gvpe/src/vpn_dns.C

/*
    vpn_dns.C -- handle the dns tunnel part of the protocol.
    Copyright (C) 2003-2004 Marc Lehmann <pcg@goof.com>
 
    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
*/

#include "config.h"

#if ENABLE_DNS

// dns processing is EXTREMELY ugly. For obvious(?) reasons.
// it's a hack, use only in emergency situations please.

#include <cstring>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sys/uio.h>
#include <errno.h>
#include <time.h>
#include <unistd.h>
#include <fcntl.h>

#include <map>

#include "netcompat.h"

#include "vpn.h"

#define MIN_RETRY 1.
#define MAX_RETRY 60.

#define MAX_OUTSTANDING 40 // max. outstanding requests
#define MAX_WINDOW      100 // max. for MAX_OUTSTANDING
#define MAX_RATE        1000 // requests/s
#define MAX_BACKLOG     (10*1024) // size of protocol backlog, must be > MAXSIZE

#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well
// 240 leaves about 4 bytes of server reply data
// every two request byte sless give room for one reply byte

// seqno has 12 bits, but the lower bit is always left as zero
// as bind caches ttl=0 records and we have to generate
// sequence numbers that always differ case-insensitively
#define SEQNO_MASK 0x07ff

/*

protocol, in shorthand :)

client -> server <req>  ANY?
server -> client <req>  TXT <rep>

<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]

if <client-id> is zero, the connection will be configured:

<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>

*/

#define MAX_LBL_SIZE 63
#define MAX_PKT_SIZE 512

#define RR_TYPE_TXT 16
#define RR_TYPE_ANY 255
#define RR_CLASS_IN 1

// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)
struct dns64
{
  static const char encode_chars[64 + 1];
  static s8 decode_chars[256];

  static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }
  static int decode_len (int bytes) { return (bytes * 6) / 8; }
  static int encode (char *dst, u8 *src, int len);
  static int decode (u8 *dst, char *src, int len);

  dns64 ();
} dns64;

// the following sequence has been crafted to
// a) look somewhat random
// b) the even (and odd) indices never share the same character as upper/lowercase
const char dns64::encode_chars[64 + 1] = "_-dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI";
s8 dns64::decode_chars[256];

dns64::dns64 ()
{
  for (int i = 0; i < 64; i++)
    decode_chars [encode_chars [i]] = i + 1;
}

int dns64::encode (char *dst, u8 *src, int len)
{
  // slow, but easy to debug
  char *beg = dst;
  unsigned int accum, bits = 0;

  while (len--)
    {
      accum <<= 8;
      accum  |= *src++;
      bits   += 8;

      while (bits >= 6)
        {
          *dst++ = encode_chars [(accum >> (bits - 6)) & 63];
          bits  -= 6;
        }
    }

  if (bits)
    *dst++ = encode_chars [(accum << (6 - bits)) & 63];

  return dst - beg;
}

int dns64::decode (u8 *dst, char *src, int len)
{
  // slow, but easy to debug
  u8 *beg = dst;
  unsigned int accum, bits = 0;

  while (len--)
    {
      s8 chr = decode_chars [(u8)*src++];

      if (!chr)
        continue;

      accum <<= 6;
      accum  |= chr - 1;
      bits   += 6;

      while (bits >= 8)
        {
          *dst++ = accum >> (bits - 8);
          bits  -= 8;
        }
    }

  return dst - beg;
}

/////////////////////////////////////////////////////////////////////////////

struct byte_stream
{
  u8 *data;
  int maxsize;
  int fill;

  byte_stream (int maxsize);
  ~byte_stream ();

  bool empty () { return !fill; }
  int size () { return fill; }

  bool put (u8 *data, unsigned int datalen);
  bool put (vpn_packet *pkt);
  vpn_packet *get ();

  u8 *begin () { return data; }
  void remove (int count);
};

byte_stream::byte_stream (int maxsize)
: maxsize (maxsize), fill (0)
{
  data = new u8 [maxsize];
}

byte_stream::~byte_stream ()
{
  delete data;
}

void byte_stream::remove (int count)
{
  if (count > fill)
    abort ();

  memmove (data, data + count, fill -= count);
}

bool byte_stream::put (u8 *data, unsigned int datalen)
{
  if (maxsize - fill < datalen)
    return false;

  memcpy (this->data + fill, data, datalen); fill += datalen;

  return true;
}

bool byte_stream::put (vpn_packet *pkt)
{
  if (maxsize - fill < pkt->len + 2)
    return false;

  data [fill++] = pkt->len >> 8;
  data [fill++] = pkt->len;

  memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len;

  return true;
}

vpn_packet *byte_stream::get ()
{
  int len = (data [0] << 8) | data [1];

  if (len > MAXSIZE && fill >= 2)
    abort (); // TODO handle this gracefully, connection reset

  if (fill < len + 2)
    return 0;

  vpn_packet *pkt = new vpn_packet;

  pkt->len = len;
  memcpy (&((*pkt)[0]), data + 2, len);
  remove (len + 2);

  return pkt;
}

/////////////////////////////////////////////////////////////////////////////

#define FLAG_QUERY    ( 0 << 15)
#define FLAG_RESPONSE ( 1 << 15)
#define FLAG_OP_MASK  (15 << 14)
#define FLAG_OP_QUERY ( 0 << 11)
#define FLAG_AA       ( 1 << 10)
#define FLAG_TC       ( 1 <<  9)
#define FLAG_RD       ( 1 <<  8)
#define FLAG_RA       ( 1 <<  7)
#define FLAG_AUTH     ( 1 <<  5)
#define FLAG_RCODE_MASK     (15 << 0)
#define FLAG_RCODE_OK       ( 0 << 0)
#define FLAG_RCODE_FORMERR  ( 1 << 0)
#define FLAG_RCODE_SERVFAIL ( 2 << 0)
#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
#define FLAG_RCODE_REFUSED  ( 5 << 0)

