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 10 // max. outstanding requests
#define MAX_WINDOW      100 // max. for MAX_OUTSTANDING
#define MAX_RATE        1 // requests/s
#define MAX_BACKLOG     (10*1024) // size of protocol backlog

/*

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;

const char dns64::encode_chars[64 + 1] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-";
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)
        break;

      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 (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 (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 (fill < len + 2)
    return 0;

  vpn_packet *pkt = new vpn_packet;
  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_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)

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;

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

struct dns_rep
{
};

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

dns_req::dns_req (connection *c, int seqno, byte_stream *stream)
: conn (c)
{
  next = 0;
  retry = 0;

  pkt = new dns_packet;

  pkt->id = dns_id++;
  pkt->flags = DEFAULT_CLIENT_FLAGS;
  pkt->qdcount = htons (1);
  pkt->ancount = 0;
  pkt->nscount = 0;
  pkt->arcount = 0;

  int offs = 6*2;
  int dlen = 255 - strlen (THISNODE->domain) - 1; // here we always have room for the max. label length

  u8 lbl[64]; //D
  char enc[65];
  int lbllen = 3;
  lbl[0] = c->conf->id; //D
  lbl[1] = seqno >> 8; //D
  lbl[2] = seqno; //D

  while (dlen > 0)
    {
      int sndlen = dlen;

      if (sndlen + lbllen > dns64::decode_len (MAX_LBL_SIZE))
        sndlen = dns64::decode_len (MAX_LBL_SIZE) - lbllen;

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

      if (sndlen + lbllen == 0)
        break;

      memcpy (lbl + lbllen, stream->begin (), sndlen);
      stream->remove (sndlen);
      lbllen += sndlen;

      dns64::encode (enc, lbl, lbllen);

      int elen = dns64::encode_len (lbllen);
      (*pkt)[offs++] = elen;
      memcpy (&((*pkt)[offs]), enc, elen);
      offs += elen;
      dlen -= elen + 1;

      lbllen = 0;
    }

  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;

  c->vpn->dns_sndpq.push_back (this);
}

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

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

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);

      printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", pkt->len,
          pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D

      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);

          for (int i = 0; i < datalen; i++)
            printf ("%02x ", data[i]);
          printf ("\n");

          
#if 0
          // now generate reply
          rep->ancount = htons (1); // one answer RR
          rep->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);

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

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

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

          int dlen = MAX_PKT_SIZE - offs - 2;

          printf ("we have room for %d bytes\n", dlen);

          int rdlen_offs = offs += 2;

          u8 txt[255];
          txt[0] = 0;
          txt[1] = 0;

          int txtlen = 2;

          while (dlen > 1)
            {
              int sndlen = --dlen;

              if (sndlen + txtlen > 255)
                sndlen = 255 - txtlen;

              sndlen = 0;

              (*rep)[offs++] = sndlen + txtlen;
              memcpy (&((*rep)[offs]), txt, txtlen);
              offs += txtlen;

              //if (sndlen + txtlen > dns_snddq.
            }

          int rdlen = offs - rdlen_offs;

          (*rep) [rdlen_offs - 2] = rdlen >> 8;
          (*rep) [rdlen_offs - 1] = rdlen;
#endif
        }
    }

  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);

  for (vector<dns_req *>::iterator i = dns_sndpq.begin ();
       i != dns_sndpq.end ();
       ++i)
    if ((*i)->pkt->id == pkt->id)
      {
        connection *c = (*i)->conn;
        printf ("GOT RESPONSE id %x %p\n", pkt->id, c);//D
        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++];

                printf ("REPLY %d:%d TTL %d RD %d\n", qtype, qclass, ttl, rdlen);

                offs += rdlen;

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

        break;
      }
}

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 (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 (!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;
  
  slog (L_NOISE, _("dnsv4, %d packets in send queue\n"), vpn->dns_sndpq.size ());

  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;

              slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id);
              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, dns_sndseq++, dns_snddq);

