DongEun Koak
DnsQuery for NetworkSocketAPI
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DnsQuery
by 
NetworkSocketAPI
Diff: DnsQuery.cpp
- Revision:
- 10:0fe2c42a0261
- Parent:
- 9:16e5208cc4ef
- Child:
- 12:e23ef3dab4b9
diff -r 16e5208cc4ef -r 0fe2c42a0261 DnsQuery.cpp
--- a/DnsQuery.cpp Sun Feb 28 11:23:59 2016 -0600
+++ b/DnsQuery.cpp Sun Feb 28 22:07:29 2016 -0600
@@ -37,57 +37,129 @@
#endif
-
-DnsQuery::DnsQuery(UDPSocket *sock,const char* hostname, char* ipaddress)
-{
- socket = sock;
- this->getHostByName(hostname, ipaddress);
-}
-
-bool DnsQuery::getHostByName(const char* hostname, char* resolvedIp)
-{
- if (isIP(hostname)) {
- strcpy(resolvedIp, hostname);
- return true;
- }
+#define DNS_COUNT (sizeof DNS_IPS / sizeof DNS_IPS[0])
+const char *DNS_IPS[] = {
+ "8.8.8.8",
+ "209.244.0.3",
+ "84.200.69.80",
+ "8.26.56.26",
+ "208.67.222.222"
+};
- const char * dnsIPs[] = {
- "8.8.8.8",
- "209.244.0.3",
- "84.200.69.80",
- "8.26.56.26",
- "208.67.222.222"
- };
- for(int i = 0; i<5; i++){
- _dnsip = dnsIPs[i];
- if(this->getIP(hostname, resolvedIp)){
- return true;
- }
-
- }
- return false;
-
-}
-
-bool DnsQuery::isIP(const char* hostname) const
+static bool isIP(const char *host)
{
int i;
- for (i = 0; hostname[i]; i++) {
- if (!(hostname[i] >= '0' && hostname[i] <= '9') && hostname[i] != '.') {
+ for (i = 0; host[i]; i++) {
+ if (!(host[i] >= '0' && host[i] <= '9') && host[i] != '.') {
return false;
}
}
- // Ending with '.' garuntees hostname
- if (i > 0 && hostname[i-1] == '.') {
+ // Ending with '.' garuntees host
+ if (i > 0 && host[i-1] == '.') {
return false;
}
return true;
}
-bool DnsQuery::getIP(const char* hostname, char* ipaddress)
+
+static bool parseRR(uint8_t *resp, int& c, char* adr )
+{
+ int n = 0;
+ while( (n=resp[c++]) != 0) {
+ if ((n & 0xc0) != 0) {
+ // This is a link
+ c++;
+ break;
+ } else {
+ c+= n; // skip this segment, not interested in string domain names
+ }
+ }
+
+ int TYPE = (((int)resp[c])<<8) + resp[c+1];
+ int CLASS = (((int)resp[c+2])<<8) + resp[c+3];
+ int RDLENGTH = (((int)resp[c+8])<<8) + resp[c+9];
+
+ INFO("Record of TYPE=%d and CLASS=%d detected !", TYPE, CLASS);
+ c+= 10;
+ if ((CLASS == 1) && (TYPE == 1)) {
+ sprintf(adr,"%d.%d.%d.%d", resp[c], resp[c+1], resp[c+2], resp[c+3]);
+ c+= RDLENGTH;
+ return true;
+ } else {
+ }
+ c+= RDLENGTH;
+
+ return false;
+}
+
+
+static bool resolve(unsigned char* resp, char* ipaddress)
+{
+
+ int ID = (((int)resp[0]) <<8) + resp[1];
+ int QR = resp[2] >>7;
+ int Opcode = (resp[2]>>3) & 0x0F;
+ int RCODE = (resp[3] & 0x0F);
+ int ANCOUNT = (((int)resp[6])<<8)+ resp[7];
+
+ INFO("Resolving response : ID = %d, QR = %d, Opcode = %d, RCODE = %d", ID, QR, Opcode, RCODE);
+ if ((ID != 1) || (QR != 1) || (Opcode != 0) || (RCODE != 0)) {
+ ERR("Received non matching response from DNS !");
+ return false;
+ }
+
+ int c = 12;
+ int d;
+ // Skip domain question
+ while( (d=resp[c++]) != 0) {
+ c+=d;
