8.2.x/src/res.c

/*
 *  ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
 *
 *  Copyright (c) 1997-2018 ircd-hybrid development team
 *
 *  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 of the License, 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
 *  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 res.c
 * \brief ircd resolver functions
 * \version $Id$
 */

/*
 * A rewrite of Darren Reed's original res.c As there is nothing
 * left of Darren's original code, this is now licensed by the hybrid group.
 * (Well, some of the function names are the same, and bits of the structs..)
 * You can use it where it is useful, free even. Buy us a beer and stuff.
 *
 * The authors takes no responsibility for any damage or loss
 * of property which results from the use of this software.
 *
 * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
 *     added callbacks and reference counting of returned hostents.
 *     --Bleep (Thomas Helvey <tomh@inxpress.net>)
 *
 * This was all needlessly complicated for irc. Simplified. No more hostent
 * All we really care about is the IP -> hostname mappings. That's all.
 *
 * Apr 28, 2003 --cryogen and Dianora
 */

#include "stdinc.h"
#include "list.h"
#include "event.h"
#include "irc_string.h"
#include "ircd.h"
#include "rng_mt.h"
#include "fdlist.h"
#include "s_bsd.h"
#include "misc.h"
#include "mempool.h"
#include "res.h"
#include "reslib.h"

#if (CHAR_BIT != 8)
#error this code needs to be able to address individual octets
#endif

static void res_readreply(fde_t *, void *);

#define MAXPACKET      1024  /**< rfc says 512 but we expand names so ... */
#define AR_TTL         600   /**< TTL in seconds for dns cache entries */

/*
 * RFC 1104/1105 wasn't very helpful about what these fields
 * should be named, so for now, we'll just name them this way.
 * We probably should look at what named calls them or something.
 */
#define TYPE_SIZE         (size_t)2
#define CLASS_SIZE        (size_t)2
#define TTL_SIZE          (size_t)4
#define RDLENGTH_SIZE     (size_t)2
#define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)

struct reslist
{
  dlink_node node;                           /**< Doubly linked list node. */
  unsigned int id;                           /**< Request ID (from request header). */
  char type;                                 /**< Current request type. */
  char retries;                              /**< Retry counter */
  unsigned int sends;                        /**< Number of sends (>1 means resent). */
  uintmax_t sentat;                          /**< Timestamp we last sent this request. */
  uintmax_t timeout;                         /**< When this request times out. */
  struct irc_ssaddr addr;                    /**< Address for this request. */
  char name[RFC1035_MAX_DOMAIN_LENGTH + 1];  /**< Hostname for this request. */
  size_t namelength;                         /**< Actual hostname length. */
  dns_callback_fnc callback;                 /**< Callback function on completion. */
  void *callback_ctx;                        /**< Context pointer for callback. */
};

static fde_t ResolverFileDescriptor;
static dlink_list request_list;
static mp_pool_t *dns_pool;


/*
 * rem_request - remove a request from the list.
 * This must also free any memory that has been allocated for
 * temporary storage of DNS results.
 */
static void
rem_request(struct reslist *request)
{
  dlinkDelete(&request->node, &request_list);
  mp_pool_release(request);
}

/*
 * make_request - Create a DNS request record for the server.
 */
static struct reslist *
make_request(dns_callback_fnc callback, void *ctx)
{
  struct reslist *request = mp_pool_get(dns_pool);

  request->sentat = CurrentTime;
  request->retries = 2;
  request->timeout = 4;  /* Start at 4 and exponential inc. */
  request->callback = callback;
  request->callback_ctx = ctx;

  dlinkAdd(request, &request->node, &request_list);
  return request;
}

/*
 * int
 * res_ourserver(inp)
 *      looks up "inp" in irc_nsaddr_list[]
 * returns:
 *      0  : not found
 *      >0 : found
 * author:
 *      paul vixie, 29may94
 *      revised for ircd, cryogen(stu) may03
 */
static int
res_ourserver(const struct irc_ssaddr *inp)
{
  const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp;
  const struct sockaddr_in *v4in = (const struct sockaddr_in *)inp;

  for (unsigned int i = 0; i < irc_nscount; ++i)
  {
    const struct irc_ssaddr *srv = &irc_nsaddr_list[i];
    const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)srv;
    const struct sockaddr_in *v4 = (const struct sockaddr_in *)srv;

