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., 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 "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 *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 = NULL, *node_next = NULL;

  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 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 *node = NULL;

  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;

    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;

        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];
  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((const 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 *node = NULL, *node_next = NULL;
  struct reslist *request = NULL;
  time_t next_time = 0;
  time_t timeout   = 0;

  DLINK_FOREACH_SAFE(node, node_next, request_list.head)
  {
    request = node->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:	5051
Committed:	Sat Dec 13 21:31:06 2014 UTC (10 years, 8 months ago) by michael
Content type:	text/x-csrc
File size:	20358 byte(s)
Log Message:	- Fixed compile warnings
#	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., 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 "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 v6in = (const struct sockaddr_in6 )inp;
151	const struct sockaddr_in v4in = (const struct sockaddr_in )inp;
152
153	for (unsigned int i = 0; i < irc_nscount; ++i)
154	{
155	const struct irc_ssaddr *srv = &irc_nsaddr_list[i];
156	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )srv;
157	const struct sockaddr_in v4 = (const struct sockaddr_in )srv;
158
159	/*
160	* Could probably just memcmp(srv, inp, srv.ss_len) here
161	* but we'll air on the side of caution - stu
162	*/
163	switch (srv->ss.ss_family)
164	{
165	case AF_INET6:
166	if (srv->ss.ss_family == inp->ss.ss_family)
167	if (v6->sin6_port == v6in->sin6_port)
168	if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
169	sizeof(struct in6_addr)))
170	return 1;
171	break;
172	case AF_INET:
173	if (srv->ss.ss_family == inp->ss.ss_family)
174	if (v4->sin_port == v4in->sin_port)
175	if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)
176	return 1;
177	break;
178	default:
179	break;
180	}
181	}
182
183	return 0;
184	}
185
186	/*
187	* start_resolver - do everything we need to read the resolv.conf file
188	* and initialize the resolver file descriptor if needed
189	*/
190	static void
191	start_resolver(void)
192	{
193	irc_res_init();
194
195	if (!ResolverFileDescriptor.flags.open)
196	{
197	if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
198	SOCK_DGRAM, 0, "UDP resolver socket") == -1)
199	return;
200
201	/* At the moment, the resolver FD data is global .. */
202	comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
203	}
204	}
205
206	/*
207	* restart_resolver - reread resolv.conf, reopen socket
208	*/
209	void
210	restart_resolver(void)
211	{
212	fd_close(&ResolverFileDescriptor);
213	start_resolver();
214	}
215
216	/*
217	* delete_resolver_queries - cleanup outstanding queries
218	* for which there no longer exist clients or conf lines.
219	*/
220	void
221	delete_resolver_queries(const void *vptr)
222	{
223	dlink_node node = NULL, node_next = NULL;
224
225	DLINK_FOREACH_SAFE(node, node_next, request_list.head)
226	{
227	struct reslist *request = node->data;
228
229	if (request->callback_ctx == vptr)
230	rem_request(request);
231	}
232	}
233
234	/*
235	* send_res_msg - sends msg to all nameservers found in the "_res" structure.
236	* This should reflect /etc/resolv.conf. We will get responses
237	* which arent needed but is easier than checking to see if nameserver
238	* isn't present. Returns number of messages successfully sent to
239	* nameservers or -1 if no successful sends.
240	*/
241	static int
242	send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
243	{
244	int sent = 0;
245	unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);
246
247	/* RES_PRIMARY option is not implemented
248	* if (res.options & RES_PRIMARY \|\| 0 == max_queries)
249	*/
250	if (max_queries == 0)
251	max_queries = 1;
252
253	for (unsigned int i = 0; i < max_queries; ++i)
254	{
255	if (sendto(ResolverFileDescriptor.fd, msg, len, 0,
256	(struct sockaddr*)&(irc_nsaddr_list[i]),
257	irc_nsaddr_list[i].ss_len) == len)
258	++sent;
259	}
260
261	return sent;
262	}
263
264	/*
265	* find_id - find a dns request id (id is determined by dn_mkquery)
266	*/
267	static struct reslist *
268	find_id(int id)
269	{
270	dlink_node *node = NULL;
271
272	DLINK_FOREACH(node, request_list.head)
273	{
274	struct reslist *request = node->data;
275
276	if (request->id == id)
277	return request;
278	}
279
280	return NULL;
281	}
282
283	/*
284	* query_name - generate a query based on class, type and name.
285	*/
286	static void
287	query_name(const char name, int query_class, int type, struct reslist request)
288	{
289	unsigned char buf[MAXPACKET];
290	int request_len = 0;
291
292	memset(buf, 0, sizeof(buf));
293
294	if ((request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf))) > 0)
295	{
296	HEADER header = (HEADER )buf;
297
298	/*
299	* Generate an unique id.
300	* NOTE: we don't have to worry about converting this to and from
301	* network byte order, the nameserver does not interpret this value
302	* and returns it unchanged.
303	*/
304	do
305	header->id = (header->id + genrand_int32()) & 0xFFFF;
306	while (find_id(header->id));
307
308	request->id = header->id;
