1 |
/* |
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vpn_dns.C -- handle the dns tunnel part of the protocol. |
3 |
Copyright (C) 2003-2005 Marc Lehmann <gvpe@schmorp.de> |
4 |
|
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This file is part of GVPE. |
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|
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GVPE is free software; you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
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(at your option) any later version. |
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|
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This program is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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|
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You should have received a copy of the GNU General Public License |
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along with gvpe; if not, write to the Free Software |
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Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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*/ |
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|
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#include "config.h" |
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|
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#if ENABLE_DNS |
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|
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// dns processing is EXTREMELY ugly. For obvious(?) reasons. |
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// it's a hack, use only in emergency situations please. |
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|
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#include <cstring> |
30 |
|
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#include <sys/types.h> |
32 |
#include <sys/socket.h> |
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#include <sys/wait.h> |
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#include <sys/uio.h> |
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#include <errno.h> |
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#include <time.h> |
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#include <unistd.h> |
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#include <fcntl.h> |
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|
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#include <map> |
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|
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#include <gmp.h> |
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|
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#include "netcompat.h" |
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|
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#include "vpn.h" |
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|
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#define MIN_RETRY 1. |
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#define MAX_RETRY 60. |
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|
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#define MAX_OUTSTANDING 400 // max. outstanding requests |
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#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING |
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#define MAX_RATE 10000 // requests/s |
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#define MAX_BACKLOG (10*1024) // size of protocol backlog, must be > MAXSIZE |
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|
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#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well |
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// 240 leaves about 4 bytes of server reply data |
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// every two request byte sless give room for one reply byte |
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|
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// seqno has 12 bits (3 bytes a 4 bits in the header) |
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#define SEQNO_MASK 0x7fff |
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#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) ) |
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|
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#define MAX_LBL_SIZE 63 |
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#define MAX_PKT_SIZE 512 |
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|
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#define RR_TYPE_TXT 16 |
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#define RR_TYPE_ANY 255 |
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#define RR_CLASS_IN 1 |
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|
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// works for cmaps up to 255 (not 256!) |
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struct charmap |
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{ |
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enum { INVALID = (u8)255 }; |
75 |
|
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char encode [256]; // index => char |
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u8 decode [256]; // char => index |
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unsigned int size; |
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|
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charmap (const char *cmap); |
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}; |
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|
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charmap::charmap (const char *cmap) |
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{ |
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char *enc = encode; |
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u8 *dec = decode; |
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|
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memset (enc, (char) 0, 256); |
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memset (dec, (char)INVALID, 256); |
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|
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for (size = 0; cmap [size]; size++) |
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{ |
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enc [size] = cmap [size]; |