    /*
     * Could probably just memcmp(srv, inp, srv.ss_len) here
     * but we'll air on the side of caution - stu
     */
    switch (srv->ss.ss_family)
    {
      case AF_INET6:
        if (srv->ss.ss_family == inp->ss.ss_family)
          if (v6->sin6_port == v6in->sin6_port)
            if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
                        sizeof(struct in6_addr)))
              return 1;
        break;
      case AF_INET:
        if (srv->ss.ss_family == inp->ss.ss_family)
          if (v4->sin_port == v4in->sin_port)
            if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)
              return 1;
        break;
      default:
        break;
    }
  }

  return 0;
}

/*
 * start_resolver - do everything we need to read the resolv.conf file
 * and initialize the resolver file descriptor if needed
 */
static void
start_resolver(void)
{
  irc_res_init();

  if (!ResolverFileDescriptor.flags.open)
  {
    if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
                  SOCK_DGRAM, 0, "UDP resolver socket") == -1)
      return;

    /* At the moment, the resolver FD data is global .. */
    comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
  }
}

/*
 * restart_resolver - reread resolv.conf, reopen socket
 */
void
restart_resolver(void)
{
  fd_close(&ResolverFileDescriptor);
  start_resolver();
}

/*
 * delete_resolver_queries - cleanup outstanding queries
 * for which there no longer exist clients or conf lines.
 */
void
delete_resolver_queries(const void *vptr)
{
  dlink_node *node, *node_next;

  DLINK_FOREACH_SAFE(node, node_next, request_list.head)
  {
    struct reslist *request = node->data;

    if (request->callback_ctx == vptr)
      rem_request(request);
  }
}

/*
 * send_res_msg - sends msg to all nameservers found in the "_res" structure.
 * This should reflect /etc/resolv.conf. We will get responses
 * which arent needed but is easier than checking to see if nameserver
 * isn't present. Returns number of messages successfully sent to
 * nameservers or -1 if no successful sends.
 */
static void
send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
{
  unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);

  /* RES_PRIMARY option is not implemented
   * if (res.options & RES_PRIMARY || 0 == max_queries)
   */
  if (max_queries == 0)
    max_queries = 1;

  for (unsigned int i = 0; i < max_queries; ++i)
    sendto(ResolverFileDescriptor.fd, msg, len, 0,
           (struct sockaddr *)&irc_nsaddr_list[i], irc_nsaddr_list[i].ss_len);
}

/*
 * find_id - find a dns request id (id is determined by dn_mkquery)
 */
static struct reslist *
find_id(unsigned int id)
{
  dlink_node *node;

  DLINK_FOREACH(node, request_list.head)
  {
    struct reslist *request = node->data;

    if (request->id == id)
      return request;
  }

  return NULL;
}

/*
 * query_name - generate a query based on class, type and name.
 */
static void
query_name(const char *name, int query_class, int type, struct reslist *request)
{
  unsigned char buf[MAXPACKET];
  int request_len = 0;

  memset(buf, 0, sizeof(buf));

  if ((request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf))) > 0)
  {
    HEADER *header = (HEADER *)buf;

    /*
     * Generate an unique id.
     * NOTE: we don't have to worry about converting this to and from
     * network byte order, the nameserver does not interpret this value
     * and returns it unchanged.
     */
    do
      header->id = (header->id + genrand_int32()) & 0xFFFF;
    while (find_id(header->id));

    request->id = header->id;
    ++request->sends;

    send_res_msg(buf, request_len, request->sends);
  }
}

/*
 * do_query_name - nameserver lookup name
 */
static void
do_query_name(dns_callback_fnc callback, void *ctx, const char *name,
              struct reslist *request, int type)
{
  char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];

  strlcpy(host_name, name, sizeof(host_name));

  if (!request)
  {
    request = make_request(callback, ctx);
    request->type = type;
    request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
  }

  request->type = type;
  query_name(host_name, C_IN, type, request);
}

/*
 * do_query_number - Use this to do reverse IP# lookups.
 */
static void
do_query_number(dns_callback_fnc callback, void *ctx,
                const struct irc_ssaddr *addr,
                struct reslist *request)
{
  char ipbuf[128] = "";

  if (addr->ss.ss_family == AF_INET)
  {
    const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
    const unsigned char *cp = (const unsigned char *)&v4->sin_addr.s_addr;

    snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
             (unsigned int)(cp[3]), (unsigned int)(cp[2]),
             (unsigned int)(cp[1]), (unsigned int)(cp[0]));
  }
  else if (addr->ss.ss_family == AF_INET6)
  {
    const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
    const unsigned char *cp = (const unsigned char *)&v6->sin6_addr.s6_addr;