#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)
#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)

struct dns_packet : net_packet
{
  u16 id;
  u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
  u16 qdcount, ancount, nscount, arcount;

  u8 data[MAXSIZE - 6 * 2];

  int decode_label (char *data, int size, int &offs);
};

int dns_packet::decode_label (char *data, int size, int &offs)
{
  char *orig = data;

  memset (data, 0, size);

  while (offs < size - 1)
    {
      u8 len = (*this)[offs++];

      if (!len)
        break;
      else if (len < 64)
        {
          if (size < len + 1 || offs + len >= MAXSIZE - 1)
            break;

          memcpy (data, &((*this)[offs]), len);

          data += len; size -= len; offs += len;
          *data++ = '.'; size--;
        }
      else
        {
          int offs2 = ((len & 63) << 8) + (*this)[offs++];

          data += decode_label (data, size, offs2);
          break;
        }
    }

  return data - orig;
}

/////////////////////////////////////////////////////////////////////////////

struct dns_req
{
  dns_packet *pkt;
  tstamp next;
  int retry;
  connection *conn;
  int seqno;

  dns_req (connection *c);
  void gen_stream_req (int seqno, byte_stream *stream);
};

static u16 dns_id = 12098; // TODO: should be per-vpn

static u16 next_id ()
{
  // the simplest lsfr with periodicity 65535 i could find
  dns_id = (dns_id << 1)
           | (((dns_id >> 1)
               ^ (dns_id >> 2)
               ^ (dns_id >> 4)
               ^ (dns_id >> 15)) & 1);

  return dns_id;
}

dns_req::dns_req (connection *c)
: conn (c)
{
  next = 0;
  retry = 0;

  pkt = new dns_packet;

  pkt->id = next_id ();
}

void dns_req::gen_stream_req (int seqno, byte_stream *stream)
{
  this->seqno = seqno;

  pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
  pkt->qdcount = htons (1);

  int offs = 6*2;
  int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2;
  // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
  // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra

  u8 data[256]; //TODO

  data[0] = THISNODE->id; //TODO
  data[1] = seqno >> 7; //TODO
  data[2] = seqno << 1; //TODO

  int datalen = dns64::decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE) - 3;

  if (datalen > stream->size ())
    datalen = stream->size ();

  char enc[256], *encp = enc;
  
  memcpy (data + 3, stream->begin (), datalen);
  int enclen = dns64::encode (enc, data, datalen + 3);
  stream->remove (datalen);

  while (enclen)
    {
      int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;

      (*pkt)[offs++] = lbllen;
      memcpy (pkt->at (offs), encp, lbllen);

      offs += lbllen;
      encp += lbllen;

      enclen -= lbllen;
    }

  const char *suffix = THISNODE->domain;

  // add tunnel domain
  for (;;)
    {
      const char *end = strchr (suffix, '.');

      if (!end)
        end = suffix + strlen (suffix);

      int len = end - suffix;

      (*pkt)[offs++] = len;
      memcpy (&((*pkt)[offs]), suffix, len);
      offs += len;

      if (!*end)
        break;

      suffix = end + 1;
    }

  (*pkt)[offs++] = 0;
  (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
  (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;

  pkt->len = offs;
}

struct dns_rcv
{
  int seqno;
  dns_packet *pkt; // reply packet
  u8 data [MAXSIZE]; // actually part of the reply packet...
  int datalen;

  dns_rcv (int seqno, u8 *data, int datalen);
  ~dns_rcv ();
};

dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
: seqno (seqno), pkt (new dns_packet), datalen (datalen)
{
  memcpy (this->data, data, datalen);
}

dns_rcv::~dns_rcv ()
{
  delete pkt;
}

/////////////////////////////////////////////////////////////////////////////

struct dns_cfg
{
  u8 id1, id2, id3;
  u8 def_ttl;
  u8 unused1;
  u16 max_size;
  u8 flags1, flags2;
};

void connection::dnsv4_receive_rep (struct dns_rcv *r)
{
  dns_rcvpq.push_back (r);

  redo:

  for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin ();
       i != dns_rcvpq.end ();
       ++i)
    if (dns_rcvseq == (*i)->seqno)
      {
        dns_rcv *r = *i;

        dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK;

        if (!dns_snddq && !dns_rcvdq)
          {
            dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
            dns_snddq = new byte_stream (MAX_BACKLOG);

            dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
          }

        if (!dns_rcvdq->put (r->data, r->datalen))
          abort (); // MUST never overflow, can be caused by data corruption, TODO

        while (vpn_packet *pkt = dns_rcvdq->get ())
          {
            sockinfo si;
            si.host = 0; si.port = 0; si.prot = PROT_DNSv4;

            vpn->recv_vpn_packet (pkt, si);
          }
      }
    else if ((u32)(*i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW * 2)
      {
       //D
       //abort();
       printf ("%d erasing %d (%d)\n", THISNODE->id, (u32)(*i)->seqno, dns_rcvseq);
        dns_rcvpq.erase (i);
        goto redo;
      }
}

dns_packet *
vpn::dnsv4_server (dns_packet *pkt)
{
  u16 flags = ntohs (pkt->flags);

