sres.c

Sofia SIP is an open-source SIP User-Agent library, compliant with the IETF RFC3261 specification.

/*
 * This file is part of the Sofia-SIP package
 *
 * Copyright (C) 2006 Nokia Corporation.
 * Copyright (C) 2006 Dimitri E. Prado.
 *
 * Contact: Pekka Pessi <[e-mail]>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 */

/**@CFILE sres.c
 * @brief Sofia DNS Resolver implementation.
 * 
 * @author Pekka Pessi <[e-mail]>
 * @author Teemu Jalava <[e-mail]>
 * @author Mikko Haataja
 * @author Kai Vehmanen <[e-mail]> 
 *         (work on the win32 nameserver discovery) 
 * @author Dimitri E. Prado 
 *         (initial version of win32 nameserver discovery)
 *
 * @todo The resolver should allow handling arbitrary records, too.
 */

#include "config.h"

#if HAVE_STDINT_H
#include <stdint.h>
#elif HAVE_INTTYPES_H
#include <inttypes.h>
#else
#if defined(HAVE_WIN32)
typedef _int8 int8_t;
typedef unsigned _int8 uint8_t;
typedef unsigned _int16 uint16_t;
typedef unsigned _int32 uint32_t;
#endif
#endif

#if HAVE_NETINET_IN_H
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#endif

#if HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif

#if HAVE_WINSOCK2_H
#include <winsock2.h>
#include <ws2tcpip.h>
#ifndef IPPROTO_IPV6		/* socklen_t is used with @RFC2133 API */
typedef int socklen_t;
#endif
#endif

#if HAVE_IPHLPAPI_H
#include <iphlpapi.h>
#endif

#include <time.h>

#include "sofia-resolv/sres.h"
#include "sofia-resolv/sres_cache.h"
#include "sofia-resolv/sres_record.h"
#include "sofia-resolv/sres_async.h"

#include <sofia-sip/su_alloc.h>
#include <sofia-sip/su_strlst.h>
#include <sofia-sip/su_errno.h>

#include "sofia-sip/htable.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include <stdlib.h>
#include <stdarg.h>
#include <stddef.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>

#include <limits.h>

#include <assert.h>

#if HAVE_WINSOCK2_H
/* Posix send() */
su_inline 
ssize_t sres_send(sres_socket_t s, void *b, size_t length, int flags)
{
  if (length > INT_MAX)
    length = INT_MAX;
  return (ssize_t)send(s, b, (int)length, flags);
}

/* Posix recvfrom() */
su_inline 
ssize_t sres_recvfrom(sres_socket_t s, void *buffer, size_t length, int flags,
		      struct sockaddr *from, socklen_t *fromlen)
{
  int retval, ilen;

  if (fromlen)
    ilen = *fromlen;

  if (length > INT_MAX)
    length = INT_MAX;

  retval = recvfrom(s, buffer, (int)length, flags, 
		    (void *)from, fromlen ? &ilen : NULL);

  if (fromlen)
    *fromlen = ilen;

  return (ssize_t)retval;
}

su_inline
int sres_close(sres_socket_t s)
{
  return closesocket(s);
}

#if !defined(IPPROTO_IPV6) && (_WIN32_WINNT < 0x0600)
#if HAVE_SIN6
#include <tpipv6.h>
#else
#if !defined(__MINGW32__)
struct sockaddr_storage {
    short ss_family;
    char ss_pad[126];
};
#endif
#endif
#endif
#else

#define sres_send(s,b,len,flags) send((s),(b),(len),(flags))
#define sres_recvfrom(s,b,len,flags,a,alen) \
  recvfrom((s),(b),(len),(flags),(a),(alen))
#define sres_close(s) close((s))
#define SOCKET_ERROR   (-1)
#define INVALID_SOCKET ((sres_socket_t)-1)
#endif

#define SRES_TIME_MAX ((time_t)LONG_MAX)

#if !HAVE_INET_PTON
int su_inet_pton(int af, char const *src, void *dst);
#else
#define su_inet_pton inet_pton
#endif
#if !HAVE_INET_NTOP
const char *su_inet_ntop(int af, void const *src, char *dst, size_t size);
#else
#define su_inet_ntop inet_ntop
#endif

#if defined(va_copy)
#elif defined(__va_copy)
#define va_copy(dst, src) __va_copy((dst), (src))
#else
#define va_copy(dst, src) (memcpy(&(dst), &(src), sizeof (va_list)))
#endif

/**
 * How often to recheck nameserver information (seconds).
 */
#ifndef HAVE_WIN32
#define SRES_UPDATE_INTERVAL_SECS        5
#else
#define SRES_UPDATE_INTERVAL_SECS        180
#endif
void sres_cache_clean(sres_cache_t *cache, time_t now);

typedef struct sres_message    sres_message_t;
typedef struct sres_config     sres_config_t;
typedef struct sres_server     sres_server_t;
typedef struct sres_nameserver sres_nameserver_t;

