trunk/src/res.c

/*
 *  ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
 *
 *  Copyright (c) 1997-2020 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 "res.h"
#include "reslib.h"
#include "memory.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;


/*
 * 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);
  xfree(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 = xcalloc(sizeof(*request));

  request->sentat = event_base->time.sec_monotonic;
  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 bool
res_ourserver(const struct irc_ssaddr *inp)
{
  for (unsigned int i = 0; i < irc_nscount; ++i)
    if (address_compare(inp, &irc_nsaddr_list[i], true) == true)
      return true;

  return false;
}

/*
 * 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 == NULL)
  {
    int fd = comm_socket(irc_nsaddr_list[0].ss.ss_family, SOCK_DGRAM, 0);
    if (fd == -1)
      return;

    ResolverFileDescriptor = fd_open(fd, true, "UDP resolver socket");

    /* 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)
{
  if (ResolverFileDescriptor)
  {
    fd_close(ResolverFileDescriptor);
    ResolverFileDescriptor = NULL;
  }

  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];

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

  int request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf));
  if (request_len > 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 == 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;
    request->addr = *addr;
  }

  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 bool
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;
  struct sockaddr_in *v4;      /* conversion */
  struct sockaddr_in6 *v6;

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

    current += (size_t)n + QFIXEDSZ;
  }

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

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

    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 false;

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

        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 true;
        break;

      case T_AAAA:
        if (request->type != T_AAAA)
          return false;

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

        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 true;
        break;

      case T_PTR:
        if (request->type != T_PTR)
          return false;

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

        request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
        return true;
        break;

      case T_CNAME:
        current += rd_length;
        break;

      default:
        return false;
        break;
    }
  }

  return false;
}

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

  while ((rc = recvfrom(F->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) == false)
      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.
     */
    struct reslist *request = find_id(header->id);
    if (request == 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) == false)
    {
      (*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(F, 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 (event_base->time.sec_monotonic >= timeout)
    {
      if (--request->retries <= 0)
      {
        (*request->callback)(request->callback_ctx, NULL, NULL, 0);
        rem_request(request);
        continue;
      }
      else
      {
        request->sentat = event_base->time.sec_monotonic;
        request->timeout += request->timeout;
        resend_query(request);
      }
    }

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

  return (next_time > event_base->time.sec_monotonic) ? next_time : (event_base->time.sec_monotonic + 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
  };