  //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len);
  int offs = 6 * 2; // skip header

  pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);

  if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC))
      && pkt->qdcount == htons (1))
    {
      char qname[MAXSIZE];
      int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);

      u16 qtype  = (*pkt) [offs++] << 8; qtype  |= (*pkt) [offs++];
      u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++];

      pkt->qdcount = htons (1);
      pkt->ancount = 0;
      pkt->nscount = 0; // should be self, as other nameservers reply like this
      pkt->arcount = 0; // a record for self, as other nameservers reply like this

      pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN);

      int dlen = strlen (THISNODE->domain);

      if (qclass == RR_CLASS_IN
          && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
          && qlen > dlen + 1
          && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))
        {
          // correct class, domain: parse
          u8 data[MAXSIZE];
          int datalen = dns64::decode (data, qname, qlen - dlen - 1);

          int client = data[0];
          int seqno  = ((data[1] << 7) | (data[2] >> 1)) & SEQNO_MASK;

          if (0 < client && client <= conns.size ())
            {
              connection *c = conns [client - 1];

              redo:

              for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
                   i != c->dns_rcvpq.end ();
                   ++i)
                if ((*i)->seqno == seqno)
                  {
                    // already seen that request: simply reply with the cached reply
                    dns_rcv *r = *i;

                    printf ("DUPLICATE %d\n", htons (r->pkt->id));//D

                    offs = r->pkt->len;
                    memcpy (pkt->at (0), r->pkt->at (0), offs);
                    goto duplicate_request;
                  }

              // new packet, queue
              dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3);
              c->dnsv4_receive_rep (rcv);

              // now generate reply
              pkt->ancount = htons (1); // one answer RR
              pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);

              (*pkt) [offs++] = 0xc0;
              (*pkt) [offs++] = 6 * 2; // same as in query section

              (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT;
              (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN;

              (*pkt) [offs++] = 0; (*pkt) [offs++] = 0;
              (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL

              int dlen = MAX_PKT_SIZE - offs - 2;

              // bind doesn't compress well, so reduce further by one label length
              dlen -= qlen;

              int rdlen_offs = offs += 2;

              while (c->dns_snddq
                     && !c->dns_snddq->empty ()
                     && dlen > 1)
                {
                  int txtlen = dlen <= 255 ? dlen - 1 : 255;

                  if (txtlen > c->dns_snddq->size ())
                    txtlen = c->dns_snddq->size ();

                  (*pkt)[offs++] = txtlen;
                  memcpy (pkt->at (offs), c->dns_snddq->begin (), txtlen);
                  offs += txtlen;
                  c->dns_snddq->remove (txtlen);

                  dlen -= txtlen + 1;
                }

              // avoid empty TXT rdata
              if (offs == rdlen_offs)
                (*pkt)[offs++] = 0;

              int rdlen = offs - rdlen_offs;

              (*pkt) [rdlen_offs - 2] = rdlen >> 8;
              (*pkt) [rdlen_offs - 1] = rdlen;

              // now update dns_rcv copy
              rcv->pkt->len = offs;
              memcpy (rcv->pkt->at (0), pkt->at (0), offs);

              duplicate_request: ;
            }
          else
            pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
        }

      pkt->len = offs;
    }

  return pkt;
}

void
vpn::dnsv4_client (dns_packet *pkt)
{
  u16 flags = ntohs (pkt->flags);
  int offs = 6 * 2; // skip header

  pkt->qdcount = ntohs (pkt->qdcount);
  pkt->ancount = ntohs (pkt->ancount);

  // go through our request list and find the corresponding request
  for (vector<dns_req *>::iterator i = dns_sndpq.begin ();
       i != dns_sndpq.end ();
       ++i)
    if ((*i)->pkt->id == pkt->id)
      {
        connection *c = (*i)->conn;
        int seqno = (*i)->seqno;
        u8 data[MAXSIZE], *datap = data;

        delete *i;
        dns_sndpq.erase (i);

        if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC))
          {
            char qname[MAXSIZE];

            while (pkt->qdcount-- && offs < MAXSIZE - 4)
              {
                int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
                offs += 4; // skip qtype, qclass
              }

            while (pkt->ancount-- && offs < MAXSIZE - 10)
              {
                pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);

                u16 qtype  = (*pkt) [offs++] << 8; qtype  |= (*pkt) [offs++];
                u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++];
                u32 ttl  = (*pkt) [offs++] << 24;
                    ttl |= (*pkt) [offs++] << 16;
                    ttl |= (*pkt) [offs++] <<  8;
                    ttl |= (*pkt) [offs++];

                u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++];

                if (rdlen <= MAXSIZE - offs)
                  {
                    // decode bytes, finally

                    while (rdlen)
                      {
                        int txtlen = (*pkt) [offs++];

                        assert (txtlen + offs < MAXSIZE - 1);

                        memcpy (datap, pkt->at (offs), txtlen);
                        datap += txtlen; offs += txtlen;

                        rdlen -= txtlen + 1;
                      }

                  }

              }
          }

        // todo: pkt now used
        c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data));

        break;
      }

  delete pkt;
}

void
vpn::dnsv4_ev (io_watcher &w, short revents)
{
  if (revents & EVENT_READ)
    {
      dns_packet *pkt = new dns_packet;
      struct sockaddr_in sa;
      socklen_t sa_len = sizeof (sa);

      pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);

      if (pkt->len > 0)
        {
          if (pkt->flags & htons (FLAG_TC))
            {
              slog (L_WARN, _("DNS request/response truncated, check protocol settings."));
              //TODO connection reset
            }

          if (THISNODE->dns_port)
            {
              pkt = dnsv4_server (pkt);
              sendto (w.fd, &((*pkt)[0]), pkt->len, 0, (sockaddr *)&sa, sa_len);
            }
          else
            dnsv4_client (pkt);
        }
    }
}

bool
connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
{
  // never initialized
  if (!dns_snddq && !dns_rcvdq)
    {
      dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
      dns_snddq = new byte_stream (MAX_BACKLOG);

      //dns_rcvseq = dns_sndseq = 0;

      dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
    }
  
  if (!dns_snddq->put (pkt))
    return false;

