPE_NS:    return "NS";
-    case PJ_DNS_TYPE_CNAME: return "CNAME";
-    case PJ_DNS_TYPE_PTR:   return "PTR";
-    case PJ_DNS_TYPE_MX:    return "MX";
-    case PJ_DNS_TYPE_TXT:   return "TXT";
-    case PJ_DNS_TYPE_SRV:   return "SRV";
-    case PJ_DNS_TYPE_NAPTR: return "NAPTR";
+#define DAY	(3600*24)
+#define HOUR	(3600)
+#define MINUTE	(60)
+
+    char *p = buf;
+    int len;
+
+    if (ttl > DAY) {
+	len = pj_ansi_snprintf(p, size, "%dd ", ttl/DAY);
+	if (len < 1)
+	    return "-err-";
+	size -= len;
+	p += len;
+	ttl %= DAY;
     }
-    return "(Unknown)";
+
+    if (ttl > HOUR) {
+	len = pj_ansi_snprintf(p, size, "%dh ", ttl/HOUR);
+	if (len < 1)
+	    return "-err-";
+	size -= len;
+	p += len;
+	ttl %= HOUR;
+    }
+
+    if (ttl > MINUTE) {
+	len = pj_ansi_snprintf(p, size, "%dm ", ttl/MINUTE);
+	if (len < 1)
+	    return "-err-";
+	size -= len;
+	p += len;
+	ttl %= MINUTE;
+    }
+
+    if (ttl > 0) {
+	len = pj_ansi_snprintf(p, size, "%ds ", ttl);
+	if (len < 1)
+	    return "-err-";
+	size -= len;
+	p += len;
+	ttl = 0;
+    }
+
+    *p = '\0';
+    return buf;
+}
+
+
+static void dump_query(unsigned index, const pj_dns_parsed_query *q)
+{
+    PJ_LOG(3,(THIS_FILE, " %d. Name: %.*s", 
+			 index, (int)q->name.slen, q->name.ptr));
+    PJ_LOG(3,(THIS_FILE, "    Type: %s (%d)", 
+			 pj_dns_get_type_name(q->type), q->type));
+    PJ_LOG(3,(THIS_FILE, "    Class: %s (%d)", 
+		         (q->dnsclass==1 ? "IN" : "<Unknown>"), q->dnsclass));
 }
 
 static void dump_answer(unsigned index, const pj_dns_parsed_rr *rr)
 {
     const pj_str_t root_name = { "<Root>", 6 };
     const pj_str_t *name = &rr->name;
+    char ttl_words[32];
 
     if (name->slen == 0)
 	name = &root_name;
 
-    PJ_LOG(3,(THIS_FILE, " %d. %s record (type=%d)", index, get_rr_name(rr->type),
+    PJ_LOG(3,(THIS_FILE, " %d. %s record (type=%d)", 
+			 index, pj_dns_get_type_name(rr->type),
 			rr->type));
     PJ_LOG(3,(THIS_FILE, "    Name: %.*s", (int)name->slen, name->ptr));
-    PJ_LOG(3,(THIS_FILE, "    TTL: %u", rr->ttl));
+    PJ_LOG(3,(THIS_FILE, "    TTL: %u (%s)", rr->ttl, 
+			  spell_ttl(ttl_words, sizeof(ttl_words), rr->ttl)));
     PJ_LOG(3,(THIS_FILE, "    Data length: %u", rr->rdlength));
 
     if (rr->type == PJ_DNS_TYPE_SRV) {
 	PJ_LOG(3,(THIS_FILE, "    SRV: prio=%d, weight=%d %.*s:%d", 
 			     rr->rdata.srv.prio, rr->rdata.srv.weight,
-			     (int)rr->rdata.srv.target.slen, rr->rdata.srv.target.ptr,
+			     (int)rr->rdata.srv.target.slen, 
+			     rr->rdata.srv.target.ptr,
 			     rr->rdata.srv.port));
     } else if (rr->type == PJ_DNS_TYPE_CNAME ||
 	       rr->type == PJ_DNS_TYPE_NS ||
@@ -72,7 +122,7 @@ static void dump_answer(unsigned index, const pj_dns_parsed_rr *rr)
 }
 
 
-PJ_DEF(void) pj_dns_dump_response(const pj_dns_parsed_response *res)
+PJ_DEF(void) pj_dns_dump_packet(const pj_dns_parsed_packet *res)
 {
     unsigned i;
 
@@ -82,18 +132,28 @@ PJ_DEF(void) pj_dns_dump_response(const pj_dns_parsed_response *res)
     PJ_LOG(3,(THIS_FILE, "Domain Name System packet (%s):",
 		(PJ_DNS_GET_QR(res->hdr.flags) ? "response" : "query")));
     PJ_LOG(3,(THIS_FILE, " Transaction ID: %d", res->hdr.id));
-    PJ_LOG(3,(THIS_FILE, " Flags: type=%s, opcode=%d, authoritative=%d, truncated=%d, rcode=%d", 
-		(PJ_DNS_GET_QR(res->hdr.flags) ? "response" : "query"),
+    PJ_LOG(3,(THIS_FILE, 
+	      " Flags: opcode=%d, authoritative=%d, truncated=%d, rcode=%d",
 		 PJ_DNS_GET_OPCODE(res->hdr.flags),
 		 PJ_DNS_GET_AA(res->hdr.flags),
 		 PJ_DNS_GET_TC(res->hdr.flags),
 		 PJ_DNS_GET_RCODE(res->hdr.flags)));
-    PJ_LOG(3,(THIS_FILE, " Nb of question RR: %d", res->hdr.qdcount));
+    PJ_LOG(3,(THIS_FILE, " Nb of queries: %d", res->hdr.qdcount));
     PJ_LOG(3,(THIS_FILE, " Nb of answer RR: %d", res->hdr.anscount));
     PJ_LOG(3,(THIS_FILE, " Nb of authority RR: %d", res->hdr.nscount));
     PJ_LOG(3,(THIS_FILE, " Nb of additional RR: %d", res->hdr.arcount));
     PJ_LOG(3,(THIS_FILE, ""));
 
+    /* Dump queries */
+    if (res->hdr.qdcount) {
+	PJ_LOG(3,(THIS_FILE, " Queries:"));
+
+	for (i=0; i<res->hdr.qdcount; ++i) {
+	    dump_query(i, &res->q[i]);
+	}
+	PJ_LOG(3,(THIS_FILE, ""));
+    }
+
     /* Dump answers */
     if (res->hdr.anscount) {
 	PJ_LOG(3,(THIS_FILE, " Answers RR:"));
diff --git a/pjlib-util/src/pjlib-util/errno.c b/pjlib-util/src/pjlib-util/errno.c
index 4bb652aa..2da114f4 100644
--- a/pjlib-util/src/pjlib-util/errno.c
+++ b/pjlib-util/src/pjlib-util/errno.c
@@ -49,10 +49,25 @@ static const struct
     PJ_BUILD_ERR( PJLIB_UTIL_EINXML,		"Invalid XML message" ),
 
     /* DNS errors */
-    PJ_BUILD_ERR( PJLIB_UTIL_EDNSQRYTOOSMALL,	"Outgoing DNS query packet buffer is too small"),
-    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINSIZE,	"Invalid packet length in DNS response"),
-    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINCLASS,	"Invalid class in DNS response"),
-    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINNAMEPTR,	"Invalid name pointer in DNS response"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSQRYTOOSMALL,	"DNS query packet buffer is too small"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINSIZE,	"Invalid DNS packet length"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINCLASS,	"Invalid DNS class"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINNAMEPTR,	"Invalid DNS name pointer"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSINNSADDR,	"Invalid DNS nameserver address"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSNONS,		"No nameserver is in DNS resolver"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSNOWORKINGNS,	"No working DNS nameserver"),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNSNOANSWERREC,	"No answer record in the DNS response"),
+
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_FORMERR,	"DNS \"Format error\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_SERVFAIL,	"DNS \"Server failure\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_NXDOMAIN,	"DNS \"Name Error\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_NOTIMPL,	"DNS \"Not Implemented\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_REFUSED,	"DNS \"Refused\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_YXDOMAIN,	"DNS \"The name exists\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_YXRRSET,	"DNS \"The RRset (name, type) exists\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_NXRRSET,	"DNS \"The RRset (name, type) does not exist\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_NOTAUTH,	"DNS \"Not authorized\""),
+    PJ_BUILD_ERR( PJLIB_UTIL_EDNS_NOTZONE,	"DNS \"The zone specified is not a zone\""),
 };
 #endif	/* PJ_HAS_ERROR_STRING */
 
diff --git a/pjlib-util/src/pjlib-util/resolver.c b/pjlib-util/src/pjlib-util/resolver.c
new file mode 100644
index 00000000..3694c8e1
--- /dev/null
+++ b/pjlib-util/src/pjlib-util/resolver.c
@@ -0,0 +1,1408 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2006 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#include <pjlib-util/resolver.h>
+#include <pjlib-util/errno.h>
+#include <pj/assert.h>
+#include <pj/ctype.h>
+#include <pj/except.h>
+#include <pj/hash.h>
+#include <pj/ioqueue.h>
+#include <pj/log.h>
+#include <pj/os.h>
+#include <pj/pool.h>
+#include <pj/pool_buf.h>
+#include <pj/string.h>
+#include <pj/sock.h>
+#include <pj/timer.h>
+
+
+#define THIS_FILE	    "resolver.c"
+
+
+/* Check that maximum DNS nameservers is not too large. 