    snprintf(ipbuf, sizeof(ipbuf),
             "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
             "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
             (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
             (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
             (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
             (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
             (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
             (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
             (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
             (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
             (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
             (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
             (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
             (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
             (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
             (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
             (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
             (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
  }

  if (!request)
  {
    request = make_request(callback, ctx);
    request->type = T_PTR;
    memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
  }

  query_name(ipbuf, C_IN, T_PTR, request);
}

/*
 * gethost_byname_type - get host address from name
 *
 */
void
gethost_byname_type(dns_callback_fnc callback, void *ctx, const char *name, int type)
{
  assert(name);
  do_query_name(callback, ctx, name, NULL, type);
}

/*
 * gethost_byaddr - get host name from address
 */
void
gethost_byaddr(dns_callback_fnc callback, void *ctx, const struct irc_ssaddr *addr)
{
  do_query_number(callback, ctx, addr, NULL);
}

static void
resend_query(struct reslist *request)
{
  switch (request->type)
  {
    case T_PTR:
      do_query_number(NULL, NULL, &request->addr, request);
      break;
    case T_A:
    case T_AAAA:
      do_query_name(NULL, NULL, request->name, request, request->type);
      break;
    default:
      break;
  }
}

/*
 * proc_answer - process name server reply
 */
static int
proc_answer(struct reslist *request, HEADER *header, unsigned char *buf, unsigned char *eob)
{
  char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
  unsigned char *current = buf + sizeof(HEADER); /* current position in buf */
  unsigned int type = 0;       /* answer type */
  unsigned int rd_length = 0;
  int n;                       /* temp count */
  struct sockaddr_in *v4;      /* conversion */
  struct sockaddr_in6 *v6;

  for (; header->qdcount > 0; --header->qdcount)
  {
    if ((n = irc_dn_skipname(current, eob)) < 0)
      break;

    current += (size_t)n + QFIXEDSZ;
  }

  /*
   * Process each answer sent to us blech.
   */
  while (header->ancount > 0 && current < eob)
  {
    --header->ancount;

    n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));

    if (n < 0  /* Broken message */ || n == 0  /* No more answers left */)
      return 0;

    hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';

    /*
     * With Address arithmetic you have to be very anal
     * this code was not working on alpha due to that
     * (spotted by rodder/jailbird/dianora)
     */
    current += (size_t)n;

    if (!((current + ANSWER_FIXED_SIZE) < eob))
      break;

    type = irc_ns_get16(current);
    current += TYPE_SIZE;
    current += CLASS_SIZE;
    current += TTL_SIZE;
    rd_length = irc_ns_get16(current);
    current += RDLENGTH_SIZE;

    /*
     * Wait to set request->type until we verify this structure
     */
    switch (type)
    {
      case T_A:
        if (request->type != T_A)
          return 0;

        /*
         * Check for invalid rd_length or too many addresses
         */
        if (rd_length != sizeof(struct in_addr))
          return 0;

        request->addr.ss_len = sizeof(struct sockaddr_in);
        v4 = (struct sockaddr_in *)&request->addr;
        v4->sin_family = AF_INET;
        memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
        return 1;
        break;
      case T_AAAA:
        if (request->type != T_AAAA)
          return 0;

        if (rd_length != sizeof(struct in6_addr))
          return 0;

        request->addr.ss_len = sizeof(struct sockaddr_in6);
        v6 = (struct sockaddr_in6 *)&request->addr;
        v6->sin6_family = AF_INET6;
        memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
        return 1;
        break;
      case T_PTR:
        if (request->type != T_PTR)
          return 0;

        n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
        if (n < 0  /* Broken message */ || n == 0  /* No more answers left */)
          return 0;

        request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
        return 1;
        break;
      case T_CNAME:
        current += rd_length;
        break;
      default:
        return 0;
        break;
    }
  }

  return 0;
}

/*
 * res_readreply - read a dns reply from the nameserver and process it.
 */
static void
res_readreply(fde_t *fd, void *data)
{
  unsigned char buf[sizeof(HEADER) + MAXPACKET];
  struct reslist *request = NULL;
  ssize_t rc = 0;
  socklen_t len = sizeof(struct irc_ssaddr);
  struct irc_ssaddr lsin;

  while ((rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
  {
    if (rc <= (ssize_t)sizeof(HEADER))
      continue;

