DNSClient.cpp

00001 // DNSClient.cpp 2013/8/27
00002 #include "mbed.h"
00003 #include "mbed_debug.h"
00004 #include "DNSClient.hpp"
00005 #include "UDPSocket.hpp"
00006 #include "dnsname.hpp"
00007 #include "eth_arch.hpp"
00008 
00009 #define DBG_DNS 0
00010 
00011 #if DBG_DNS
00012 #define DBG2(...) do{debug("[DNS]%p %d %s ", this,__LINE__,__PRETTY_FUNCTION__); debug(__VA_ARGS__); } while(0);
00013 #else
00014 #define DBG2(...) while(0);
00015 #endif
00016 
00017 using namespace wiznet_space;
00018 
00019 DNSClient::DNSClient(const char* hostname) : m_state(MYNETDNS_START), m_udp(NULL) {
00020     m_hostname = hostname;
00021 }
00022 
00023 DNSClient::DNSClient(Endpoint* pHost) : m_state(MYNETDNS_START), m_udp(NULL) {
00024 }
00025 
00026 DNSClient::~DNSClient() {
00027     if (m_udp) {
00028         delete m_udp;
00029     }
00030 }
00031 
00032 void DNSClient::callback()
00033 {
00034     uint8_t buf[512];
00035     Endpoint host;
00036     int len = m_udp->receiveFrom(host, (char*)buf, sizeof(buf));
00037     if (len < 0) {
00038         return;
00039     }
00040     if (memcmp(buf+0, m_id, 2) != 0) { //verify
00041         return;
00042     }
00043     int rcode = response(buf, len);
00044     if (rcode == 0) {
00045         m_state = MYNETDNS_OK;
00046     } else {
00047         m_state = MYNETDNS_NOTFOUND;
00048     }
00049 }
00050 
00051 int DNSClient::response(uint8_t buf[], int size) {
00052     int rcode = buf[3] & 0x0f;
00053     if (rcode != 0) {
00054         return rcode;
00055     }
00056     int qdcount = buf[4]<<8|buf[5];
00057     int ancount = buf[6]<<8|buf[7];
00058     int pos = 12;
00059     while(qdcount-- > 0) {
00060         dnsname qname(buf);
00061         pos = qname.decode(pos); // qname
00062         pos += 4; // qtype qclass
00063     }
00064     while(ancount-- > 0) {
00065         dnsname name(buf);
00066         pos = name.decode(pos); // name
00067         int type = buf[pos]<<8|buf[pos+1];
00068         pos += 8; // type class TTL  
00069         int rdlength = buf[pos]<<8|buf[pos+1]; pos += 2;
00070         int rdata_pos = pos;
00071         pos += rdlength;
00072         if (type == 1) { // A record
00073             ip = (buf[rdata_pos]<<24) | (buf[rdata_pos+1]<<16) | (buf[rdata_pos+2]<<8) | buf[rdata_pos+3];
00074         }
00075 #if DBG_DNS
00076         printf("%s", name.str.c_str());
00077         if (type == 1) {
00078             printf(" A %d.%d.%d.%d\n", 
00079                 buf[rdata_pos],buf[rdata_pos+1],buf[rdata_pos+2],buf[rdata_pos+3]);
00080         } else if (type == 5) {
00081             dnsname rdname(buf);
00082             rdname.decode(rdata_pos);
00083             printf(" CNAME %s\n", rdname.str.c_str());
00084         } else {
00085             printf(" TYPE:%d", type);
00086             printfBytes(" RDATA:", &buf[rdata_pos], rdlength);
00087         }
00088 #endif
00089     }
00090     return rcode;
00091 }
00092 
00093 int DNSClient::query(uint8_t buf[], int size, const char* hostname) {
00094     const uint8_t header[] = {
00095         0x00,0x00,0x01,0x00, // id=0x0000 QR=0 rd=1 opcode=0 rcode=0
00096         0x00,0x01,0x00,0x00, // qdcount=1 ancount=0
00097         0x00,0x00,0x00,0x00};// nscount=0 arcount=0 
00098     const uint8_t tail[] = {0x00,0x01,0x00,0x01}; // qtype=A qclass=IN
00099     memcpy(buf, header, sizeof(header));
00100     int t = rand();
00101     m_id[0] = t>>8;
00102     m_id[1] = t;
00103     memcpy(buf, m_id, 2); 
00104     dnsname qname(buf);
00105     int pos = qname.encode(sizeof(header), (char*)hostname);
00106     memcpy(buf+pos, tail, sizeof(tail));
00107     pos += sizeof(tail);
00108     return pos;
00109 }
00110 
00111 void DNSClient::resolve(const char* hostname) {
00112     if (m_udp == NULL) {
00113         m_udp = new UDPSocket;
00114     }
00115     m_udp->init();
00116     m_udp->set_blocking(false);
00117     Endpoint server;
00118     server.set_address("8.8.8.8", 53); // DNS
00119     m_udp->bind(rand()&0x7fff);
00120     uint8_t buf[256];                
00121     int size = query(buf, sizeof(buf), hostname);
00122 #if DBG_DNS
00123     printf("hostname:[%s]\n", hostname);
00124     printHex(buf, size);
00125 #endif
00126     m_udp->sendTo(server, (char*)buf, size);
00127     m_interval.reset();
00128     m_interval.start();
00129 }
00130 
00131 void DNSClient::poll() {
00132 #if DBG_DNS
00133     printf("%p m_state: %d, m_udp: %p\n", this, m_state, m_udp);
00134     wait_ms(400);
00135 #endif
00136     switch(m_state) {
00137         case MYNETDNS_START:
00138             m_retry = 0;
00139             resolve(m_hostname);
00140             m_state = MYNETDNS_PROCESSING;
00141             break;
00142         case MYNETDNS_PROCESSING: 
00143             break;
00144         case MYNETDNS_NOTFOUND: 
00145             break;
00146         case MYNETDNS_ERROR: 
00147             break;
00148         case MYNETDNS_OK:
00149             DBG2("m_retry=%d, m_interval=%d\n", m_retry, m_interval.read_ms());
00150             break;
00151     }
00152     if (m_interval.read_ms() > 1000) {
00153         m_interval.stop();
00154         DBG2("timeout m_retry=%d\n", m_retry);
00155         if (++m_retry >= 2) {
00156             m_state = MYNETDNS_ERROR;
00157         } else {
00158             resolve(m_hostname);
00159             m_state = MYNETDNS_PROCESSING;
00160         }
00161     }
00162 }
00163 
00164 bool DNSClient::lookup(const char* hostname) {
00165     m_hostname = hostname;
00166     m_state = MYNETDNS_START;
00167     while(1) {
00168         poll();
00169         callback();
00170         if (m_state != MYNETDNS_PROCESSING) {
00171             break;
00172         } 
00173     }
00174     return m_state == MYNETDNS_OK;
00175 }
00176