+ * This has got todo with the datatype to index the nameserver in the query.
+ */
+#if PJ_DNS_RESOLVER_MAX_NS > 256
+#   error "PJ_DNS_RESOLVER_MAX_NS is too large (max=256)"
+#endif
+
+
+#define RES_HASH_TABLE_SIZE 127		/**< Hash table size (must be 2^n-1 */
+#define PORT		    53		/**< Default NS port.		    */
+#define Q_HASH_TABLE_SIZE   127		/**< Query hash table size	    */
+#define TIMER_SIZE	    127		/**< Initial number of timers.	    */
+#define MAX_FD		    3		/**< Maximum internal sockets.	    */
+
+#define RES_BUF_SZ	    PJ_DNS_RESOLVER_RES_BUF_SIZE
+#define UDPSZ		    PJ_DNS_RESOLVER_MAX_UDP_SIZE
+
+
+/* Nameserver state */
+enum ns_state
+{
+    STATE_PROBING,
+    STATE_ACTIVE,
+    STATE_BAD,
+};
+
+/* 
+ * Each nameserver entry.
+ * A name server is identified by its socket address (IP and port).
+ * Each NS will have a flag to indicate whether it's properly functioning.
+ */
+struct nameserver
+{
+    pj_sockaddr_in  addr;		/**< Server address.		    */
+
+    enum ns_state   state;		/**< Nameserver state.		    */
+    pj_time_val	    state_expiry;	/**< Time set next state.	    */
+    pj_time_val	    rt_delay;		/**< Response time.		    */
+    
+
+    /* For calculating rt_delay: */
+    pj_uint16_t	    q_id;		/**< Query ID.			    */
+    pj_time_val	    sent_time;		/**< Time this query is sent.	    */
+};
+
+
+/* Child query list head 
+ * See comments on pj_dns_async_query below.
+ */
+struct query_head
+{
+    PJ_DECL_LIST_MEMBER(pj_dns_async_query);
+};
+
+
+/* Key to look for outstanding query and/or cached response */
+struct res_key
+{
+    pj_uint16_t		     qtype;		    /**< Query type.	    */
+    char		     name[PJ_MAX_HOSTNAME]; /**< Name being queried */
+};
+
+
+/* 
+ * This represents each asynchronous query entry.
+ * This entry will be put in two hash tables, the first one keyed on the DNS 
+ * transaction ID to match response with the query, and the second one keyed
+ * on "res_key" structure above to match a new request against outstanding 
+ * requests.
+ *
+ * An asynchronous entry may have child entries; child entries are subsequent
+ * queries to the same resource while there is pending query on the same
+ * DNS resource name and type. When a query has child entries, once the
+ * response is received (or error occurs), the response will trigger callback
+ * invocations for all childs entries.
+ *
+ * Note: when application cancels the query, the callback member will be
+ *       set to NULL, but for simplicity, the query will be let running.
+ */
+struct pj_dns_async_query
+{
+    PJ_DECL_LIST_MEMBER(pj_dns_async_query);	/**< List member.	    */
+
+    pj_dns_resolver	*resolver;	/**< The resolver instance.	    */
+    pj_uint16_t		 id;		/**< Transaction ID.		    */
+
+    unsigned		 transmit_cnt;	/**< Number of transmissions.	    */
+
+    struct res_key	 key;		/**< Key to index this query.	    */
+    char		 hbufid[PJ_HASH_ENTRY_SIZE];	/**< Hash buffer 1  */
+    char		 hbufkey[PJ_HASH_ENTRY_SIZE];	/**< Hash buffer 2  */
+    pj_timer_entry	 timer_entry;	/**< Timer to manage timeouts	    */
+    unsigned		 options;	/**< Query options.		    */
+    void		*user_data;	/**< Application data.		    */
+    pj_dns_callback	*cb;		/**< Callback to be called.	    */
+    struct query_head	 child_head;	/**< Child queries list head.	    */
+};
+
+
+/* This structure is used to keep cached response entry.
+ * The cache is a hash table keyed on "res_key" structure above.
