/*
  * $Id$
  *
  * resolver/dns related functions, dns cache and failover
  *
  * Copyright (C) 2006 iptelorg GmbH
  *
  * This file is part of ser, a free SIP server.
  *
  * ser 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 of the License, or
  * (at your option) any later version
  *
  * ser is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *

  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software

  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

 /* History:
  * --------
  *  2006-07-13  created by andrei

  *  2007-06-16  naptr support (andrei)

  *  2007-07-30  DNS cache measurements added (Gergo)

  */
 

 /**
  * @file
  * @brief SIP-router core :: resolver/dns related functions, dns cache and failover
  * @ingroup core
  * Module: @ref core
  */
 
 

 
 #ifndef __dns_cache_h
 #define __dns_cache_h
 
 #include "str.h"

 #include "config.h" /* MAX_BRANCHES */

 #include "timer.h"
 #include "ip_addr.h"
 #include "atomic_ops.h"
 #include "resolve.h"
 
 
 #if defined(USE_DNS_FAILOVER) && !defined(USE_DNS_CACHE)
 #error "DNS FAILOVER requires DNS CACHE support (define USE_DNS_CACHE)"
 #endif
 

 #if defined(DNS_WATCHDOG_SUPPORT) && !defined(USE_DNS_CACHE)
 #error "DNS WATCHDOG requires DNS CACHE support (define USE_DNS_CACHE)"
 #endif
 

 #define DEFAULT_DNS_NEG_CACHE_TTL 60 /* 1 min. */
 #define DEFAULT_DNS_CACHE_MIN_TTL 0 /* (disabled) */
 #define DEFAULT_DNS_CACHE_MAX_TTL ((unsigned int)(-1)) /* (maxint) */
 #define DEFAULT_DNS_MAX_MEM 500 /* 500 Kb */
 

 /** @brief uncomment the define below for SRV weight based load balancing */

 #define DNS_SRV_LB
 

 #define DNS_LU_LST
 

 /** @brief dns functions return them as negative values (e.g. return -E_DNS_NO_IP)
  *

  * listed in the order of importance ( if more errors, only the most important
  * is returned)
  */
 enum dns_errors{
 					E_DNS_OK=0,

 					E_DNS_EOR, /**< no more records (not an error)

 					              -- returned only by the dns_resolve*

 								  functions when called iteratively,; it
 								  signals the end of the ip/records list */

 					E_DNS_UNKNOWN /**< unkown error */,
 					E_DNS_INTERNAL_ERR /**< internal error */,

 					E_DNS_BAD_SRV_ENTRY,

 					E_DNS_NO_SRV /**< unresolvable srv record */,

 					E_DNS_BAD_IP_ENTRY,

 					E_DNS_NO_IP /**< unresolvable a or aaaa records*/,
 					E_DNS_BAD_IP /**< the ip is invalid */,
 					E_DNS_BLACKLIST_IP /**< the ip is blacklisted */,
 					E_DNS_NAME_TOO_LONG /**< try again with a shorter name */,
 					E_DNS_AF_MISMATCH /**< ipv4 or ipv6 only requested, but

 										 name contains an ip addr. of the
 										 opossite type */ ,

 					E_DNS_NO_NAPTR /**< unresolvable naptr record */,
 					E_DNS_CRITICAL /**< critical error, marks the end

 									  of the error table (always last) */
 };
 
 
 

 /** @brief return a short string, printable error description (err <=0) */

 const char* dns_strerror(int err);
 

 /** @brief dns entry error flags */

 #define DNS_BAD_NAME     1 /* unresolvable */
 

 /** @name dns requests flags */
 /*@{ */

 #define DNS_NO_FLAGS	0
 #define DNS_IPV4_ONLY	1
 #define DNS_IPV6_ONLY	2
 #define DNS_IPV6_FIRST	4

 #define DNS_SRV_RR_LB	8  /**< SRV RR weight based load balancing */
 #define DNS_TRY_NAPTR	16 /**< enable naptr lookup */
 /*@} */

