trunk/src/res.c

/*
 *  ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
 *
 *  Copyright (c) 1997-2014 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *  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 "client.h"
#include "event.h"
#include "irc_string.h"
#include "ircd.h"
#include "numeric.h"
#include "rng_mt.h"
#include "fdlist.h"
#include "s_bsd.h"
#include "log.h"
#include "misc.h"
#include "send.h"
#include "memory.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. */
  int id;                                    /**< Request ID (from request header). */
  int sent;                                  /**< Number of requests sent */
  char type;                                 /**< Current request type. */
  char retries;                              /**< Retry counter */
  unsigned int sends;                        /**< Number of sends (>1 means resent). */
  time_t sentat;                             /**< Timestamp we last sent this request. */
  time_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 *v6;
  const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp;
  const struct sockaddr_in *v4;
  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];
    v6 = (const struct sockaddr_in6 *)srv;
    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 *ptr = NULL, *ptr_next = NULL;

  DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
  {
    struct reslist *request = ptr->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 int
send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
{
  int sent = 0;
  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)
  {
    if (sendto(ResolverFileDescriptor.fd, msg, len, 0,
        (struct sockaddr*)&(irc_nsaddr_list[i]),
        irc_nsaddr_list[i].ss_len) == len)
      ++sent;
  }

  return sent;
}

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

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

    request->sent += 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 == NULL)
  {
    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 == NULL)
  {
    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;

        v4 = (struct sockaddr_in *)&request->addr;
        request->addr.ss_len = sizeof(struct sockaddr_in);
        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];
  HEADER *header;
  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 *)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);
}

void
report_dns_servers(struct Client *source_p)
{
  char ipaddr[HOSTIPLEN + 1] = "";

  for (unsigned int i = 0; i < irc_nscount; ++i)
  {
    getnameinfo((struct sockaddr *)&(irc_nsaddr_list[i]),
                irc_nsaddr_list[i].ss_len, ipaddr,
                sizeof(ipaddr), NULL, 0, NI_NUMERICHOST);
    sendto_one_numeric(source_p, &me, RPL_STATSALINE, ipaddr);
  }
}

/*
 * timeout_query_list - Remove queries from the list which have been
 * there too long without being resolved.
 */
static time_t
timeout_query_list(void)
{
  dlink_node *ptr = NULL, *ptr_next = NULL;
  struct reslist *request = NULL;
  time_t next_time = 0;
  time_t timeout   = 0;

  DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
  {
    request = ptr->data;
    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();
}