+ */
+struct cached_res
+{
+    PJ_DECL_LIST_MEMBER(struct cached_res);
+
+    struct res_key	     key;	    /**< Resource key.		    */
+    char		     buf[RES_BUF_SZ];/**< Resource buffer.	    */
+    char		     hbuf[PJ_HASH_ENTRY_SIZE];	/**< Hash buffer    */
+    pj_time_val		     expiry_time;   /**< Expiration time.	    */
+    pj_dns_parsed_packet    *pkt;	    /**< The response packet.	    */
+};
+
+
+/* Resolver entry */
+struct pj_dns_resolver
+{
+    pj_str_t		 name;		/**< Resolver instance name for id. */
+
+    /* Internals */
+    pj_pool_t		*pool;		/**< Internal pool.		    */
+    pj_mutex_t		*mutex;		/**< Mutex protection.		    */
+    pj_bool_t		 own_timer;	/**< Do we own timer?		    */
+    pj_timer_heap_t	*timer;		/**< Timer instance.		    */
+    pj_bool_t		 own_ioqueue;	/**< Do we own ioqueue?		    */
+    pj_ioqueue_t	*ioqueue;	/**< Ioqueue instance.		    */
+    char		 tmp_pool[1500];/**< Temporary pool buffer.	    */
+
+    /* Socket */
+    pj_sock_t		 udp_sock;	/**< UDP socket.		    */
+    pj_ioqueue_key_t	*udp_key;	/**< UDP socket ioqueue key.	    */
+    unsigned char	 udp_rx_pkt[UDPSZ];/**< UDP receive buffer.	    */
+    unsigned char	 udp_tx_pkt[UDPSZ];/**< UDP receive buffer.	    */
+    pj_ssize_t		 udp_len;	/**< Length of received packet.	    */
+    pj_ioqueue_op_key_t	 udp_op_key;	/**< UDP read operation key.	    */
+    pj_sockaddr_in	 udp_src_addr;	/**< Source address of packet	    */
+    int			 udp_addr_len;	/**< Source address length.	    */
+
+    /* Settings */
+    pj_dns_settings	 settings;	/**< Resolver settings.		    */
+
+    /* Nameservers */
+    unsigned		 ns_count;	/**< Number of name servers.	    */
+    struct nameserver	 ns[PJ_DNS_RESOLVER_MAX_NS];	/**< Array of NS.   */
+
+    /* Last DNS transaction ID used. */
+    pj_uint16_t		 last_id;
+
+    /* Hash table for cached response */
+    pj_hash_table_t	*hrescache;	/**< Cached response in hash table  */
+
+    /* Cached response free list */
+    struct cached_res	 res_free_nodes;
+
+    /* Pending asynchronous query, hashed by transaction ID. */
+    pj_hash_table_t	*hquerybyid;
+
+    /* Pending asynchronous query, hashed by "res_key" */
+    pj_hash_table_t	*hquerybyres;
+
+    /* Query entries free list */
+    struct query_head	 query_free_nodes;
+};
+
+
+/* Callback from ioqueue when packet is received */
+static void on_read_complete(pj_ioqueue_key_t *key, 
+                             pj_ioqueue_op_key_t *op_key, 
+                             pj_ssize_t bytes_read);
+
+/* Callback to be called when query has timed out */
+static void on_timeout( pj_timer_heap_t *timer_heap,
+			struct pj_timer_entry *entry);
+
+/* Select which nameserver to use */
+static pj_status_t select_nameservers(pj_dns_resolver *resolver,
+				      unsigned *count,
+				      unsigned servers[]);
+
+
+/*
+ * Create the resolver.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_create( pj_pool_factory *pf,
+					    const char *name,
+					    unsigned options,
+					    pj_timer_heap_t *timer,
+					    pj_ioqueue_t *ioqueue,
+					    pj_dns_resolver **p_resolver)
+{
+    pj_pool_t *pool;
+    pj_dns_resolver *resv;
+    pj_ioqueue_callback socket_cb;
+    pj_status_t status;
+
+    /* Sanity check */
+    PJ_ASSERT_RETURN(pf && p_resolver, PJ_EINVAL);
+
+    if (name == NULL)
+	name = THIS_FILE;
+
+    /* Create and initialize resolver instance */
+    pool = pj_pool_create(pf, name, 4000, 4000, NULL);
+    if (!pool)
+	return PJ_ENOMEM;
+
+    /* Create pool and name */
+    resv = pj_pool_zalloc(pool, sizeof(struct pj_dns_resolver));
+    resv->pool = pool;
+    resv->udp_sock = PJ_INVALID_SOCKET;
+    pj_strdup2_with_null(pool, &resv->name, name);
+    
+    /* Create the mutex */
+    status = pj_mutex_create_recursive(pool, name, &resv->mutex);
+    if (status != PJ_SUCCESS)
+	goto on_error;
+
+    /* Timer, ioqueue, and settings */
+    resv->timer = timer;
+    resv->ioqueue = ioqueue;
+    resv->last_id = 1;
+    resv->settings.options = options;
+    resv->settings.qretr_delay = PJ_DNS_RESOLVER_QUERY_RETRANSMIT_DELAY;
+    resv->settings.qretr_count = PJ_DNS_RESOLVER_QUERY_RETRANSMIT_COUNT;
+    resv->settings.cache_max_ttl = PJ_DNS_RESOLVER_MAX_TTL;
+
+    /* Create the timer heap if one is not specified */
+    if (resv->timer == NULL) {
+	status = pj_timer_heap_create(pool, TIMER_SIZE, &resv->timer);
+	if (status != PJ_SUCCESS)
+	    goto on_error;
+    }
+
+    /* Create the ioqueue if one is not specified */
+    if (resv->ioqueue == NULL) {
+	status = pj_ioqueue_create(pool, MAX_FD, &resv->ioqueue);
+	if (status != PJ_SUCCESS)
+	    goto on_error;
+    }
+
+    /* Response cache hash table and item list */
+    resv->hrescache = pj_hash_create(pool, RES_HASH_TABLE_SIZE);
+    pj_list_init(&resv->res_free_nodes);
+
+    /* Query hash table and free list. */
+    resv->hquerybyid = pj_hash_create(pool, Q_HASH_TABLE_SIZE);
+    resv->hquerybyres = pj_hash_create(pool, Q_HASH_TABLE_SIZE);
+    pj_list_init(&resv->query_free_nodes);
+
+    /* Create the UDP socket */
+    status = pj_sock_socket(PJ_AF_INET, PJ_SOCK_DGRAM, 0, &resv->udp_sock);
+    if (status != PJ_SUCCESS)
+	goto on_error;
+
+    /* Register to ioqueue */
+    pj_bzero(&socket_cb, sizeof(socket_cb));
+    socket_cb.on_read_complete = &on_read_complete;
+    status = pj_ioqueue_register_sock(pool, resv->ioqueue, resv->udp_sock,
+				      resv, &socket_cb, &resv->udp_key);
+    if (status != PJ_SUCCESS)
+	goto on_error;
+
+    pj_ioqueue_op_key_init(&resv->udp_op_key, sizeof(resv->udp_op_key));
+
+    /* Start asynchronous read to the UDP socket */
+    resv->udp_len = sizeof(resv->udp_rx_pkt);
+    resv->udp_addr_len = sizeof(resv->udp_src_addr);
+    status = pj_ioqueue_recvfrom(resv->udp_key, &resv->udp_op_key, 
+				 resv->udp_rx_pkt, &resv->udp_len, 
+				 PJ_IOQUEUE_ALWAYS_ASYNC,
+				 &resv->udp_src_addr, &resv->udp_addr_len);
+    if (status != PJ_EPENDING)
+	goto on_error;
+
+
+    /* Looks like everything is okay */
+    *p_resolver = resv;
+    return PJ_SUCCESS;
+
+on_error:
+    pj_dns_resolver_destroy(resv, PJ_FALSE);
+    return status;
+}
+
+
+/*
+ * Destroy DNS resolver instance.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_destroy( pj_dns_resolver *resolver,
+					     pj_bool_t notify)
+{
+    PJ_ASSERT_RETURN(resolver, PJ_EINVAL);
+
+    if (notify) {
+	/*
+	 * Notify pending queries if requested.
+	 */
+	pj_hash_iterator_t it_buf, *it;
+
+	it = pj_hash_first(resolver->hquerybyid, &it_buf);
+	while (it) {
+	    pj_dns_async_query *q = pj_hash_this(resolver->hquerybyid, it);
+	    pj_dns_async_query *cq;
+	    if (q->cb)
+		(*q->cb)(q->user_data, PJ_ECANCELLED, NULL);
+
+	    cq = q->child_head.next;
+	    while (cq != (pj_dns_async_query*)&q->child_head) {
+		if (cq->cb)
+		    (*cq->cb)(cq->user_data, PJ_ECANCELLED, NULL);
+		cq = cq->next;
+	    }
+	    it = pj_hash_next(resolver->hquerybyid, it);
+	}
+    }
+
+    if (resolver->own_timer && resolver->timer) {
+	pj_timer_heap_destroy(resolver->timer);
+	resolver->timer = NULL;
+    }
+
+    if (resolver->own_ioqueue && resolver->ioqueue) {
+	pj_ioqueue_destroy(resolver->ioqueue);
+	resolver->ioqueue = NULL;
+    }
+
+    if (resolver->udp_key != NULL) {
+	pj_ioqueue_unregister(resolver->udp_key);
+	resolver->udp_key = NULL;
+	resolver->udp_sock = PJ_INVALID_SOCKET;
+    } else if (resolver->udp_sock != PJ_INVALID_SOCKET) {
+	pj_sock_close(resolver->udp_sock);
+	resolver->udp_sock = PJ_INVALID_SOCKET;
+    }
+
+    if (resolver->mutex) {
+	pj_mutex_destroy(resolver->mutex);
+	resolver->mutex = NULL;
+    }
+
+    if (resolver->pool) {
+	pj_pool_t *pool = resolver->pool;
+	resolver->pool = NULL;
+	pj_pool_release(pool);
+    }
+    return PJ_SUCCESS;
+}
+
+
+
+/*
+ * Configure name servers for the DNS resolver. 
