Suga koubou / Mbed 2 deprecated TinyResolver

Tiny DNS Resolver

Dependencies:   EthernetNetIf mbed

TinyResolver.cpp@0:477d4e2f281a, 2011-07-21 (annotated)

Committer:
okini3939
Date:
Thu Jul 21 16:53:11 2011 +0000
Revision:
0:477d4e2f281a

        

        
Who changed what in which revision?

        

            
                
UserRevisionLine numberNew contents of line

            
            


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/*





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 * mbed Tiny DNS Resolver





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 * Copyright (c) 2011 Hiroshi Suga





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 * Released under the MIT License: http://mbed.org/license/mit





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 */





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/** @file





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 * @brief Tiny DNS Resolver





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 */





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#include "mbed.h"





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#include "EthernetNetIf.h"





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#include "UDPSocket.h"





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#include "TinyResolver.h"





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// host to network short





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#define htons( x ) ( (( (x) << 8 ) & 0xFF00) | (( (x) >> 8 ) & 0x00FF) )





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#define ntohs( x ) htons(x)





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// host to network long





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#define htonl( x ) ( (( (x) << 24 ) & 0xFF000000)  \





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                   | (( (x) <<  8 ) & 0x00FF0000)  \





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                   | (( (x) >>  8 ) & 0x0000FF00)  \





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                   | (( (x) >> 24 ) & 0x000000FF)  )





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#define ntohl( x ) htonl(x)





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extern EthernetNetIf eth;





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static UDPSocket *dns;





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static volatile unsigned long dnsaddr;





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static volatile unsigned long id;





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int createDnsRequest (char *name, char *buf) {





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    struct DnsHeader *dnsHeader;





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    struct DnsQuestionEnd *dnsEnd;





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    int len, num;





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    id ++;





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    dnsHeader = (struct DnsHeader*)buf;





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    dnsHeader->id = htons(id);





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    dnsHeader->flags = htons(0x100);





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    dnsHeader->questions = htons(1);





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    dnsHeader->answers = 0;





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    dnsHeader->authorities = 0;





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    dnsHeader->additional = 0;





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    len = sizeof(struct DnsHeader);





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    while ((num = (int)strchr(name, '.')) != NULL) {





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        num = num - (int)name;





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        buf[len] = num;





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        len ++;





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        strncpy(&buf[len], name, num); 





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        name = name + num + 1;





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        len = len + num;





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    }





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    if ((num = strlen(name)) != NULL) {





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        buf[len] = num;





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        len ++; 





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        strncpy(&buf[len], name, num); 





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        len = len + num;





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    }





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    buf[len] = 0;





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    len ++; 





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    dnsEnd = (struct DnsQuestionEnd *)&buf[len];





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    dnsEnd->type = htons(DNS_QUERY_A);





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    dnsEnd->clas = htons(DNS_CLASS_IN);





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    return len + sizeof(struct DnsQuestionEnd);





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}





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int getDnsResponse (const char *buf, int len, uint32_t *addr) {





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    int i;





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    struct DnsHeader *dnsHeader;





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    struct DnsAnswer *dnsAnswer;





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    // header





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    dnsHeader = (struct DnsHeader*)buf;





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    if (ntohs(dnsHeader->id) != id || (ntohs(dnsHeader->flags) & 0x800f) != 0x8000) {





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        return -1;





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    }





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    // skip question





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    for (i = sizeof(struct DnsHeader); buf[i] && i < len; i ++);





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    i = i + 1 + sizeof(struct DnsQuestionEnd);





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    // answer





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    while (i < len) {





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        dnsAnswer = (struct DnsAnswer*)&buf[i];





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        if (dnsAnswer->clas != htons(DNS_CLASS_IN)) {





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            return -1;





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        }





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        i = i + sizeof(struct DnsAnswer);





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        if (dnsAnswer->type == htons(DNS_QUERY_A)) {





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            // A record





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            *addr = ((uint32_t)buf[i] << 24) + ((uint32_t)buf[i + 1] << 16) + ((uint32_t)buf[i + 2] << 8) + (uint32_t)buf[i + 3];





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            return 0;





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        }





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        // next answer





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        i = i + dnsAnswer->length;





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    }





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    return -1;





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}





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void isr_dns (UDPSocketEvent e) {





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    char buf[512];





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    Host dsthost;





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    int len;





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    if (e == UDPSOCKET_READABLE) {





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        // recv responce;





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        len = dns->recvfrom(buf, sizeof(buf), &dsthost);





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#ifdef DEBUG





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        for (int i = 0; i < len; i ++) {





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            printf(" %02x", (unsigned char)buf[i]);





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        }





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        puts("\r");





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#endif





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        if (len >= sizeof(struct DnsHeader)) {





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            getDnsResponse(buf, len, (uint32_t*)&dnsaddr);





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        }





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    }





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}





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int getHostByName (IpAddr nameserver, const char *name, uint32_t *addr) {





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    UDPSocketErr err;





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    Host myhost, dnshost;





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    char buf[100];





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    int i, len;





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    // localhost





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    if (!strcmp(name, "localhost")) {





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        *addr = 0x0f000001;





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        return 0;





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    }





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    dnsaddr = 0;





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    dns = new UDPSocket;





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    dns->setOnEvent(isr_dns);





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    // bind





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    myhost.setIp(eth.getIp());





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    myhost.setPort(DNS_SRC_PORT);





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    err = dns->bind(myhost);





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    if (err != UDPSOCKET_OK) goto exit;





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    // send request





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    dnshost.setIp(nameserver);





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    dnshost.setPort(DNS_PORT);





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    len = createDnsRequest((char*)name, buf);





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#ifdef DEBUG





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    for (int i = 0; i < len; i ++) {





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        printf(" %02x", (unsigned char)buf[i]);





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    }





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    puts("\r");





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#endif





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    dns->sendto(buf, len, &dnshost);





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    // wait responce





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    for (i = 0; i < DNS_TIMEOUT / 10; i ++) {





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        if (dnsaddr) {





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            // responce





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            *addr = dnsaddr;





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            break;





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        }





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        if (i % 500 == 499) {





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            // retry





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            dns->sendto(buf, len, &dnshost);





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        }





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        Net::poll();





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        wait_ms(10);





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    }





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exit:





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    dns->resetOnEvent();





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    delete dns;





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    return dnsaddr ? 0 : -1;





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}