Diff: services/mDNS/mDNSResponder.cpp

Revision:

2:816cbd922d3e

Parent:

1:59820ca5c83a

Child:

3:e1d86543ec50

--- a/services/mDNS/mDNSResponder.cpp	Thu Jul 22 00:08:38 2010 +0000
+++ b/services/mDNS/mDNSResponder.cpp	Sat Jul 24 20:59:52 2010 +0000
@@ -1,408 +1,471 @@
-/* Class: mDNSResponder
- * Copyright 1991, 2003, 2010 Dirk-Willem van Gulik <dirkx(at)apache(punto)org>
- * 
- * License: Any BSD or ASF License.
- *
- * Rough and ready port of some mDNS code. 
- *
- * Typical use is something like
- *
- * EthernetNetIf eth;  
- * HTTPServer svr;
- * mDNSResponder mdns;
- * 
- * int main()...
- *
- *   // get internet
- *   EthernetErr ethErr = eth.setup();
- *   ... etc ..
- *
- *   // set up some server
- *   svr.addHandler<SimpleHandler>("/"); //Default handler
- *   svr.bind(80); * *  
-  
- *  // Extract the IP address.
- *   IpAddr ip = eth.getIp();
- *   printf("mbed IP Address is %d.%d.%d.%d\r\n", ip[0], ip[1], ip[2], ip[3]);
- *
- *   // Announce ourselves.
- *   mdns.announce(ip, "fred", "_http._tcp", 80, "The Little Server that Could", "path=/demo");
- *
- *   while()... enter some run loop
- *   ...
- *
- *  This will cause http://fred.local./demo to be announced as 'The Little Server that Could'.
- *
- *  Or as another example: (http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt)
- *  and the various RFCs:
- *
- *     mdns.announce(ip, "_ssh._tcp", 22, SSH to Serial Gateway", NULL);
- *
- * CAVEAT - a lot of the buffer overrun and copy checks
- *          where removed; and this is not anywhere near
- *          threadsafve or sane. Not for production use.
- */
-
-#include "mDNSResponder.h"
-#include <stdio.h>
-
-// #define MCAST 192,168,1,71
-
-mDNSResponder::mDNSResponder() : NetService(false), 
-    moi_txt(NULL), moi_port(0), moi_ip(0), 
-    moi_name(NULL), moi_proto(NULL),
-    moi_local_proto(NULL), moi_local_name(NULL), moi_local_pglue(NULL),
-    announcer()
-{
-    // nothing yet...
-}
-
-mDNSResponder::~mDNSResponder() {
-      announcer.stop();
-      close();
-}
-
-void mDNSResponder::announce(IpAddr ip, const char * ldn, const char * proto, uint16_t port, const char * name, char ** txt) {
-    Host localhost(IpAddr(MCAST), MDNS_PORT, NULL /* fqdn */);
-
-    m_pUDPSocket = new UDPSocket;
-    m_pUDPSocket->bind(localhost);
-
-    m_pUDPSocket->setOnEvent(this, &mDNSResponder::onUDPSocketEvent);
-
-    moi_port = port;
-    moi_txt = txt;
-    moi_ip = ip;
-    moi_proto = proto;
-    moi_name = name;
-
-    moi_local_proto = (char *)malloc(128);
-    moi_local_name = (char *)malloc(128);
-    moi_local_pglue = (char *)malloc(128);
-
-    #define LOCAL "local"
-    snprintf(moi_local_proto,128,"%s.%s.", moi_proto, LOCAL);
-    snprintf(moi_local_name,128,"%s.%s.", ldn, LOCAL);
-    snprintf(moi_local_pglue,128,"%s.%s.%s.", moi_name,moi_proto, LOCAL);
-    
-    // Gratuis intro - and repeat such regularly..