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_set_ns( pj_dns_resolver *resolver,
+					    unsigned count,
+					    const pj_str_t servers[],
+					    const pj_uint16_t ports[])
+{
+    unsigned i;
+    pj_time_val now;
+    pj_status_t status;
+
+    PJ_ASSERT_RETURN(resolver && count && servers, PJ_EINVAL);
+
+    pj_mutex_lock(resolver->mutex);
+
+    if (count > PJ_DNS_RESOLVER_MAX_NS)
+	count = PJ_DNS_RESOLVER_MAX_NS;
+
+    resolver->ns_count = 0;
+    pj_bzero(resolver->ns, sizeof(resolver->ns));
+
+    pj_gettimeofday(&now);
+
+    for (i=0; i<count; ++i) {
+	struct nameserver *ns = &resolver->ns[i];
+
+	status = pj_sockaddr_in_init(&ns->addr, &servers[i], 
+				     (pj_uint16_t)(ports ? ports[i] : PORT));
+	if (status != PJ_SUCCESS) {
+	    pj_mutex_unlock(resolver->mutex);
+	    return PJLIB_UTIL_EDNSINNSADDR;
+	}
+
+	ns->state = STATE_ACTIVE;
+	ns->state_expiry = now;
+	ns->rt_delay.sec = 10;
+    }
+    
+    resolver->ns_count = count;
+
+    pj_mutex_unlock(resolver->mutex);
+    return PJ_SUCCESS;
+}
+
+
+
+/*
+ * Modify the resolver settings.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_set_settings(pj_dns_resolver *resolver,
+						 const pj_dns_settings *st)
+{
+    PJ_ASSERT_RETURN(resolver && st, PJ_EINVAL);
+
+    pj_mutex_lock(resolver->mutex);
+    pj_memcpy(&resolver->settings, st, sizeof(*st));
+    pj_mutex_unlock(resolver->mutex);
+    return PJ_SUCCESS;
+}
+
+
+/*
+ * Get the resolver current settings.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_get_settings( pj_dns_resolver *resolver,
+						  pj_dns_settings *st)
+{
+    PJ_ASSERT_RETURN(resolver && st, PJ_EINVAL);
+
+    pj_mutex_lock(resolver->mutex);
+    pj_memcpy(st, &resolver->settings, sizeof(*st));
+    pj_mutex_unlock(resolver->mutex);
+    return PJ_SUCCESS;
+}
+
+
+/*
+ * Poll for events from the resolver. 
+ */
+PJ_DEF(void) pj_dns_resolver_handle_events(pj_dns_resolver *resolver,
+					   const pj_time_val *timeout)
+{
+    PJ_ASSERT_ON_FAIL(resolver, return);
+
+    pj_mutex_lock(resolver->mutex);
+    pj_timer_heap_poll(resolver->timer, NULL);
+    pj_mutex_unlock(resolver->mutex);
+
+    pj_ioqueue_poll(resolver->ioqueue, timeout);
+}
+
+
+/* Get one query node from the free node, if any, or allocate 
+ * a new one.
+ */
+static pj_dns_async_query *alloc_qnode(pj_dns_resolver *resolver,
+				       unsigned options,
+				       void *user_data,
+				       pj_dns_callback *cb)
+{
+    pj_dns_async_query *q;
+
+    /* Merge query options with resolver options */
+    options |= resolver->settings.options;
+
+    if (!pj_list_empty(&resolver->query_free_nodes)) {
+	q = resolver->query_free_nodes.next;
+	pj_list_erase(q);
+	pj_bzero(q, sizeof(*q));
+    } else {
+	q = pj_pool_zalloc(resolver->pool, sizeof(*q));
+    }
+
+    /* Init query */
+    q->resolver = resolver;
+    q->options = options;
+    q->user_data = user_data;
+    q->cb = cb;
+    pj_list_init(&q->child_head);
+
+    return q;
+}
+
+
+/*
+ * Transmit query.
+ */
+static pj_status_t transmit_query(pj_dns_resolver *resolver,
+				  pj_dns_async_query *q)
+{
+    unsigned pkt_size;
+    unsigned i, server_cnt;
+    unsigned servers[PJ_DNS_RESOLVER_MAX_NS];
+    pj_time_val now;
+    pj_str_t name;
+    pj_time_val delay;
+    pj_status_t status;
+
+    /* Create DNS query packet */
+    pkt_size = sizeof(resolver->udp_tx_pkt);
+    name = pj_str(q->key.name);
+    status = pj_dns_make_query(resolver->udp_tx_pkt, &pkt_size, 
+			       q->id, q->key.qtype, &name);
+    if (status != PJ_SUCCESS) {
+	return status;
+    }
+
+    /* Select which nameserver(s) to send requests to. */
+    server_cnt = PJ_ARRAY_SIZE(servers);
+    status = select_nameservers(resolver, &server_cnt, servers);
+    if (status != PJ_SUCCESS) {
+	return status;
+    }
+
+    if (server_cnt == 0) {
+	return PJLIB_UTIL_EDNSNOWORKINGNS;
+    }
+
+    /* Start retransmit/timeout timer for the query */
+    pj_assert(q->timer_entry.id == 0);
+    q->timer_entry.id = 1;
+    q->timer_entry.user_data = q;
+    q->timer_entry.cb = &on_timeout;
+
+    delay.sec = 0;
+    delay.msec = resolver->settings.qretr_delay;
+    pj_time_val_normalize(&delay);
+    status = pj_timer_heap_schedule(resolver->timer, &q->timer_entry, &delay);
+    if (status != PJ_SUCCESS) {
+	return status;
+    }
+
+    /* Get current time. */
+    pj_gettimeofday(&now);
+
+    /* Send the packet to name servers */
+    for (i=0; i<server_cnt; ++i) {
+	pj_ssize_t sent  = (pj_ssize_t) pkt_size;
+	struct nameserver *ns = &resolver->ns[servers[i]];
+
+	pj_sock_sendto(resolver->udp_sock, resolver->udp_tx_pkt, &sent, 0,
+		       &resolver->ns[servers[i]].addr, sizeof(pj_sockaddr_in));
+
+	PJ_LOG(4,(resolver->name.ptr, 
+		  "%s %d bytes to NS %d (%s:%d): DNS %s query for %s",
+		  (q->transmit_cnt==0? "Transmitting":"Re-transmitting"),
+		  (int)sent, servers[i],
+		  pj_inet_ntoa(ns->addr.sin_addr), 
+		  (int)pj_ntohs(ns->addr.sin_port),
+		  pj_dns_get_type_name(q->key.qtype), 
+		  q->key.name));
+
+	if (ns->q_id == 0) {
+	    ns->q_id = q->id;
+	    ns->sent_time = now;
+	}
+    }
+
+    ++q->transmit_cnt;
+
+    return PJ_SUCCESS;
+}
+
+
+/*
+ * Initialize resource key for hash table lookup.