 /** @name ip blacklist error flags */
 /*@{ */

 #define IP_ERR_BAD_DST      2 /* destination is marked as bad (e.g. bad ip) */
 #define IP_ERR_SND          3 /* send error while using this as destination */
 #define IP_ERR_TIMEOUT      4 /* timeout waiting for a response */
 #define IP_ERR_TCP_CON      5 /* could not establish tcp connection */

 /*@} */

 /** @brief stripped down dns rr 
 	@note name, type and class are not needed, contained in struct dns_query */

 struct dns_rr{
 	struct dns_rr* next;

 	void* rdata; /**< depends on the type */
 	ticks_t expire; /**< = ttl + crt_time */
 	unsigned char err_flags; /**< if 0 everything is ok */

 
 };
 
 
 
 #ifdef DNS_LU_LST
 struct dns_lu_lst{  /* last used ordered list */
 	struct dns_lu_lst* next;
 	struct dns_lu_lst* prev;
 };
 #endif
 
 struct dns_hash_entry{
 	/* hash table links */
 	struct dns_hash_entry* next;
 	struct dns_hash_entry* prev;
 #ifdef DNS_LU_LST
 	struct dns_lu_lst last_used_lst;
 #endif
 	struct dns_rr* rr_lst;
 	atomic_t refcnt;
 	ticks_t last_used;
 	ticks_t expire; /* when the whole entry will expire */
 	int total_size;
 	unsigned short type;
 	unsigned char err_flags;
 	unsigned char name_len; /* can be maximum 255 bytes */

 	char name[1]; /* variable length, name, null terminated

 	                 (actual lenght = name_len +1)*/
 };
 
 

 #if MAX_BRANCHES < 16
 /* forking is limited by tm to 12 by default */
 typedef unsigned short srv_flags_t;
 #elif MAX_BRANCHES < 32

 typedef unsigned int srv_flags_t;

 #else
 typedef unsigned long long srv_flags_t;
 #endif

 
 struct dns_srv_handle{

 	struct dns_hash_entry* srv; /**< srv entry */
 	struct dns_hash_entry* a;   /**< a or aaaa current entry */

 #ifdef DNS_SRV_LB
 	srv_flags_t srv_tried_rrs;
 #endif

 	unsigned short port; /**< current port */
 	unsigned char srv_no; /**< current record no. in the srv entry */
 	unsigned char ip_no;  /**< current record no. in the a/aaaa entry */
 	unsigned char proto;  /**< protocol number */

 };
 
 
 
 const char* dns_strerror(int err);
 

 void fix_dns_flags(str *gname, str *name);
 int use_dns_failover_fixup(void *handle, str *gname, str *name, void **val);
 int use_dns_cache_fixup(void *handle, str *gname, str *name, void **val);
 int dns_cache_max_mem_fixup(void *handle, str *gname, str *name, void **val);

 int init_dns_cache();

 #ifdef USE_DNS_CACHE_STATS
 int init_dns_cache_stats(int iproc_num);
 #define DNS_CACHE_ALL_STATS "dc_all_stats"
 #endif

 void destroy_dns_cache();
 
 
 void dns_hash_put(struct dns_hash_entry* e);
 void dns_hash_put_shm_unsafe(struct dns_hash_entry* e);
 
 inline static void dns_srv_handle_put(struct dns_srv_handle* h)
 {
 	if (h){
 		if (h->srv){
 			dns_hash_put(h->srv);
 			h->srv=0;
 		}
 		if (h->a){
 			dns_hash_put(h->a);
 			h->a=0;
 		}
 	}
 }
 
 
 

 /** @brief use it when copying, it manually increases the ref cound */

 inline static void dns_srv_handle_ref(struct dns_srv_handle *h)
 {
 	if (h){
 		if (h->srv)
 			atomic_inc(&h->srv->refcnt);
 		if (h->a)
 			atomic_inc(&h->a->refcnt);
 	}
 }
 
 
 

 /** @brief safe copy increases the refcnt, src must not change while in this function

  * WARNING: the copy must be dns_srv_handle_put ! */
 inline static void dns_srv_handle_cpy(struct dns_srv_handle* dst,
 										struct dns_srv_handle* src)
 {
 	dns_srv_handle_ref(src);
 	*dst=*src;
 }
 