-    //
-    mDNSResponder::sendReply(0, localhost);
-    announcer.start();
-}
-
-void mDNSResponder::close() {
-    m_pUDPSocket->resetOnEvent();
-    m_pUDPSocket->close();
-    delete m_pUDPSocket;
-}
-
-
-
-void mDNSResponder::poll() { //Called by NetServices
-    if (announcer.read_ms() > 1000  * MDNS_INTERVAL) {
-    
-        Host mch(IpAddr(MCAST), MDNS_PORT, NULL);
-        mDNSResponder::sendReply(0, mch);
-
-        announcer.reset();
-    }
-}
-
-char * index(char * str, char c) {
-    for(;str && *str;str++) {
-        if (*str == c) return str;
-     };
-     return NULL;
-}
-
-#ifndef THREADINGCOMPRESS
-#ifndef MAXCACHEDNSLABELS 
-#define MAXCACHEDNSLABELS (10)
-#endif
-static int labelCacheCnt = 0;
-static uint16_t _cache_off[MAXCACHEDNSLABELS];
-static char * _cache_och[MAXCACHEDNSLABELS];
-static char * labelCacheOffset = 0;
-
-void initLabelCache(char * off) {
-    labelCacheOffset = off;
-    labelCacheCnt = 0;
-    memset(_cache_off,0, sizeof(_cache_off)); // Rely on min value to be 12
-};
-
-uint16_t checkLabelCache(char * name) {
-    for(int i=0; i < MAXCACHEDNSLABELS; i++)
-        if (_cache_off[i] && !strcmp(_cache_och[i],name))
-            return _cache_off[i];
-    return 0;
-};
-
-void addLabelCache(char * p, char * name) {
-    _cache_off[labelCacheCnt] = p - labelCacheOffset;
-    _cache_och[labelCacheCnt] = name;
-
-    labelCacheCnt++;
-    // we intentionally do not wack the first entries - as they are the most
-    // likely ones to be used.
-    if (labelCacheCnt>=MAXCACHEDNSLABELS)
-        labelCacheCnt = MAXCACHEDNSLABELS / 3;
-};
-#else
-#define initLabelCache(x) {} /* Ignored */
-#define checkLabelCache(x) (0) /* never a hit */
-#define addLabelCache(x,y) {} /* Ignored */
-#endif
-
-char * breakname(char *p, char *name) {
-   int l = 0, de = 1;
-   char * q;
-   uint16_t off;
-   
-   do {
-        if (off = checkLabelCache(name)) {
-                *p++ = 192 + (off >> 8);
-                *p++ =       (off &  0xFF);
-                return p;
-        } else {
-            addLabelCache(p, name);
-        };
-                
-        q = index(name,'.');
-        if (!q) {
-            q = name + strlen(name);
-            de = 0;
-        };
-        l = q - name;
-        *p++ = l;
-        memcpy(p, name, l);
-        p+=l;
-        name = q + 1;
-    } while(l && *name);
-    
-    // terminating root field if any (not the case for 
-    // things like TXTs).
-    if (de) *p++ = 0;
-    return p;
-}
-
-char * mRR(char *p, char * name, uint16_t tpe, uint16_t cls, uint32_t ttl)
-{
-    uint16_t i;
-    uint32_t j;
-
-    p = breakname(p, name);
-
-    // NOTE: Cannot assume proper byte boundaries.
-    //
-    i = htons(tpe); // Type 
-    memcpy(p, &i,  2);
-    p+=2;
-
-    i = htons(cls); // Class 
-    memcpy(p, &i, 2);
-    p+=2;
-
-    j = htonl(ttl); // TTL (4 bytes)
-    memcpy(p, &j, 4);
-    p+=4;
-
-    return p;
-}
-
-char * mRRLABEL(char *p, char * name, uint16_t tpe, char ** rr) {
-    uint16_t i;
-
-    p = mRR(p, name, tpe, 1, MDNS_TTL); // Type, IN, TTL
-
-    // RR String
-    char * q = p + 2;
-    
-    for(;*rr;rr++) 
-        q = breakname(q, *rr);
-    
-    i = htons(q - p - 2); // RDLEN
-    memcpy(p, &i, 2);
-    return q;
-}    
-
-char * mPTR(char *p, char * name, char * r) {
-    char *rr[] = { r, NULL };
-    return mRRLABEL(p, name, 12 /* PTR */, rr );
-}
-    
-char * mTXT(char *p, char * name, char ** rr) {
-    return mRRLABEL(p, name, 16 /* TXT */, rr);
-}
-
-char * mARR(char *p, char * name, IpAddr ip) {
-    uint16_t i;
-
-    p = mRR(p, name, 1, 1, MDNS_TTL ); // A, IN
-    
-    i = htons(4); // RDLEN - we're just doing a single IPv4 address - our primary link ?
-    memcpy(p, &i, 2);
-
-    // IP already in network order.    