+ */
+static void init_res_key(struct res_key *key, int type, const pj_str_t *name)
+{
+    unsigned i, len;
+    char *dst = key->name;
+    const char *src = name->ptr;
+
+    pj_bzero(key, sizeof(struct res_key));
+    key->qtype = (pj_uint16_t)type;
+
+    len = name->slen;
+    if (len > PJ_MAX_HOSTNAME) len = PJ_MAX_HOSTNAME;
+
+    /* Copy key, in lowercase */
+    for (i=0; i<len; ++i) {
+	*dst++ = (char)pj_tolower(*src++);
+    }
+}
+
+
+/*
+ * Create and start asynchronous DNS query for a single resource.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_start_query( pj_dns_resolver *resolver,
+						 const pj_str_t *name,
+						 int type,
+						 unsigned options,
+						 pj_dns_callback *cb,
+						 void *user_data,
+						 pj_dns_async_query **p_query)
+{
+    pj_time_val now;
+    struct res_key key;
+    struct cached_res *cache;
+    pj_dns_async_query *q;
+    pj_uint32_t hval;
+    pj_status_t status = PJ_SUCCESS;
+
+    /* Validate arguments */
+    PJ_ASSERT_RETURN(resolver && name && type, PJ_EINVAL);
+
+    /* Check name is not too long. */
+    PJ_ASSERT_RETURN(name->slen>0 && name->slen < PJ_MAX_HOSTNAME,
+		     PJ_ENAMETOOLONG);
+
+    /* Check type */
+    PJ_ASSERT_RETURN(type > 0 && type < 0xFFFF, PJ_EINVAL);
+
+    if (p_query)
+	*p_query = NULL;
+
+    /* Build resource key for looking up hash tables */
+    init_res_key(&key, type, name);
+
+    /* Start working with the resolver */
+    pj_mutex_lock(resolver->mutex);
+
+    /* Get current time. */
+    pj_gettimeofday(&now);
+
+    /* First, check if we have cached response for the specified name/type,
+     * and the cached entry has not expired.
+     */
+    hval = 0;
+    cache = pj_hash_get(resolver->hrescache, &key, sizeof(key), &hval);
+    if (cache) {
+	/* We've found a cached entry. */
+
+	/* Check for expiration */
+	if (PJ_TIME_VAL_GT(cache->expiry_time, now)) {
+
+	    /* Log */
+	    PJ_LOG(5,(resolver->name.ptr, 
+		      "Picked up DNS %s record for %.*s in cache",
+		      pj_dns_get_type_name(type),
+		      (int)name->slen, name->ptr));
+
+	    /* Map DNS Rcode in the response into PJLIB status name space */
+	    status = PJ_DNS_GET_RCODE(cache->pkt->hdr.flags);
+	    status = PJ_STATUS_FROM_DNS_RCODE(status);
+
+	    /* This cached response is still valid. Just return this
+	     * response to caller.
+	     */
+	    if (cb) {
+		(*cb)(user_data, status, cache->pkt);
+	    }
+
+	    /* Done. No host resolution is necessary */
+
+	    /* Must return PJ_SUCCESS */
+	    status = PJ_SUCCESS;
+
+	    goto on_return;
+	}
+
+	/* At this point, we have a cached entry, but this entry has expired.
+	 * Remove this entry from the cached list.
+	 */
+	pj_hash_set(NULL, resolver->hrescache, &key, sizeof(key), 0, NULL);
+
+	/* Store the entry into free nodes */
+	pj_list_push_back(&resolver->res_free_nodes, cache);
+
+	/* Must continue with creating a query now */
+    }
+
+    /* Next, check if we have pending query on the same resource */
+    q = pj_hash_get(resolver->hquerybyres, &key, sizeof(key), NULL);
+    if (q) {
+	/* Yes, there's another pending query to the same key.
+	 * Just create a new child query and add this query to
+	 * pending query's child queries.
+	 */
+	pj_dns_async_query *nq;
+
+	nq = alloc_qnode(resolver, options, user_data, cb);
+	pj_list_push_back(&q->child_head, nq);
+
+	/* Done. This child query will be notified once the "parent"
+	 * query completes.
+	 */
+	status = PJ_SUCCESS;
+	goto on_return;
+    } 
+
+    /* There's no pending query to the same key, initiate a new one. */
+    q = alloc_qnode(resolver, options, user_data, cb);
+
+    /* Save the ID and key */
+    q->id = resolver->last_id++;
+    if (resolver->last_id == 0)
+	resolver->last_id = 1;
+    pj_memcpy(&q->key, &key, sizeof(struct res_key));
+
+    /* Send the query */
+    status = transmit_query(resolver, q);
+    if (status != PJ_SUCCESS) {
+	pj_list_push_back(&resolver->query_free_nodes, q);
+	goto on_return;
+    }
+
+    /* Add query entry to the hash tables */
+    pj_hash_set_np(resolver->hquerybyid, &q->id, sizeof(q->id), 
+		   0, q->hbufid, q);
+    pj_hash_set_np(resolver->hquerybyres, &q->key, sizeof(q->key),
+		   0, q->hbufkey, q);
+
+    if (p_query)
+	*p_query = q;
+
+on_return:
+    pj_mutex_unlock(resolver->mutex);
+    return status;
+}
+
+
+/*
+ * Cancel a pending query.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_cancel_query(pj_dns_async_query *query,
+						 pj_bool_t notify)
+{
+    pj_dns_callback *cb;
+
+    PJ_ASSERT_RETURN(query, PJ_EINVAL);
+
+    pj_mutex_lock(query->resolver->mutex);
+
+    cb = query->cb;
+    query->cb = NULL;
+
+    if (notify)
+	(*cb)(query->user_data, PJ_ECANCELLED, NULL);
+
+    pj_mutex_unlock(query->resolver->mutex);
+    return PJ_SUCCESS;
+}
+
+
+
+/* Set nameserver state */
+static void set_nameserver_state(pj_dns_resolver *resolver,
+				 unsigned index,
+				 enum ns_state state,
+				 const pj_time_val *now)
+{
+    struct nameserver *ns = &resolver->ns[index];
+
+    ns->state = state;
+    ns->state_expiry = *now;
+
+    if (state == STATE_PROBING)
+	ns->state_expiry.sec += ((PJ_DNS_RESOLVER_QUERY_RETRANSMIT_COUNT + 2) *
+				 PJ_DNS_RESOLVER_QUERY_RETRANSMIT_DELAY) / 1000;
+    else if (state == STATE_ACTIVE)
+	ns->state_expiry.sec += PJ_DNS_RESOLVER_GOOD_NS_TTL;
+    else
+	ns->state_expiry.sec += PJ_DNS_RESOLVER_BAD_NS_TTL;
+
+}
+
+
+/* Select which nameserver(s) to use. Note this may return multiple
+ * name servers. The algorithm to select which nameservers to be
+ * sent the request to is as follows:
+ *  - select the first nameserver that is known to be good for the
+ *    last PJ_DNS_RESOLVER_GOOD_NS_TTL interval.
+ *  - for all NSes, if last_known_good >= PJ_DNS_RESOLVER_GOOD_NS_TTL, 
+ *    include the NS to re-check again that the server is still good,
+ *    unless the NS is known to be bad in the last PJ_DNS_RESOLVER_BAD_NS_TTL
+ *    interval.
+ *  - for all NSes, if last_known_bad >= PJ_DNS_RESOLVER_BAD_NS_TTL, 
+ *    also include the NS to re-check again that the server is still bad.