309	++request->sends;
310
311	request->sent += send_res_msg(buf, request_len, request->sends);
312	}
313	}
314
315	/*
316	* do_query_name - nameserver lookup name
317	*/
318	static void
319	do_query_name(dns_callback_fnc callback, void ctx, const char name,
320	struct reslist *request, int type)
321	{
322	char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];
323
324	strlcpy(host_name, name, sizeof(host_name));
325
326	if (request == NULL)
327	{
328	request = make_request(callback, ctx);
329	request->type = type;
330	request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
331	}
332
333	request->type = type;
334	query_name(host_name, C_IN, type, request);
335	}
336
337	/*
338	* do_query_number - Use this to do reverse IP# lookups.
339	*/
340	static void
341	do_query_number(dns_callback_fnc callback, void *ctx,
342	const struct irc_ssaddr *addr,
343	struct reslist *request)
344	{
345	char ipbuf[128] = "";
346
347	if (addr->ss.ss_family == AF_INET)
348	{
349	const struct sockaddr_in v4 = (const struct sockaddr_in )addr;
350	const unsigned char cp = (const unsigned char )&v4->sin_addr.s_addr;
351
352	snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
353	(unsigned int)(cp[3]), (unsigned int)(cp[2]),
354	(unsigned int)(cp[1]), (unsigned int)(cp[0]));
355	}
356	else if (addr->ss.ss_family == AF_INET6)
357	{
358	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )addr;
359	const unsigned char cp = (const unsigned char )&v6->sin6_addr.s6_addr;
360
361	snprintf(ipbuf, sizeof(ipbuf),
362	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
363	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
364	(unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
365	(unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
366	(unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
367	(unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
368	(unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
369	(unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
370	(unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
371	(unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
372	(unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
373	(unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
374	(unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
375	(unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
376	(unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
377	(unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
378	(unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
379	(unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
380	}
381
382	if (request == NULL)
383	{
384	request = make_request(callback, ctx);
385	request->type = T_PTR;
386	memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
387	}
388
389	query_name(ipbuf, C_IN, T_PTR, request);
390	}
391
392	/*
393	* gethost_byname_type - get host address from name
394	*
395	*/
396	void
397	gethost_byname_type(dns_callback_fnc callback, void ctx, const char name, int type)
398	{
399	assert(name);
400	do_query_name(callback, ctx, name, NULL, type);
401	}
402
403	/*
404	* gethost_byaddr - get host name from address
405	*/
406	void
407	gethost_byaddr(dns_callback_fnc callback, void ctx, const struct irc_ssaddr addr)
408	{
409	do_query_number(callback, ctx, addr, NULL);
410	}
411
412	static void
413	resend_query(struct reslist *request)
414	{
415	switch (request->type)
416	{
417	case T_PTR:
418	do_query_number(NULL, NULL, &request->addr, request);
419	break;
420	case T_A:
421	case T_AAAA:
422	do_query_name(NULL, NULL, request->name, request, request->type);
423	break;
424	default:
425	break;
426	}
427	}
428
429	/*
430	* proc_answer - process name server reply
431	*/
432	static int
433	proc_answer(struct reslist request, HEADER header, unsigned char buf, unsigned char eob)
434	{
435	char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
436	unsigned char current = buf + sizeof(HEADER); / current position in buf */
437	unsigned int type = 0; /* answer type */
438	unsigned int rd_length = 0;
439	int n; /* temp count */
440	struct sockaddr_in v4; / conversion */
441	struct sockaddr_in6 *v6;
442
443	for (; header->qdcount > 0; --header->qdcount)
444	{
445	if ((n = irc_dn_skipname(current, eob)) < 0)
446	break;
447
448	current += (size_t)n + QFIXEDSZ;
449	}
450
451	/*
452	* Process each answer sent to us blech.
453	*/
454	while (header->ancount > 0 && current < eob)
455	{
456	header->ancount--;
457
458	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
459
460	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
461	return 0;
462
463	hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';
464
465	/*
466	* With Address arithmetic you have to be very anal
467	* this code was not working on alpha due to that
468	* (spotted by rodder/jailbird/dianora)
469	*/
470	current += (size_t)n;
471
472	if (!((current + ANSWER_FIXED_SIZE) < eob))
473	break;
474
475	type = irc_ns_get16(current);
476	current += TYPE_SIZE;
477	current += CLASS_SIZE;
478	current += TTL_SIZE;
479	rd_length = irc_ns_get16(current);
480	current += RDLENGTH_SIZE;
481
482	/*
483	* Wait to set request->type until we verify this structure
484	*/
485	switch (type)
486	{
487	case T_A:
488	if (request->type != T_A)
489	return 0;
490
491	/*
492	* Check for invalid rd_length or too many addresses
493	*/
494	if (rd_length != sizeof(struct in_addr))
495	return 0;
496
497	request->addr.ss_len = sizeof(struct sockaddr_in);