  // start timer if neccessary
  if (!THISNODE->dns_port && !dnsv4_tw.active)
    dnsv4_cb (dnsv4_tw);

  return true;
}

void
connection::dnsv4_cb (time_watcher &w)
{
  // check for timeouts and (re)transmit
  tstamp next = NOW + 60;
  dns_req *send = 0;
  
  for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin ();
       i != vpn->dns_sndpq.end ();
       ++i)
    {
      dns_req *r = *i;

      if (r->next <= NOW)
        {
          if (!send)
            {
              send = r;

              if (r->retry)//D
                printf ("req %d, retry %d\n", r->pkt->id, r->retry);
              r->retry++;
              r->next = NOW + r->retry;
            }
        }

      if (r->next < next)
        next = r->next;
    }

  if (!send
      && vpn->dns_sndpq.size () < MAX_OUTSTANDING)
    {
      send = new dns_req (this);
      send->gen_stream_req (dns_sndseq, dns_snddq);
      vpn->dns_sndpq.push_back (send);

      dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
    }

  tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);

  if (send)
    {
      dns_packet *pkt = send->pkt;

      next = min_next;

      sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ());
    }
  else if (next < min_next)
    next = min_next;

  w.start (next);
}

#endif

Revision:	1.6
Committed:	Thu Mar 3 08:38:32 2005 UTC (19 years, 2 months ago) by pcg
Content type:	text/plain
Branch:	MAIN
Changes since 1.5:	+32 -26 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	pcg	1.1	/*
2			vpn_dns.C -- handle the dns tunnel part of the protocol.
3			Copyright (C) 2003-2004 Marc Lehmann <pcg@goof.com>
4
5			This program is free software; you can redistribute it and/or modify
6			it under the terms of the GNU General Public License as published by
7			the Free Software Foundation; either version 2 of the License, or
8			(at your option) any later version.
9
10			This program is distributed in the hope that it will be useful,
11			but WITHOUT ANY WARRANTY; without even the implied warranty of
12			MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13			GNU General Public License for more details.
14
15			You should have received a copy of the GNU General Public License
16			along with this program; if not, write to the Free Software
17			Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18			*/
19
20			#include "config.h"
21
22			#if ENABLE_DNS
23
24			// dns processing is EXTREMELY ugly. For obvious(?) reasons.
25			// it's a hack, use only in emergency situations please.
26
27			#include <cstring>
28
29			#include <sys/types.h>
30			#include <sys/socket.h>
31			#include <sys/wait.h>
32			#include <sys/uio.h>
33			#include <errno.h>
34			#include <time.h>
35			#include <unistd.h>
36			#include <fcntl.h>
37
38			#include <map>
39
40			#include "netcompat.h"
41
42			#include "vpn.h"
43
44			#define MIN_RETRY 1.
45			#define MAX_RETRY 60.
46
47	pcg	1.5	#define MAX_OUTSTANDING 40 // max. outstanding requests
48	pcg	1.4	#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING
49	pcg	1.5	#define MAX_RATE 1000 // requests/s
50			#define MAX_BACKLOG (10*1024) // size of protocol backlog, must be > MAXSIZE
51
52			#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well
53			// 240 leaves about 4 bytes of server reply data
54			// every two request byte sless give room for one reply byte
55
56	pcg	1.6	// seqno has 12 bits, but the lower bit is always left as zero
57			// as bind caches ttl=0 records and we have to generate
58			// sequence numbers that always differ case-insensitively
59			#define SEQNO_MASK 0x07ff
60	pcg	1.1
61			/*
62
63			protocol, in shorthand :)
64
65	pcg	1.2	client -> server <req> ANY?
66			server -> client <req> TXT <rep>
67	pcg	1.1
68	pcg	1.2	<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
69			<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
70
71			if <client-id> is zero, the connection will be configured:
72
73			<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
74	pcg	1.1
75			*/
76
77	pcg	1.2	#define MAX_LBL_SIZE 63
78			#define MAX_PKT_SIZE 512
79
80			#define RR_TYPE_TXT 16
81			#define RR_TYPE_ANY 255
82			#define RR_CLASS_IN 1
83
84			// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)
85			struct dns64
86			{
87			static const char encode_chars[64 + 1];
88			static s8 decode_chars[256];
89
90			static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }
91			static int decode_len (int bytes) { return (bytes * 6) / 8; }
92	pcg	1.4	static int encode (char dst, u8 src, int len);
93			static int decode (u8 dst, char src, int len);
94	pcg	1.2
95			dns64 ();
96			} dns64;
97
98	pcg	1.6	// the following sequence has been crafted to
99			// a) look somewhat random
