gvpe/src/vpn_dns.C

/*
    vpn_dns.C -- handle the dns tunnel part of the protocol.
    Copyright (C) 2003-2005 Marc Lehmann <gvpe@schmorp.de>
 
    This file is part of GVPE.

    GVPE 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 gvpe; 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:	1.7
Committed:	Thu Mar 3 16:54:34 2005 UTC (19 years, 2 months ago) by pcg
Content type:	text/plain
Branch:	MAIN
Changes since 1.6:	+5 -3 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	pcg	1.7	Copyright (C) 2003-2005 Marc Lehmann <gvpe@schmorp.de>
4	pcg	1.1
5	pcg	1.7	This file is part of GVPE.
6
7			GVPE is free software; you can redistribute it and/or modify
8	pcg	1.1	it under the terms of the GNU General Public License as published by
9			the Free Software Foundation; either version 2 of the License, or
10			(at your option) any later version.
11
12			This program is distributed in the hope that it will be useful,
13			but WITHOUT ANY WARRANTY; without even the implied warranty of
14			MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15			GNU General Public License for more details.
16
17			You should have received a copy of the GNU General Public License
18	pcg	1.7	along with gvpe; if not, write to the Free Software
19	pcg	1.1	Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20			*/
21
22			#include "config.h"
23
24			#if ENABLE_DNS
25
26			// dns processing is EXTREMELY ugly. For obvious(?) reasons.
27			// it's a hack, use only in emergency situations please.
28
29			#include <cstring>
30
31			#include <sys/types.h>
32			#include <sys/socket.h>
33			#include <sys/wait.h>
34			#include <sys/uio.h>
35			#include <errno.h>
36			#include <time.h>
37			#include <unistd.h>
38			#include <fcntl.h>
39
40			#include <map>
41
42			#include "netcompat.h"
43
44			#include "vpn.h"
45
46			#define MIN_RETRY 1.
47			#define MAX_RETRY 60.
48
49	pcg	1.5	#define MAX_OUTSTANDING 40 // max. outstanding requests
50	pcg	1.4	#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING
51	pcg	1.5	#define MAX_RATE 1000 // requests/s
52			#define MAX_BACKLOG (10*1024) // size of protocol backlog, must be > MAXSIZE
53
54			#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well
55			// 240 leaves about 4 bytes of server reply data
56			// every two request byte sless give room for one reply byte
57
58	pcg	1.6	// seqno has 12 bits, but the lower bit is always left as zero
59			// as bind caches ttl=0 records and we have to generate
60			// sequence numbers that always differ case-insensitively
61			#define SEQNO_MASK 0x07ff
62	pcg	1.1
63			/*
64
65			protocol, in shorthand :)
66
67	pcg	1.2	client -> server <req> ANY?
68			server -> client <req> TXT <rep>
69	pcg	1.1
70	pcg	1.2	<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
71			<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
72
73			if <client-id> is zero, the connection will be configured:
74
75			<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
76	pcg	1.1
77			*/
78
79	pcg	1.2	#define MAX_LBL_SIZE 63
80			#define MAX_PKT_SIZE 512
81
82			#define RR_TYPE_TXT 16
83			#define RR_TYPE_ANY 255
84			#define RR_CLASS_IN 1
85
86			// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)
87			struct dns64