/*
 * init_resolver - initialize resolver and resolver library
 */
void
init_resolver(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:	4468
Committed:	Wed Aug 13 19:00:50 2014 UTC (11 years ago) by michael
Content type:	text/x-csrc
File size:	20347 byte(s)
Log Message:	- res.c:query_name(): get rid of useless typecasting
#	Content
1	/*
2	* ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
3	*
4	* Copyright (c) 1997-2014 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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 "client.h"
49	#include "event.h"
50	#include "irc_string.h"
51	#include "ircd.h"
52	#include "numeric.h"
53	#include "rng_mt.h"
54	#include "fdlist.h"
55	#include "s_bsd.h"
56	#include "log.h"
57	#include "misc.h"
58	#include "send.h"
59	#include "memory.h"
60	#include "mempool.h"
61	#include "res.h"
62	#include "reslib.h"
63
64	#if (CHAR_BIT != 8)
65	#error this code needs to be able to address individual octets
66	#endif
67
68	static void res_readreply(fde_t , void );
69
70	#define MAXPACKET 1024 /*< rfc says 512 but we expand names so ... /
71	#define AR_TTL 600 /*< TTL in seconds for dns cache entries /
72
73	/*
74	* RFC 1104/1105 wasn't very helpful about what these fields
75	* should be named, so for now, we'll just name them this way.
76	* We probably should look at what named calls them or something.
77	*/
78	#define TYPE_SIZE (size_t)2
79	#define CLASS_SIZE (size_t)2
80	#define TTL_SIZE (size_t)4
81	#define RDLENGTH_SIZE (size_t)2
82	#define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
83
84	struct reslist
85	{
86	dlink_node node; /*< Doubly linked list node. /
87	int id; /*< Request ID (from request header). /
88	int sent; /*< Number of requests sent /
89	char type; /*< Current request type. /
90	char retries; /*< Retry counter /
91	unsigned int sends; /*< Number of sends (>1 means resent). /
92	time_t sentat; /*< Timestamp we last sent this request. /
93	time_t timeout; /*< When this request times out. /
94	struct irc_ssaddr addr; /*< Address for this request. /
95	char name[RFC1035_MAX_DOMAIN_LENGTH + 1]; /*< Hostname for this request. /
96	size_t namelength; /*< Actual hostname length. /
97	dns_callback_fnc callback; /*< Callback function on completion. /
98	void callback_ctx; /< Context pointer for callback. /
99	};
100
101	static fde_t ResolverFileDescriptor;
102	static dlink_list request_list;
103	static mp_pool_t *dns_pool;
104
105
106	/*
107	* rem_request - remove a request from the list.
108	* This must also free any memory that has been allocated for
109	* temporary storage of DNS results.
110	*/
111	static void
112	rem_request(struct reslist *request)
113	{
114	dlinkDelete(&request->node, &request_list);
115	mp_pool_release(request);
116	}
117
118	/*
119	* make_request - Create a DNS request record for the server.
120	*/
121	static struct reslist *
122	make_request(dns_callback_fnc callback, void *ctx)
123	{
124	struct reslist *request = mp_pool_get(dns_pool);
125
126	request->sentat = CurrentTime;
127	request->retries = 2;
128	request->timeout = 4; /* Start at 4 and exponential inc. */
129	request->callback = callback;
130	request->callback_ctx = ctx;
131
132	dlinkAdd(request, &request->node, &request_list);
133	return request;
134	}
135
136	/*
137	* int
138	* res_ourserver(inp)
139	* looks up "inp" in irc_nsaddr_list[]
140	* returns:
141	* 0 : not found
142	* >0 : found
143	* author:
144	* paul vixie, 29may94
145	* revised for ircd, cryogen(stu) may03
146	*/
147	static int
148	res_ourserver(const struct irc_ssaddr *inp)
149	{
150	const struct sockaddr_in6 *v6;
151	const struct sockaddr_in6 v6in = (const struct sockaddr_in6 )inp;
152	const struct sockaddr_in *v4;
153	const struct sockaddr_in v4in = (const struct sockaddr_in )inp;
154
155	for (unsigned int i = 0; i < irc_nscount; ++i)
156	{
157	const struct irc_ssaddr *srv = &irc_nsaddr_list[i];
158	v6 = (const struct sockaddr_in6 *)srv;
159	v4 = (const struct sockaddr_in *)srv;
160
161	/*
162	* Could probably just memcmp(srv, inp, srv.ss_len) here
163	* but we'll air on the side of caution - stu
164	*/
165	switch (srv->ss.ss_family)
166	{
167	case AF_INET6:
168	if (srv->ss.ss_family == inp->ss.ss_family)
169	if (v6->sin6_port == v6in->sin6_port)
170	if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
171	sizeof(struct in6_addr)))
172	return 1;
173	break;
174	case AF_INET:
175	if (srv->ss.ss_family == inp->ss.ss_family)
176	if (v4->sin_port == v4in->sin_port)
177	if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)
178	return 1;
179	break;
180	default:
181	break;
182	}
183	}
184
185	return 0;
186	}
187
188	/*
189	* start_resolver - do everything we need to read the resolv.conf file