100			// b) the even (and odd) indices never share the same character as upper/lowercase
101			const char dns64::encode_chars[64 + 1] = "_-dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI";
102	pcg	1.2	s8 dns64::decode_chars[256];
103
104			dns64::dns64 ()
105			{
106			for (int i = 0; i < 64; i++)
107			decode_chars [encode_chars [i]] = i + 1;
108			}
109
110	pcg	1.4	int dns64::encode (char dst, u8 src, int len)
111	pcg	1.2	{
112			// slow, but easy to debug
113	pcg	1.4	char *beg = dst;
114	pcg	1.2	unsigned int accum, bits = 0;
115
116			while (len--)
117			{
118			accum <<= 8;
119			accum \|= *src++;
120			bits += 8;
121
122			while (bits >= 6)
123			{
124			*dst++ = encode_chars [(accum >> (bits - 6)) & 63];
125			bits -= 6;
126			}
127			}
128
129			if (bits)
130			*dst++ = encode_chars [(accum << (6 - bits)) & 63];
131	pcg	1.4
132			return dst - beg;
133	pcg	1.2	}
134
135	pcg	1.4	int dns64::decode (u8 dst, char src, int len)
136	pcg	1.2	{
137			// slow, but easy to debug
138	pcg	1.4	u8 *beg = dst;
139	pcg	1.2	unsigned int accum, bits = 0;
140
141			while (len--)
142			{
143			s8 chr = decode_chars [(u8)*src++];
144
145			if (!chr)
146	pcg	1.5	continue;
147	pcg	1.2
148			accum <<= 6;
149			accum \|= chr - 1;
150			bits += 6;
151
152			while (bits >= 8)
153			{
154			*dst++ = accum >> (bits - 8);
155			bits -= 8;
156			}
157			}
158	pcg	1.4
159			return dst - beg;
160			}
161
162			/////////////////////////////////////////////////////////////////////////////
163
164			struct byte_stream
165			{
166			u8 *data;
167			int maxsize;
168			int fill;
169
170			byte_stream (int maxsize);
171			~byte_stream ();
172
173			bool empty () { return !fill; }
174			int size () { return fill; }
175
176	pcg	1.5	bool put (u8 *data, unsigned int datalen);
177	pcg	1.4	bool put (vpn_packet *pkt);
178			vpn_packet *get ();
179
180			u8 *begin () { return data; }
181			void remove (int count);
182			};
183
184			byte_stream::byte_stream (int maxsize)
185			: maxsize (maxsize), fill (0)
186			{
187			data = new u8 [maxsize];
188			}
189
190			byte_stream::~byte_stream ()
191			{
192			delete data;
193			}
194
195			void byte_stream::remove (int count)
196			{
197			if (count > fill)
198			abort ();
199
200			memmove (data, data + count, fill -= count);
201			}
202
203	pcg	1.5	bool byte_stream::put (u8 *data, unsigned int datalen)
204			{
205			if (maxsize - fill < datalen)
206			return false;
207
208			memcpy (this->data + fill, data, datalen); fill += datalen;
209
210			return true;
211			}
212
213	pcg	1.4	bool byte_stream::put (vpn_packet *pkt)
214			{
215			if (maxsize - fill < pkt->len + 2)
216			return false;
217
218			data [fill++] = pkt->len >> 8;
219			data [fill++] = pkt->len;
220
221			memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len;
222
223			return true;
224			}
225
226			vpn_packet *byte_stream::get ()
227			{
228			int len = (data [0] << 8) \| data [1];
229
230	pcg	1.5	if (len > MAXSIZE && fill >= 2)
231			abort (); // TODO handle this gracefully, connection reset
232
233	pcg	1.4	if (fill < len + 2)
234			return 0;
235
236			vpn_packet *pkt = new vpn_packet;
237	pcg	1.5
238			pkt->len = len;
239	pcg	1.4	memcpy (&((*pkt)[0]), data + 2, len);
240			remove (len + 2);
241
242			return pkt;
243	pcg	1.2	}
244
245	pcg	1.3	/////////////////////////////////////////////////////////////////////////////
246
247	pcg	1.2	#define FLAG_QUERY ( 0 << 15)
248			#define FLAG_RESPONSE ( 1 << 15)
249			#define FLAG_OP_MASK (15 << 14)
250			#define FLAG_OP_QUERY ( 0 << 11)
251			#define FLAG_AA ( 1 << 10)
252			#define FLAG_TC ( 1 << 9)
253			#define FLAG_RD ( 1 << 8)
254			#define FLAG_RA ( 1 << 7)
255	pcg	1.5	#define FLAG_AUTH ( 1 << 5)
256	pcg	1.2	#define FLAG_RCODE_MASK (15 << 0)
257			#define FLAG_RCODE_OK ( 0 << 0)
258			#define FLAG_RCODE_FORMERR ( 1 << 0)
259			#define FLAG_RCODE_SERVFAIL ( 2 << 0)
260			#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
261			#define FLAG_RCODE_REFUSED ( 5 << 0)
262
263			#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY \| FLAG_OP_QUERY \| FLAG_RD)
264	pcg	1.5	#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE \| FLAG_OP_QUERY \| FLAG_AA \| FLAG_RD \| FLAG_RA)
265	pcg	1.2
266			struct dns_packet : net_packet
267			{
268			u16 id;
269			u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
270			u16 qdcount, ancount, nscount, arcount;
271
272			u8 data[MAXSIZE - 6 * 2];
273
274			int decode_label (char *data, int size, int &offs);
275			};
276
277			int dns_packet::decode_label (char *data, int size, int &offs)
278			{
279			char *orig = data;
280
281			memset (data, 0, size);
282
283			while (offs < size - 1)
284			{
285			u8 len = (*this)[offs++];
286
287			if (!len)
288			break;