-    memcpy(p+2, &ip, 4);
-    
-    return p + 2 + 4;
-}    
-    
-char * mSRV(char *p, char * name, uint16_t port, char * rr) {
-    uint16_t i;
-    char * q;
-    
-    p = mRR(p, name, 33, 1, MDNS_TTL); // SRV, IN
-    
-    // Keep space for RDLEN
-    q = p; p+=2;
-    
-    i = htons(1); // Priority
-    memcpy(p, &i, 2); p+=2;
-    
-    i = htons(0); // Weight (see rfc2782)
-    memcpy(p, &i, 2); p+=2;
-
-    i = htons(port); // Port
-    memcpy(p, &i, 2); p+=2;
-    
-    p = breakname(p, rr);
-    
-    i = htons(p - q - 2); // RDLEN
-    memcpy(q, &i, 2);
-        
-    return p;
-}    
-
-char * qANY(char *p, char * name, uint16_t tpe, uint16_t cls) {
-    uint16_t i;
-    p = breakname(p, name); // QNAME
-
-    i = htons(tpe); // QTYPE
-    memcpy(p, &i, 2); p+=2;
-    
-    i = htons(cls); // QCLASS
-    memcpy(p, &i, 2); p+=2;
-    
-    return p;
-}
-
-char * qPTR(char *p, char *name) {
-    return qANY(p,name,12 /* PTR */,1);
-}
-
-    
-void mDNSResponder::sendReply(uint16_t tid, Host dst) {
-    // sent a reply - basically a precooked A/PTR/SRV with the TransactionID
-    // and my URI squeezed in.
-    char out[ 1500 ], *p;
-    DNSPacket * op = (DNSPacket *) out;
-    
-    initLabelCache(out); // Offsets are relative to the ID header.
-
-    op->tid = ntohs(tid);
-    op->flags = ntohs(0x8000U); // Answer
-    op->question_count = ntohs(1); // Courtesy copy of the question.
-    op->answer_count = ntohs(1); // The PTR record asked for
-    op->a_count = ntohs(0);
-    
-    // The 2 or 3 extra records (A, SRV and optional TXT) we know will be needed next
-    op->aa_count = ntohs(moi_txt ? 3 : 2);
-    
-    p = out + 12;
-    
-    p = qPTR(p,moi_local_proto);
-    p = mPTR(p,moi_local_proto, moi_local_pglue);
-    p = mSRV(p,moi_local_pglue,80, moi_local_name);
-    if (moi_txt && * moi_txt)
-         p = mTXT(p,moi_local_pglue,moi_txt);
-    p = mARR(p,moi_local_name,moi_ip); // fill out my own IP address.
-
-    m_pUDPSocket->sendto(out,p-out,&dst);
-}
-
-void mDNSResponder::onUDPSocketEvent(UDPSocketEvent e) {
-    char udp[ 1500 ];
-    Host from;
-    int len;
-
-    switch (e) {
-        case UDPSOCKET_READABLE: //The only event for now
-            // parse through the packet; find any PTR requests
-            // and respond to any for _http._tcp._local.
-            while ( len = m_pUDPSocket->recvfrom( (char*)&udp, sizeof(udp), &from )) {
-                DNSPacket * dp = (DNSPacket *) udp;
-                unsigned int tid = ntohs(dp->tid);
-                unsigned int flags = ntohs(dp->flags);
-                unsigned int nQ = ntohs(dp->question_count);
-                unsigned int nA = ntohs(dp->answer_count);
-
-                if (flags & 2 != 0 || nQ == 0)
-                    continue; // we only want questions
-
-                #define MAXDEPTH 64
-                #define MAXRR 192 /* including dot */
-                
-                // assume nQ zero terminated fields followed by Qtype & Qclass
-                char * p = udp + 12;
-                for (int i = 0; i < nQ; i++) {
-                    char buff[ MAXDEPTH * MAXRR ], * ep = buff;
-                    int depth = 0;
-                    int l;
-                    char * q = 0;
-
-                    do {
-                        while (((l = *p++) < 192) && (l > 0)) {
-                            if (p + l >= udp + len) {
-                                printf("RR longer than packet\r\n");
-                                return;
-                            };
-
-                            memcpy(ep,p,l);
-                            ep[l]='.';
-                            ep += l + 1;
-                            // printf("%d:%s.", p-udp-12,buff);
-                            p += l;
-                        };
-                        if (l >= 192) {
-                            // construct an offset pointer by wiping the top 1 bits
-                            // and then getting the remaining 8 bytes to make 14.