190	* and initialize the resolver file descriptor if needed
191	*/
192	static void
193	start_resolver(void)
194	{
195	irc_res_init();
196
197	if (!ResolverFileDescriptor.flags.open)
198	{
199	if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
200	SOCK_DGRAM, 0, "UDP resolver socket") == -1)
201	return;
202
203	/* At the moment, the resolver FD data is global .. */
204	comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
205	}
206	}
207
208	/*
209	* restart_resolver - reread resolv.conf, reopen socket
210	*/
211	void
212	restart_resolver(void)
213	{
214	fd_close(&ResolverFileDescriptor);
215	start_resolver();
216	}
217
218	/*
219	* delete_resolver_queries - cleanup outstanding queries
220	* for which there no longer exist clients or conf lines.
221	*/
222	void
223	delete_resolver_queries(const void *vptr)
224	{
225	dlink_node ptr = NULL, ptr_next = NULL;
226
227	DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
228	{
229	struct reslist *request = ptr->data;
230
231	if (request->callback_ctx == vptr)
232	rem_request(request);
233	}
234	}
235
236	/*
237	* send_res_msg - sends msg to all nameservers found in the "_res" structure.
238	* This should reflect /etc/resolv.conf. We will get responses
239	* which arent needed but is easier than checking to see if nameserver
240	* isn't present. Returns number of messages successfully sent to
241	* nameservers or -1 if no successful sends.
242	*/
243	static int
244	send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
245	{
246	int sent = 0;
247	unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);
248
249	/* RES_PRIMARY option is not implemented
250	* if (res.options & RES_PRIMARY \|\| 0 == max_queries)
251	*/
252	if (max_queries == 0)
253	max_queries = 1;
254
255	for (unsigned int i = 0; i < max_queries; ++i)
256	{
257	if (sendto(ResolverFileDescriptor.fd, msg, len, 0,
258	(struct sockaddr*)&(irc_nsaddr_list[i]),
259	irc_nsaddr_list[i].ss_len) == len)
260	++sent;
261	}
262
263	return sent;
264	}
265
266	/*
267	* find_id - find a dns request id (id is determined by dn_mkquery)
268	*/
269	static struct reslist *
270	find_id(int id)
271	{
272	dlink_node *ptr = NULL;
273
274	DLINK_FOREACH(ptr, request_list.head)
275	{
276	struct reslist *request = ptr->data;
277
278	if (request->id == id)
279	return request;
280	}
281
282	return NULL;
283	}
284
285	/*
286	* query_name - generate a query based on class, type and name.
287	*/
288	static void
289	query_name(const char name, int query_class, int type, struct reslist request)
290	{
291	unsigned char buf[MAXPACKET];
292	int request_len = 0;
293
294	memset(buf, 0, sizeof(buf));
295
296	if ((request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf))) > 0)
297	{
298	HEADER header = (HEADER )buf;
299
300	/*
301	* Generate an unique id.
302	* NOTE: we don't have to worry about converting this to and from
303	* network byte order, the nameserver does not interpret this value
304	* and returns it unchanged.
305	*/
306	do
307	header->id = (header->id + genrand_int32()) & 0xFFFF;
308	while (find_id(header->id));
309
310	request->id = header->id;
311	++request->sends;
312
313	request->sent += send_res_msg(buf, request_len, request->sends);
314	}
315	}
316
317	/*
318	* do_query_name - nameserver lookup name
319	*/
320	static void
321	do_query_name(dns_callback_fnc callback, void ctx, const char name,
322	struct reslist *request, int type)
323	{
324	char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];
325
326	strlcpy(host_name, name, sizeof(host_name));
327
328	if (request == NULL)
329	{
330	request = make_request(callback, ctx);
331	request->type = type;
332	request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
333	}
334
335	request->type = type;
336	query_name(host_name, C_IN, type, request);
337	}
338
339	/*
340	* do_query_number - Use this to do reverse IP# lookups.
341	*/
342	static void
343	do_query_number(dns_callback_fnc callback, void *ctx,
344	const struct irc_ssaddr *addr,
345	struct reslist *request)
346	{
347	char ipbuf[128] = "";
348
349	if (addr->ss.ss_family == AF_INET)
350	{
351	const struct sockaddr_in v4 = (const struct sockaddr_in )addr;
352	const unsigned char cp = (const unsigned char )&v4->sin_addr.s_addr;
353
354	snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
355	(unsigned int)(cp[3]), (unsigned int)(cp[2]),
356	(unsigned int)(cp[1]), (unsigned int)(cp[0]));
357	}
358	else if (addr->ss.ss_family == AF_INET6)
359	{
360	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )addr;
361	const unsigned char cp = (const unsigned char )&v6->sin6_addr.s6_addr;
362
363	snprintf(ipbuf, sizeof(ipbuf),