+ */
+static pj_status_t select_nameservers(pj_dns_resolver *resolver,
+				      unsigned *count,
+				      unsigned servers[])
+{
+    unsigned i, max_count=*count;
+    int min;
+    pj_time_val now;
+
+    pj_assert(max_count > 0);
+
+    *count = 0;
+    servers[0] = 0xFFFF;
+
+    /* Check that nameservers are configured. */
+    if (resolver->ns_count == 0)
+	return PJLIB_UTIL_EDNSNONS;
+
+    pj_gettimeofday(&now);
+
+    /* Select one Active nameserver with best response time. */
+    for (min=-1, i=0; i<resolver->ns_count; ++i) {
+	struct nameserver *ns = &resolver->ns[i];
+
+	if (ns->state != STATE_ACTIVE)
+	    continue;
+
+	if (min == -1)
+	    min = i;
+	else if (PJ_TIME_VAL_LT(ns->rt_delay, resolver->ns[min].rt_delay))
+	    min = i;
+    }
+    if (min != -1) {
+	servers[0] = min;
+	++(*count);
+    }
+
+    /* Scan nameservers. */
+    for (i=0; i<resolver->ns_count && *count < max_count; ++i) {
+	struct nameserver *ns = &resolver->ns[i];
+
+	if (PJ_TIME_VAL_LTE(ns->state_expiry, now)) {
+	    if (ns->state == STATE_PROBING) {
+		set_nameserver_state(resolver, i, STATE_BAD, &now);
+	    } else {
+		set_nameserver_state(resolver, i, STATE_PROBING, &now);
+		if ((int)i != min) {
+		    servers[*count] = i;
+		    ++(*count);
+		}
+	    }
+	} else if (ns->state == STATE_PROBING && (int)i != min) {
+	    servers[*count] = i;
+	    ++(*count);
+	}
+    }
+
+    return PJ_SUCCESS;
+}
+
+
+/* Update name server status */
+static void report_nameserver_status(pj_dns_resolver *resolver,
+				     const pj_sockaddr_in *ns_addr,
+				     const pj_dns_parsed_packet *pkt)
+{
+    unsigned i;
+    int rcode;
+    pj_uint32_t q_id;
+    pj_time_val now;
+    pj_bool_t is_good;
+
+    /* Only mark nameserver as "bad" if it returned non-parseable response or
+     * it returned the following status codes
+     */
+    if (pkt) {
+	rcode = PJ_DNS_GET_RCODE(pkt->hdr.flags);
+	q_id = pkt->hdr.id;
+    } else {
+	rcode = 0;
+	q_id = (pj_uint32_t)-1;
+    }
+
+    if (!pkt || rcode == PJ_DNS_RCODE_SERVFAIL ||
+	        rcode == PJ_DNS_RCODE_REFUSED ||
+	        rcode == PJ_DNS_RCODE_NOTAUTH) 
+    {
+	is_good = PJ_FALSE;
+    } else {
+	is_good = PJ_TRUE;
+    }
+
+
+    /* Mark time */
+    pj_gettimeofday(&now);
+
+    /* Recheck all nameservers. */
+    for (i=0; i<resolver->ns_count; ++i) {
+	struct nameserver *ns = &resolver->ns[i];
+
+	if (ns->addr.sin_addr.s_addr == ns_addr->sin_addr.s_addr &&
+	    ns->addr.sin_port == ns_addr->sin_port &&
+	    ns->addr.sin_family == ns_addr->sin_family)
+	{
+	    if (q_id == ns->q_id) {
+		/* Calculate response time */
+		pj_time_val rt = now;
+		PJ_TIME_VAL_SUB(rt, ns->sent_time);
+		ns->rt_delay = rt;
+		ns->q_id = 0;
+	    }
+	    set_nameserver_state(resolver, i, 
+				 (is_good ? STATE_ACTIVE : STATE_BAD), &now);
+	    break;
+	}
+    }
+}
+
+
+/* Update response cache */
+static void update_res_cache(pj_dns_resolver *resolver,
+			     const struct res_key *key,
+			     pj_status_t status,
+			     pj_bool_t set_expiry,
+			     const pj_dns_parsed_packet *pkt)
+{
+    struct cached_res *cache;
+    pj_pool_t *res_pool;
+    pj_uint32_t hval=0, ttl;
+    PJ_USE_EXCEPTION;
+
+    /* If status is unsuccessful, clear the same entry from the cache */
+    if (status != PJ_SUCCESS) {
+	cache = pj_hash_get(resolver->hrescache, key, sizeof(*key), &hval);
+	if (cache)
+	    pj_list_push_back(&resolver->res_free_nodes, cache);
+	pj_hash_set(NULL, resolver->hrescache, key, sizeof(*key), hval, NULL);
+    }
+
+
+    /* Calculate expiration time. */
+    if (set_expiry) {
+	if (pkt->hdr.anscount == 0) {
+	    /* If we don't have answers for the name, then give a different
+	     * ttl value (note: PJ_DNS_RESOLVER_INVALID_TTL may be zero, 
+	     * which means that invalid names won't be kept in the cache)
+	     */
+	    ttl = PJ_DNS_RESOLVER_INVALID_TTL;
+
+	} else {
+	    /* Otherwise get the minimum TTL from the answers */
+	    unsigned i;
+	    ttl = 0xFFFFFFFF;
+	    for (i=0; i<pkt->hdr.anscount; ++i) {
+		if (pkt->ans[i].ttl < ttl)
+		    ttl = pkt->ans[i].ttl;
+	    }
+	}
+    } else {
+	ttl = 0xFFFFFFFF;
+    }
+
+    /* Apply maximum TTL */
+    if (ttl > resolver->settings.cache_max_ttl)
+	ttl = resolver->settings.cache_max_ttl;
+
+    /* If TTL is zero, clear the same entry in the hash table */
+    if (ttl == 0) {
+	cache = pj_hash_get(resolver->hrescache, key, sizeof(*key), &hval);
+	if (cache)
+	    pj_list_push_back(&resolver->res_free_nodes, cache);
+	pj_hash_set(NULL, resolver->hrescache, key, sizeof(*key), hval, NULL);
+	return;
+    }
+
+    /* Get a cache response entry */
+    cache = pj_hash_get(resolver->hrescache, key, sizeof(*key), &hval);
+    if (cache == NULL) {
+	if (!pj_list_empty(&resolver->res_free_nodes)) {
+	    cache = resolver->res_free_nodes.next;
+	    pj_list_erase(cache);
+	} else {
+	    cache = pj_pool_zalloc(resolver->pool, sizeof(*cache));
+	}
+    }
+
+    /* Duplicate the packet */
+    res_pool = pj_pool_create_on_buf("respool", cache->buf, sizeof(cache->buf));
+    PJ_TRY {
+	cache->pkt = NULL;
+	pj_dns_packet_dup(res_pool, pkt, &cache->pkt);
+    }
+    PJ_CATCH_ANY {
+	PJ_LOG(1,(THIS_FILE, 
+		  "Not enough memory to duplicate DNS response. Response was "
+		  "truncated."));
+    }
+    PJ_END;
+
+    /* Calculate expiration time */
+    if (set_expiry) {
+	pj_gettimeofday(&cache->expiry_time);
+	cache->expiry_time.sec += ttl;
+    } else {
+	cache->expiry_time.sec = 0x7FFFFFFFL;
+	cache->expiry_time.msec = 0;
+    }
+
+    /* Copy key to the cached response */
+    pj_memcpy(&cache->key, key, sizeof(*key));
+
+    /* Update the hash table */