-                            l -= 192;
-                            l = l << 8;
-                            l += *p++;
-                            // rescue our reference; as we've not gotten the Qt's yet.
-                            if (!q) q = p;
-
-                            // printf(" [->%d] ",l);
-                            p = udp + l;
-
-                            if (p >= udp + len || p < udp + 12) {
-                                printf("Pointer to wrong place\r\n");
-                                return;
-                            };
-                        };
-                        if (depth++ >= MAXDEPTH) {
-                            printf("Too deep\r\n");
-                            return;
-                        };
-                    } while (l);
-                    *ep = 0;
-                    // in case no compression was used at all.
-                    if (!q) q = p;
-
-                    unsigned int Qt = htons(q[0] + q[1]*256);
-                    unsigned int Qc = htons(q[2] + q[3]*256);
-                    p = q + 4;
-                    
-                    printf("Q for %s\r\n", buff);
-                    // We want PTR records on the INternet of our type
-                    if ((Qt == 12) && (Qc == 1) && !(strcmp(buff,moi_local_proto))) 
-                        sendReply(tid,from);                        
-                };
-            }
-            break;
-    }
-}
-
-
+/* Class: mDNSResponder
+ * Copyright 1991, 2003, 2010 Dirk-Willem van Gulik <dirkx(at)apache(punto)org>
+ *
+ * License: Any BSD or ASF License.
+ *
+ * Rough and ready port of some mDNS code.
+ *
+ * Typical use is something like
+ *
+ * EthernetNetIf eth;
+ * HTTPServer svr;
+ * mDNSResponder mdns;
+ *
+ * int main()...
+ *
+ *   // get internet
+ *   EthernetErr ethErr = eth.setup();
+ *   ... etc ..
+ *
+ *   // set up some server
+ *   svr.addHandler<SimpleHandler>("/"); //Default handler
+ *   svr.bind(80); * *
+
+ *  // Extract the IP address.
+ *   IpAddr ip = eth.getIp();
+ *   printf("mbed IP Address is %d.%d.%d.%d\r\n", ip[0], ip[1], ip[2], ip[3]);
+ *
+ *   // Announce ourselves.
+ *   mdns.announce(ip, "fred", "_http._tcp", 80, "The Little Server that Could", "path=/demo");
+ *
+ *   while()... enter some run loop
+ *   ...
+ *
+ *  This will cause http://fred.local./demo to be announced as 'The Little Server that Could'.
+ *
+ *  Or as another example: (http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt)
+ *  and the various RFCs:
+ *
+ *     mdns.announce(ip, "_ssh._tcp", 22, SSH to Serial Gateway", NULL);
+ *
+ * CAVEAT - a lot of the buffer overrun and copy checks
+ *          where removed; and this is not anywhere near
+ *          threadsafve or sane. Not for production use.
+ */
+#include "lwip/opt.h"
+#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
+
+#include "mDNSResponder.h"
+#include <stdio.h>
+
+#ifndef DNS_RRTYPE_SRV
+#define DNS_RRTYPE_SRV (33)
+#endif
+
+mDNSResponder::mDNSResponder() : NetService(false),
+        moi_txt(NULL), moi_port(0), moi_ip(0),
+        moi_name(NULL), moi_proto(NULL),
+        moi_local_proto(NULL), moi_local_name(NULL), moi_local_pglue(NULL),
+        announcer() {
+    // nothing yet...
+}
+
+mDNSResponder::~mDNSResponder() {
+    announcer.stop();
+    close();
+}
+
+void mDNSResponder::announce(IpAddr ip, const char * ldn, const char * proto, uint16_t port, const char * name, char ** txt) {
+    Host localhost(IpAddr(MCAST), MDNS_PORT, NULL /* fqdn */);
+
+    m_pUDPSocket = new UDPSocket;
+    m_pUDPSocket->bind(localhost);
+
+    m_pUDPSocket->setOnEvent(this, &mDNSResponder::onUDPSocketEvent);
+
+    moi_port = port;
+    moi_txt = txt;
+    moi_ip = ip;
+    moi_proto = proto;
+    moi_name = name;
+
+    moi_local_proto = (char *)malloc(128);
+    moi_local_name = (char *)malloc(128);
+    moi_local_pglue = (char *)malloc(128);
+
+#define LOCAL "local"
+    snprintf(moi_local_proto,128,"%s.%s.", moi_proto, LOCAL);
+    snprintf(moi_local_name,128,"%s.%s.", ldn, LOCAL);
+    snprintf(moi_local_pglue,128,"%s.%s.%s.", moi_name,moi_proto, LOCAL);
+
+    // Gratuis intro - and repeat such regularly..