289			else if (len < 64)
290			{
291			if (size < len + 1 \|\| offs + len >= MAXSIZE - 1)
292			break;
293
294			memcpy (data, &((*this)[offs]), len);
295
296			data += len; size -= len; offs += len;
297			*data++ = '.'; size--;
298			}
299			else
300			{
301			int offs2 = ((len & 63) << 8) + (*this)[offs++];
302
303			data += decode_label (data, size, offs2);
304			break;
305			}
306			}
307
308			return data - orig;
309			}
310
311	pcg	1.3	/////////////////////////////////////////////////////////////////////////////
312
313			struct dns_req
314			{
315			dns_packet *pkt;
316			tstamp next;
317			int retry;
318	pcg	1.4	connection *conn;
319	pcg	1.5	int seqno;
320	pcg	1.3
321	pcg	1.5	dns_req (connection *c);
322			void gen_stream_req (int seqno, byte_stream *stream);
323	pcg	1.3	};
324
325	pcg	1.5	static u16 dns_id = 12098; // TODO: should be per-vpn
326
327			static u16 next_id ()
328	pcg	1.3	{
329	pcg	1.5	// the simplest lsfr with periodicity 65535 i could find
330			dns_id = (dns_id << 1)
331			\| (((dns_id >> 1)
332			^ (dns_id >> 2)
333			^ (dns_id >> 4)
334			^ (dns_id >> 15)) & 1);
335	pcg	1.3
336	pcg	1.5	return dns_id;
337			}
338	pcg	1.3
339	pcg	1.5	dns_req::dns_req (connection *c)
340	pcg	1.4	: conn (c)
341	pcg	1.3	{
342			next = 0;
343			retry = 0;
344
345			pkt = new dns_packet;
346
347	pcg	1.5	pkt->id = next_id ();
348			}
349
350			void dns_req::gen_stream_req (int seqno, byte_stream *stream)
351			{
352			this->seqno = seqno;
353
354			pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
355	pcg	1.4	pkt->qdcount = htons (1);
356	pcg	1.3
357	pcg	1.4	int offs = 6*2;
358	pcg	1.5	int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2;
359			// MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
360			// so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
361
362			u8 data[256]; //TODO
363	pcg	1.4
364	pcg	1.5	data[0] = THISNODE->id; //TODO
365	pcg	1.6	data[1] = seqno >> 7; //TODO
366			data[2] = seqno << 1; //TODO
367	pcg	1.4
368	pcg	1.5	int datalen = dns64::decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE) - 3;
369	pcg	1.4
370	pcg	1.5	if (datalen > stream->size ())
371			datalen = stream->size ();
372	pcg	1.4
373	pcg	1.5	char enc[256], *encp = enc;
374
375			memcpy (data + 3, stream->begin (), datalen);
376			int enclen = dns64::encode (enc, data, datalen + 3);
377			stream->remove (datalen);
378	pcg	1.4
379	pcg	1.5	while (enclen)
380			{
381			int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
382
383			(*pkt)[offs++] = lbllen;
384			memcpy (pkt->at (offs), encp, lbllen);
385	pcg	1.4
386	pcg	1.5	offs += lbllen;
387			encp += lbllen;
388	pcg	1.4
389	pcg	1.5	enclen -= lbllen;
390	pcg	1.4	}
391
392			const char *suffix = THISNODE->domain;
393	pcg	1.3
394	pcg	1.4	// add tunnel domain
395			for (;;)
396			{
397			const char *end = strchr (suffix, '.');
398
399			if (!end)
400			end = suffix + strlen (suffix);
401
402			int len = end - suffix;
403
404			(*pkt)[offs++] = len;
405			memcpy (&((*pkt)[offs]), suffix, len);
406			offs += len;
407
408			if (!*end)
409			break;
410
411			suffix = end + 1;
412			}
413
414			(*pkt)[offs++] = 0;
415			(pkt)[offs++] = RR_TYPE_ANY >> 8; (pkt)[offs++] = RR_TYPE_ANY;
416			(pkt)[offs++] = RR_CLASS_IN >> 8; (pkt)[offs++] = RR_CLASS_IN;
417
418			pkt->len = offs;
419	pcg	1.5	}
420
421			struct dns_rcv
422			{
423			int seqno;
424			dns_packet *pkt; // reply packet
425			u8 data [MAXSIZE]; // actually part of the reply packet...
426			int datalen;
427
428	pcg	1.6	dns_rcv (int seqno, u8 *data, int datalen);
429	pcg	1.5	~dns_rcv ();
430			};
431
432	pcg	1.6	dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
433	pcg	1.5	: seqno (seqno), pkt (new dns_packet), datalen (datalen)
434			{
435			memcpy (this->data, data, datalen);
436			}
437	pcg	1.4
438	pcg	1.5	dns_rcv::~dns_rcv ()
439			{
440			delete pkt;
441	pcg	1.3	}
442
443			/////////////////////////////////////////////////////////////////////////////
444
445	pcg	1.2	struct dns_cfg
446			{
447			u8 id1, id2, id3;
448			u8 def_ttl;
449			u8 unused1;
450			u16 max_size;
451			u8 flags1, flags2;
452			};
453
454	pcg	1.5	void connection::dnsv4_receive_rep (struct dns_rcv *r)
455			{
456			dns_rcvpq.push_back (r);
457
458			redo:
459
460			for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin ();
461			i != dns_rcvpq.end ();
462			++i)
463			if (dns_rcvseq == (*i)->seqno)
464			{
465			dns_rcv r = i;
466
467			dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK;
468
469			if (!dns_snddq && !dns_rcvdq)
470			{
471			dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
472			dns_snddq = new byte_stream (MAX_BACKLOG);
473
474			dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
475			}