88			{
89			static const char encode_chars[64 + 1];
90			static s8 decode_chars[256];
91
92			static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }
93			static int decode_len (int bytes) { return (bytes * 6) / 8; }
94	pcg	1.4	static int encode (char dst, u8 src, int len);
95			static int decode (u8 dst, char src, int len);
96	pcg	1.2
97			dns64 ();
98			} dns64;
99
100	pcg	1.6	// the following sequence has been crafted to
101			// a) look somewhat random
102			// b) the even (and odd) indices never share the same character as upper/lowercase
103			const char dns64::encode_chars[64 + 1] = "_-dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI";
104	pcg	1.2	s8 dns64::decode_chars[256];
105
106			dns64::dns64 ()
107			{
108			for (int i = 0; i < 64; i++)
109			decode_chars [encode_chars [i]] = i + 1;
110			}
111
112	pcg	1.4	int dns64::encode (char dst, u8 src, int len)
113	pcg	1.2	{
114			// slow, but easy to debug
115	pcg	1.4	char *beg = dst;
116	pcg	1.2	unsigned int accum, bits = 0;
117
118			while (len--)
119			{
120			accum <<= 8;
121			accum \|= *src++;
122			bits += 8;
123
124			while (bits >= 6)
125			{
126			*dst++ = encode_chars [(accum >> (bits - 6)) & 63];
127			bits -= 6;
128			}
129			}
130
131			if (bits)
132			*dst++ = encode_chars [(accum << (6 - bits)) & 63];
133	pcg	1.4
134			return dst - beg;
135	pcg	1.2	}
136
137	pcg	1.4	int dns64::decode (u8 dst, char src, int len)
138	pcg	1.2	{
139			// slow, but easy to debug
140	pcg	1.4	u8 *beg = dst;
141	pcg	1.2	unsigned int accum, bits = 0;
142
143			while (len--)
144			{
145			s8 chr = decode_chars [(u8)*src++];
146
147			if (!chr)
148	pcg	1.5	continue;
149	pcg	1.2
150			accum <<= 6;
151			accum \|= chr - 1;
152			bits += 6;
153
154			while (bits >= 8)
155			{
156			*dst++ = accum >> (bits - 8);
157			bits -= 8;
158			}
159			}
160	pcg	1.4
161			return dst - beg;
162			}
163
164			/////////////////////////////////////////////////////////////////////////////
165
166			struct byte_stream
167			{
168			u8 *data;
169			int maxsize;
170			int fill;
171
172			byte_stream (int maxsize);
173			~byte_stream ();
174
175			bool empty () { return !fill; }
176			int size () { return fill; }
177
178	pcg	1.5	bool put (u8 *data, unsigned int datalen);
179	pcg	1.4	bool put (vpn_packet *pkt);
180			vpn_packet *get ();
181
182			u8 *begin () { return data; }
183			void remove (int count);
184			};
185
186			byte_stream::byte_stream (int maxsize)
187			: maxsize (maxsize), fill (0)
188			{
189			data = new u8 [maxsize];
190			}
191
192			byte_stream::~byte_stream ()
193			{
194			delete data;
195			}
196
197			void byte_stream::remove (int count)
198			{
199			if (count > fill)
200			abort ();
201
202			memmove (data, data + count, fill -= count);
203			}
204
205	pcg	1.5	bool byte_stream::put (u8 *data, unsigned int datalen)
206			{
207			if (maxsize - fill < datalen)
208			return false;
209
210			memcpy (this->data + fill, data, datalen); fill += datalen;
211
212			return true;
213			}
214
215	pcg	1.4	bool byte_stream::put (vpn_packet *pkt)
216			{
217			if (maxsize - fill < pkt->len + 2)
218			return false;
219
220			data [fill++] = pkt->len >> 8;
221			data [fill++] = pkt->len;
222