+    //
+    mDNSResponder::sendReply(DNS_RRTYPE_PTR, 0, localhost);
+    announcer.start();
+}
+
+void mDNSResponder::close() {
+    m_pUDPSocket->resetOnEvent();
+    m_pUDPSocket->close();
+    delete m_pUDPSocket;
+}
+
+
+
+void mDNSResponder::poll() { //Called by NetServices
+    if (announcer.read_ms() > 1000  * MDNS_INTERVAL) {
+
+        Host mch(IpAddr(MCAST), MDNS_PORT, NULL);
+        mDNSResponder::sendReply(DNS_RRTYPE_PTR, 0, mch);
+
+        announcer.reset();
+    }
+}
+
+char * index(char * str, char c) {
+    for (;str && *str;str++) {
+        if (*str == c) return str;
+    };
+    return NULL;
+}
+
+#ifndef THREADINGCOMPRESS
+#ifndef MAXCACHEDNSLABELS
+#define MAXCACHEDNSLABELS (10)
+#endif
+static int labelCacheCnt = 0;
+static uint16_t _cache_off[MAXCACHEDNSLABELS];
+static char * _cache_och[MAXCACHEDNSLABELS];
+static char * labelCacheOffset = 0;
+
+void initLabelCache(char * off) {
+    labelCacheOffset = off;
+    labelCacheCnt = 0;
+    memset(_cache_off,0, sizeof(_cache_off)); // Rely on min value to be 12
+};
+
+uint16_t checkLabelCache(char * name) {
+    for (int i=0; i < MAXCACHEDNSLABELS; i++)
+        if (_cache_off[i] && !strcmp(_cache_och[i],name))
+            return _cache_off[i];
+    return 0;
+};
+
+void addLabelCache(char * p, char * name) {
+    _cache_off[labelCacheCnt] = p - labelCacheOffset;
+    _cache_och[labelCacheCnt] = name;
+
+    labelCacheCnt++;
+    // we intentionally do not wack the first entries - as they are the most
+    // likely ones to be used.
+    if (labelCacheCnt>=MAXCACHEDNSLABELS)
+        labelCacheCnt = MAXCACHEDNSLABELS / 3;
+};
+#else
+#define initLabelCache(x) {} /* Ignored */
+#define checkLabelCache(x) (0) /* never a hit */
+#define addLabelCache(x,y) {} /* Ignored */
+#endif
+
+char * breakname(char *p, char *name) {
+    int l = 0, de = 1;
+    char * q;
+    uint16_t off;
+
+    do {
+        if ((off = checkLabelCache(name))) {
+            *p++ = 192 + (off >> 8);
+            *p++ =       (off &  0xFF);
+            return p;
+        } else {
+            addLabelCache(p, name);
+        };
+
+        q = index(name,'.');
+        if (!q) {
+            q = name + strlen(name);
+            de = 0;
+        };
+        l = q - name;
+        *p++ = l;
+        memcpy(p, name, l);
+        p+=l;
+        name = q + 1;
+    } while (l && *name && de);
+
+    // terminating root field if any (not the case for
+    // things like TXTs).
+    if (de) *p++ = 0;
+    return p;
+}
+
+char * mRR(char *p, char * name, uint16_t tpe, uint16_t cls, uint32_t ttl) {
+    uint16_t i = 0;
+    uint32_t j = 0;
+
+    p = breakname(p, name);
+
+    // NOTE: Cannot assume proper byte boundaries.