  start_resolver();
  event_add(&event_timeout_resolver, NULL);
}
Revision:	9202
Committed:	Fri Jan 24 23:52:04 2020 UTC (5 years, 7 months ago) by michael
Content type:	text/x-csrc
File size:	18718 byte(s)
Log Message:	- Stylistic changes
#	Content
1	/*
2	* ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
3	*
4	* Copyright (c) 1997-2020 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 "res.h"
56	#include "reslib.h"
57	#include "memory.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
98
99	/*
100	* rem_request - remove a request from the list.
101	* This must also free any memory that has been allocated for
102	* temporary storage of DNS results.
103	*/
104	static void
105	rem_request(struct reslist *request)
106	{
107	dlinkDelete(&request->node, &request_list);
108	xfree(request);
109	}
110
111	/*
112	* make_request - Create a DNS request record for the server.
113	*/
114	static struct reslist *
115	make_request(dns_callback_fnc callback, void *ctx)
116	{
117	struct reslist request = xcalloc(sizeof(request));
118
119	request->sentat = event_base->time.sec_monotonic;
120	request->retries = 2;
121	request->timeout = 4; /* Start at 4 and exponential inc. */
122	request->callback = callback;
123	request->callback_ctx = ctx;
124
125	dlinkAdd(request, &request->node, &request_list);
126	return request;
127	}
128
129	/*
130	* int
131	* res_ourserver(inp)
132	* looks up "inp" in irc_nsaddr_list[]
133	* returns:
134	* 0 : not found
135	* >0 : found
136	* author:
137	* paul vixie, 29may94
138	* revised for ircd, cryogen(stu) may03
139	*/
140	static bool
141	res_ourserver(const struct irc_ssaddr *inp)
142	{
143	for (unsigned int i = 0; i < irc_nscount; ++i)
144	if (address_compare(inp, &irc_nsaddr_list[i], true) == true)
145	return true;
146
147	return false;
148	}
149
150	/*
151	* start_resolver - do everything we need to read the resolv.conf file
152	* and initialize the resolver file descriptor if needed
153	*/
154	static void
155	start_resolver(void)
156	{
157	irc_res_init();
158
159	if (ResolverFileDescriptor == NULL)
160	{
161	int fd = comm_socket(irc_nsaddr_list[0].ss.ss_family, SOCK_DGRAM, 0);
162	if (fd == -1)
163	return;
164
165	ResolverFileDescriptor = fd_open(fd, true, "UDP resolver socket");
166
167	/* At the moment, the resolver FD data is global .. */
168	comm_setselect(ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
169	}
170	}
171
172	/*
173	* restart_resolver - reread resolv.conf, reopen socket
174	*/
175	void
176	restart_resolver(void)
177	{
178	if (ResolverFileDescriptor)
179	{
180	fd_close(ResolverFileDescriptor);
181	ResolverFileDescriptor = NULL;
182	}
183
184	start_resolver();
185	}
186
187	/*
188	* delete_resolver_queries - cleanup outstanding queries
189	* for which there no longer exist clients or conf lines.
190	*/
191	void
192	delete_resolver_queries(const void *vptr)
193	{
194	dlink_node node, node_next;
195
196	DLINK_FOREACH_SAFE(node, node_next, request_list.head)
197	{
198	struct reslist *request = node->data;
199
200	if (request->callback_ctx == vptr)
201	rem_request(request);
202	}
203	}
204
205	/*
206	* send_res_msg - sends msg to all nameservers found in the "_res" structure.
207	* This should reflect /etc/resolv.conf. We will get responses
208	* which arent needed but is easier than checking to see if nameserver
209	* isn't present. Returns number of messages successfully sent to
210	* nameservers or -1 if no successful sends.
211	*/
212	static void
213	send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
214	{
215	unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);
216
217	/* RES_PRIMARY option is not implemented
218	* if (res.options & RES_PRIMARY \|\| 0 == max_queries)
219	*/
220	if (max_queries == 0)
221	max_queries = 1;
222
223	for (unsigned int i = 0; i < max_queries; ++i)
224	sendto(ResolverFileDescriptor->fd, msg, len, 0,
225	(struct sockaddr *)&irc_nsaddr_list[i], irc_nsaddr_list[i].ss_len);
226	}
227
228	/*
229	* find_id - find a dns request id (id is determined by dn_mkquery)
230	*/
231	static struct reslist *
232	find_id(unsigned int id)
233	{
234	dlink_node *node;
235
236	DLINK_FOREACH(node, request_list.head)
237	{
238	struct reslist *request = node->data;
239
240	if (request->id == id)
241	return request;
242	}
243
244	return NULL;
245	}
246
247	/*
248	* query_name - generate a query based on class, type and name.
249	*/
250	static void
251	query_name(const char name, int query_class, int type, struct reslist request)
252	{
253	unsigned char buf[MAXPACKET];
254
255	memset(buf, 0, sizeof(buf));
256
257	int request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf));
258	if (request_len > 0)
259	{
260	HEADER header = (HEADER )buf;
261
262	/*
263	* Generate an unique id.
264	* NOTE: we don't have to worry about converting this to and from
265	* network byte order, the nameserver does not interpret this value
266	* and returns it unchanged.
267	*/
268	do
269	header->id = (header->id + genrand_int32()) & 0xFFFF;
270	while (find_id(header->id));
271
272	request->id = header->id;
273	++request->sends;
274
275	send_res_msg(buf, request_len, request->sends);
276	}
277	}
278
279	/*
280	* do_query_name - nameserver lookup name
