src/c-api/1035.h

#ifndef _1035_h
#define _1035_h

// be familiar with rfc1035 if you want to know what all the variable names mean, but this hides most of the dirty work
// all of this code depends on the buffer space a packet is in being 4096 and zero'd before the packet is copied in
// also conveniently decodes srv rr's, type 33, see rfc2782

// should be reasonably large, for udp
#define MAX_PACKET_LEN 4000

struct question
{
  unsigned char *name;
  unsigned short int type;
  unsigned short int q_class;
};

#define QTYPE_A 1
#define QTYPE_NS 2
#define QTYPE_CNAME 5
#define QTYPE_PTR 12
#define QTYPE_SRV 33

struct resource
{
  unsigned char *name;
  unsigned short int type;
  unsigned short int r_class;
  unsigned long int ttl;
  unsigned short int rdlength;
  unsigned char *rdata;
  union {
    struct { unsigned long int ip; char *name; } a;
    struct { unsigned char *name; } ns;
    struct { unsigned char *name; } cname;
    struct { unsigned char *name; } ptr;
    struct { unsigned short int priority, weight, port; unsigned char *name; } srv;
  } known;
};

struct message
{
    // external data
    unsigned short int id;
    struct { 
      unsigned short qr:1, 
        opcode:4, 
        aa:1, 
        tc:1, 
        rd:1, 
        ra:1, 
        z:3, 
        rcode:4; 
    } header;
    unsigned short int qdcount, ancount, nscount, arcount;
    struct question *qd;
    struct resource *an, *ns, *ar;

    // internal variables
    unsigned char *_buf, *_labels[20];
    int _len, _label;
    
    // packet acts as padding, easier mem management
    unsigned char _packet[MAX_PACKET_LEN];

    // target is not in mutlicast
    char* target_host;
    int target_port;
};

// returns the next short/long off the buffer (and advances it)
unsigned short int net2short(unsigned char **buf);
unsigned long int net2long(unsigned char **buf);

// copies the short/long into the buffer (and advances it)
void short2net(unsigned short int i, unsigned char **buf);
void long2net(unsigned long int l, unsigned char **buf);

// parse packet into message, packet must be at least MAX_PACKET_LEN and message must be zero'd for safety
void message_parse(struct message *m, unsigned char *packet);

// create a message for sending out on the wire
struct message *message_wire(void);

// append a question to the wire message
void message_qd(struct message *m, 
                unsigned char *name, 
                unsigned short int type, 
                unsigned short int aClass);

// append a resource record to the message, all called in order!
// @todo replace by variant with target_host
void message_an(struct message *m, 
                unsigned char *name, 
                unsigned short int type, 
                unsigned short int aClass, 
                unsigned long int ttl);

void _message_an(struct message *m,
                 unsigned char *name,
                 unsigned short int type,
                 unsigned short int aClass,
                 unsigned long int ttl,
                 char* target_host,
                 unsigned int target_port);

// @todo replace by variant with target_host
void message_ns(struct message *m, 
                unsigned char *name, 
                unsigned short int type, 
                unsigned short int aClass, 
                unsigned long int ttl);

void _message_ns(struct message *m, 
                 unsigned char *name, 
                 unsigned short int type, 
                 unsigned short int aClass, 
                 unsigned long int ttl,
                 char* target_host,
                 int target_port);

// @todo replace by variant with target_host
void message_ar(struct message *m, 
                unsigned char *name, 
                unsigned short int type, 
                unsigned short int aClass, 
                unsigned long int ttl);

void _message_ar(struct message *m, 
                 unsigned char *name, 
                 unsigned short int type, 
                 unsigned short int aClass, 
                 unsigned long int ttl,
                 char* target_host,
                 int target_port);

// append various special types of resource data blocks
void message_rdata_long(struct message *m, unsigned long int l);
void message_rdata_name(struct message *m, unsigned char *name);
void message_rdata_srv(struct message *m, unsigned short int priority, unsigned short int weight, unsigned short int port, unsigned char *name);
void message_rdata_raw(struct message *m, unsigned char *rdata, unsigned short int rdlength);

// return the wire format (and length) of the message, just free message when done
unsigned char *message_packet(struct message *m);
int message_packet_len(struct message *m);


#endif

---