    /*
     * Check against possibly fake replies
     */
    if (!res_ourserver(&lsin))
      continue;

    /*
     * Convert DNS reply reader from Network byte order to CPU byte order.
     */
    HEADER *header = (HEADER *)buf;
    header->ancount = ntohs(header->ancount);
    header->qdcount = ntohs(header->qdcount);
    header->nscount = ntohs(header->nscount);
    header->arcount = ntohs(header->arcount);

    /*
     * Response for an id which we have already received an answer for
     * just ignore this response.
     */
    if ((request = find_id(header->id)) == NULL)
      continue;

    if (header->rcode != NO_ERRORS || header->ancount == 0)
    {
      /*
       * If a bad error was returned, stop here and don't send
       * any more (no retries granted).
       */
      (*request->callback)(request->callback_ctx, NULL, NULL, 0);
      rem_request(request);
      continue;
    }

    /*
     * If this fails there was an error decoding the received packet.
     * We only give it one shot. If it fails, just leave the client
     * unresolved.
     */
    if (!proc_answer(request, header, buf, buf + rc))
    {
      (*request->callback)(request->callback_ctx, NULL, NULL, 0);
      rem_request(request);
      continue;
    }

    if (request->type == T_PTR)
    {
      if (request->namelength == 0)
      {
        /*
         * Got a PTR response with no name, something bogus is happening
         * don't bother trying again, the client address doesn't resolve
         */
        (*request->callback)(request->callback_ctx, NULL, NULL, 0);
        rem_request(request);
        continue;
      }

      /*
       * Lookup the 'authoritative' name that we were given for the ip#.
       */
      if (request->addr.ss.ss_family == AF_INET6)
        gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
      else
        gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);

      rem_request(request);
    }
    else
    {
      /*
       * Got a name and address response, client resolved
       */
      (*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
      rem_request(request);
    }

    continue;
  }

  comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
}

/*
 * timeout_query_list - Remove queries from the list which have been
 * there too long without being resolved.
 */
static uintmax_t
timeout_query_list(void)
{
  dlink_node *node, *node_next;
  uintmax_t next_time = 0;

  DLINK_FOREACH_SAFE(node, node_next, request_list.head)
  {
    struct reslist *request = node->data;
    uintmax_t timeout = request->sentat + request->timeout;

    if (CurrentTime >= timeout)
    {
      if (--request->retries <= 0)
      {
        (*request->callback)(request->callback_ctx, NULL, NULL, 0);
        rem_request(request);
        continue;
      }
      else
      {
        request->sentat = CurrentTime;
        request->timeout += request->timeout;
        resend_query(request);
      }
    }

    if (next_time == 0 || timeout < next_time)
      next_time = timeout;
  }

  return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
}

/*
 * timeout_resolver - check request list
 */
static void
timeout_resolver(void *unused)
{
  timeout_query_list();
}

/*
 * resolver_init - initialize resolver and resolver library
 */
void
resolver_init(void)
{
  static struct event event_timeout_resolver =
  {
    .name = "timeout_resolver",
    .handler = timeout_resolver,
    .when = 1
  };

  dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS);