476
477			if (!dns_rcvdq->put (r->data, r->datalen))
478			abort (); // MUST never overflow, can be caused by data corruption, TODO
479
480			while (vpn_packet *pkt = dns_rcvdq->get ())
481			{
482			sockinfo si;
483			si.host = 0; si.port = 0; si.prot = PROT_DNSv4;
484
485			vpn->recv_vpn_packet (pkt, si);
486			}
487			}
488	pcg	1.6	else if ((u32)(i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW 2)
489	pcg	1.5	{
490	pcg	1.6	//D
491			//abort();
492			printf ("%d erasing %d (%d)\n", THISNODE->id, (u32)(*i)->seqno, dns_rcvseq);
493	pcg	1.5	dns_rcvpq.erase (i);
494			goto redo;
495			}
496			}
497
498	pcg	1.4	dns_packet *
499			vpn::dnsv4_server (dns_packet *pkt)
500	pcg	1.2	{
501	pcg	1.4	u16 flags = ntohs (pkt->flags);
502	pcg	1.2
503	pcg	1.4	//memcpy (&((rep)[0]), &((pkt)[0]), pkt->len);
504			int offs = 6 * 2; // skip header
505	pcg	1.2
506	pcg	1.4	pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_FORMERR);
507	pcg	1.2
508	pcg	1.4	if (!(flags & (FLAG_RESPONSE \| FLAG_OP_MASK \| FLAG_TC))
509			&& pkt->qdcount == htons (1))
510			{
511			char qname[MAXSIZE];
512			int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
513
514			u16 qtype = (pkt) [offs++] << 8; qtype \|= (pkt) [offs++];
515			u16 qclass = (pkt) [offs++] << 8; qclass \|= (pkt) [offs++];
516	pcg	1.2
517	pcg	1.4	pkt->qdcount = htons (1);
518			pkt->ancount = 0;
519			pkt->nscount = 0; // should be self, as other nameservers reply like this
520			pkt->arcount = 0; // a record for self, as other nameservers reply like this
521	pcg	1.2
522	pcg	1.4	pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_NXDOMAIN);
523	pcg	1.2
524	pcg	1.4	int dlen = strlen (THISNODE->domain);
525	pcg	1.2
526	pcg	1.4	if (qclass == RR_CLASS_IN
527			&& (qtype == RR_TYPE_ANY \|\| qtype == RR_TYPE_TXT)
528			&& qlen > dlen + 1
529			&& !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))
530	pcg	1.2	{
531	pcg	1.5	// correct class, domain: parse
532	pcg	1.4	u8 data[MAXSIZE];
533			int datalen = dns64::decode (data, qname, qlen - dlen - 1);
534	pcg	1.2
535	pcg	1.5	int client = data[0];
536	pcg	1.6	int seqno = ((data[1] << 7) \| (data[2] >> 1)) & SEQNO_MASK;
537	pcg	1.2
538	pcg	1.5	if (0 < client && client <= conns.size ())
539			{
540			connection *c = conns [client - 1];
541
542	pcg	1.6	redo:
543
544	pcg	1.5	for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
545			i != c->dns_rcvpq.end ();
546			++i)
547			if ((*i)->seqno == seqno)
548			{
549	pcg	1.6	// already seen that request: simply reply with the cached reply
550	pcg	1.5	dns_rcv r = i;
551	pcg	1.4
552	pcg	1.6	printf ("DUPLICATE %d\n", htons (r->pkt->id));//D
553
554	pcg	1.5	offs = r->pkt->len;
555			memcpy (pkt->at (0), r->pkt->at (0), offs);
556			goto duplicate_request;
557			}
558	pcg	1.4
559	pcg	1.5	// new packet, queue
560	pcg	1.6	dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3);
561			c->dnsv4_receive_rep (rcv);
562	pcg	1.4
563	pcg	1.5	// now generate reply
564			pkt->ancount = htons (1); // one answer RR
565			pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_OK);
566	pcg	1.4
567	pcg	1.5	(*pkt) [offs++] = 0xc0;
568			(pkt) [offs++] = 6 2; // same as in query section
569	pcg	1.4
570	pcg	1.5	(pkt) [offs++] = RR_TYPE_TXT >> 8; (pkt) [offs++] = RR_TYPE_TXT;
571			(pkt) [offs++] = RR_CLASS_IN >> 8; (pkt) [offs++] = RR_CLASS_IN;
572	pcg	1.2
573	pcg	1.5	(pkt) [offs++] = 0; (pkt) [offs++] = 0;
574			(pkt) [offs++] = 0; (pkt) [offs++] = 0; // TTL
575	pcg	1.2
576	pcg	1.5	int dlen = MAX_PKT_SIZE - offs - 2;
577	pcg	1.2
578	pcg	1.5	// bind doesn't compress well, so reduce further by one label length
579			dlen -= qlen;
580	pcg	1.2
581	pcg	1.5	int rdlen_offs = offs += 2;
582	pcg	1.2
583	pcg	1.5	while (c->dns_snddq
584			&& !c->dns_snddq->empty ()
585			&& dlen > 1)
586			{
587			int txtlen = dlen <= 255 ? dlen - 1 : 255;
588	pcg	1.2
589	pcg	1.5	if (txtlen > c->dns_snddq->size ())
590			txtlen = c->dns_snddq->size ();
591	pcg	1.2
592	pcg	1.5	(*pkt)[offs++] = txtlen;
593			memcpy (pkt->at (offs), c->dns_snddq->begin (), txtlen);
594			offs += txtlen;
595			c->dns_snddq->remove (txtlen);
596	pcg	1.2
597	pcg	1.5	dlen -= txtlen + 1;
598			}
599	pcg	1.2
600	pcg	1.5	// avoid empty TXT rdata
601			if (offs == rdlen_offs)
602			(*pkt)[offs++] = 0;
603	pcg	1.2
604	pcg	1.5	int rdlen = offs - rdlen_offs;
605	pcg	1.2
606	pcg	1.5	(*pkt) [rdlen_offs - 2] = rdlen >> 8;
607			(*pkt) [rdlen_offs - 1] = rdlen;
608	pcg	1.4
609	pcg	1.6	// now update dns_rcv copy
610			rcv->pkt->len = offs;
611			memcpy (rcv->pkt->at (0), pkt->at (0), offs);
612
613	pcg	1.5	duplicate_request: ;
614			}
615			else
616			pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_FORMERR);
617	pcg	1.2	}
618	pcg	1.6
619			pkt->len = offs;