223			memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len;
224
225			return true;
226			}
227
228			vpn_packet *byte_stream::get ()
229			{
230			int len = (data [0] << 8) \| data [1];
231
232	pcg	1.5	if (len > MAXSIZE && fill >= 2)
233			abort (); // TODO handle this gracefully, connection reset
234
235	pcg	1.4	if (fill < len + 2)
236			return 0;
237
238			vpn_packet *pkt = new vpn_packet;
239	pcg	1.5
240			pkt->len = len;
241	pcg	1.4	memcpy (&((*pkt)[0]), data + 2, len);
242			remove (len + 2);
243
244			return pkt;
245	pcg	1.2	}
246
247	pcg	1.3	/////////////////////////////////////////////////////////////////////////////
248
249	pcg	1.2	#define FLAG_QUERY ( 0 << 15)
250			#define FLAG_RESPONSE ( 1 << 15)
251			#define FLAG_OP_MASK (15 << 14)
252			#define FLAG_OP_QUERY ( 0 << 11)
253			#define FLAG_AA ( 1 << 10)
254			#define FLAG_TC ( 1 << 9)
255			#define FLAG_RD ( 1 << 8)
256			#define FLAG_RA ( 1 << 7)
257	pcg	1.5	#define FLAG_AUTH ( 1 << 5)
258	pcg	1.2	#define FLAG_RCODE_MASK (15 << 0)
259			#define FLAG_RCODE_OK ( 0 << 0)
260			#define FLAG_RCODE_FORMERR ( 1 << 0)
261			#define FLAG_RCODE_SERVFAIL ( 2 << 0)
262			#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
263			#define FLAG_RCODE_REFUSED ( 5 << 0)
264
265			#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY \| FLAG_OP_QUERY \| FLAG_RD)
266	pcg	1.5	#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE \| FLAG_OP_QUERY \| FLAG_AA \| FLAG_RD \| FLAG_RA)
267	pcg	1.2
268			struct dns_packet : net_packet
269			{
270			u16 id;
271			u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
272			u16 qdcount, ancount, nscount, arcount;
273
274			u8 data[MAXSIZE - 6 * 2];
275
276			int decode_label (char *data, int size, int &offs);
277			};
278
279			int dns_packet::decode_label (char *data, int size, int &offs)
280			{
281			char *orig = data;
282
283			memset (data, 0, size);
284
285			while (offs < size - 1)
286			{
287			u8 len = (*this)[offs++];
288
289			if (!len)
290			break;
291			else if (len < 64)
292			{
293			if (size < len + 1 \|\| offs + len >= MAXSIZE - 1)
294			break;
295
296			memcpy (data, &((*this)[offs]), len);
297
298			data += len; size -= len; offs += len;
299			*data++ = '.'; size--;
300			}
301			else
302			{
303			int offs2 = ((len & 63) << 8) + (*this)[offs++];
304
305			data += decode_label (data, size, offs2);
306			break;
307			}
308			}
309
310			return data - orig;
311			}
312
313	pcg	1.3	/////////////////////////////////////////////////////////////////////////////
314
315			struct dns_req
316			{
317			dns_packet *pkt;
318			tstamp next;
319			int retry;
320	pcg	1.4	connection *conn;
321	pcg	1.5	int seqno;
322	pcg	1.3
323	pcg	1.5	dns_req (connection *c);
324			void gen_stream_req (int seqno, byte_stream *stream);
325	pcg	1.3	};
326
327	pcg	1.5	static u16 dns_id = 12098; // TODO: should be per-vpn
328
329			static u16 next_id ()
330	pcg	1.3	{
331	pcg	1.5	// the simplest lsfr with periodicity 65535 i could find
332			dns_id = (dns_id << 1)
333			\| (((dns_id >> 1)
334			^ (dns_id >> 2)
335			^ (dns_id >> 4)
336			^ (dns_id >> 15)) & 1);
337	pcg	1.3
338	pcg	1.5	return dns_id;
339			}
340	pcg	1.3
341	pcg	1.5	dns_req::dns_req (connection *c)
342	pcg	1.4	: conn (c)
343	pcg	1.3	{