364	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
365	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
366	(unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
367	(unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
368	(unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
369	(unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
370	(unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
371	(unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
372	(unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
373	(unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
374	(unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
375	(unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
376	(unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
377	(unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
378	(unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
379	(unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
380	(unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
381	(unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
382	}
383
384	if (request == NULL)
385	{
386	request = make_request(callback, ctx);
387	request->type = T_PTR;
388	memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
389	}
390
391	query_name(ipbuf, C_IN, T_PTR, request);
392	}
393
394	/*
395	* gethost_byname_type - get host address from name
396	*
397	*/
398	void
399	gethost_byname_type(dns_callback_fnc callback, void ctx, const char name, int type)
400	{
401	assert(name);
402	do_query_name(callback, ctx, name, NULL, type);
403	}
404
405	/*
406	* gethost_byaddr - get host name from address
407	*/
408	void
409	gethost_byaddr(dns_callback_fnc callback, void ctx, const struct irc_ssaddr addr)
410	{
411	do_query_number(callback, ctx, addr, NULL);
412	}
413
414	static void
415	resend_query(struct reslist *request)
416	{
417	switch (request->type)
418	{
419	case T_PTR:
420	do_query_number(NULL, NULL, &request->addr, request);
421	break;
422	case T_A:
423	case T_AAAA:
424	do_query_name(NULL, NULL, request->name, request, request->type);
425	break;
426	default:
427	break;
428	}
429	}
430
431	/*
432	* proc_answer - process name server reply
433	*/
434	static int
435	proc_answer(struct reslist request, HEADER header, unsigned char buf, unsigned char eob)
436	{
437	char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
438	unsigned char current = buf + sizeof(HEADER); / current position in buf */
439	unsigned int type = 0; /* answer type */
440	unsigned int rd_length = 0;
441	int n; /* temp count */
442	struct sockaddr_in v4; / conversion */
443	struct sockaddr_in6 *v6;
444
445	for (; header->qdcount > 0; --header->qdcount)
446	{
447	if ((n = irc_dn_skipname(current, eob)) < 0)
448	break;
449
450	current += (size_t)n + QFIXEDSZ;
451	}
452
453	/*
454	* Process each answer sent to us blech.
455	*/
456	while (header->ancount > 0 && current < eob)
457	{
458	header->ancount--;
459
460	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
461
462	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
463	return 0;
464
465	hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';
466
467	/*
468	* With Address arithmetic you have to be very anal
469	* this code was not working on alpha due to that
470	* (spotted by rodder/jailbird/dianora)
471	*/
472	current += (size_t)n;
473
474	if (!((current + ANSWER_FIXED_SIZE) < eob))
475	break;
476
477	type = irc_ns_get16(current);
478	current += TYPE_SIZE;
479	current += CLASS_SIZE;
480	current += TTL_SIZE;
481	rd_length = irc_ns_get16(current);
482	current += RDLENGTH_SIZE;
483
484	/*
485	* Wait to set request->type until we verify this structure
486	*/
487	switch (type)
488	{
489	case T_A:
490	if (request->type != T_A)
491	return 0;
492
493	/*
494	* Check for invalid rd_length or too many addresses
495	*/
496	if (rd_length != sizeof(struct in_addr))
497	return 0;
498
499	v4 = (struct sockaddr_in *)&request->addr;
500	request->addr.ss_len = sizeof(struct sockaddr_in);
501	v4->sin_family = AF_INET;
502	memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
503	return 1;
504	break;
505	case T_AAAA:
506	if (request->type != T_AAAA)
507	return 0;
508
509	if (rd_length != sizeof(struct in6_addr))
510	return 0;
511
512	request->addr.ss_len = sizeof(struct sockaddr_in6);
513	v6 = (struct sockaddr_in6 *)&request->addr;
514	v6->sin6_family = AF_INET6;
515	memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
516	return 1;
517	break;
518	case T_PTR:
519	if (request->type != T_PTR)
520	return 0;
521
522	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
523	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
524	return 0;
525
