tinysvcmdns.h

// This file is the concatenation of mdnsd.h and mdns.h
// from tinysvcmdns with minor modifications
// The code was taken from https://bitbucket.org/geekman/tinysvcmdns at revision e34b562

/*
 * tinysvcmdns - a tiny MDNS implementation for publishing services
 * Copyright (C) 2011 Darell Tan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _TINYSVCMDNS_H

//******************************************************//
//                      mdns.h                          //
//******************************************************//
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#ifdef _WIN32
#include <winsock.h>
#else
#include <arpa/inet.h>
#endif

#define MALLOC_ZERO_STRUCT(x, type)                                                                \
  x = malloc(sizeof(struct type));                                                                 \
  memset(x, 0, sizeof(struct type));

#define DECL_MALLOC_ZERO_STRUCT(x, type) struct type *MALLOC_ZERO_STRUCT(x, type)

struct rr_data_srv {
  uint16_t priority;
  uint16_t weight;
  uint16_t port;
  uint8_t *target; // host
};

struct rr_data_txt {
  struct rr_data_txt *next;
  uint8_t *txt;
};

struct rr_data_nsec {
  // uint8_t *name;        // same as record

  // NSEC occupies the 47th bit, 5 bytes
  // uint8_t bitmap_len;   // = 5
  uint8_t bitmap[5]; // network order: first byte contains LSB
};

struct rr_data_ptr {
  uint8_t *name; // NULL if entry is to be used
  struct rr_entry *entry;
};

struct rr_data_a {
  uint32_t addr;
};

struct rr_data_aaaa {
  struct in6_addr *addr;
};

struct rr_entry {
  uint8_t *name;

  enum rr_type {
    RR_A = 0x01,
    RR_PTR = 0x0C,
    RR_TXT = 0x10,
    RR_AAAA = 0x1C,
    RR_SRV = 0x21,
    RR_NSEC = 0x2F,
    RR_ANY = 0xFF,
  } type;

  uint32_t ttl;

  // for use in Questions only
  char unicast_query;

  // for use in Answers only
  char cache_flush;

  uint16_t rr_class;

  // RR data
  union {
    struct rr_data_nsec NSEC;
    struct rr_data_srv SRV;
    struct rr_data_txt TXT;
    struct rr_data_ptr PTR;
    struct rr_data_a A;
    struct rr_data_aaaa AAAA;
  } data;
};

struct rr_list {
  struct rr_entry *e;
  struct rr_list *next;
};

struct rr_group {
  uint8_t *name;

  struct rr_list *rr;

  struct rr_group *next;
};

#define MDNS_FLAG_RESP (1 << 15) // Query=0 / Response=1
#define MDNS_FLAG_AA (1 << 10)   // Authoritative
#define MDNS_FLAG_TC (1 << 9)    // TrunCation
#define MDNS_FLAG_RD (1 << 8)    // Recursion Desired
#define MDNS_FLAG_RA (1 << 7)    // Recursion Available
#define MDNS_FLAG_Z (1 << 6)     // Reserved (zero)

#define MDNS_FLAG_GET_RCODE(x) (x & 0x0F)
#define MDNS_FLAG_GET_OPCODE(x) ((x >> 11) & 0x0F)

// gets the PTR target name, either from "name" member or "entry" member
#define MDNS_RR_GET_PTR_NAME(rr)                                                                   \
  (rr->data.PTR.name != NULL ? rr->data.PTR.name : rr->data.PTR.entry->name)

struct mdns_pkt {
  uint16_t id; // transaction ID
  uint16_t flags;
  uint16_t num_qn;
  uint16_t num_ans_rr;
  uint16_t num_auth_rr;
  uint16_t num_add_rr;

  struct rr_list *rr_qn;   // questions
  struct rr_list *rr_ans;  // answer RRs
  struct rr_list *rr_auth; // authority RRs
  struct rr_list *rr_add;  // additional RRs
};

struct mdns_pkt *mdns_parse_pkt(uint8_t *pkt_buf, size_t pkt_len);

void mdns_init_reply(struct mdns_pkt *pkt, uint16_t id);
size_t mdns_encode_pkt(struct mdns_pkt *answer, uint8_t *pkt_buf, size_t pkt_len);

void mdns_pkt_destroy(struct mdns_pkt *p);
void rr_group_destroy(struct rr_group *group);
struct rr_group *rr_group_find(struct rr_group *g, uint8_t *name);
struct rr_entry *rr_entry_find(struct rr_list *rr_list, uint8_t *name, uint16_t type);
struct rr_entry *rr_entry_match(struct rr_list *rr_list, struct rr_entry *entry);
void rr_group_add(struct rr_group **group, struct rr_entry *rr);

int rr_list_count(struct rr_list *rr);
int rr_list_append(struct rr_list **rr_head, struct rr_entry *rr);
struct rr_entry *rr_list_remove(struct rr_list **rr_head, struct rr_entry *rr);
void rr_list_destroy(struct rr_list *rr, char destroy_items);

struct rr_entry *rr_create_ptr(uint8_t *name, struct rr_entry *d_rr);
struct rr_entry *rr_create_srv(uint8_t *name, uint16_t port, uint8_t *target);
struct rr_entry *rr_create_aaaa(uint8_t *name, struct in6_addr *addr);
struct rr_entry *rr_create_a(uint8_t *name, uint32_t addr);
struct rr_entry *rr_create(uint8_t *name, enum rr_type type);
void rr_set_nsec(struct rr_entry *rr_nsec, enum rr_type type);
void rr_add_txt(struct rr_entry *rr_txt, const char *txt);

const char *rr_get_type_name(enum rr_type type);

uint8_t *create_label(const char *txt);
uint8_t *create_nlabel(const char *name);
char *nlabel_to_str(const uint8_t *name);
uint8_t *dup_label(const uint8_t *label);
uint8_t *dup_nlabel(const uint8_t *n);
uint8_t *join_nlabel(const uint8_t *n1, const uint8_t *n2);

// compares 2 names
static inline int cmp_nlabel(const uint8_t *L1, const uint8_t *L2) {
  return strcmp((char *)L1, (char *)L2);
}

//******************************************************//
//                      mdnsd.h                         //
//******************************************************//

struct mdnsd;
struct mdns_service;

// starts a MDNS responder instance
// returns NULL if unsuccessful
struct mdnsd *mdnsd_start();

// stops the given MDNS responder instance
void mdnsd_stop(struct mdnsd *s);

// sets the hostname for the given MDNS responder instance
void mdnsd_set_hostname(struct mdnsd *svr, const char *hostname, uint32_t ip);

// sets the hostname for the given MDNS responder instance, with an ipv6 address
void mdnsd_set_hostname_v6(struct mdnsd *svr, const char *hostname, struct in6_addr *addr);

// adds an additional RR
void mdnsd_add_rr(struct mdnsd *svr, struct rr_entry *rr);

// registers a service with the MDNS responder instance
struct mdns_service *mdnsd_register_svc(struct mdnsd *svr, const char *instance_name,
                                        const char *type, uint16_t port, const char *hostname,
                                        const char *txt[]);

// destroys the mdns_service struct returned by mdnsd_register_svc()
void mdns_service_destroy(struct mdns_service *srv);

#endif // _TINYSVCMDNS_H