344			next = 0;
345			retry = 0;
346
347			pkt = new dns_packet;
348
349	pcg	1.5	pkt->id = next_id ();
350			}
351
352			void dns_req::gen_stream_req (int seqno, byte_stream *stream)
353			{
354			this->seqno = seqno;
355
356			pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
357	pcg	1.4	pkt->qdcount = htons (1);
358	pcg	1.3
359	pcg	1.4	int offs = 6*2;
360	pcg	1.5	int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2;
361			// MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
362			// so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
363
364			u8 data[256]; //TODO
365	pcg	1.4
366	pcg	1.5	data[0] = THISNODE->id; //TODO
367	pcg	1.6	data[1] = seqno >> 7; //TODO
368			data[2] = seqno << 1; //TODO
369	pcg	1.4
370	pcg	1.5	int datalen = dns64::decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE) - 3;
371	pcg	1.4
372	pcg	1.5	if (datalen > stream->size ())
373			datalen = stream->size ();
374	pcg	1.4
375	pcg	1.5	char enc[256], *encp = enc;
376
377			memcpy (data + 3, stream->begin (), datalen);
378			int enclen = dns64::encode (enc, data, datalen + 3);
379			stream->remove (datalen);
380	pcg	1.4
381	pcg	1.5	while (enclen)
382			{
383			int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
384
385			(*pkt)[offs++] = lbllen;
386			memcpy (pkt->at (offs), encp, lbllen);
387	pcg	1.4
388	pcg	1.5	offs += lbllen;
389			encp += lbllen;
390	pcg	1.4
391	pcg	1.5	enclen -= lbllen;
392	pcg	1.4	}
393
394			const char *suffix = THISNODE->domain;
395	pcg	1.3
396	pcg	1.4	// add tunnel domain
397			for (;;)
398			{
399			const char *end = strchr (suffix, '.');
400
401			if (!end)
402			end = suffix + strlen (suffix);
403
404			int len = end - suffix;
405
406			(*pkt)[offs++] = len;
407			memcpy (&((*pkt)[offs]), suffix, len);
408			offs += len;
409
410			if (!*end)
411			break;
412
413			suffix = end + 1;
414			}
415
416			(*pkt)[offs++] = 0;
417			(pkt)[offs++] = RR_TYPE_ANY >> 8; (pkt)[offs++] = RR_TYPE_ANY;
418			(pkt)[offs++] = RR_CLASS_IN >> 8; (pkt)[offs++] = RR_CLASS_IN;
419
420			pkt->len = offs;
421	pcg	1.5	}
422
423			struct dns_rcv
424			{
425			int seqno;
426			dns_packet *pkt; // reply packet
427			u8 data [MAXSIZE]; // actually part of the reply packet...
428			int datalen;
429
430	pcg	1.6	dns_rcv (int seqno, u8 *data, int datalen);
431	pcg	1.5	~dns_rcv ();
432			};
433
434	pcg	1.6	dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
435	pcg	1.5	: seqno (seqno), pkt (new dns_packet), datalen (datalen)
436			{
437			memcpy (this->data, data, datalen);
438			}
439	pcg	1.4
440	pcg	1.5	dns_rcv::~dns_rcv ()
441			{
442			delete pkt;
443	pcg	1.3	}
444
445			/////////////////////////////////////////////////////////////////////////////
446
447	pcg	1.2	struct dns_cfg
448			{
449			u8 id1, id2, id3;
450			u8 def_ttl;
451			u8 unused1;
452			u16 max_size;
453			u8 flags1, flags2;
454			};
455
456	pcg	1.5	void connection::dnsv4_receive_rep (struct dns_rcv *r)
457			{
458			dns_rcvpq.push_back (r);
459
460			redo:
461
462			for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin ();
463			i != dns_rcvpq.end ();
464			++i)
465			if (dns_rcvseq == (*i)->seqno)
466			{
467			dns_rcv r = i;
468
469			dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK;