 
 

 /** @brief same as above but assume shm_lock held (for internal tm use only) */

 inline static void dns_srv_handle_put_shm_unsafe(struct dns_srv_handle* h)
 {
 	if (h){
 		if (h->srv){
 			dns_hash_put_shm_unsafe(h->srv);
 			h->srv=0;
 		}
 		if (h->a){
 			dns_hash_put_shm_unsafe(h->a);
 			h->a=0;
 		}
 	}
 }
 
 
 

 /** @brief get "next" ip next time a dns_srv_handle function is called

  * params: h   - struct dns_srv_handler

  *         err - return code of the last dns_*_resolve* call

  * returns: 0 if it doesn't make sense to try another record,
  * 1 otherwise
  */
 inline static int dns_srv_handle_next(struct dns_srv_handle* h, int err)
 {
 	if (err<0) return 0;
 	h->ip_no++;
 	return (h->srv || h->a);
 }
 
 
 
 inline static void dns_srv_handle_init(struct dns_srv_handle* h)
 {
 	h->srv=h->a=0;
 	h->srv_no=h->ip_no=0;

 	h->port=0;
 	h->proto=0;

 #ifdef DNS_SRV_LB
 	h->srv_tried_rrs=0;
 #endif

 }
 
 
 

 /** @brief performes a srv query on name

  * Params:  name  - srv query target (e.g. _sip._udp.foo.bar)
  *          ip    - result: first good ip found
  *          port  - result: corresponding port number
  *          flags - resolve options (like ipv4 only, ipv6 prefered a.s.o)
  * Returns: < 0 on error (can be passed to dns_strerror(), 0 on success
  */
 int dns_srv_get_ip(str* name, struct ip_addr* ip, unsigned short* port,
 					int flags);
 

 /** @brief performs an A, AAAA (or both) query/queries

  * Params:  name  - query target (e.g. foo.bar)
  *          ip    - result: first good ip found
  *          flags - resolve options (like ipv4 only, ipv6 prefered a.s.o)
  * Returns: < 0 on error (can be passed to dns_strerror(), 0 on success
  */
 int dns_get_ip(str* name, struct ip_addr* ip, int flags);
 
 struct hostent* dns_srv_get_he(str* name, unsigned short* port, int flags);
 struct hostent* dns_get_he(str* name, int flags);
 
 

 /** @brief resolve name to an ip, using srv record. Can be called multiple times

  * to iterate on all the possible ips, e.g :
  * dns_srv_handle_init(h);
  * ret_code=dns_sip_resolve(h,...);
  *  while( dns_srv_handle_next(h, ret_code){ ret_code=dns_sip_resolve(h...); }
  * dns_srv_handle_put(h);
  * WARNING: dns_srv_handle_init() must be called to initialize h and
  *  dns_srv_handle_put(h) must be called when h is no longer needed
  */
 int dns_sip_resolve(struct dns_srv_handle* h,  str* name, struct ip_addr* ip,

 					unsigned short* port, char* proto, int flags);

 /** @brief same as above, but fills su intead of changing port and filling an ip */

 inline static int dns_sip_resolve2su(struct dns_srv_handle* h,
 									 union sockaddr_union* su,
 									 str* name, unsigned short port,

 									 char* proto, int flags)

 {
 	struct ip_addr ip;
 	int ret;

 	ret=dns_sip_resolve(h, name, &ip, &port, proto, flags);
 	if (ret>=0)
 		init_su(su, &ip, port);
 	return ret;
 }

 /** @brief deletes all the entries from the cache */

 void dns_cache_flush(void);
 

 #ifdef DNS_WATCHDOG_SUPPORT

 /** @brief sets the state of the DNS servers:

  * 1: at least one server is up
  * 0: all the servers are down
  */
 void dns_set_server_state(int state);

 /** @brief returns the state of the DNS servers */

 int dns_get_server_state(void);

 #endif /* DNS_WATCHDOG_SUPPORT */
 

 #endif