+    //
+    i = htons(tpe); // Type
+    memcpy(p, &i,  2);
+    p+=2;
+
+    i = htons(cls); // Class
+    memcpy(p, &i, 2);
+    p+=2;
+
+    j = htonl(ttl); // TTL (4 bytes)
+    memcpy(p, &j, 4);
+    p+=4;
+
+    return p;
+}
+
+char * mRRLABEL(char *p, char * name, uint16_t tpe, char ** rr) {
+    uint16_t i;
+
+    p = mRR(p, name, tpe, DNS_RRCLASS_IN, MDNS_TTL); // Type, IN, TTL
+
+    // RR String
+    char * q = p + 2;
+
+    for (;*rr;rr++)
+        q = breakname(q, *rr);
+
+    i = htons(q - p - 2); // RDLEN
+    memcpy(p, &i, 2);
+    return q;
+}
+
+char * mPTR(char *p, char * name, char * r) {
+    char *rr[] = { r, NULL };
+    return mRRLABEL(p, name, DNS_RRTYPE_PTR, rr );
+}
+
+char * mTXT(char *p, char * name, char ** rr) {
+    return mRRLABEL(p, name, DNS_RRTYPE_TXT, rr);
+}
+
+char * mARR(char *p, char * name, IpAddr ip) {
+    uint16_t i;
+
+    p = mRR(p, name, DNS_RRTYPE_A, DNS_RRCLASS_IN, MDNS_TTL ); // A, IN
+
+    i = htons(4); // RDLEN - we're just doing a single IPv4 address - our primary link ?
+    memcpy(p, &i, 2);
+
+    // IP already in network order.
+    memcpy(p+2, &ip, 4);
+
+    return p + 2 + 4;
+}
+
+char * mSRV(char *p, char * name, uint16_t port, char * rr) {
+    uint16_t i = 0;
+    char * q;
+
+    p = mRR(p, name, DNS_RRTYPE_SRV, DNS_RRCLASS_IN, MDNS_TTL); // SRV, IN
+
+    // Keep space for RDLEN
+    q = p;
+    p+=2;
+
+    i = htons(1); // Priority
+    memcpy(p, &i, 2);
+    p+=2;
+
+    i = htons(0); // Weight (see rfc2782)
+    memcpy(p, &i, 2);
+    p+=2;
+
+    i = htons(port); // Port
+    memcpy(p, &i, 2);
+    p+=2;
+
+    p = breakname(p, rr);
+
+    i = htons(p - q - 2); // RDLEN
+    memcpy(q, &i, 2);
+
+    return p;
+}
+
+char * qANY(char *p, char * name, uint16_t tpe, uint16_t cls) {
+    uint16_t i = 0;
+    p = breakname(p, name); // QNAME
+
+    i = htons(tpe); // QTYPE
+    memcpy(p, &i, 2);
+    p+=2;
+
+    i = htons(cls); // QCLASS
+    memcpy(p, &i, 2);
+    p+=2;
+
+    return p;
+}
+
+char * qPTR(char *p, char *name) {
+    return qANY(p,name,DNS_RRTYPE_PTR,DNS_RRCLASS_IN);
+}
+
+char * qA(char *p, char *name) {
+    return qANY(p,name,DNS_RRTYPE_A,DNS_RRCLASS_IN);
+}
+
+char * qSRV(char *p, char *name) {
+    return qANY(p,name,DNS_RRTYPE_SRV,DNS_RRCLASS_IN);
+}
+
+void mDNSResponder::sendReply(uint16_t t, uint16_t tid, Host dst) {
+    // sent a reply - basically a precooked A/PTR/SRV with the TransactionID
+    // and my URI squeezed in.
+    char out[ 1500 ], *p;
+    DNSPacket * op = (DNSPacket *) out;
+
+    initLabelCache(out); // Offsets are relative to the ID header.
+
+    op->tid = ntohs(tid);
+    op->flags = ntohs(0x8000U); // Answer
+    op->question_count = ntohs(1); // Courtesy copy of the question.
+    op->answer_count = ntohs(1); // The record asked for
+    op->a_count = ntohs(0);
+    p = out + 12;
+    
+    switch(t) {
+    case DNS_RRTYPE_PTR:    // PTR record, SRV, optional TXT and A with my own address.
+         op->aa_count = ntohs(moi_txt ? 3 : 2);
+        p = qPTR(p,moi_local_proto);
+        
+        p = mPTR(p,moi_local_proto, moi_local_pglue);
+        if (moi_txt && * moi_txt)
+            p = mTXT(p,moi_local_pglue,moi_txt);
+            
+        break;
+    case DNS_RRTYPE_A:    // A record (and nothing else)
+        op->aa_count = ntohs(1);
+        p = qA(p,moi_local_name);
+        break;
+
+    case DNS_RRTYPE_SRV:   // SRV record and a gratious A record to complete.
