Diff: DNSClient/DNSClient.cpp

Revision:

15:14382459c8b7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DNSClient/DNSClient.cpp	Thu Jun 15 20:29:03 2017 +0000
@@ -0,0 +1,245 @@
+// DNSClient.cpp 2013/8/27
+#include "mbed.h"
+#include "mbed_debug.h"
+#include "DNSClient.h"
+#include "UDPSocket.h"
+#include "dnsname.h"
+#include "wiznet.h"
+
+#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
+
+static SocketAddress theDnsServer;
+
+DNSClient::DNSClient() : m_state(MYNETDNS_START), m_udp(NULL) {
+    m_ns = NULL;
+
+    //default to google
+    theDnsServer.set_ip_address("8.8.8.8"); // DNS
+    theDnsServer.set_port(53); // DNS
+}
+
+DNSClient::DNSClient(NetworkStack *ns, const char* hostname) : m_state(MYNETDNS_START), m_udp(NULL) {
+    m_hostname = hostname;
+    m_ns       = ns;
+    
+    //default to google
+    theDnsServer.set_ip_address("8.8.8.8"); // DNS
+    theDnsServer.set_port(53); // DNS
+}
+
+DNSClient::DNSClient(NetworkStack *ns, SocketAddress* pHost) : m_state(MYNETDNS_START), m_udp(NULL) {
+    m_ns = ns;
+
+    //default to google
+    theDnsServer.set_ip_address("8.8.8.8"); // DNS
+    theDnsServer.set_port(53); // DNS
+}
+
+DNSClient::~DNSClient() {
+    if (m_udp) {
+        delete m_udp;
+    }
+}
+
+int DNSClient::setup(NetworkStack *ns) {
+    m_ns = ns;
+    return 0;
+}
+
+bool DNSClient::set_server(const char* serverip, int port) {
+    theDnsServer.set_ip_address(serverip); 
+    theDnsServer.set_port(port);
+    return true;
+}
+
+void DNSClient::callback()
+{
+    uint8_t buf[512];
+    SocketAddress host;
+    int len = m_udp->recvfrom(&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
+            m_ip = (buf[rdata_pos]<<24) | (buf[rdata_pos+1]<<16) | (buf[rdata_pos+2]<<8) | buf[rdata_pos+3];
+            sprintf(m_ipaddr, "%d.%d.%d.%d", buf[rdata_pos],buf[rdata_pos+1],buf[rdata_pos+2],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->open(m_ns);
+    }
+    m_udp->set_blocking(false);
+    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(theDnsServer, (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;
+        }
+    }
+}
+
+//tests for a valid IP address, returns 0 if invalid IP address format, returns ip address if valid
+static uint32_t
+isValidIP(const char* ip) {
+    int i1, i2, i3, i4;
+    int len = strlen(ip);
+
+    if (len < 7) return 0;
+
+    //count the number of dots, there must be 3
+    int dotcount = 0;
+    for (int i = 0; i < len; i++) {
+        if (ip[i] == '.' ) dotcount++;
+    }
+
+    //there must be exactly 3 dots
+    if (dotcount != 3) return 0;
+
+    sscanf((char*)ip, "%d.%d.%d.%d", &i1, &i2, &i3, &i4);
+
+    if (strlen(ip) <= 16 && (i1 >= 0 && i1 <= 255) && (i2 >= 0 && i2 <= 255) &&
+            (i3 >= 0 && i3 <= 255) && (i4 >= 0 && i4 <= 255)) {
+        return ((i1<<24) | (i2<<16) | (i3<<8) | i4);
+    }
+    return 0;
+}
+
+bool DNSClient::lookup(const char* hostname) {
+    m_hostname = hostname;
+    
+    uint32_t ip = isValidIP(hostname);
+
+    //check if hostname is an IP address
+    if (ip > 0) {
+        //if it is already an IP address just return immediately
+        m_ip = ip;
+        strcpy(m_ipaddr, hostname);
+        m_state = MYNETDNS_OK;
+        return true;
+    }
+    
+    m_state = MYNETDNS_START;
+    while(1) {
+        poll();
+        callback();
+        if (m_state != MYNETDNS_PROCESSING) {
+            break;
+        } 
+    }
+    
+    if (m_udp) {
+        delete m_udp;
+        m_udp = NULL;
+    }
+    return m_state == MYNETDNS_OK;
+}