620	pcg	1.4	}
621
622			return pkt;
623			}
624
625			void
626			vpn::dnsv4_client (dns_packet *pkt)
627			{
628			u16 flags = ntohs (pkt->flags);
629			int offs = 6 * 2; // skip header
630
631			pkt->qdcount = ntohs (pkt->qdcount);
632			pkt->ancount = ntohs (pkt->ancount);
633
634	pcg	1.5	// go through our request list and find the corresponding request
635	pcg	1.4	for (vector<dns_req *>::iterator i = dns_sndpq.begin ();
636			i != dns_sndpq.end ();
637			++i)
638			if ((*i)->pkt->id == pkt->id)
639			{
640			connection c = (i)->conn;
641	pcg	1.5	int seqno = (*i)->seqno;
642			u8 data[MAXSIZE], *datap = data;
643
644	pcg	1.4	delete *i;
645			dns_sndpq.erase (i);
646
647			if (flags & (FLAG_RESPONSE \| FLAG_OP_MASK \| FLAG_TC))
648			{
649			char qname[MAXSIZE];
650
651			while (pkt->qdcount-- && offs < MAXSIZE - 4)
652			{
653			int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
654			offs += 4; // skip qtype, qclass
655			}
656
657			while (pkt->ancount-- && offs < MAXSIZE - 10)
658			{
659			pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
660
661			u16 qtype = (pkt) [offs++] << 8; qtype \|= (pkt) [offs++];
662			u16 qclass = (pkt) [offs++] << 8; qclass \|= (pkt) [offs++];
663			u32 ttl = (*pkt) [offs++] << 24;
664			ttl \|= (*pkt) [offs++] << 16;
665			ttl \|= (*pkt) [offs++] << 8;
666			ttl \|= (*pkt) [offs++];
667
668			u16 rdlen = (pkt) [offs++] << 8; rdlen \|= (pkt) [offs++];
669
670	pcg	1.5	if (rdlen <= MAXSIZE - offs)
671			{
672			// decode bytes, finally
673
674			while (rdlen)
675			{
676			int txtlen = (*pkt) [offs++];
677
678			assert (txtlen + offs < MAXSIZE - 1);
679
680			memcpy (datap, pkt->at (offs), txtlen);
681			datap += txtlen; offs += txtlen;
682	pcg	1.4
683	pcg	1.5	rdlen -= txtlen + 1;
684			}
685	pcg	1.4
686			}
687	pcg	1.5
688	pcg	1.4	}
689			}
690
691	pcg	1.6	// todo: pkt now used
692			c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data));
693	pcg	1.5
694	pcg	1.4	break;
695			}
696	pcg	1.5
697			delete pkt;
698	pcg	1.4	}
699
700			void
701			vpn::dnsv4_ev (io_watcher &w, short revents)
702			{
703			if (revents & EVENT_READ)
704			{
705			dns_packet *pkt = new dns_packet;
706			struct sockaddr_in sa;
707			socklen_t sa_len = sizeof (sa);
708
709			pkt->len = recvfrom (w.fd, &((pkt)[0]), MAXSIZE, 0, (sockaddr )&sa, &sa_len);
710
711			if (pkt->len > 0)
712	pcg	1.5	{
713			if (pkt->flags & htons (FLAG_TC))
714			{
715			slog (L_WARN, _("DNS request/response truncated, check protocol settings."));
716			//TODO connection reset
717			}
718
719			if (THISNODE->dns_port)
720			{
721			pkt = dnsv4_server (pkt);
722			sendto (w.fd, &((pkt)[0]), pkt->len, 0, (sockaddr )&sa, sa_len);
723			}
724			else
725			dnsv4_client (pkt);
726			}
727	pcg	1.1	}
728			}
729
730			bool
731	pcg	1.3	connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
732			{
733	pcg	1.4	// never initialized
734			if (!dns_snddq && !dns_rcvdq)
735			{
736			dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
737			dns_snddq = new byte_stream (MAX_BACKLOG);
738
739	pcg	1.5	//dns_rcvseq = dns_sndseq = 0;
740	pcg	1.4
741			dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
742			}
743
744			if (!dns_snddq->put (pkt))
745	pcg	1.3	return false;
746
747	pcg	1.4	// start timer if neccessary
748	pcg	1.5	if (!THISNODE->dns_port && !dnsv4_tw.active)
749	pcg	1.4	dnsv4_cb (dnsv4_tw);
750	pcg	1.3
751			return true;
752			}
753
754			void
755			connection::dnsv4_cb (time_watcher &w)
756	pcg	1.1	{
757	pcg	1.3	// check for timeouts and (re)transmit
758			tstamp next = NOW + 60;
759	pcg	1.4	dns_req *send = 0;
760	pcg	1.3
761	pcg	1.4	for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin ();
762			i != vpn->dns_sndpq.end ();
763	pcg	1.3	++i)
764			{
765			dns_req r = i;
766
767			if (r->next <= NOW)
768			{
769	pcg	1.4	if (!send)
770			{
771			send = r;
772
773	pcg	1.5	if (r->retry)//D
774			printf ("req %d, retry %d\n", r->pkt->id, r->retry);
775	pcg	1.4	r->retry++;
776			r->next = NOW + r->retry;
777			}
778	pcg	1.3	}
779
780			if (r->next < next)
781			next = r->next;
782			}
783
784	pcg	1.4	if (!send
785			&& vpn->dns_sndpq.size () < MAX_OUTSTANDING)
786	pcg	1.5	{
787			send = new dns_req (this);
788			send->gen_stream_req (dns_sndseq, dns_snddq);
789			vpn->dns_sndpq.push_back (send);
790
791			dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
792			}
793	pcg	1.4
794			tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
795
796			if (send)
797			{
798			dns_packet *pkt = send->pkt;
799
800			next = min_next;
801
802			sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ());
803			}
804			else if (next < min_next)
805			next = min_next;
806
807	pcg	1.3	w.start (next);
808	pcg	1.1	}
809
810			#endif
811