/** Default path to resolv.conf */
static char const sres_conf_file_path[] = "/etc/resolv.conf";

/** EDNS0 support. @internal */
enum edns { 
  edns_not_tried = -1,
  edns_not_supported = 0,
  edns0_configured = 1,
  edns0_supported = 2,
};

struct sres_server {
  sres_socket_t           dns_socket;

  char                    dns_name[48];     /**< Server name */
  struct sockaddr_storage dns_addr[1];  /**< Server node address */
  ssize_t                 dns_addrlen;  /**< Size of address */

  enum edns               dns_edns;	/**< Server supports edns. */

  /** ICMP/temporary error received, zero when successful. */
  time_t                  dns_icmp;
  /** Persistent error, zero when successful or timeout. 
   *
   * Never selected if dns_error is SRES_TIME_MAX.
   */
  time_t                  dns_error;
};

HTABLE_DECLARE_WITH(sres_qtable, qt, sres_query_t, unsigned, size_t);

struct sres_resolver_s {
  su_home_t           res_home[1];

  void               *res_userdata;
  sres_cache_t       *res_cache;

  time_t              res_now;
  sres_qtable_t       res_queries[1];   /**< Table of active queries */

  char const         *res_cnffile;      /**< Configuration file name */
  char const        **res_options;      /**< Option strings */

  sres_config_t const *res_config;
  time_t              res_checked;

  unsigned long       res_updated;
  sres_update_f      *res_updcb;
  sres_async_t       *res_async;
  sres_schedule_f    *res_schedulecb;
  short               res_update_all;

  uint16_t            res_id;
  short               res_i_server;  /**< Current server to try 
					(when doing round-robin) */
  short               res_n_servers; /**< Number of servers */
  sres_server_t     **res_servers;
};

/* Parsed configuration. @internal */
struct sres_config {
  su_home_t c_home[1];

  time_t c_modified;
  char const *c_filename;

  /* domain and search */
  char const *c_search[SRES_MAX_SEARCH + 1];

  /* nameserver */
  struct sres_nameserver {
    struct sockaddr_storage ns_addr[1];
    ssize_t ns_addrlen;
  } *c_nameservers[SRES_MAX_NAMESERVERS + 1];

  /* sortlist */
  struct sres_sortlist {
    struct sockaddr_storage addr[1];
    ssize_t addrlen;
    char const *name;
  } *c_sortlist[SRES_MAX_SORTLIST + 1];

  uint16_t    c_port;	     /**< Server port to use */

  /* options */
  struct sres_options {
    uint16_t timeout;
    uint16_t attempts;
    uint16_t ndots;
    enum edns edns;
    unsigned debug:1;
    unsigned rotate:1;
    unsigned check_names:1;
    unsigned inet6:1;
    unsigned ip6int:1;
    unsigned ip6bytestring:1;
  } c_opt;
};

struct sres_query_s {
  unsigned        q_hash;
  sres_resolver_t*q_res;
  sres_answer_f  *q_callback;
  sres_context_t *q_context;
  char           *q_name;
  time_t          q_timestamp;
  uint16_t        q_type;
  uint16_t        q_class;
  uint16_t        q_id;			/**< If nonzero, not answered */
  uint16_t        q_retry_count;
  uint8_t         q_n_servers;
  uint8_t         q_i_server;
  int8_t          q_edns;
  uint8_t         q_n_subs;
  sres_query_t   *q_subqueries[1 + SRES_MAX_SEARCH];
  sres_record_t **q_subanswers[1 + SRES_MAX_SEARCH];
};


struct sres_message {
  uint16_t m_offset;
  uint16_t m_size;
  char const *m_error;
  union {
    struct {
      /* Header defined in RFC 1035 section 4.1.1 (page 26) */
      uint16_t mh_id;		/* Query ID */
      uint16_t mh_flags;	/* Flags */
      uint16_t mh_qdcount;	/* Question record count */
      uint16_t mh_ancount;	/* Answer record count */
      uint16_t mh_nscount;	/* Authority records count */
      uint16_t mh_arcount;	/* Additional records count */
    } mp_header;
    uint8_t mp_data[1500 - 40];	/**< IPv6 datagram */
  } m_packet;
#define m_id      m_packet.mp_header.mh_id
#define m_flags   m_packet.mp_header.mh_flags
#define m_qdcount m_packet.mp_header.mh_qdcount
#define m_ancount m_packet.mp_header.mh_ancount
#define m_nscount m_packet.mp_header.mh_nscount
#define m_arcount m_packet.mp_header.mh_arcount 
#define m_data    m_packet.mp_data
};