+    pj_hash_set_np(resolver->hrescache, &cache->key, sizeof(*key), hval,
+		   cache->hbuf, cache);
+}
+
+
+/* Callback to be called when query has timed out */
+static void on_timeout( pj_timer_heap_t *timer_heap,
+			struct pj_timer_entry *entry)
+{
+    pj_dns_resolver *resolver;
+    pj_dns_async_query *q, *cq;
+    pj_status_t status;
+
+    PJ_UNUSED_ARG(timer_heap);
+
+    q = entry->user_data;
+    resolver = q->resolver;
+
+    pj_mutex_lock(resolver->mutex);
+
+    /* Recheck that this query is still pending, since there is a slight
+     * possibility of race condition (timer elapsed while at the same time
+     * response arrives)
+     */
+    if (pj_hash_get(resolver->hquerybyid, &q->id, sizeof(q->id), NULL)==NULL) {
+	/* Yeah, this query is done. */
+	pj_mutex_unlock(resolver->mutex);
+	return;
+    }
+
+    /* Invalidate id. */
+    q->timer_entry.id = 0;
+
+    /* Check to see if we should retransmit instead of time out */
+    if (q->transmit_cnt < PJ_DNS_RESOLVER_QUERY_RETRANSMIT_COUNT) {
+	status = transmit_query(resolver, q);
+	if (status == PJ_SUCCESS) {
+	    pj_mutex_unlock(resolver->mutex);
+	    return;
+	} else {
+	    /* Error occurs */
+	    char errmsg[PJ_ERR_MSG_SIZE];
+
+	    pj_strerror(status, errmsg, sizeof(errmsg));
+	    PJ_LOG(4,(resolver->name.ptr,
+		      "Error transmitting request: %s", errmsg));
+
+	    /* Let it fallback to timeout section below */
+	}
+    }
+
+    /* Clear hash table entries */
+    pj_hash_set(NULL, resolver->hquerybyid, &q->id, sizeof(q->id), 0, NULL);
+    pj_hash_set(NULL, resolver->hquerybyres, &q->key, sizeof(q->key), 0, NULL);
+
+    /* Call application callback, if any. */
+    if (q->cb)
+	(*q->cb)(q->user_data, PJ_ETIMEDOUT, NULL);
+
+    /* Call application callback for child queries. */
+    cq = q->child_head.next;
+    while (cq != (void*)&q->child_head) {
+	if (cq->cb)
+	    (*cq->cb)(cq->user_data, PJ_ETIMEDOUT, NULL);
+	cq = cq->next;
+    }
+
+    /* Clear data */
+    q->timer_entry.id = 0;
+    q->user_data = NULL;
+
+    /* Put child entries into recycle list */
+    cq = q->child_head.next;
+    while (cq != (void*)&q->child_head) {
+	pj_dns_async_query *next = cq->next;
+	pj_list_push_back(&resolver->query_free_nodes, cq);
+	cq = next;
+    }
+
+    /* Put query entry into recycle list */
+    pj_list_push_back(&resolver->query_free_nodes, q);
+
+    pj_mutex_unlock(resolver->mutex);
+}
+
+
+/* Callback from ioqueue when packet is received */
+static void on_read_complete(pj_ioqueue_key_t *key, 
+                             pj_ioqueue_op_key_t *op_key, 
+                             pj_ssize_t bytes_read)
+{
+    pj_dns_resolver *resolver;
+    pj_pool_t *pool;
+    pj_dns_parsed_packet *dns_pkt;
+    pj_dns_async_query *q;
+    pj_status_t status;
+    PJ_USE_EXCEPTION;
+
+
+    resolver = pj_ioqueue_get_user_data(key);
+    pj_mutex_lock(resolver->mutex);
+
+
+    /* Check for errors */
+    if (bytes_read < 0) {
+	char errmsg[PJ_ERR_MSG_SIZE];
+
+	status = -bytes_read;
+	pj_strerror(status, errmsg, sizeof(errmsg));
+	PJ_LOG(4,(resolver->name.ptr, 
+		  "DNS resolver read error from %s:%d: %s", 
+		  pj_inet_ntoa(resolver->udp_src_addr.sin_addr),
+		  pj_ntohs(resolver->udp_src_addr.sin_port),
+		  errmsg));
+
+	goto read_next_packet;
+    }
+
+    PJ_LOG(5,(resolver->name.ptr, 
+	      "Received %d bytes DNS response from %s:%d",
+	      (int)bytes_read, 
+	      pj_inet_ntoa(resolver->udp_src_addr.sin_addr),
+	      pj_ntohs(resolver->udp_src_addr.sin_port)));
+
+
+    /* Check for zero packet */
+    if (bytes_read == 0)
+	goto read_next_packet;
+
+    /* Create temporary pool from a fixed buffer */
+    pool = pj_pool_create_on_buf("restmp", resolver->tmp_pool, 
+				 sizeof(resolver->tmp_pool));
+
+    /* Parse DNS response */
+    status = -1;
+    dns_pkt = NULL;
+    PJ_TRY {
+	status = pj_dns_parse_packet(pool, resolver->udp_rx_pkt, 
+				     (unsigned)bytes_read, &dns_pkt);
+    }
+    PJ_CATCH_ANY {
+	status = PJ_ENOMEM;
+    }
+    PJ_END;
+
+    /* Update nameserver status */
+    report_nameserver_status(resolver, &resolver->udp_src_addr, dns_pkt);
+
+    /* Handle parse error */
+    if (status != PJ_SUCCESS) {
+	char errmsg[PJ_ERR_MSG_SIZE];
+
+	pj_strerror(status, errmsg, sizeof(errmsg));
+	PJ_LOG(3,(resolver->name.ptr, 
+		  "Error parsing DNS response from %s:%d: %s", 
+		  pj_inet_ntoa(resolver->udp_src_addr.sin_addr), 
+		  pj_ntohs(resolver->udp_src_addr.sin_port), 
+		  errmsg));
+	goto read_next_packet;
+    }
+
+    /* Find the query based on the transaction ID */
+    q = pj_hash_get(resolver->hquerybyid, &dns_pkt->hdr.id, 
+		    sizeof(dns_pkt->hdr.id), NULL);
+    if (!q) {
+	PJ_LOG(5,(resolver->name.ptr, 
+		  "Unable to find query for DNS response id=%d from %s:%d "
+		  "(the query may had been answered by other name servers)",
+		  (unsigned)dns_pkt->hdr.id,
+		  pj_inet_ntoa(resolver->udp_src_addr.sin_addr), 
+		  pj_ntohs(resolver->udp_src_addr.sin_port)));
+	goto read_next_packet;
+    }
+
+    /* Map DNS Rcode in the response into PJLIB status name space */
+    status = PJ_STATUS_FROM_DNS_RCODE(PJ_DNS_GET_RCODE(dns_pkt->hdr.flags));
+
+    /* Cancel query timeout timer. */
+    pj_assert(q->timer_entry.id != 0);
+    pj_timer_heap_cancel(resolver->timer, &q->timer_entry);
+    q->timer_entry.id = 0;
+
+    /* Clear hash table entries */
+    pj_hash_set(NULL, resolver->hquerybyid, &q->id, sizeof(q->id), 0, NULL);
+    pj_hash_set(NULL, resolver->hquerybyres, &q->key, sizeof(q->key), 0, NULL);
+
+    /* Notify applications first, to allow application to modify the 
+     * record before it is saved to the hash table.
