Diff: DNSClient/DNSClient.cpp

Revision:

0:e11e8793c3ce

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DNSClient/DNSClient.cpp	Wed Aug 20 00:28:37 2014 +0000
@@ -0,0 +1,173 @@
+// DNSClient.cpp 2013/8/27
+#include "mbed.h"
+#include "mbed_debug.h"
+#include "DNSClient.h"
+#include "UDPSocket.h"
+#include "dnsname.h"
+#include "wiznet.h"
+
+#define DBG_DNS 0
+
+#if DBG_DNS
+#define DBG2(...) do{debug("[DNS]%p %d %s ", this,__LINE__,__PRETTY_FUNCTION__); debug(__VA_ARGS__); } while(0);
+#else
+#define DBG2(...) while(0);
+#endif
+
+DNSClient::DNSClient(const char* hostname) : m_state(MYNETDNS_START), m_udp(NULL) {
+    m_hostname = hostname;
+}
+
+DNSClient::DNSClient(Endpoint* pHost) : m_state(MYNETDNS_START), m_udp(NULL) {
+}
+
+DNSClient::~DNSClient() {
+    if (m_udp) {
+        delete m_udp;
+    }
+}
+
+void DNSClient::callback()
+{
+    uint8_t buf[512];
+    Endpoint host;
+    int len = m_udp->receiveFrom(host, (char*)buf, sizeof(buf));
+    if (len < 0) {
+        return;
+    }
+    if (memcmp(buf+0, m_id, 2) != 0) { //verify
+        return;
+    }
+    int rcode = response(buf, len);
+    if (rcode == 0) {
+        m_state = MYNETDNS_OK;
+    } else {
+        m_state = MYNETDNS_NOTFOUND;
+    }
+}
+
+int DNSClient::response(uint8_t buf[], int size) {
+    int rcode = buf[3] & 0x0f;
+    if (rcode != 0) {
+        return rcode;
+    }
+    int qdcount = buf[4]<<8|buf[5];
+    int ancount = buf[6]<<8|buf[7];
+    int pos = 12;
+    while(qdcount-- > 0) {
+        dnsname qname(buf);
+        pos = qname.decode(pos); // qname
+        pos += 4; // qtype qclass
+    }
+    while(ancount-- > 0) {
+        dnsname name(buf);
+        pos = name.decode(pos); // name
+        int type = buf[pos]<<8|buf[pos+1];
+        pos += 8; // type class TTL  
+        int rdlength = buf[pos]<<8|buf[pos+1]; pos += 2;
+        int rdata_pos = pos;
+        pos += rdlength;
+        if (type == 1) { // A record
+            ip = (buf[rdata_pos]<<24) | (buf[rdata_pos+1]<<16) | (buf[rdata_pos+2]<<8) | buf[rdata_pos+3];
+        }
+#if DBG_DNS
+        printf("%s", name.str.c_str());
+        if (type == 1) {
+            printf(" A %d.%d.%d.%d\n", 
+                buf[rdata_pos],buf[rdata_pos+1],buf[rdata_pos+2],buf[rdata_pos+3]);
+        } else if (type == 5) {
+            dnsname rdname(buf);
+            rdname.decode(rdata_pos);
+            printf(" CNAME %s\n", rdname.str.c_str());
+        } else {
+            printf(" TYPE:%d", type);
+            printfBytes(" RDATA:", &buf[rdata_pos], rdlength);
+        }
+#endif
+    }
+    return rcode;
+}
+
+int DNSClient::query(uint8_t buf[], int size, const char* hostname) {
+    const uint8_t header[] = {
+        0x00,0x00,0x01,0x00, // id=0x0000 QR=0 rd=1 opcode=0 rcode=0
+        0x00,0x01,0x00,0x00, // qdcount=1 ancount=0
+        0x00,0x00,0x00,0x00};// nscount=0 arcount=0 
+    const uint8_t tail[] = {0x00,0x01,0x00,0x01}; // qtype=A qclass=IN
+    memcpy(buf, header, sizeof(header));
+    int t = rand();
+    m_id[0] = t>>8;
+    m_id[1] = t;
+    memcpy(buf, m_id, 2); 
+    dnsname qname(buf);
+    int pos = qname.encode(sizeof(header), (char*)hostname);
+    memcpy(buf+pos, tail, sizeof(tail));
+    pos += sizeof(tail);
+    return pos;
+}
+
+void DNSClient::resolve(const char* hostname) {
+    if (m_udp == NULL) {
+        m_udp = new UDPSocket;
+    }
+    m_udp->init();
+    m_udp->set_blocking(false);
+    Endpoint server;
+    server.set_address("8.8.8.8", 53); // DNS
+    m_udp->bind(rand()&0x7fff);
+    uint8_t buf[256];                
+    int size = query(buf, sizeof(buf), hostname);
+#if DBG_DNS
+    printf("hostname:[%s]\n", hostname);
+    printHex(buf, size);
+#endif
+    m_udp->sendTo(server, (char*)buf, size);
+    m_interval.reset();
+    m_interval.start();
+}
+
+void DNSClient::poll() {
+#if DBG_DNS
+    printf("%p m_state: %d, m_udp: %p\n", this, m_state, m_udp);
+    wait_ms(400);
+#endif
+    switch(m_state) {
+        case MYNETDNS_START:
+            m_retry = 0;
+            resolve(m_hostname);
+            m_state = MYNETDNS_PROCESSING;
+            break;
+        case MYNETDNS_PROCESSING: 
+            break;
+        case MYNETDNS_NOTFOUND: 
+            break;
+        case MYNETDNS_ERROR: 
+            break;
+        case MYNETDNS_OK:
+            DBG2("m_retry=%d, m_interval=%d\n", m_retry, m_interval.read_ms());
+            break;
+    }
+    if (m_interval.read_ms() > 1000) {
+        m_interval.stop();
+        DBG2("timeout m_retry=%d\n", m_retry);
+        if (++m_retry >= 2) {
+            m_state = MYNETDNS_ERROR;
+        } else {
+            resolve(m_hostname);
+            m_state = MYNETDNS_PROCESSING;
+        }
+    }
+}
+
+bool DNSClient::lookup(const char* hostname) {
+    m_hostname = hostname;
+    m_state = MYNETDNS_START;
+    while(1) {
+        poll();
+        callback();
+        if (m_state != MYNETDNS_PROCESSING) {
+            break;
+        } 
+    }
+    return m_state == MYNETDNS_OK;
+}