Every body, I have write program to read the dns txt record, but it has some issue, who can tell my why? Following is my source code
char blockItem[512];
bzero(blockItem,512);
/*Temp Save the txt record value*/
int responseLength;
/*The Length of response*/
int i;
/*For Loop Controller*/
ns_msg query_parse_msg;
/*List of response message
* For txt record , It sould only one response!
* */
ns_rr query_parse_rr;
/*One response message*/
u_char responseByte[512];
/*Variable that for storage query answer.*/
bzero(responseByte,512);
/*Clear variable*/
if ((responseLength = res_query(host,C_IN,T_TXT,responseByte,512)) < 0)
{
/*Query DNS Server*/
return HOSTNOTFIND;
}
else
{
if (ns_initparse(responseByte,responseLength,&query_parse_msg) < 0)
{
/*Pass the answer to ns_msg(May be it mean cut the dns header)*/
printf("%s\n","Cannot Read response Message");
return NOTSUCCESSFUL;
}
else
{
for (i =0;i < ns_msg_count(query_parse_msg,ns_s_an);i++)
{
/*Count the toolly response*/
if (ns_parserr(&query_parse_msg,ns_s_an,i,&query_parse_rr))
{
/*Pass the msg list to rr.*/
printf("%s\n","Parse failed!");
return NOTSUCCESSFUL;
}
else
{
u_char const *rdata = (u_char*)(ns_rr_rdata(query_parse_rr) );
char *blockItem;
blockItem=(char*)rdata;
blockItem[strlen((char*)rdata)-2] = '\0';
/*Pass the ns_rr to char data type.*/
printf("Normal:%s\n",(u_char *)blockItem);
}
}
}
OutPut: Fv=spf1 redirect=_spf.google.com
But original txt record should be v=spf1 redirect=_spf.google.com
My issue is u_char const *rdata = (u_char*)(ns_rr_rdata(query_parse_rr) )
If i change it to u_char const *rdata = (u_char*)(ns_rr_rdata(query_parse_rr) +1)
Output will change to: v=spf1 redirect=_spf.google.com
Also , I has refer how to query MX record, i found that has +2, Anything can tell me why??
TXT record RDATA format is
MX record RDATA format is
(RFC 1035, paragraphs 3.3.14 and 3.3.9)