+     */
+    if (q->cb)
+	(*q->cb)(q->user_data, status, dns_pkt);
+
+    /* If query has subqueries, notify subqueries's application callback */
+    if (!pj_list_empty(&q->child_head)) {
+	pj_dns_async_query *child_q;
+
+	child_q = q->child_head.next;
+	while (child_q != (pj_dns_async_query*)&q->child_head) {
+	    if (child_q->cb)
+		(*child_q->cb)(child_q->user_data, status, dns_pkt);
+	    child_q = child_q->next;
+	}
+    }
+
+    /* We don't need NS and query section in the packet, so trim them. */
+    dns_pkt->hdr.qdcount = 0;
+    dns_pkt->hdr.nscount = 0;
+
+    /* Save/update response cache. */
+    update_res_cache(resolver, &q->key, status, PJ_TRUE, dns_pkt);
+    
+    /* Recycle query objects, starting with the child queries */
+    if (!pj_list_empty(&q->child_head)) {
+	pj_dns_async_query *child_q;
+
+	child_q = q->child_head.next;
+	while (child_q != (pj_dns_async_query*)&q->child_head) {
+	    pj_dns_async_query *next = child_q->next;
+	    pj_list_erase(child_q);
+	    pj_list_push_back(&resolver->query_free_nodes, child_q);
+	    child_q = next;
+	}
+    }
+    pj_list_push_back(&resolver->query_free_nodes, q);
+
+read_next_packet:
+    bytes_read = sizeof(resolver->udp_rx_pkt);
+    resolver->udp_addr_len = sizeof(resolver->udp_src_addr);
+    status = pj_ioqueue_recvfrom(resolver->udp_key, op_key, 
+				 resolver->udp_rx_pkt,
+				 &bytes_read, PJ_IOQUEUE_ALWAYS_ASYNC,
+				 &resolver->udp_src_addr, 
+				 &resolver->udp_addr_len);
+    if (status != PJ_EPENDING) {
+	char errmsg[PJ_ERR_MSG_SIZE];
+
+	pj_strerror(status, errmsg, sizeof(errmsg));	
+	PJ_LOG(4,(resolver->name.ptr, "DNS resolver ioqueue read error: %s",
+		  errmsg));
+
+	pj_assert(!"Unhandled error");
+    }
+
+    pj_mutex_unlock(resolver->mutex);
+}
+
+
+/*
+ * Put the specified DNS packet into DNS cache. This function is mainly used
+ * for testing the resolver, however it can also be used to inject entries
+ * into the resolver.
+ */
+PJ_DEF(pj_status_t) pj_dns_resolver_add_entry( pj_dns_resolver *resolver,
+					       const pj_dns_parsed_packet *pkt,
+					       pj_bool_t set_ttl)
+{
+    struct res_key key;
+
+    /* Sanity check */
+    PJ_ASSERT_RETURN(resolver && pkt, PJ_EINVAL);
+
+    /* Packet must be a DNS response */
+    PJ_ASSERT_RETURN(PJ_DNS_GET_QR(pkt->hdr.flags) & 1, PJ_EINVAL);
+
+    /* Make sure there are answers in the packet */
+    PJ_ASSERT_RETURN(pkt->hdr.anscount && pkt->ans ||
+		     pkt->hdr.qdcount && pkt->q,
+		     PJLIB_UTIL_EDNSNOANSWERREC);
+
+    pj_mutex_lock(resolver->mutex);
+
+    /* Build resource key for looking up hash tables */
+    pj_bzero(&key, sizeof(struct res_key));
+    if (pkt->hdr.anscount) {
+	/* Make sure name is not too long. */
+	PJ_ASSERT_RETURN(pkt->ans[0].name.slen < PJ_MAX_HOSTNAME, 
+			 PJ_ENAMETOOLONG);
+
+	init_res_key(&key, pkt->ans[0].type, &pkt->ans[0].name);
+
+    } else {
+	/* Make sure name is not too long. */
+	PJ_ASSERT_RETURN(pkt->q[0].name.slen < PJ_MAX_HOSTNAME, 
+			 PJ_ENAMETOOLONG);
+
+	init_res_key(&key, pkt->q[0].type, &pkt->q[0].name);
+    }
+
+    /* Insert entry. */
+    update_res_cache(resolver, &key, PJ_SUCCESS, set_ttl, pkt);
+
+    pj_mutex_unlock(resolver->mutex);
+
+    return PJ_SUCCESS;
+}
+
+
+/*
+ * Get the total number of response in the response cache.
+ */
+PJ_DEF(unsigned) pj_dns_resolver_get_cached_count(pj_dns_resolver *resolver)
+{
+    unsigned count;
+
+    PJ_ASSERT_RETURN(resolver, 0);
+
+    pj_mutex_lock(resolver->mutex);
+    count = pj_hash_count(resolver->hrescache);
+    pj_mutex_unlock(resolver->mutex);
+
+    return count;
+}
+
+
+/*
+ * Dump resolver state to the log.
+ */
+PJ_DEF(void) pj_dns_resolver_dump(pj_dns_resolver *resolver,
+				  pj_bool_t detail)
+{
+#if PJ_LOG_MAX_LEVEL >= 3
+    unsigned i;
+    pj_time_val now;
+
+    pj_mutex_lock(resolver->mutex);
+
+    pj_gettimeofday(&now);
+
+    PJ_LOG(3,(resolver->name.ptr, " Dumping resolver state:"));
+
+    PJ_LOG(3,(resolver->name.ptr, "  Name servers:"));
+    for (i=0; i<resolver->ns_count; ++i) {
+	const char *state_names[] = { "probing", "active", "bad"};
+	struct nameserver *ns = &resolver->ns[i];
+
+	PJ_LOG(3,(resolver->name.ptr,
+		  "   NS %d: %s:%d (state=%s until %ds, rtt=%d ms)",
+		  i, pj_inet_ntoa(ns->addr.sin_addr),
+		  pj_ntohs(ns->addr.sin_port),
+		  state_names[ns->state],
+		  ns->state_expiry.sec - now.sec,
+		  PJ_TIME_VAL_MSEC(ns->rt_delay)));
+    }
+
+    PJ_LOG(3,(resolver->name.ptr, "  Nb. of cached responses: %u",
+	      pj_hash_count(resolver->hrescache)));
+    if (detail) {
+	pj_hash_iterator_t itbuf, *it;
+	it = pj_hash_first(resolver->hrescache, &itbuf);
+	while (it) {
+	    struct cached_res *cache = pj_hash_this(resolver->hrescache, it);
+	    PJ_LOG(3,(resolver->name.ptr, 
+		      "   Type %s: %s",
+		      pj_dns_get_type_name(cache->key.qtype), 
+		      cache->key.name));
+	    it = pj_hash_next(resolver->hrescache, it);
+	}
+    }
+    PJ_LOG(3,(resolver->name.ptr, "  Nb. of cached response free nodes: %u",
+	      pj_list_size(&resolver->res_free_nodes)));
+    PJ_LOG(3,(resolver->name.ptr, "  Nb. of pending queries: %u (%u)",
+	      pj_hash_count(resolver->hquerybyid),
+	      pj_hash_count(resolver->hquerybyres)));
+    if (detail) {
+	pj_hash_iterator_t itbuf, *it;
+	it = pj_hash_first(resolver->hquerybyid, &itbuf);
+	while (it) {
+	    struct pj_dns_async_query *q;
+	    q = pj_hash_this(resolver->hquerybyid, it);
+	    PJ_LOG(3,(resolver->name.ptr, 
+		      "   Type %s: %s",
+		      pj_dns_get_type_name(q->key.qtype), 
+		      q->key.name));
+	    it = pj_hash_next(resolver->hquerybyid, it);
+	}
+    }
+    PJ_LOG(3,(resolver->name.ptr, "  Nb. of pending query free nodes: %u",
+	      pj_list_size(&resolver->query_free_nodes)));
+    PJ_LOG(3,(resolver->name.ptr, "  Nb. of timer entries: %u",
+	      pj_timer_heap_count(resolver->timer)));
+    PJ_LOG(3,(resolver->name.ptr, "  Pool capacity: %d, used size: %d",
+	      pj_pool_get_capacity(resolver->pool),
+	      pj_pool_get_used_size(resolver->pool)));
+
+    pj_mutex_unlock(resolver->mutex);
+#endif
+}
+