526	request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
527	return 1;
528	break;
529	case T_CNAME:
530	current += rd_length;
531	break;
532	default:
533	return 0;
534	break;
535	}
536	}
537
538	return 0;
539	}
540
541	/*
542	* res_readreply - read a dns reply from the nameserver and process it.
543	*/
544	static void
545	res_readreply(fde_t fd, void data)
546	{
547	unsigned char buf[sizeof(HEADER) + MAXPACKET];
548	HEADER *header;
549	struct reslist *request = NULL;
550	ssize_t rc = 0;
551	socklen_t len = sizeof(struct irc_ssaddr);
552	struct irc_ssaddr lsin;
553
554	while ((rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
555	{
556	if (rc <= (ssize_t)sizeof(HEADER))
557	continue;
558
559	/*
560	* Check against possibly fake replies
561	*/
562	if (!res_ourserver(&lsin))
563	continue;
564
565	/*
566	* Convert DNS reply reader from Network byte order to CPU byte order.
567	*/
568	header = (HEADER *)buf;
569	header->ancount = ntohs(header->ancount);
570	header->qdcount = ntohs(header->qdcount);
571	header->nscount = ntohs(header->nscount);
572	header->arcount = ntohs(header->arcount);
573
574	/*
575	* Response for an id which we have already received an answer for
576	* just ignore this response.
577	*/
578	if ((request = find_id(header->id)) == NULL)
579	continue;
580
581	if (header->rcode != NO_ERRORS \|\| header->ancount == 0)
582	{
583	/*
584	* If a bad error was returned, stop here and don't
585	* send any more (no retries granted).
586	*/
587	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
588	rem_request(request);
589	continue;
590	}
591
592	/*
593	* If this fails there was an error decoding the received packet.
594	* We only give it one shot. If it fails, just leave the client
595	* unresolved.
596	*/
597	if (!proc_answer(request, header, buf, buf + rc))
598	{
599	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
600	rem_request(request);
601	continue;
602	}
603
604	if (request->type == T_PTR)
605	{
606	if (request->namelength == 0)
607	{
608	/*
609	* Got a PTR response with no name, something bogus is happening
610	* don't bother trying again, the client address doesn't resolve
611	*/
612	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
613	rem_request(request);
614	continue;
615	}
616
617	/*
618	* Lookup the 'authoritative' name that we were given for the ip#.
619	*/
620	if (request->addr.ss.ss_family == AF_INET6)
621	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
622	else
623	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
624	rem_request(request);
625	}
626	else
627	{
628	/*
629	* Got a name and address response, client resolved
630	*/
631	(*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
632	rem_request(request);
633	}
634
635	continue;
636	}
637
638	comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
639	}
640
641	void
642	report_dns_servers(struct Client *source_p)
643	{
644	char ipaddr[HOSTIPLEN + 1] = "";
645
646	for (unsigned int i = 0; i < irc_nscount; ++i)
647	{
648	getnameinfo((struct sockaddr *)&(irc_nsaddr_list[i]),
649	irc_nsaddr_list[i].ss_len, ipaddr,
650	sizeof(ipaddr), NULL, 0, NI_NUMERICHOST);
651	sendto_one_numeric(source_p, &me, RPL_STATSALINE, ipaddr);
652	}
653	}
654
655	/*
656	* timeout_query_list - Remove queries from the list which have been
657	* there too long without being resolved.
658	*/
659	static time_t
660	timeout_query_list(void)
661	{
662	dlink_node ptr = NULL, ptr_next = NULL;
663	struct reslist *request = NULL;
664	time_t next_time = 0;
665	time_t timeout = 0;
666
667	DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
668	{
669	request = ptr->data;
670	timeout = request->sentat + request->timeout;
671
672	if (CurrentTime >= timeout)
673	{
674	if (--request->retries <= 0)
675	{
676	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
677	rem_request(request);
678	continue;
679	}
680	else
681	{
682	request->sentat = CurrentTime;
683	request->timeout += request->timeout;
684	resend_query(request);
685	}
686	}
687
688	if (next_time == 0 \|\| timeout < next_time)
689	next_time = timeout;
690	}
691
692	return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
693	}
694
695	/*
696	* timeout_resolver - check request list
697	*/
698	static void
699	timeout_resolver(void *unused)
700	{
701	timeout_query_list();
702	}
703
704	/*
705	* init_resolver - initialize resolver and resolver library
706	*/
707	void
708	init_resolver(void)
709	{
710	static struct event event_timeout_resolver =
711	{
712	.name = "timeout_resolver",
713	.handler = timeout_resolver,
714	.when = 1
715	};
716
717	dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS);
718
719	start_resolver();
720	event_add(&event_timeout_resolver, NULL);
721	}