  start_resolver();
  event_add(&event_timeout_resolver, NULL);
}
Revision:	8280
Committed:	Tue Feb 20 19:30:33 2018 UTC (6 years, 1 month ago) by michael
Content type:	text/x-csrc
File size:	19596 byte(s)
Log Message:	- Update copyright years
#	Content
1	/*
2	* ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
3	*
4	* Copyright (c) 1997-2018 ircd-hybrid development team
5	*
6	* This program is free software; you can redistribute it and/or modify
7	* it under the terms of the GNU General Public License as published by
8	* the Free Software Foundation; either version 2 of the License, or
9	* (at your option) any later version.
10	*
11	* This program is distributed in the hope that it will be useful,
12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14	* GNU General Public License for more details.
15	*
16	* You should have received a copy of the GNU General Public License
17	* along with this program; if not, write to the Free Software
18	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
19	* USA
20	*/
21
22	/*! \file res.c
23	* \brief ircd resolver functions
24	* \version $Id$
25	*/
26
27	/*
28	* A rewrite of Darren Reed's original res.c As there is nothing
29	* left of Darren's original code, this is now licensed by the hybrid group.
30	* (Well, some of the function names are the same, and bits of the structs..)
31	* You can use it where it is useful, free even. Buy us a beer and stuff.
32	*
33	* The authors takes no responsibility for any damage or loss
34	* of property which results from the use of this software.
35	*
36	* July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
37	* added callbacks and reference counting of returned hostents.
38	* --Bleep (Thomas Helvey <tomh@inxpress.net>)
39	*
40	* This was all needlessly complicated for irc. Simplified. No more hostent
41	* All we really care about is the IP -> hostname mappings. That's all.
42	*
43	* Apr 28, 2003 --cryogen and Dianora
44	*/
45
46	#include "stdinc.h"
47	#include "list.h"
48	#include "event.h"
49	#include "irc_string.h"
50	#include "ircd.h"
51	#include "rng_mt.h"
52	#include "fdlist.h"
53	#include "s_bsd.h"
54	#include "misc.h"
55	#include "mempool.h"
56	#include "res.h"
57	#include "reslib.h"
58
59	#if (CHAR_BIT != 8)
60	#error this code needs to be able to address individual octets
61	#endif
62
63	static void res_readreply(fde_t , void );
64
65	#define MAXPACKET 1024 /*< rfc says 512 but we expand names so ... /
66	#define AR_TTL 600 /*< TTL in seconds for dns cache entries /
67
68	/*
69	* RFC 1104/1105 wasn't very helpful about what these fields
70	* should be named, so for now, we'll just name them this way.
71	* We probably should look at what named calls them or something.
72	*/
73	#define TYPE_SIZE (size_t)2
74	#define CLASS_SIZE (size_t)2
75	#define TTL_SIZE (size_t)4
76	#define RDLENGTH_SIZE (size_t)2
77	#define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
78
79	struct reslist
80	{
81	dlink_node node; /*< Doubly linked list node. /
82	unsigned int id; /*< Request ID (from request header). /
83	char type; /*< Current request type. /
84	char retries; /*< Retry counter /
85	unsigned int sends; /*< Number of sends (>1 means resent). /
86	uintmax_t sentat; /*< Timestamp we last sent this request. /
87	uintmax_t timeout; /*< When this request times out. /
88	struct irc_ssaddr addr; /*< Address for this request. /
89	char name[RFC1035_MAX_DOMAIN_LENGTH + 1]; /*< Hostname for this request. /
90	size_t namelength; /*< Actual hostname length. /
91	dns_callback_fnc callback; /*< Callback function on completion. /
92	void callback_ctx; /< Context pointer for callback. /
93	};
94
95	static fde_t ResolverFileDescriptor;
96	static dlink_list request_list;
97	static mp_pool_t *dns_pool;
98
99
100	/*
101	* rem_request - remove a request from the list.
102	* This must also free any memory that has been allocated for
103	* temporary storage of DNS results.
104	*/
105	static void
106	rem_request(struct reslist *request)
107	{
108	dlinkDelete(&request->node, &request_list);
109	mp_pool_release(request);
110	}
111
112	/*
113	* make_request - Create a DNS request record for the server.
114	*/
115	static struct reslist *
116	make_request(dns_callback_fnc callback, void *ctx)
117	{
118	struct reslist *request = mp_pool_get(dns_pool);
119
120	request->sentat = CurrentTime;
121	request->retries = 2;
122	request->timeout = 4; /* Start at 4 and exponential inc. */
123	request->callback = callback;
124	request->callback_ctx = ctx;
125
126	dlinkAdd(request, &request->node, &request_list);
127	return request;
128	}
129
130	/*
131	* int
132	* res_ourserver(inp)
133	* looks up "inp" in irc_nsaddr_list[]
134	* returns:
135	* 0 : not found
136	* >0 : found
137	* author:
138	* paul vixie, 29may94
139	* revised for ircd, cryogen(stu) may03
140	*/
141	static int
142	res_ourserver(const struct irc_ssaddr *inp)