  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:	1.4
Committed:	Wed Mar 2 05:49:31 2005 UTC (19 years, 2 months ago) by pcg
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+349 -93 lines
Log Message:	* empty log message *
#	Content
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	#define MAX_OUTSTANDING 10 // max. outstanding requests
48	#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING
49	#define MAX_RATE 1 // requests/s
50	#define MAX_BACKLOG (10*1024) // size of protocol backlog
51
52	/*
53
54	protocol, in shorthand :)
55
56	client -> server <req> ANY?
57	server -> client <req> TXT <rep>
58
59	<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
60	<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
61
62	if <client-id> is zero, the connection will be configured:
63
64	<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
65
66	*/
67
68	#define MAX_LBL_SIZE 63
69	#define MAX_PKT_SIZE 512
70
71	#define RR_TYPE_TXT 16
72	#define RR_TYPE_ANY 255
73	#define RR_CLASS_IN 1
74
75	// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)
76	struct dns64
77	{
78	static const char encode_chars[64 + 1];
79	static s8 decode_chars[256];
80
81	static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }
82	static int decode_len (int bytes) { return (bytes * 6) / 8; }
83	static int encode (char dst, u8 src, int len);
84	static int decode (u8 dst, char src, int len);
85
86	dns64 ();
87	} dns64;
88
89	const char dns64::encode_chars[64 + 1] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-";
90	s8 dns64::decode_chars[256];
91
92	dns64::dns64 ()
93	{
94	for (int i = 0; i < 64; i++)
95	decode_chars [encode_chars [i]] = i + 1;
96	}
97
98	int dns64::encode (char dst, u8 src, int len)
99	{
100	// slow, but easy to debug
101	char *beg = dst;
102	unsigned int accum, bits = 0;
103
104	while (len--)
105	{
106	accum <<= 8;
107	accum \|= *src++;
108	bits += 8;
109
110	while (bits >= 6)
111	{
112	*dst++ = encode_chars [(accum >> (bits - 6)) & 63];
113	bits -= 6;
114	}
115	}
116
117	if (bits)
118	*dst++ = encode_chars [(accum << (6 - bits)) & 63];
119
120	return dst - beg;
121	}
122
123	int dns64::decode (u8 dst, char src, int len)
124	{
125	// slow, but easy to debug
126	u8 *beg = dst;
127	unsigned int accum, bits = 0;
128
129	while (len--)
130	{
131	s8 chr = decode_chars [(u8)*src++];
132
133	if (!chr)
134	break;
135
136	accum <<= 6;
137	accum \|= chr - 1;
138	bits += 6;
139
140	while (bits >= 8)
141	{
142	*dst++ = accum >> (bits - 8);
143	bits -= 8;
144	}
145	}
146
147	return dst - beg;
148	}
149
150	/////////////////////////////////////////////////////////////////////////////
151
152	struct byte_stream
153	{
154	u8 *data;
155	int maxsize;
156	int fill;
157
158	byte_stream (int maxsize);
159	~byte_stream ();
160
161	bool empty () { return !fill; }
162	int size () { return fill; }
163
164	bool put (vpn_packet *pkt);
165	vpn_packet *get ();
166
167	u8 *begin () { return data; }
168	void remove (int count);
169	};
170
171	byte_stream::byte_stream (int maxsize)
172	: maxsize (maxsize), fill (0)
173	{
174	data = new u8 [maxsize];
175	}
176
177	byte_stream::~byte_stream ()
178	{
179	delete data;
180	}
181
182	void byte_stream::remove (int count)
183	{
184	if (count > fill)
185	abort ();
186
187	memmove (data, data + count, fill -= count);
188	}
189
190	bool byte_stream::put (vpn_packet *pkt)
191	{
192	if (maxsize - fill < pkt->len + 2)
193	return false;
194
195	data [fill++] = pkt->len >> 8;
196	data [fill++] = pkt->len;
197
