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/* dns.c - Asynchronous DNS resolver
 * partial rewrite of DNS client code from libowfat by fefe
 * (http://www.fefe.de/libowfat/), originally written and put
 * into public domain July 4 2002 (http://online.securityfocus.com/archive/1/280642)
 * by D.J. Bernstein (http://cr.yp.to/).
 * The idea was to provide a simple async resolver API in standard libc style
 * which does not base on crappy resolver functions from ISC libresolv.
 * To keep this piece of code simple, slim and portable I decided to reimplement
 * some of the functions using libc functions/types rather than the ones from fefe.
 * Bug reports and stuff go to <smoli@paranoya.ch>
 * $Id: dns.h,v 2002/10/22 19:23:42 smoln Exp $
/* This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.
 * If not, write to the Free Software Foundation,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

#ifndef IAC_DNS_H_
#define IAC_DNS_H_

#include <time.h>
#include <poll.h>
#include <sys/select.h>
#include <netinet/in.h>

#define DNS_C_IN    "\0\1"
#define DNS_C_ANY   "\0\377"

#define DNS_T_A     "\0\1"
#define DNS_T_NS    "\0\2"
#define DNS_T_CNAME "\0\5"
#define DNS_T_SOA   "\0\6"
#define DNS_T_PTR   "\0\14"
#define DNS_T_HINFO "\0\15"
#define DNS_T_MX    "\0\17"
#define DNS_T_TXT   "\0\20"
#define DNS_T_RP    "\0\21"
#define DNS_T_SIG   "\0\30"
#define DNS_T_KEY   "\0\31"
#define DNS_T_AAAA  "\0\34"
#define DNS_T_AXFR  "\0\374"
#define DNS_T_ANY   "\0\377"

#define DEFAULT_TIMEOUT 20         /* 20 seconds timeout */

typedef enum {
  DNS_ALL,              /* do callback on any of the events below */
  DNS_IP4,              /* got an ipv4 address */
  DNS_IP6,              /* got an ipv6 address */
  DNS_NAME              /* got a domain name */
} dns_event_type;

struct dns_resolver;

typedef void (dns_event_handler)(struct dns_resolver *dns, dns_event_type type);

struct dns_resolver {
  char                 *query;     /* 0, or dynamically allocated */
  unsigned int          querylen;
  char                 *packet;    /* 0, or dynamically allocated */
  unsigned int          packetlen;
  int                   s1;        /* 0, or 1 + an open file descriptor */
  int                   tcpstate;
  unsigned int          udploop;
  unsigned int          curserver;
  time_t                deadline;
  unsigned int          pos;
  const char           *servers;
  struct in6_addr       localip;
  unsigned int          scope_id;
  char                  qtype[2];
  int                   ans;
  time_t                timeout;
  void                 *userarg;
  dns_event_handler    *callback;

#define dns_is_idle(dns) (!(dns)->s1)
#define dns_is_busy(dns)  ((dns)->s1)

#define DNS_NAME4_DOMAIN 31
#define DNS_NAME6_DOMAIN (4 * 16 + 10)
#define IP4_FMT 20

/* bzero a resolver struct and set timeout to a sane value */
static __inline__ void dns_init(struct dns_resolver *dns) { memset(dns, 0, sizeof(struct dns_resolver)); dns->timeout = DEFAULT_TIMEOUT; }

/* callbacks not implemented */
#if 0
static __inline__ void dns_set_callback(struct dns_resolver *dns, dns_event_handler *handler) { dns->callback = handler; }

static __inline__ void dns_set_userarg(struct dns_resolver *dns, void *userarg) { dns->userarg = userarg; }
static __inline__ void *dns_get_userarg(struct dns_resolver *dns) { return dns->userarg; }
static __inline__ void dns_set_timeout(struct dns_resolver *dns, time_t seconds) { dns->timeout = seconds; }

   start an A or a PTR query.
extern int dns_name_lookup(struct dns_resolver *dns, const char *name);
extern int dns_addr_lookup(struct dns_resolver *dns, struct in_addr address);

   returns 1 when the fdset has been modified.
extern int dns_pre_poll(struct dns_resolver *dns, struct pollfd *pfds);
extern int dns_pre_select(struct dns_resolver *dns, fd_set *readset, fd_set *writeset);

   returns 0 when lookup is in progress, -1 on error/timeout and 1 when an answer has been received.
   pfs must point to a free location in your pollfd array.
extern int dns_post_poll(struct dns_resolver *dns, const struct pollfd *pfds);
extern int dns_post_select(struct dns_resolver *dns, const fd_set *readset, const fd_set *writeset);

   when the post poll call returned 1 the answer(s) can be retrieved by these functions.
extern int dns_get_addr(struct dns_resolver *dns, struct in_addr *addr);
extern int dns_get_name(struct dns_resolver *dns, char *buf, size_t n);

   free allocated packet buffers, close socket etc.
extern void dns_free(struct dns_resolver *dns);

#endif /* IAC_DNS_H_ */

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