143	{
144	const struct sockaddr_in6 v6in = (const struct sockaddr_in6 )inp;
145	const struct sockaddr_in v4in = (const struct sockaddr_in )inp;
146
147	for (unsigned int i = 0; i < irc_nscount; ++i)
148	{
149	const struct irc_ssaddr *srv = &irc_nsaddr_list[i];
150	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )srv;
151	const struct sockaddr_in v4 = (const struct sockaddr_in )srv;
152
153	/*
154	* Could probably just memcmp(srv, inp, srv.ss_len) here
155	* but we'll air on the side of caution - stu
156	*/
157	switch (srv->ss.ss_family)
158	{
159	case AF_INET6:
160	if (srv->ss.ss_family == inp->ss.ss_family)
161	if (v6->sin6_port == v6in->sin6_port)
162	if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
163	sizeof(struct in6_addr)))
164	return 1;
165	break;
166	case AF_INET:
167	if (srv->ss.ss_family == inp->ss.ss_family)
168	if (v4->sin_port == v4in->sin_port)
169	if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)
170	return 1;
171	break;
172	default:
173	break;
174	}
175	}
176
177	return 0;
178	}
179
180	/*
181	* start_resolver - do everything we need to read the resolv.conf file
182	* and initialize the resolver file descriptor if needed
183	*/
184	static void
185	start_resolver(void)
186	{
187	irc_res_init();
188
189	if (!ResolverFileDescriptor.flags.open)
190	{
191	if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
192	SOCK_DGRAM, 0, "UDP resolver socket") == -1)
193	return;
194
195	/* At the moment, the resolver FD data is global .. */
196	comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
197	}
198	}
199
200	/*
201	* restart_resolver - reread resolv.conf, reopen socket
202	*/
203	void
204	restart_resolver(void)
205	{
206	fd_close(&ResolverFileDescriptor);
207	start_resolver();
208	}
209
210	/*
211	* delete_resolver_queries - cleanup outstanding queries
212	* for which there no longer exist clients or conf lines.
213	*/
214	void
215	delete_resolver_queries(const void *vptr)
216	{
217	dlink_node node, node_next;
218
219	DLINK_FOREACH_SAFE(node, node_next, request_list.head)
220	{
221	struct reslist *request = node->data;
222
223	if (request->callback_ctx == vptr)
224	rem_request(request);
225	}
226	}
227
228	/*
229	* send_res_msg - sends msg to all nameservers found in the "_res" structure.
230	* This should reflect /etc/resolv.conf. We will get responses
231	* which arent needed but is easier than checking to see if nameserver
232	* isn't present. Returns number of messages successfully sent to
233	* nameservers or -1 if no successful sends.
234	*/
235	static void
236	send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
237	{
238	unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);
239
240	/* RES_PRIMARY option is not implemented
241	* if (res.options & RES_PRIMARY \|\| 0 == max_queries)
242	*/
243	if (max_queries == 0)
244	max_queries = 1;
245
246	for (unsigned int i = 0; i < max_queries; ++i)
247	sendto(ResolverFileDescriptor.fd, msg, len, 0,
248	(struct sockaddr *)&irc_nsaddr_list[i], irc_nsaddr_list[i].ss_len);
249	}
250
251	/*
252	* find_id - find a dns request id (id is determined by dn_mkquery)
253	*/
254	static struct reslist *
255	find_id(unsigned int id)
256	{
257	dlink_node *node;
258
259	DLINK_FOREACH(node, request_list.head)
260	{
261	struct reslist *request = node->data;
262
263	if (request->id == id)
264	return request;
265	}
266
267	return NULL;
268	}
269
270	/*
271	* query_name - generate a query based on class, type and name.
272	*/
273	static void
274	query_name(const char name, int query_class, int type, struct reslist request)
275	{
276	unsigned char buf[MAXPACKET];
277	int request_len = 0;
278
279	memset(buf, 0, sizeof(buf));
280
281	if ((request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf))) > 0)
282	{
283	HEADER header = (HEADER )buf;
284
285	/*
286	* Generate an unique id.
287	* NOTE: we don't have to worry about converting this to and from
288	* network byte order, the nameserver does not interpret this value
289	* and returns it unchanged.
290	*/
291	do
292	header->id = (header->id + genrand_int32()) & 0xFFFF;
293	while (find_id(header->id));
294
295	request->id = header->id;
296	++request->sends;
297
298	send_res_msg(buf, request_len, request->sends);
299	}
300	}
301
302	/*
303	* do_query_name - nameserver lookup name
304	*/
305	static void
306	do_query_name(dns_callback_fnc callback, void ctx, const char name,
307	struct reslist *request, int type)
308	{
309	char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];
310
311	strlcpy(host_name, name, sizeof(host_name));
312
313	if (!request)
314	{
315	request = make_request(callback, ctx);
316	request->type = type;
317	request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
318	}
319
320	request->type = type;
321	query_name(host_name, C_IN, type, request);
322	}
323
324	/*
325	* do_query_number - Use this to do reverse IP# lookups.