198	memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len;
199
200	return true;
201	}
202
203	vpn_packet *byte_stream::get ()
204	{
205	int len = (data [0] << 8) \| data [1];
206
207	if (fill < len + 2)
208	return 0;
209
210	vpn_packet *pkt = new vpn_packet;
211	memcpy (&((*pkt)[0]), data + 2, len);
212	remove (len + 2);
213
214	return pkt;
215	}
216
217	/////////////////////////////////////////////////////////////////////////////
218
219	#define FLAG_QUERY ( 0 << 15)
220	#define FLAG_RESPONSE ( 1 << 15)
221	#define FLAG_OP_MASK (15 << 14)
222	#define FLAG_OP_QUERY ( 0 << 11)
223	#define FLAG_AA ( 1 << 10)
224	#define FLAG_TC ( 1 << 9)
225	#define FLAG_RD ( 1 << 8)
226	#define FLAG_RA ( 1 << 7)
227	#define FLAG_RCODE_MASK (15 << 0)
228	#define FLAG_RCODE_OK ( 0 << 0)
229	#define FLAG_RCODE_FORMERR ( 1 << 0)
230	#define FLAG_RCODE_SERVFAIL ( 2 << 0)
231	#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
232	#define FLAG_RCODE_REFUSED ( 5 << 0)
233
234	#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY \| FLAG_OP_QUERY \| FLAG_RD)
235	#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE \| FLAG_OP_QUERY \| FLAG_AA \| FLAG_RD)
236
237	struct dns_packet : net_packet
238	{
239	u16 id;
240	u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
241	u16 qdcount, ancount, nscount, arcount;
242
243	u8 data[MAXSIZE - 6 * 2];
244
245	int decode_label (char *data, int size, int &offs);
246	};
247
248	int dns_packet::decode_label (char *data, int size, int &offs)
249	{
250	char *orig = data;
251
252	memset (data, 0, size);
253
254	while (offs < size - 1)
255	{
256	u8 len = (*this)[offs++];
257
258	if (!len)
259	break;
260	else if (len < 64)
261	{
262	if (size < len + 1 \|\| offs + len >= MAXSIZE - 1)
263	break;
264
265	memcpy (data, &((*this)[offs]), len);
266
267	data += len; size -= len; offs += len;
268	*data++ = '.'; size--;
269	}
270	else
271	{
272	int offs2 = ((len & 63) << 8) + (*this)[offs++];
273
274	data += decode_label (data, size, offs2);
275	break;
276	}
277	}
278
279	return data - orig;
280	}
281
282	/////////////////////////////////////////////////////////////////////////////
283
284	struct dns_req
285	{
286	dns_packet *pkt;
287	tstamp next;
288	int retry;
289	connection *conn;
290
291	dns_req (connection c, int seqno, byte_stream stream);
292	};
293
294	struct dns_rep
295	{
296	};
297
298	static u16 dns_id; // TODO: should be per-vpn
299
300	dns_req::dns_req (connection c, int seqno, byte_stream stream)
301	: conn (c)
302	{
303	next = 0;
304	retry = 0;
305
306	pkt = new dns_packet;
307
308	pkt->id = dns_id++;
309	pkt->flags = DEFAULT_CLIENT_FLAGS;
310	pkt->qdcount = htons (1);
311	pkt->ancount = 0;
312	pkt->nscount = 0;
313	pkt->arcount = 0;
314
315	int offs = 6*2;
316	int dlen = 255 - strlen (THISNODE->domain) - 1; // here we always have room for the max. label length
317
318	u8 lbl[64]; //D
319	char enc[65];
320	int lbllen = 3;
321	lbl[0] = c->conf->id; //D
322	lbl[1] = seqno >> 8; //D
323	lbl[2] = seqno; //D
324
325	while (dlen > 0)
326	{
327	int sndlen = dlen;
328
329	if (sndlen + lbllen > dns64::decode_len (MAX_LBL_SIZE))
330	sndlen = dns64::decode_len (MAX_LBL_SIZE) - lbllen;
331
332	if (sndlen > stream->size ())
333	sndlen = stream->size ();
334
335	if (sndlen + lbllen == 0)
336	break;
337
338	memcpy (lbl + lbllen, stream->begin (), sndlen);
339	stream->remove (sndlen);
340	lbllen += sndlen;
341
342	dns64::encode (enc, lbl, lbllen);
343
344	int elen = dns64::encode_len (lbllen);
345	(*pkt)[offs++] = elen;
346	memcpy (&((*pkt)[offs]), enc, elen);
347	offs += elen;