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dec [(u8)enc [size]] = size; |
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} |
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|
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assert (size < 256); |
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} |
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|
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#define MAX_DEC_LEN 500 |
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#define MAX_ENC_LEN (MAX_DEC_LEN * 2) |
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#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS) |
103 |
|
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// ugly. minimum base is 16(!) |
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struct basecoder |
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{ |
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charmap cmap; |
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unsigned int enc_len [MAX_DEC_LEN]; |
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unsigned int dec_len [MAX_ENC_LEN]; |
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|
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unsigned int encode_len (unsigned int len); |
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unsigned int decode_len (unsigned int len); |
113 |
|
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unsigned int encode (char *dst, u8 *src, unsigned int len); |
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unsigned int decode (u8 *dst, char *src, unsigned int len); |
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|
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basecoder (const char *cmap); |
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}; |
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|
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basecoder::basecoder (const char *cmap) |
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: cmap (cmap) |
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{ |
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for (unsigned int len = 0; len < MAX_DEC_LEN; ++len) |
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{ |
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u8 src [MAX_DEC_LEN]; |
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u8 dst [MAX_ENC_LEN]; |
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|
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memset (src, 255, len); |
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|
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mp_limb_t m [MAX_LIMBS]; |
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mp_size_t n; |
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|
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n = mpn_set_str (m, src, len, 256); |
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n = mpn_get_str (dst, this->cmap.size, m, n); |
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|
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for (int i = 0; !dst [i]; ++i) |
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n--; |
138 |
|
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enc_len [len] = n; |
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dec_len [n] = len; |
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} |
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} |
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|
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unsigned int basecoder::encode_len (unsigned int len) |
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{ |
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return enc_len [len]; |
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} |
148 |
|
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unsigned int basecoder::decode_len (unsigned int len) |
150 |
{ |
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while (len && !dec_len [len]) |
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--len; |
153 |
|
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return dec_len [len]; |
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} |
156 |
|
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unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len) |
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{ |
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if (!len) |
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return 0; |
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|
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int elen = encode_len (len); |
163 |
|
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mp_limb_t m [MAX_LIMBS]; |
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mp_size_t n; |
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|
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u8 dst_ [MAX_ENC_LEN]; |
168 |
|
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n = mpn_set_str (m, src, len, 256); |
170 |
n = mpn_get_str (dst_, cmap.size, m, n); |
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|
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int plen = elen; // for padding |
173 |
|
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while (n < plen) |
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{ |
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*dst++ = cmap.encode [0]; |
177 |
plen--; |
178 |
} |
179 |
|
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for (unsigned int i = n - plen; i < n; ++i) |
181 |
*dst++ = cmap.encode [dst_ [i]]; |
182 |
|
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return elen; |
184 |
} |
185 |
|
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unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) |
187 |
{ |
188 |
if (!len) |
189 |
return 0; |
190 |
|
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u8 src_ [MAX_ENC_LEN]; |
192 |
unsigned int elen = 0; |
193 |
|
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while (len--) |
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{ |
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u8 val = cmap.decode [(u8)*src++]; |
197 |
|
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if (val != charmap::INVALID) |
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src_ [elen++] = val; |
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} |
201 |
|
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int dlen = decode_len (elen); |