326	*/
327	static void
328	do_query_number(dns_callback_fnc callback, void *ctx,
329	const struct irc_ssaddr *addr,
330	struct reslist *request)
331	{
332	char ipbuf[128] = "";
333
334	if (addr->ss.ss_family == AF_INET)
335	{
336	const struct sockaddr_in v4 = (const struct sockaddr_in )addr;
337	const unsigned char cp = (const unsigned char )&v4->sin_addr.s_addr;
338
339	snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
340	(unsigned int)(cp[3]), (unsigned int)(cp[2]),
341	(unsigned int)(cp[1]), (unsigned int)(cp[0]));
342	}
343	else if (addr->ss.ss_family == AF_INET6)
344	{
345	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )addr;
346	const unsigned char cp = (const unsigned char )&v6->sin6_addr.s6_addr;
347
348	snprintf(ipbuf, sizeof(ipbuf),
349	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
350	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
351	(unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
352	(unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
353	(unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
354	(unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
355	(unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
356	(unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
357	(unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
358	(unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
359	(unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
360	(unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
361	(unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
362	(unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
363	(unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
364	(unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
365	(unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
366	(unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
367	}
368
369	if (!request)
370	{
371	request = make_request(callback, ctx);
372	request->type = T_PTR;
373	memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
374	}
375
376	query_name(ipbuf, C_IN, T_PTR, request);
377	}
378
379	/*
380	* gethost_byname_type - get host address from name
381	*
382	*/
383	void
384	gethost_byname_type(dns_callback_fnc callback, void ctx, const char name, int type)
385	{
386	assert(name);
387	do_query_name(callback, ctx, name, NULL, type);
388	}
389
390	/*
391	* gethost_byaddr - get host name from address
392	*/
393	void
394	gethost_byaddr(dns_callback_fnc callback, void ctx, const struct irc_ssaddr addr)
395	{
396	do_query_number(callback, ctx, addr, NULL);
397	}
398
399	static void
400	resend_query(struct reslist *request)
401	{
402	switch (request->type)
403	{
404	case T_PTR:
405	do_query_number(NULL, NULL, &request->addr, request);
406	break;
407	case T_A:
408	case T_AAAA:
409	do_query_name(NULL, NULL, request->name, request, request->type);
410	break;
411	default:
412	break;
413	}
414	}
415
416	/*
417	* proc_answer - process name server reply
418	*/
419	static int
420	proc_answer(struct reslist request, HEADER header, unsigned char buf, unsigned char eob)
421	{
422	char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
423	unsigned char current = buf + sizeof(HEADER); / current position in buf */
424	unsigned int type = 0; /* answer type */
425	unsigned int rd_length = 0;
426	int n; /* temp count */
427	struct sockaddr_in v4; / conversion */
428	struct sockaddr_in6 *v6;
429
430	for (; header->qdcount > 0; --header->qdcount)
431	{
432	if ((n = irc_dn_skipname(current, eob)) < 0)
433	break;
434
435	current += (size_t)n + QFIXEDSZ;
436	}
437
438	/*
439	* Process each answer sent to us blech.
440	*/
441	while (header->ancount > 0 && current < eob)
442	{
443	--header->ancount;
444
445	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
446
447	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
448	return 0;
449
450	hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';
451
452	/*
453	* With Address arithmetic you have to be very anal
454	* this code was not working on alpha due to that
455	* (spotted by rodder/jailbird/dianora)
456	*/
457	current += (size_t)n;
458
459	if (!((current + ANSWER_FIXED_SIZE) < eob))
460	break;
461
462	type = irc_ns_get16(current);
463	current += TYPE_SIZE;
464	current += CLASS_SIZE;
465	current += TTL_SIZE;
466	rd_length = irc_ns_get16(current);
467	current += RDLENGTH_SIZE;
468
469	/*
470	* Wait to set request->type until we verify this structure
471	*/
472	switch (type)
473	{
474	case T_A:
475	if (request->type != T_A)
476	return 0;
477
478	/*
479	* Check for invalid rd_length or too many addresses
480	*/
481	if (rd_length != sizeof(struct in_addr))
482	return 0;
483
484	request->addr.ss_len = sizeof(struct sockaddr_in);
485	v4 = (struct sockaddr_in *)&request->addr;
486	v4->sin_family = AF_INET;
487	memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