+        op->aa_count = ntohs(moi_txt ? 2 : 1);
+        p = qSRV(p,moi_local_pglue);
+        
+        p = mPTR(p,moi_local_proto, moi_local_pglue);
+        if (moi_txt && * moi_txt)
+            p = mTXT(p,moi_local_pglue,moi_txt);
+        break;
+        }
+    p = mARR(p,moi_local_name,moi_ip);     
+    m_pUDPSocket->sendto(out,p-out,&dst);
+}
+
+char * decodeQBlock(char * udp, int len, char *p, char  * fqdn, int fqdn_size, uint32_t *Qclass, uint32_t *Qtype)
+{
+    char * endp = udp + len;
+    int depth = 0;
+    int l, ll = 0;
+    char * q = 0;
+    char * ep = fqdn;
+    
+    do {
+        while (((l = *p++) < 192) && (l > 0)) 
+        {
+            if (p + l >= endp) {
+                printf("RR longer than packet\r\n");
+                return NULL;
+            };
+            
+            if (ll + l + 1 > fqdn_size) {
+                printf("FQDN too long\r\n");
+                return NULL;
+            }
+            
+            memcpy(ep,p,l);
+            ep[l]='.';
+            ep += l + 1;
+            p += l;
+            ll += l + 1;
+        };
+
+        if (l >= 192) {
+            // construct an offset pointer by wiping the top 1 bits
+            // and then getting the remaining 8 bytes to make 14.
+            l -= 192;
+            l = l << 8;
+            l += *p++;
+            
+            // rescue our reference; as we've not gotten the Qt's yet
+            // and these follow the last entry in our record (and not
+            // that from the compressed values.
+            //
+            if (!q) q = p;
+
+            // printf(" [->%d] ",l);
+            p = udp + l;
+
+            if (p >= udp + len || p < udp + 12) {
+                printf("Pointer to wrong place\r\n");
+                return NULL;
+            };
+        };
+        
+        if (depth++ >= 128) {
+            printf("Far too deep\r\n");
+            return NULL;
+        };
+    } while (l);
+    
+    // Terminate the FQDN string.
+    *ep = 0;
+    
+    // in case no compression was used at all.
+    if (!q) 
+        q = p;
+
+    *Qtype = htons(q[0] + q[1]*256);
+    *Qclass = htons(q[2] + q[3]*256);
+    return p;
+}
+
+void mDNSResponder::onUDPSocketEvent(UDPSocketEvent e) {
+    char udp[ 1500 ];
+    Host from;
+    int len;
+
+    switch (e) {
+        case UDPSOCKET_READABLE: //The only event for now
+            // parse through the packet; find any PTR requests
+            // and respond to any for _http._tcp._local.
+            while ((len = m_pUDPSocket->recvfrom( (char*)&udp, sizeof(udp), &from ))) {
+                DNSPacket * dp = (DNSPacket *) udp;
+                unsigned int tid = ntohs(dp->tid);
+                unsigned int flags = ntohs(dp->flags);
+                unsigned int nQ = ntohs(dp->question_count);
+                // unsigned int nA = ntohs(dp->answer_count);
+
+                if (flags & 2 != 0 || nQ == 0)
+                    continue; // we only want questions
+
+                // assume nQ NON terminated fields followed by Qtype & Qclass
+                //
+                char * p = udp + 12;
+                for (int i = 0; i < nQ; i++) {
+                    char fqdn[ 256 ];
+                    uint32_t Qt, Qc;
+                    
+                    if (!((p = decodeQBlock(udp,len,p,fqdn,sizeof(fqdn),&Qc, &Qt))))
+                        return;
+                        
+                    // We only deal with INternet.
+                    //
+                    if (Qc != DNS_RRCLASS_IN)
+                        continue;
+                    
+                    printf("Q type %d for %s\r\n", Qt, fqdn);
+                    
+                    // We want PTR records on the INternet of our type. Also do ANY.
+                    //
+                    if ((Qt == DNS_RRTYPE_PTR || Qt == 255) && !(strcmp(fqdn,moi_local_proto)))
+                        sendReply(DNS_RRTYPE_PTR,tid,from);
+                    else if ((Qt == DNS_RRTYPE_A || Qt == 255)  && !(strcmp(fqdn,moi_local_name)))
+                        sendReply(DNS_RRTYPE_A,tid,from);
+                    else if ((Qt == DNS_RRTYPE_SRV || Qt == 255)  && !(strcmp(fqdn,moi_local_pglue)))
+                        sendReply(DNS_RRTYPE_SRV,tid,from);
+                };
+            }
+            break;
+    }
+}
+#endif