#define sr_refcount sr_record->r_refcount
#define sr_name     sr_record->r_name
#define sr_status   sr_record->r_status
#define sr_size     sr_record->r_size
#define sr_type     sr_record->r_type
#define sr_class    sr_record->r_class
#define sr_ttl      sr_record->r_ttl
#define sr_rdlen    sr_record->r_rdlen
#define sr_parsed   sr_record->r_parsed
#define sr_rdata    sr_generic->g_data

enum {
  SRES_HDR_QR = (1 << 15),
  SRES_HDR_QUERY = (0 << 11),
  SRES_HDR_IQUERY = (1 << 11),
  SRES_HDR_STATUS = (2 << 11),
  SRES_HDR_OPCODE = (15 << 11),	/* mask */
  SRES_HDR_AA = (1 << 10),
  SRES_HDR_TC = (1 << 9),
  SRES_HDR_RD = (1 << 8),
  SRES_HDR_RA = (1 << 7),
  SRES_HDR_RCODE = (15 << 0)	/* mask of return code */
};

HTABLE_PROTOS_WITH(sres_qtable, qt, sres_query_t, unsigned, size_t);

#define CHOME(cache) ((su_home_t *)(cache))

/** Get address from sockaddr storage. */
#if HAVE_SIN6
#define SS_ADDR(ss) \
  ((ss)->ss_family == AF_INET ? \
   (void *)&((struct sockaddr_in *)ss)->sin_addr : \
  ((ss)->ss_family == AF_INET6 ? \
   (void *)&((struct sockaddr_in6 *)ss)->sin6_addr : \
   (void *)&((struct sockaddr *)ss)->sa_data))
#else
#define SS_ADDR(ss) \
  ((ss)->ss_family == AF_INET ? \
   (void *)&((struct sockaddr_in *)ss)->sin_addr : \
   (void *)&((struct sockaddr *)ss)->sa_data)
#endif

static int sres_config_changed_servers(sres_config_t const *new_c, 
				       sres_config_t const *old_c);
static sres_server_t **sres_servers_new(sres_resolver_t *res,
					sres_config_t const *c);

/** Generate new 16-bit identifier for DNS query. */
static uint16_t
sres_new_id(sres_resolver_t *res)
{
  return res->res_id ? res->res_id++ : (res->res_id = 2, 1);
}

/** Return true if we have a search list or a local domain name. */
static int 
sres_has_search_domain(sres_resolver_t *res) 
{
  return res->res_config->c_search[0] != NULL;
}

static void sres_resolver_destructor(void *);

sres_resolver_t *
sres_resolver_new_with_cache_va(char const *conf_file_path,
				sres_cache_t *cache,
				char const *options, 
				va_list va);
static
sres_resolver_t *
sres_resolver_new_internal(sres_cache_t *cache,
			   sres_config_t const *config,
			   char const *conf_file_path,
			   char const **options);

static void sres_servers_close(sres_resolver_t *res,
			       sres_server_t **servers);

static int sres_servers_count(sres_server_t * const *servers);

static sres_socket_t sres_server_socket(sres_resolver_t *res,
					sres_server_t *dns);

static sres_query_t * sres_query_alloc(sres_resolver_t *res,
				       sres_answer_f *callback,
				       sres_context_t *context,
				       uint16_t type,
				       char const * domain);

static void sres_free_query(sres_resolver_t *res, sres_query_t *q);

static 
int sres_sockaddr2string(sres_resolver_t *, 
			 char name[], size_t namelen, 
			 struct sockaddr const *);

static 
sres_config_t *sres_parse_resolv_conf(sres_resolver_t *res,
				      char const **options);

static
sres_server_t *sres_next_server(sres_resolver_t *res, 
				uint8_t *in_out_i,
				int always);

static
int sres_send_dns_query(sres_resolver_t *res, sres_query_t *q);

static 
void sres_answer_subquery(sres_context_t *context, 
			  sres_query_t *query,
			  sres_record_t **answers);

static
sres_record_t **
sres_combine_results(sres_resolver_t *res,
		     sres_record_t **search_results[SRES_MAX_SEARCH + 1]);

static
void sres_query_report_error(sres_query_t *q,
			     sres_record_t **answers);

static void
sres_resend_dns_query(sres_resolver_t *res, sres_query_t *q, int timeout);

static 
sres_server_t *sres_server_by_socket(sres_resolver_t const *ts,
				     sres_socket_t socket);

static
int sres_resolver_report_error(sres_resolver_t *res, 
			       sres_socket_t socket,
			       int errcode,
			       struct sockaddr_storage *remote,
			       socklen_t remotelen,