488	return 1;
489	break;
490	case T_AAAA:
491	if (request->type != T_AAAA)
492	return 0;
493
494	if (rd_length != sizeof(struct in6_addr))
495	return 0;
496
497	request->addr.ss_len = sizeof(struct sockaddr_in6);
498	v6 = (struct sockaddr_in6 *)&request->addr;
499	v6->sin6_family = AF_INET6;
500	memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
501	return 1;
502	break;
503	case T_PTR:
504	if (request->type != T_PTR)
505	return 0;
506
507	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
508	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
509	return 0;
510
511	request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
512	return 1;
513	break;
514	case T_CNAME:
515	current += rd_length;
516	break;
517	default:
518	return 0;
519	break;
520	}
521	}
522
523	return 0;
524	}
525
526	/*
527	* res_readreply - read a dns reply from the nameserver and process it.
528	*/
529	static void
530	res_readreply(fde_t fd, void data)
531	{
532	unsigned char buf[sizeof(HEADER) + MAXPACKET];
533	struct reslist *request = NULL;
534	ssize_t rc = 0;
535	socklen_t len = sizeof(struct irc_ssaddr);
536	struct irc_ssaddr lsin;
537
538	while ((rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
539	{
540	if (rc <= (ssize_t)sizeof(HEADER))
541	continue;
542
543	/*
544	* Check against possibly fake replies
545	*/
546	if (!res_ourserver(&lsin))
547	continue;
548
549	/*
550	* Convert DNS reply reader from Network byte order to CPU byte order.
551	*/
552	HEADER header = (HEADER )buf;
553	header->ancount = ntohs(header->ancount);
554	header->qdcount = ntohs(header->qdcount);
555	header->nscount = ntohs(header->nscount);
556	header->arcount = ntohs(header->arcount);
557
558	/*
559	* Response for an id which we have already received an answer for
560	* just ignore this response.
561	*/
562	if ((request = find_id(header->id)) == NULL)
563	continue;
564
565	if (header->rcode != NO_ERRORS \|\| header->ancount == 0)
566	{
567	/*
568	* If a bad error was returned, stop here and don't send
569	* any more (no retries granted).
570	*/
571	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
572	rem_request(request);
573	continue;
574	}
575
576	/*
577	* If this fails there was an error decoding the received packet.
578	* We only give it one shot. If it fails, just leave the client
579	* unresolved.
580	*/
581	if (!proc_answer(request, header, buf, buf + rc))
582	{
583	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
584	rem_request(request);
585	continue;
586	}
587
588	if (request->type == T_PTR)
589	{
590	if (request->namelength == 0)
591	{
592	/*
593	* Got a PTR response with no name, something bogus is happening
594	* don't bother trying again, the client address doesn't resolve
595	*/
596	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
597	rem_request(request);
598	continue;
599	}
600
601	/*
602	* Lookup the 'authoritative' name that we were given for the ip#.
603	*/
604	if (request->addr.ss.ss_family == AF_INET6)
605	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
606	else
607	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
608
609	rem_request(request);
610	}
611	else
612	{
613	/*
614	* Got a name and address response, client resolved
615	*/
616	(*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
617	rem_request(request);
618	}
619
620	continue;
621	}
622
623	comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
624	}
625
626	/*
627	* timeout_query_list - Remove queries from the list which have been
628	* there too long without being resolved.
629	*/
630	static uintmax_t
631	timeout_query_list(void)
632	{
633	dlink_node node, node_next;
634	uintmax_t next_time = 0;
635
636	DLINK_FOREACH_SAFE(node, node_next, request_list.head)
637	{
638	struct reslist *request = node->data;
639	uintmax_t timeout = request->sentat + request->timeout;
640
641	if (CurrentTime >= timeout)
642	{
643	if (--request->retries <= 0)
644	{
645	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
646	rem_request(request);
647	continue;
648	}
649	else
650	{
651	request->sentat = CurrentTime;
652	request->timeout += request->timeout;
653	resend_query(request);
654	}
655	}
656
657	if (next_time == 0 \|\| timeout < next_time)
658	next_time = timeout;
659	}
660
661	return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
662	}
663
664	/*
665	* timeout_resolver - check request list
666	*/
667	static void
668	timeout_resolver(void *unused)
669	{
670	timeout_query_list();
671	}
672
673	/*
674	* resolver_init - initialize resolver and resolver library
675	*/
676	void
677	resolver_init(void)
678	{
679	static struct event event_timeout_resolver =
680	{
681	.name = "timeout_resolver",
682	.handler = timeout_resolver,
683	.when = 1
684	};
685
686	dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS);
687
688	start_resolver();
689	event_add(&event_timeout_resolver, NULL);
690	}