dns.h

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/* dns.h */

/* Constants and data structures used for DNS */

#define DNSTIMEOUT  3000        /* Timeout for a response (ms)  */
#define DNSRETRY    3       /* Number of times to retry */
#define DNSPORT     53      /* Well-known DNS UDP port  */
#define DNSLPORT    51525       /* Local UDP port to use    */
#define DNSDATASIZ  500     /* Size of the data area    */


/* Format of a DNS Query/Response packet */

struct  dnspkt {
    uint16  id;         /* DNS Query ID         */
    struct  {
        byte    rd:1;       /* Recursion Desired        */
        byte    tc:1;       /* Truncation           */
        byte    aa:1;       /* Authoritative Answer     */
        byte    opcode:4;   /* Operation Code       */
        byte    qr:1;       /* Query=0, Response=1      */
    };
    struct  {
        byte    rcode:4;    /* Response Code        */
        byte    z:3;        /* Reserved, must be 0      */
        byte    ra:1;       /* Recursion Available      */
    };
    uint16  qucount;        /* No. of Questions     */
    uint16  ancount;        /* No. of RRs in Answer     */
    uint16  nscount;        /* No of Name Server RRs    */
    uint16  arcount;        /* No. of RRs in Additional info*/
    char    data[DNSDATASIZ];   /* DNS data area        */
};

/* QType Values */

#define DNS_QT_A    1       /* DNS Address Type (A)     */
#define DNS_QT_NS   2       /* DNS Name Server Type     */

/* QClass values */

#define DNS_QC_IN   1       /* DNS QClass Internet      */

/* Format of a DNS Question */

struct  dns_q {
    char    *qname;         /* Domain Name in the query */
    uint16  *qtype;         /* Question Type        */
    uint16  *qclass;        /* Question Class       */
};

/* Format of a DNS Resource Record */

struct  dns_rr {
    char    *rname;         /* Domain Name          */
    uint16  *rtype;         /* Resource Record Type     */
    uint16  *rclass;        /* Resource Record Class    */
    uint32  *ttl;           /* Resource Record Time-to-Live */
    uint16  *rdlen;         /* Resource Record RD Length    */
    char    *rdata;         /* Resource Record Data area    */
};