498	v4 = (struct sockaddr_in *)&request->addr;
499	v4->sin_family = AF_INET;
500	memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
501	return 1;
502	break;
503	case T_AAAA:
504	if (request->type != T_AAAA)
505	return 0;
506
507	if (rd_length != sizeof(struct in6_addr))
508	return 0;
509
510	request->addr.ss_len = sizeof(struct sockaddr_in6);
511	v6 = (struct sockaddr_in6 *)&request->addr;
512	v6->sin6_family = AF_INET6;
513	memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
514	return 1;
515	break;
516	case T_PTR:
517	if (request->type != T_PTR)
518	return 0;
519
520	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
521	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
522	return 0;
523
524	request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
525	return 1;
526	break;
527	case T_CNAME:
528	current += rd_length;
529	break;
530	default:
531	return 0;
532	break;
533	}
534	}
535
536	return 0;
537	}
538
539	/*
540	* res_readreply - read a dns reply from the nameserver and process it.
541	*/
542	static void
543	res_readreply(fde_t fd, void data)
544	{
545	unsigned char buf[sizeof(HEADER) + MAXPACKET];
546	HEADER *header;
547	struct reslist *request = NULL;
548	ssize_t rc = 0;
549	socklen_t len = sizeof(struct irc_ssaddr);
550	struct irc_ssaddr lsin;
551
552	while ((rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
553	{
554	if (rc <= (ssize_t)sizeof(HEADER))
555	continue;
556
557	/*
558	* Check against possibly fake replies
559	*/
560	if (!res_ourserver(&lsin))
561	continue;
562
563	/*
564	* Convert DNS reply reader from Network byte order to CPU byte order.
565	*/
566	header = (HEADER *)buf;
567	header->ancount = ntohs(header->ancount);
568	header->qdcount = ntohs(header->qdcount);
569	header->nscount = ntohs(header->nscount);
570	header->arcount = ntohs(header->arcount);
571
572	/*
573	* Response for an id which we have already received an answer for
574	* just ignore this response.
575	*/
576	if ((request = find_id(header->id)) == NULL)
577	continue;
578
579	if (header->rcode != NO_ERRORS \|\| header->ancount == 0)
580	{
581	/*
582	* If a bad error was returned, stop here and don't
583	* send any more (no retries granted).
584	*/
585	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
586	rem_request(request);
587	continue;
588	}
589
590	/*
591	* If this fails there was an error decoding the received packet.
592	* We only give it one shot. If it fails, just leave the client
593	* unresolved.
594	*/
595	if (!proc_answer(request, header, buf, buf + rc))
596	{
597	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
598	rem_request(request);
599	continue;
600	}
601
602	if (request->type == T_PTR)
603	{
604	if (request->namelength == 0)
605	{
606	/*
607	* Got a PTR response with no name, something bogus is happening
608	* don't bother trying again, the client address doesn't resolve
609	*/
610	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
611	rem_request(request);
612	continue;
613	}
614
615	/*
616	* Lookup the 'authoritative' name that we were given for the ip#.
617	*/
618	if (request->addr.ss.ss_family == AF_INET6)
619	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
620	else
621	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
622	rem_request(request);
623	}
624	else
625	{
626	/*
627	* Got a name and address response, client resolved
628	*/
629	(*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
630	rem_request(request);
631	}
632
633	continue;
634	}
635
636	comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
637	}
638
639	void
640	report_dns_servers(struct Client *source_p)
641	{
642	char ipaddr[HOSTIPLEN + 1] = "";
643
644	for (unsigned int i = 0; i < irc_nscount; ++i)
645	{
646	getnameinfo((const struct sockaddr *)&(irc_nsaddr_list[i]),
647	irc_nsaddr_list[i].ss_len, ipaddr,
648	sizeof(ipaddr), NULL, 0, NI_NUMERICHOST);
649	sendto_one_numeric(source_p, &me, RPL_STATSALINE, ipaddr);
650	}
651	}
652
653	/*
654	* timeout_query_list - Remove queries from the list which have been
655	* there too long without being resolved.
656	*/
657	static time_t
658	timeout_query_list(void)
659	{
660	dlink_node node = NULL, node_next = NULL;
661	struct reslist *request = NULL;
662	time_t next_time = 0;
663	time_t timeout = 0;
664
665	DLINK_FOREACH_SAFE(node, node_next, request_list.head)
666	{
667	request = node->data;
668	timeout = request->sentat + request->timeout;
669
670	if (CurrentTime >= timeout)
671	{
672	if (--request->retries <= 0)
673	{
674	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
675	rem_request(request);
676	continue;
677	}
678	else
679	{
680	request->sentat = CurrentTime;
681	request->timeout += request->timeout;
682	resend_query(request);
683	}
684	}
685
686	if (next_time == 0 \|\| timeout < next_time)
687	next_time = timeout;
688	}
689
690	return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
691	}
692
693	/*
694	* timeout_resolver - check request list
695	*/
696	static void
697	timeout_resolver(void *unused)
698	{
699	timeout_query_list();
700	}
701
702	/*
703	* init_resolver - initialize resolver and resolver library
704	*/
705	void
706	init_resolver(void)
707	{
708	static struct event event_timeout_resolver =
709	{
710	.name = "timeout_resolver",
711	.handler = timeout_resolver,
712	.when = 1
713	};
714
715	dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS);
716
717	start_resolver();
718	event_add(&event_timeout_resolver, NULL);
719	}