348	dlen -= elen + 1;
349
350	lbllen = 0;
351	}
352
353	const char *suffix = THISNODE->domain;
354
355	// add tunnel domain
356	for (;;)
357	{
358	const char *end = strchr (suffix, '.');
359
360	if (!end)
361	end = suffix + strlen (suffix);
362
363	int len = end - suffix;
364
365	(*pkt)[offs++] = len;
366	memcpy (&((*pkt)[offs]), suffix, len);
367	offs += len;
368
369	if (!*end)
370	break;
371
372	suffix = end + 1;
373	}
374
375	(*pkt)[offs++] = 0;
376	(pkt)[offs++] = RR_TYPE_ANY >> 8; (pkt)[offs++] = RR_TYPE_ANY;
377	(pkt)[offs++] = RR_CLASS_IN >> 8; (pkt)[offs++] = RR_CLASS_IN;
378
379	pkt->len = offs;
380
381	c->vpn->dns_sndpq.push_back (this);
382	}
383
384	/////////////////////////////////////////////////////////////////////////////
385
386	struct dns_cfg
387	{
388	u8 id1, id2, id3;
389	u8 def_ttl;
390	u8 unused1;
391	u16 max_size;
392	u8 flags1, flags2;
393	};
394
395	dns_packet *
396	vpn::dnsv4_server (dns_packet *pkt)
397	{
398	u16 flags = ntohs (pkt->flags);
399
400	//memcpy (&((rep)[0]), &((pkt)[0]), pkt->len);
401	int offs = 6 * 2; // skip header
402
403	pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_FORMERR);
404
405	if (!(flags & (FLAG_RESPONSE \| FLAG_OP_MASK \| FLAG_TC))
406	&& pkt->qdcount == htons (1))
407	{
408	char qname[MAXSIZE];
409	int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
410
411	printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", pkt->len,
412	pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D
413
414	u16 qtype = (pkt) [offs++] << 8; qtype \|= (pkt) [offs++];
415	u16 qclass = (pkt) [offs++] << 8; qclass \|= (pkt) [offs++];
416
417	pkt->qdcount = htons (1);
418	pkt->ancount = 0;
419	pkt->nscount = 0; // should be self, as other nameservers reply like this
420	pkt->arcount = 0; // a record for self, as other nameservers reply like this
421
422	pkt->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_NXDOMAIN);
423
424	int dlen = strlen (THISNODE->domain);
425
426	if (qclass == RR_CLASS_IN
427	&& (qtype == RR_TYPE_ANY \|\| qtype == RR_TYPE_TXT)
428	&& qlen > dlen + 1
429	&& !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))
430	{
431	// correct class, domain, parse
432	u8 data[MAXSIZE];
433	int datalen = dns64::decode (data, qname, qlen - dlen - 1);
434
435	for (int i = 0; i < datalen; i++)
436	printf ("%02x ", data[i]);
437	printf ("\n");
438
439
440
441
442	#if 0
443	// now generate reply
444	rep->ancount = htons (1); // one answer RR
445	rep->flags = htons (DEFAULT_SERVER_FLAGS \| FLAG_RCODE_OK);
446
447	(*rep) [offs++] = 0xc0;
448	(rep) [offs++] = 6 2; // same as in query section
449
450	(rep) [offs++] = RR_TYPE_TXT >> 8; (rep) [offs++] = RR_TYPE_TXT;
451	(rep) [offs++] = RR_CLASS_IN >> 8; (rep) [offs++] = RR_CLASS_IN;
452
453	(rep) [offs++] = 0; (rep) [offs++] = 0;
454	(rep) [offs++] = 0; (rep) [offs++] = 0; // TTL
455
456	int dlen = MAX_PKT_SIZE - offs - 2;
457
458	printf ("we have room for %d bytes\n", dlen);
459
460	int rdlen_offs = offs += 2;
461
462	u8 txt[255];
463	txt[0] = 0;
464	txt[1] = 0;
465
466	int txtlen = 2;
467
468	while (dlen > 1)
469	{
470	int sndlen = --dlen;
471
472	if (sndlen + txtlen > 255)
473	sndlen = 255 - txtlen;
474
475	sndlen = 0;
476
477	(*rep)[offs++] = sndlen + txtlen;
478	memcpy (&((*rep)[offs]), txt, txtlen);
479	offs += txtlen;
480
481	//if (sndlen + txtlen > dns_snddq.
482	}
483
484	int rdlen = offs - rdlen_offs;
485
486	(*rep) [rdlen_offs - 2] = rdlen >> 8;
487	(*rep) [rdlen_offs - 1] = rdlen;
488	#endif
489	}
490	}
491
492	pkt->len = offs;
493	return pkt;
