/*
* resolver/dns related functions, dns cache and failover
*
* Copyright (C) 2006 iptelorg GmbH
*
* This file is part of Kamailio, a free SIP server.
*
* Kamailio 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
*
* Kamailio 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* @brief Kamailio core :: resolver/dns related functions, dns cache and failover
* @author andrei
* @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 flags,
* shall be on the power of 2 */
/*@{ */
#define DNS_FLAG_BAD_NAME 1 /**< error flag: unresolvable */
#define DNS_FLAG_PERMANENT 2 /**< permanent record, never times out,
never deleted, never overwritten
unless explicitely requested */
/*@} */
/** @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 */
};
#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 ent_flags; /* entry flags: unresolvable/permanent */
unsigned char name_len; /* can be maximum 255 bytes */
char name[1]; /* variable length, name, null terminated
(actual lenght = name_len +1)*/
};
/* to fit in the limit of MAX_BRANCHES */
#if MAX_BRANCHES_LIMIT < 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(void);
#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);
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 Delete all the entries from the cache.
* If del_permanent is 0, then only the
* non-permanent entries are deleted.
*/
void dns_cache_flush(int del_permanent);
#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 */
/** @brief Adds a new record to the cache.
* If there is an existing record with the same name and value
* (ip address in case of A/AAAA record, name in case of SRV record)
* only the remaining fields are updated.
*
* Note that permanent records cannot be overwritten unless
* the new record is also permanent. A permanent record
* completely replaces a non-permanent one.
*
* Currently only A, AAAA, and SRV records are supported.
*/
int dns_cache_add_record(unsigned short type,
str *name,
int ttl,
str *value,
int priority,
int weight,
int port,
int flags);
/** @brief Delete a single record from the cache,
* i.e. the record with the same name and value
* (ip address in case of A/AAAA record, name in case of SRV record).
*
* Currently only A, AAAA, and SRV records are supported.
*/
int dns_cache_delete_single_record(unsigned short type,
str *name,
str *value,
int flags);
#endif