470
471			if (!dns_snddq && !dns_rcvdq)
472			{
473			dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
474			dns_snddq = new byte_stream (MAX_BACKLOG);
475
476			dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
477			}
478
479			if (!dns_rcvdq->put (r->data, r->datalen))
480			abort (); // MUST never overflow, can be caused by data corruption, TODO
481
482			while (vpn_packet *pkt = dns_rcvdq->get ())
483			{
484			sockinfo si;
485			si.host = 0; si.port = 0; si.prot = PROT_DNSv4;
486
487			vpn->recv_vpn_packet (pkt, si);
488			}
489			}
490	pcg	1.6	else if ((u32)(i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW 2)
491	pcg	1.5	{
492	pcg	1.6	//D
493			//abort();
494			printf ("%d erasing %d (%d)\n", THISNODE->id, (u32)(*i)->seqno, dns_rcvseq);
495	pcg	1.5	dns_rcvpq.erase (i);
496			goto redo;
497			}
498			}
499
500	pcg	1.4	dns_packet *
501			vpn::dnsv4_server (dns_packet *pkt)
502	pcg	1.2	{
503	pcg	1.4	u16 flags = ntohs (pkt->flags);
504	pcg	1.2
505	pcg	1.4	//memcpy (&((rep)[0]), &((pkt)[0]), pkt->len);
506			int offs = 6 * 2; // skip header
507	pcg	1.2
508	pcg	1.4	pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_FORMERR);
509	pcg	1.2
510	pcg	1.4	if (!(flags & (FLAG_RESPONSE \| FLAG_OP_MASK \| FLAG_TC))
511			&& pkt->qdcount == htons (1))
512			{
513			char qname[MAXSIZE];
514			int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
515
516			u16 qtype = (pkt) [offs++] << 8; qtype \|= (pkt) [offs++];
517			u16 qclass = (pkt) [offs++] << 8; qclass \|= (pkt) [offs++];
518	pcg	1.2
519	pcg	1.4	pkt->qdcount = htons (1);
520			pkt->ancount = 0;
521			pkt->nscount = 0; // should be self, as other nameservers reply like this
522			pkt->arcount = 0; // a record for self, as other nameservers reply like this
523	pcg	1.2
524	pcg	1.4	pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_NXDOMAIN);
525	pcg	1.2
526	pcg	1.4	int dlen = strlen (THISNODE->domain);
527	pcg	1.2
528	pcg	1.4	if (qclass == RR_CLASS_IN
529			&& (qtype == RR_TYPE_ANY \|\| qtype == RR_TYPE_TXT)
530			&& qlen > dlen + 1
531			&& !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))
532	pcg	1.2	{
533	pcg	1.5	// correct class, domain: parse
534	pcg	1.4	u8 data[MAXSIZE];
535			int datalen = dns64::decode (data, qname, qlen - dlen - 1);
536	pcg	1.2
537	pcg	1.5	int client = data[0];
538	pcg	1.6	int seqno = ((data[1] << 7) \| (data[2] >> 1)) & SEQNO_MASK;
539	pcg	1.2
540	pcg	1.5	if (0 < client && client <= conns.size ())
541			{
542			connection *c = conns [client - 1];
543
544	pcg	1.6	redo:
545
546	pcg	1.5	for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
547			i != c->dns_rcvpq.end ();
548			++i)
549			if ((*i)->seqno == seqno)
550			{
551	pcg	1.6	// already seen that request: simply reply with the cached reply
552	pcg	1.5	dns_rcv r = i;
553	pcg	1.4
554	pcg	1.6	printf ("DUPLICATE %d\n", htons (r->pkt->id));//D
555
556	pcg	1.5	offs = r->pkt->len;
557			memcpy (pkt->at (0), r->pkt->at (0), offs);
558			goto duplicate_request;
559			}
560	pcg	1.4
561	pcg	1.5	// new packet, queue
562	pcg	1.6	dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3);
563			c->dnsv4_receive_rep (rcv);
564	pcg	1.4
565	pcg	1.5	// now generate reply
566			pkt->ancount = htons (1); // one answer RR
