关于DNS查询包的格式

leihelin5201314 2011-04-02 11:24:27

typedef struct//报文head

{

    	unsigned short id;

    	unsigned short flags;

    	unsigned short ques;

    	unsigned short answer;

    	unsigned short author;

    	unsigned short addition;

}DNSHEAD,*pDNSHEAD;



typedef struct//报文的查询部分

{

    	//unsigned char *domain;

    	unsigned short type;

    	unsigned short class;

}SEARCH,*pSEARCH;



void genDNSPacket(char *addr,char *dnssendbuff)

{      //将head加到dnssendbuff里面，结果dnssendbuff里面没有这部分

    	pDNSHEAD pdnshead = (pDNSHEAD)malloc(sizeof(DNSHEAD));

    	pSEARCH psearch = (pSEARCH)malloc(sizeof(SEARCH));



	pdnshead->id = htons(0x0000);

    	pdnshead->flags = htons(0x000);

    	pdnshead->ques = htons(0x0000);

    	pdnshead->answer = htons(0x0000);

    	pdnshead->author = htons(0x0000);

    	pdnshead->addition = htons(0x0000);



    	memcpy(dnssendbuff,pdnshead,sizeof(DNSHEAD));

	printf("pdnshead=%s\n",(char *)pdnshead);

	printf("sizeof(DNSHEAD)=%d\n",sizeof(DNSHEAD));

	printf("dnssendbuff=%s\n",dnssendbuff);



        //将domain  www.hao123.com加到报文

    	char *domain = (char *)malloc(15 *sizeof(char)); //3www6hao1233com0

    	char num;

    	char *pbuf;

   

    	int length = 0;

    	num = 0x03;

    	pbuf = "www";

    	memcpy(domain + length,&num,sizeof(num));

    	length += sizeof(num);

    	memcpy(domain+ length,pbuf,strlen(pbuf));

    	length += strlen(pbuf);



    	num = 0x06;

    	pbuf = "dnspod";

    	memcpy(domain + length,&num,sizeof(num));

    	length += sizeof(num);

    	memcpy(domain + length,pbuf,strlen(pbuf));

    	length += strlen(pbuf);



	num = 0x03;

    	pbuf = "com";

    	memcpy(domain + length,&num,sizeof(num));

    	length += sizeof(num);

    	memcpy(domain + length,pbuf,strlen(pbuf));

    	length += strlen(pbuf);

	printf("domain=%s\n",domain);



    	num = 0x00;

    	memcpy(domain + length,&num,sizeof(num));

	length += sizeof(num);

    	memcpy(dnssendbuff + sizeof(DNSHEAD),domain,16);

	printf("strlen(domain)=%d\n",strlen(domain));

	memcpy( dnssendbuff, domain, 16);

 

        /将search加到dnssendbuff里面，结果dnssendbuff里面没有这部分

    	psearch->type = htons(0x0001);

    	psearch->class = htons(0x0001);



    	memcpy(dnssendbuff + sizeof(DNSHEAD) + 16,psearch,sizeof(SEARCH));

	printf("strlen(dnssendbuff)=%d\n",strlen(dnssendbuff));

	printf("dnssendbuff=%s\n",dnssendbuff);

}

我ping hao123.com,然后wireshark抓包得到的结构看了下，发现我在程序里边的head部分和最后面的查询类和查询类型部分没加到报文里边，报文打出来之后只出现了个 3www6hao1233com ,没发现head和search部分，估计是我的这两部分的程序不正确，希望牛人帮我看下，谢谢！

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