+ }
+ c+= 4; // skip QTYPE and QCLASS
+
+ // Here comes the resource record
+ for (int ans = 0 ; ans < ANCOUNT; ans++) {
+ if (parseRR(resp, c, ipaddress)) {
+ return true;
+ }
+ }
+
+ return false;
+}
+
+
+int32_t dnsQuery(NetworkInterface *iface, const char *host, char *ip)
+{
+ if (isIP(host)) {
+ strcpy(ip, host);
+ return 0;
+ }
+
+ UDPSocket sock(iface);
+ int32_t err;
+
+ for (unsigned i = 0; i < DNS_COUNT; i++) {
+ err = sock.open(DNS_IPS[0], 53);
+ if (err < 0) {
+ return err;
+ }
+
+ err = dnsQuery(&sock, host, ip);
+ if (err >= 0) {
+ return sock.close();
+ } else if (err != NS_ERROR_DNS_FAILURE) {
+ sock.close();
+ return err;
+ }
+ }
+
+ sock.close();
+ return NS_ERROR_DNS_FAILURE;
+}
+
+int32_t dnsQuery(UDPSocket *socket, const char *hostname, char *ipaddress)
{
INFO("%s", hostname);
int len = 0;
@@ -132,11 +204,8 @@
// Set QCLASS
packet[c++] = 0;
packet[c++] = 1;
-
-
- // Ready to send to DNS
- socket->open(_dnsip, 53);
+
INFO("Sending packet of length %d",packetlen);
/*
for( int i = 0 ; i < c ; i++) {
@@ -162,85 +231,20 @@
*/
if (response_length > 0 ) {
if (!resolve(packet, ipaddress)) {
- socket->close();
delete packet;
ERR("NO IP FOUND\n");
- return false;
+ return NS_ERROR_DNS_FAILURE;
}
// cleanup and return
delete packet;
- socket->close();
- return true;
+ return 0;
} else {
ERR("SocketRecvFrom returned %d !", response_length);
}
- socket->close();
delete packet;
ERR("NO IP FOUND\n");
- return false;
+ return NS_ERROR_DNS_FAILURE;
}
-bool DnsQuery::resolve(unsigned char* resp, char* ipaddress)
-{
-
- int ID = (((int)resp[0]) <<8) + resp[1];
- int QR = resp[2] >>7;
- int Opcode = (resp[2]>>3) & 0x0F;
- int RCODE = (resp[3] & 0x0F);
- int ANCOUNT = (((int)resp[6])<<8)+ resp[7];
-
- INFO("Resolving response : ID = %d, QR = %d, Opcode = %d, RCODE = %d", ID, QR, Opcode, RCODE);
- if ((ID != 1) || (QR != 1) || (Opcode != 0) || (RCODE != 0)) {
- ERR("Received non matching response from DNS !");
- return false;
- }
-
- int c = 12;
- int d;
- // Skip domain question
- while( (d=resp[c++]) != 0) {
- c+=d;
- }
- c+= 4; // skip QTYPE and QCLASS
-
- // Here comes the resource record
- for (int ans = 0 ; ans < ANCOUNT; ans++) {
- if (parseRR(resp, c, ipaddress)) {
- return true;
- }
- }
-
- return false;
-}
-
-bool DnsQuery::parseRR(uint8_t *resp, int& c, char* adr )
-{
- int n = 0;
- while( (n=resp[c++]) != 0) {
- if ((n & 0xc0) != 0) {
- // This is a link
- c++;
- break;
- } else {
- c+= n; // skip this segment, not interested in string domain names
- }
- }
-
- int TYPE = (((int)resp[c])<<8) + resp[c+1];
- int CLASS = (((int)resp[c+2])<<8) + resp[c+3];
- int RDLENGTH = (((int)resp[c+8])<<8) + resp[c+9];
-
- INFO("Record of TYPE=%d and CLASS=%d detected !", TYPE, CLASS);
- c+= 10;
- if ((CLASS == 1) && (TYPE == 1)) {
- sprintf(adr,"%d.%d.%d.%d", resp[c], resp[c+1], resp[c+2], resp[c+3]);
- c+= RDLENGTH;
- return true;
- } else {
- }
- c+= RDLENGTH;
-
- return false;
-}