281	*/
282	static void
283	do_query_name(dns_callback_fnc callback, void ctx, const char name,
284	struct reslist *request, int type)
285	{
286	char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];
287
288	strlcpy(host_name, name, sizeof(host_name));
289
290	if (request == NULL)
291	{
292	request = make_request(callback, ctx);
293	request->type = type;
294	request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
295	}
296
297	request->type = type;
298	query_name(host_name, C_IN, type, request);
299	}
300
301	/*
302	* do_query_number - Use this to do reverse IP# lookups.
303	*/
304	static void
305	do_query_number(dns_callback_fnc callback, void *ctx,
306	const struct irc_ssaddr *addr,
307	struct reslist *request)
308	{
309	char ipbuf[128] = "";
310
311	if (addr->ss.ss_family == AF_INET)
312	{
313	const struct sockaddr_in v4 = (const struct sockaddr_in )addr;
314	const unsigned char cp = (const unsigned char )&v4->sin_addr.s_addr;
315
316	snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
317	(unsigned int)(cp[3]), (unsigned int)(cp[2]),
318	(unsigned int)(cp[1]), (unsigned int)(cp[0]));
319	}
320	else if (addr->ss.ss_family == AF_INET6)
321	{
322	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )addr;
323	const unsigned char cp = (const unsigned char )&v6->sin6_addr.s6_addr;
324
325	snprintf(ipbuf, sizeof(ipbuf),
326	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
327	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
328	(unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
329	(unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
330	(unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
331	(unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
332	(unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
333	(unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
334	(unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
335	(unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
336	(unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
337	(unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
338	(unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
339	(unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
340	(unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
341	(unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
342	(unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
343	(unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
344	}
345
346	if (request == NULL)
347	{
348	request = make_request(callback, ctx);
349	request->type = T_PTR;
350	request->addr = *addr;
351	}
352
353	query_name(ipbuf, C_IN, T_PTR, request);
354	}
355
356	/*
357	* gethost_byname_type - get host address from name
358	*
359	*/
360	void
361	gethost_byname_type(dns_callback_fnc callback, void ctx, const char name, int type)
362	{
363	assert(name);
364	do_query_name(callback, ctx, name, NULL, type);
365	}
366
367	/*
368	* gethost_byaddr - get host name from address
369	*/
370	void
371	gethost_byaddr(dns_callback_fnc callback, void ctx, const struct irc_ssaddr addr)
372	{
373	do_query_number(callback, ctx, addr, NULL);
374	}
375
376	static void
377	resend_query(struct reslist *request)
378	{
379	switch (request->type)
380	{
381	case T_PTR:
382	do_query_number(NULL, NULL, &request->addr, request);
383	break;
384	case T_A:
385	case T_AAAA:
386	do_query_name(NULL, NULL, request->name, request, request->type);
387	break;
388	default:
389	break;
390	}
391	}
392
393	/*
394	* proc_answer - process name server reply
395	*/
396	static bool
397	proc_answer(struct reslist request, HEADER header, unsigned char buf, unsigned char eob)
398	{
399	char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
400	unsigned char current = buf + sizeof(HEADER); / current position in buf */
401	unsigned int type = 0; /* answer type */
402	unsigned int rd_length = 0;
403	struct sockaddr_in v4; / conversion */
404	struct sockaddr_in6 *v6;
405
406	for (; header->qdcount > 0; --header->qdcount)
407	{
408	int n = irc_dn_skipname(current, eob);
409	if (n < 0)
410	break;
411
412	current += (size_t)n + QFIXEDSZ;
413	}
414
415	/*
416	* Process each answer sent to us blech.
417	*/
418	while (header->ancount > 0 && current < eob)
419	{
420	--header->ancount;
421
422	int n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
423	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
424	return false;
425
426	hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';
427
428	/*
429	* With Address arithmetic you have to be very anal
430	* this code was not working on alpha due to that
431	* (spotted by rodder/jailbird/dianora)
432	*/
433	current += (size_t)n;
434
435	if (!((current + ANSWER_FIXED_SIZE) < eob))
436	break;
437
438	type = irc_ns_get16(current);
439	current += TYPE_SIZE;
440	current += CLASS_SIZE;
441	current += TTL_SIZE;
442	rd_length = irc_ns_get16(current);
443	current += RDLENGTH_SIZE;
444
445	/*
446	* Wait to set request->type until we verify this structure
447	*/
448	switch (type)
449	{
450	case T_A:
451	if (request->type != T_A)
452	return false;
453
454	/*
455	* Check for invalid rd_length or too many addresses
456	*/