494	}
495
496	void
497	vpn::dnsv4_client (dns_packet *pkt)
498	{
499	u16 flags = ntohs (pkt->flags);
500	int offs = 6 * 2; // skip header
501
502	pkt->qdcount = ntohs (pkt->qdcount);
503	pkt->ancount = ntohs (pkt->ancount);
504
505	for (vector<dns_req *>::iterator i = dns_sndpq.begin ();
506	i != dns_sndpq.end ();
507	++i)
508	if ((*i)->pkt->id == pkt->id)
509	{
510	connection c = (i)->conn;
511	printf ("GOT RESPONSE id %x %p\n", pkt->id, c);//D
512	delete *i;
513	dns_sndpq.erase (i);
514
515	if (flags & (FLAG_RESPONSE \| FLAG_OP_MASK \| FLAG_TC))
516	{
517	char qname[MAXSIZE];
518
519	while (pkt->qdcount-- && offs < MAXSIZE - 4)
520	{
521	int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
522	offs += 4; // skip qtype, qclass
523	}
524
525	while (pkt->ancount-- && offs < MAXSIZE - 10)
526	{
527	pkt->decode_label ((char *)qname, MAXSIZE - offs, offs);
528
529	u16 qtype = (pkt) [offs++] << 8; qtype \|= (pkt) [offs++];
530	u16 qclass = (pkt) [offs++] << 8; qclass \|= (pkt) [offs++];
531	u32 ttl = (*pkt) [offs++] << 24;
532	ttl \|= (*pkt) [offs++] << 16;
533	ttl \|= (*pkt) [offs++] << 8;
534	ttl \|= (*pkt) [offs++];
535
536	u16 rdlen = (pkt) [offs++] << 8; rdlen \|= (pkt) [offs++];
537
538	printf ("REPLY %d:%d TTL %d RD %d\n", qtype, qclass, ttl, rdlen);
539
540	offs += rdlen;
541
542	if (MAXSIZE - offs < rdlen)
543	{
544	// decode bytes, finally
545	}
546	}
547	}
548
549	break;
550	}
551	}
552
553	void
554	vpn::dnsv4_ev (io_watcher &w, short revents)
555	{
556	if (revents & EVENT_READ)
557	{
558	dns_packet *pkt = new dns_packet;
559	struct sockaddr_in sa;
560	socklen_t sa_len = sizeof (sa);
561
562	pkt->len = recvfrom (w.fd, &((pkt)[0]), MAXSIZE, 0, (sockaddr )&sa, &sa_len);
563
564	if (pkt->len > 0)
565	if (THISNODE->dns_port)
566	{
567	pkt = dnsv4_server (pkt);
568	sendto (w.fd, &((pkt)[0]), pkt->len, 0, (sockaddr )&sa, sa_len);
569	}
570	else
571	dnsv4_client (pkt);
572	}
573	}
574
575	bool
576	connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
577	{
578	// never initialized
579	if (!dns_snddq && !dns_rcvdq)
580	{
581	dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
582	dns_snddq = new byte_stream (MAX_BACKLOG);
583
584	dns_rcvseq = dns_sndseq = 0;
585
586	dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4);
587	}
588
589	if (!dns_snddq->put (pkt))
590	return false;
591
592	// start timer if neccessary
593	if (!dnsv4_tw.active)
594	dnsv4_cb (dnsv4_tw);
595
596	return true;
597	}
598
599	void
600	connection::dnsv4_cb (time_watcher &w)
601	{
602	// check for timeouts and (re)transmit
603	tstamp next = NOW + 60;
604	dns_req *send = 0;
605
606	slog (L_NOISE, _("dnsv4, %d packets in send queue\n"), vpn->dns_sndpq.size ());
607
608	for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin ();
609	i != vpn->dns_sndpq.end ();
610	++i)
611	{
612	dns_req r = i;
613
614	if (r->next <= NOW)
615	{
616	if (!send)
617	{
618	send = r;
619
620	slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id);
621	r->retry++;
622	r->next = NOW + r->retry;
623	}
624	}
625
626	if (r->next < next)
627	next = r->next;
628	}
629
630	if (!send
631	&& vpn->dns_sndpq.size () < MAX_OUTSTANDING)
632	send = new dns_req (this, dns_sndseq++, dns_snddq);
633
634	tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
635
636	if (send)
637	{
638	dns_packet *pkt = send->pkt;
639
640	next = min_next;
641
642	sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ());
643	}
644	else if (next < min_next)
645	next = min_next;
646
647	w.start (next);
648	}
649
650	#endif
651