567			pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_OK);
568	pcg	1.4
569	pcg	1.5	(*pkt) [offs++] = 0xc0;
570			(pkt) [offs++] = 6 2; // same as in query section
571	pcg	1.4
572	pcg	1.5	(pkt) [offs++] = RR_TYPE_TXT >> 8; (pkt) [offs++] = RR_TYPE_TXT;
573			(pkt) [offs++] = RR_CLASS_IN >> 8; (pkt) [offs++] = RR_CLASS_IN;
574	pcg	1.2
575	pcg	1.5	(pkt) [offs++] = 0; (pkt) [offs++] = 0;
576			(pkt) [offs++] = 0; (pkt) [offs++] = 0; // TTL
577	pcg	1.2
578	pcg	1.5	int dlen = MAX_PKT_SIZE - offs - 2;
579	pcg	1.2
580	pcg	1.5	// bind doesn't compress well, so reduce further by one label length
581			dlen -= qlen;
582	pcg	1.2
583	pcg	1.5	int rdlen_offs = offs += 2;
584	pcg	1.2
585	pcg	1.5	while (c->dns_snddq
586			&& !c->dns_snddq->empty ()
587			&& dlen > 1)
588			{
589			int txtlen = dlen <= 255 ? dlen - 1 : 255;
590	pcg	1.2
591	pcg	1.5	if (txtlen > c->dns_snddq->size ())
592			txtlen = c->dns_snddq->size ();
593	pcg	1.2
594	pcg	1.5	(*pkt)[offs++] = txtlen;
595			memcpy (pkt->at (offs), c->dns_snddq->begin (), txtlen);
596			offs += txtlen;
597			c->dns_snddq->remove (txtlen);
598	pcg	1.2
599	pcg	1.5	dlen -= txtlen + 1;
600			}
601	pcg	1.2
602	pcg	1.5	// avoid empty TXT rdata
603			if (offs == rdlen_offs)
604			(*pkt)[offs++] = 0;
605	pcg	1.2
606	pcg	1.5	int rdlen = offs - rdlen_offs;
607	pcg	1.2
608	pcg	1.5	(*pkt) [rdlen_offs - 2] = rdlen >> 8;
609			(*pkt) [rdlen_offs - 1] = rdlen;
610	pcg	1.4
611	pcg	1.6	// now update dns_rcv copy
612			rcv->pkt->len = offs;
613			memcpy (rcv->pkt->at (0), pkt->at (0), offs);
614
615	pcg	1.5	duplicate_request: ;
616			}
617			else
618			pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_FORMERR);
619	pcg	1.2	}
620	pcg	1.6
621			pkt->len = offs;
622	pcg	1.4	}
623
624			return pkt;
625			}
626
627			void
628			vpn::dnsv4_client (dns_packet *pkt)
629			{
630			u16 flags = ntohs (pkt->flags);
631			int offs = 6 * 2; // skip header
632
633			pkt->qdcount = ntohs (pkt->qdcount);
634			pkt->ancount = ntohs (pkt->ancount);
635
636	pcg	1.5	// go through our request list and find the corresponding request
637	pcg	1.4	for (vector<dns_req *>::iterator i = dns_sndpq.begin ();
638			i != dns_sndpq.end ();
639			++i)
640			if ((*i)->pkt->id == pkt->id)
641			{
642			connection c = (i)->conn;
643	pcg	1.5	int seqno = (*i)->seqno;
644			u8 data[MAXSIZE], *datap = data;
645
646	pcg	1.4	delete *i;
647			dns_sndpq.erase (i);
648
649			if (flags & (FLAG_RESPONSE \| FLAG_OP_MASK \| FLAG_TC))
650			{
651			char qname[MAXSIZE];
652
653			while (pkt->qdcount-- && offs < MAXSIZE - 4)
654			{
655			int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
656			offs += 4; // skip qtype, qclass
657			}
658
659			while (pkt->ancount-- && offs < MAXSIZE - 10)
660			{
661			pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
662
663			u16 qtype = (pkt) [offs++] << 8; qtype \|= (pkt) [offs++];
664			u16 qclass = (pkt) [offs++] << 8; qclass \|= (pkt) [offs++];
665			u32 ttl = (*pkt) [offs++] << 24;
666			ttl \|= (*pkt) [offs++] << 16;
667			ttl \|= (*pkt) [offs++] << 8;
668			ttl \|= (*pkt) [offs++];
669
670			u16 rdlen = (pkt) [offs++] << 8; rdlen \|= (pkt) [offs++];
671
672	pcg	1.5	if (rdlen <= MAXSIZE - offs)
673			{
674			// decode bytes, finally