457	if (rd_length != sizeof(struct in_addr))
458	return false;
459
460	request->addr.ss_len = sizeof(struct sockaddr_in);
461	v4 = (struct sockaddr_in *)&request->addr;
462	v4->sin_family = AF_INET;
463	memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
464	return true;
465	break;
466
467	case T_AAAA:
468	if (request->type != T_AAAA)
469	return false;
470
471	if (rd_length != sizeof(struct in6_addr))
472	return false;
473
474	request->addr.ss_len = sizeof(struct sockaddr_in6);
475	v6 = (struct sockaddr_in6 *)&request->addr;
476	v6->sin6_family = AF_INET6;
477	memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
478	return true;
479	break;
480
481	case T_PTR:
482	if (request->type != T_PTR)
483	return false;
484
485	n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
486	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
487	return false;
488
489	request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
490	return true;
491	break;
492
493	case T_CNAME:
494	current += rd_length;
495	break;
496
497	default:
498	return false;
499	break;
500	}
501	}
502
503	return false;
504	}
505
506	/*
507	* res_readreply - read a dns reply from the nameserver and process it.
508	*/
509	static void
510	res_readreply(fde_t F, void data)
511	{
512	unsigned char buf[sizeof(HEADER) + MAXPACKET];
513	ssize_t rc;
514	socklen_t len = sizeof(struct irc_ssaddr);
515	struct irc_ssaddr lsin;
516
517	while ((rc = recvfrom(F->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
518	{
519	if (rc <= (ssize_t)sizeof(HEADER))
520	continue;
521
522	/*
523	* Check against possibly fake replies
524	*/
525	if (res_ourserver(&lsin) == false)
526	continue;
527
528	/*
529	* Convert DNS reply reader from Network byte order to CPU byte order.
530	*/
531	HEADER header = (HEADER )buf;
532	header->ancount = ntohs(header->ancount);
533	header->qdcount = ntohs(header->qdcount);
534	header->nscount = ntohs(header->nscount);
535	header->arcount = ntohs(header->arcount);
536
537	/*
538	* Response for an id which we have already received an answer for
539	* just ignore this response.
540	*/
541	struct reslist *request = find_id(header->id);
542	if (request == NULL)
543	continue;
544
545	if (header->rcode != NO_ERRORS \|\| header->ancount == 0)
546	{
547	/*
548	* If a bad error was returned, stop here and don't send
549	* any more (no retries granted).
550	*/
551	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
552	rem_request(request);
553	continue;
554	}
555
556	/*
557	* If this fails there was an error decoding the received packet.
558	* We only give it one shot. If it fails, just leave the client
559	* unresolved.
560	*/
561	if (proc_answer(request, header, buf, buf + rc) == false)
562	{
563	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
564	rem_request(request);
565	continue;
566	}
567
568	if (request->type == T_PTR)
569	{
570	if (request->namelength == 0)
571	{
572	/*
573	* Got a PTR response with no name, something bogus is happening
574	* don't bother trying again, the client address doesn't resolve
575	*/
576	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
577	rem_request(request);
578	continue;
579	}
580
581	/*
582	* Lookup the 'authoritative' name that we were given for the ip#.
583	*/
584	if (request->addr.ss.ss_family == AF_INET6)
585	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
586	else
587	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
588
589	rem_request(request);
590	}
591	else
592	{
593	/*
594	* Got a name and address response, client resolved
595	*/
596	(*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
597	rem_request(request);
598	}
599
600	continue;
601	}
602
603	comm_setselect(F, COMM_SELECT_READ, res_readreply, NULL, 0);
604	}
605
606	/*
607	* timeout_query_list - Remove queries from the list which have been
608	* there too long without being resolved.
609	*/
610	static uintmax_t
611	timeout_query_list(void)
612	{
613	dlink_node node, node_next;
614	uintmax_t next_time = 0;
615
616	DLINK_FOREACH_SAFE(node, node_next, request_list.head)
617	{
618	struct reslist *request = node->data;
619	uintmax_t timeout = request->sentat + request->timeout;
620
621	if (event_base->time.sec_monotonic >= timeout)
622	{
623	if (--request->retries <= 0)
624	{
625	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
626	rem_request(request);
627	continue;
628	}
629	else
630	{
631	request->sentat = event_base->time.sec_monotonic;
632	request->timeout += request->timeout;
633	resend_query(request);
634	}
635	}
636
637	if (next_time == 0 \|\| timeout < next_time)
638	next_time = timeout;
639	}
640
641	return (next_time > event_base->time.sec_monotonic) ? next_time : (event_base->time.sec_monotonic + AR_TTL);
642	}
643
644	/*
645	* timeout_resolver - check request list
646	*/
647	static void
648	timeout_resolver(void *unused)
649	{
650	timeout_query_list();
651	}
652
653	/*
654	* resolver_init - initialize resolver and resolver library
655	*/
656	void
657	resolver_init(void)
658	{
659	static struct event event_timeout_resolver =
660	{
661	.name = "timeout_resolver",
662	.handler = timeout_resolver,
663	.when = 1
664	};
665
666	start_resolver();
667	event_add(&event_timeout_resolver, NULL);
668	}