675
676			while (rdlen)
677			{
678			int txtlen = (*pkt) [offs++];
679
680			assert (txtlen + offs < MAXSIZE - 1);
681
682			memcpy (datap, pkt->at (offs), txtlen);
683			datap += txtlen; offs += txtlen;
684	pcg	1.4
685	pcg	1.5	rdlen -= txtlen + 1;
686			}
687	pcg	1.4
688			}
689	pcg	1.5
690	pcg	1.4	}
691			}
692
693	pcg	1.6	// todo: pkt now used
694			c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data));
695	pcg	1.5
696	pcg	1.4	break;
697			}
698	pcg	1.5
699			delete pkt;
700	pcg	1.4	}
701
702			void
703			vpn::dnsv4_ev (io_watcher &w, short revents)
704			{
705			if (revents & EVENT_READ)
706			{
707			dns_packet *pkt = new dns_packet;
708			struct sockaddr_in sa;
709			socklen_t sa_len = sizeof (sa);
710
711			pkt->len = recvfrom (w.fd, &((pkt)[0]), MAXSIZE, 0, (sockaddr )&sa, &sa_len);
712
713			if (pkt->len > 0)
714	pcg	1.5	{
715			if (pkt->flags & htons (FLAG_TC))
716			{
717			slog (L_WARN, _("DNS request/response truncated, check protocol settings."));
718			//TODO connection reset
719			}
720
721			if (THISNODE->dns_port)
722			{
723			pkt = dnsv4_server (pkt);
724			sendto (w.fd, &((pkt)[0]), pkt->len, 0, (sockaddr )&sa, sa_len);
725			}
726			else
727			dnsv4_client (pkt);
728			}
729	pcg	1.1	}
730			}
731
732			bool
733	pcg	1.3	connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
734			{
735	pcg	1.4	// never initialized
736			if (!dns_snddq && !dns_rcvdq)
737			{
738			dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
739			dns_snddq = new byte_stream (MAX_BACKLOG);
740
741	pcg	1.5	//dns_rcvseq = dns_sndseq = 0;
742	pcg	1.4
743			dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
744			}
745
746			if (!dns_snddq->put (pkt))
747	pcg	1.3	return false;
748
749	pcg	1.4	// start timer if neccessary
750	pcg	1.5	if (!THISNODE->dns_port && !dnsv4_tw.active)
751	pcg	1.4	dnsv4_cb (dnsv4_tw);
752	pcg	1.3
753			return true;
754			}
755
756			void
757			connection::dnsv4_cb (time_watcher &w)
758	pcg	1.1	{
759	pcg	1.3	// check for timeouts and (re)transmit
760			tstamp next = NOW + 60;
761	pcg	1.4	dns_req *send = 0;
762	pcg	1.3
763	pcg	1.4	for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin ();
764			i != vpn->dns_sndpq.end ();
765	pcg	1.3	++i)
766			{
767			dns_req r = i;
768
769			if (r->next <= NOW)
770			{
771	pcg	1.4	if (!send)
772			{
773			send = r;
774
775	pcg	1.5	if (r->retry)//D
776			printf ("req %d, retry %d\n", r->pkt->id, r->retry);
777	pcg	1.4	r->retry++;
778			r->next = NOW + r->retry;
779			}
780	pcg	1.3	}
781
782			if (r->next < next)
783			next = r->next;
784			}
785
786	pcg	1.4	if (!send
787			&& vpn->dns_sndpq.size () < MAX_OUTSTANDING)
788	pcg	1.5	{
789			send = new dns_req (this);
790			send->gen_stream_req (dns_sndseq, dns_snddq);
791			vpn->dns_sndpq.push_back (send);
792
793			dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
794			}
795	pcg	1.4
796			tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
797
798			if (send)
799			{
800			dns_packet *pkt = send->pkt;
801
802			next = min_next;
803
804			sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ());
805			}
806			else if (next < min_next)
807			next = min_next;
808
809	pcg	1.3	w.start (next);
810	pcg	1.1	}
811
812			#endif
813