203 |
|
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mp_limb_t m [MAX_LIMBS]; |
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mp_size_t n; |
206 |
|
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u8 dst_ [MAX_DEC_LEN]; |
208 |
|
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n = mpn_set_str (m, src_, elen, cmap.size); |
210 |
n = mpn_get_str (dst_, 256, m, n); |
211 |
|
212 |
if (n < dlen) |
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{ |
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memset (dst, 0, dlen - n); |
215 |
memcpy (dst + dlen - n, dst_, n); |
216 |
} |
217 |
else |
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memcpy (dst, dst_ + n - dlen, dlen); |
219 |
|
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return dlen; |
221 |
} |
222 |
|
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#if 0 |
224 |
struct test { test (); } test; |
225 |
|
226 |
test::test () |
227 |
{ |
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basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz"); |
229 |
|
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u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz"; |
231 |
static char enc[200]; |
232 |
static u8 dec[200]; |
233 |
|
234 |
for (int i = 1; i < 20; i++) |
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{ |
236 |
int elen = cdc.encode (enc, in, i); |
237 |
int dlen = cdc.decode (dec, enc, elen); |
238 |
|
239 |
printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec); |
240 |
} |
241 |
abort (); |
242 |
} |
243 |
#endif |
244 |
|
245 |
// the following sequence has been crafted to |
246 |
// a) look somewhat random |
247 |
// b) the even (and odd) indices never share the same character as upper/lowercase |
248 |
// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) |
249 |
// the other sequences are obviously derived |
250 |
//static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); |
251 |
static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); |
252 |
//static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet |
253 |
static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyO"); |
254 |
|
255 |
///////////////////////////////////////////////////////////////////////////// |
256 |
|
257 |
#define HDRSIZE 6 |
258 |
|
259 |
inline void encode_header (char *data, int clientid, int seqno) |
260 |
{ |
261 |
u8 hdr[3] = { clientid, seqno >> 8, seqno }; |
262 |
|
263 |
assert (clientid < 256); |
264 |
|
265 |
cdc26.encode (data, hdr, 3); |
266 |
} |
267 |
|
268 |
inline void decode_header (char *data, int &clientid, int &seqno) |
269 |
{ |
270 |
u8 hdr[3]; |
271 |
|
272 |
cdc26.decode (hdr, data, HDRSIZE); |
273 |
|
274 |
printf ("DEC %02x %02x %02x %02x\n", hdr[0], hdr[1], hdr[2], hdr[3]); |
275 |
|
276 |
clientid = hdr[0]; |
277 |
seqno = (hdr[1] << 8) | hdr[2]; |
278 |
} |
279 |
|
280 |
///////////////////////////////////////////////////////////////////////////// |
281 |
|
282 |
struct byte_stream |
283 |
{ |
284 |
u8 *data; |
285 |
int maxsize; |
286 |
int fill; |
287 |
|
288 |
byte_stream (int maxsize); |
289 |
~byte_stream (); |
290 |
|
291 |
bool empty () { return !fill; } |
292 |
int size () { return fill; } |
293 |
|
294 |
bool put (u8 *data, unsigned int datalen); |
295 |
bool put (vpn_packet *pkt); |
296 |
vpn_packet *get (); |
297 |
|
298 |
u8 *begin () { return data; } |
299 |
void remove (int count); |
300 |
}; |
301 |
|
302 |
byte_stream::byte_stream (int maxsize) |
303 |
: maxsize (maxsize), fill (0) |
304 |
{ |
305 |
data = new u8 [maxsize]; |
306 |
} |
307 |
|
308 |
byte_stream::~byte_stream () |
309 |
{ |
310 |
delete data; |
311 |
} |
312 |
|
313 |
void byte_stream::remove (int count) |
314 |
{ |
315 |
if (count > fill) |
316 |
abort (); |
317 |
|
318 |
memmove (data, data + count, fill -= count); |
319 |
} |
320 |
|
321 |
bool byte_stream::put (u8 *data, unsigned int datalen) |
322 |
{ |
323 |
if (maxsize - fill < datalen) |
324 |
return false; |
325 |
|
326 |
memcpy (this->data + fill, data, datalen); fill += datalen; |
327 |
|
328 |
return true; |
329 |
} |
330 |
|
331 |
bool byte_stream::put (vpn_packet *pkt) |
332 |
{ |
333 |
if (maxsize - fill < pkt->len + 2) |
334 |
return false; |
335 |
|
336 |
data [fill++] = pkt->len >> 8; |
337 |
data [fill++] = pkt->len; |
338 |
|
339 |
memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len; |
340 |
|
341 |
return true; |
342 |
} |
343 |
|
344 |
vpn_packet *byte_stream::get () |
345 |
{ |
346 |
int len = (data [0] << 8) | data [1]; |
347 |
|
348 |
if (len > MAXSIZE && fill >= 2) |
349 |
abort (); // TODO handle this gracefully, connection reset |
350 |
|
351 |
if (fill < len + 2) |
352 |
return 0; |
353 |
|
354 |
vpn_packet *pkt = new vpn_packet; |
355 |
|
356 |
pkt->len = len; |
357 |
memcpy (&((*pkt)[0]), data + 2, len); |
358 |
remove (len + 2); |
359 |
|
360 |
return pkt; |
361 |
} |
362 |
|
363 |
///////////////////////////////////////////////////////////////////////////// |
364 |
|
365 |
#define FLAG_QUERY ( 0 << 15) |
366 |
#define FLAG_RESPONSE ( 1 << 15) |
367 |
#define FLAG_OP_MASK (15 << 14) |
368 |
#define FLAG_OP_QUERY ( 0 << 11) |
369 |
#define FLAG_AA ( 1 << 10) |
370 |
#define FLAG_TC ( 1 << 9) |
371 |
#define FLAG_RD ( 1 << 8) |
372 |
#define FLAG_RA ( 1 << 7) |
373 |
#define FLAG_AUTH ( 1 << 5) |
374 |
#define FLAG_RCODE_MASK (15 << 0) |
375 |
#define FLAG_RCODE_OK ( 0 << 0) |
376 |
#define FLAG_RCODE_FORMERR ( 1 << 0) |
377 |
#define FLAG_RCODE_SERVFAIL ( 2 << 0) |
378 |
#define FLAG_RCODE_NXDOMAIN ( 3 << 0) |
379 |
#define FLAG_RCODE_REFUSED ( 5 << 0) |
380 |
|
381 |
#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) |
382 |
#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) |
383 |
|
384 |
struct dns_packet : net_packet |
385 |
{ |
386 |
u16 id; |
387 |
u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 |
388 |
u16 qdcount, ancount, nscount, arcount; |
389 |
|
390 |
u8 data[MAXSIZE - 6 * 2]; |
391 |
|
392 |
int decode_label (char *data, int size, int &offs); |
393 |
}; |
394 |
|
395 |
int dns_packet::decode_label (char *data, int size, int &offs) |
396 |
{ |
397 |
char *orig = data; |
398 |
|
399 |
memset (data, 0, size); |
400 |
|
401 |
while (offs < size - 1) |
402 |
{ |
403 |
u8 len = (*this)[offs++]; |
404 |
|
405 |
if (!len) |
406 |
break; |
407 |
else if (len < 64) |
408 |
{ |
409 |
if (size < len + 1 || offs + len >= MAXSIZE - 1) |
410 |
break; |
411 |
|
412 |
memcpy (data, &((*this)[offs]), len); |
413 |
|
414 |
data += len; size -= len; offs += len; |
415 |
*data++ = '.'; size--; |
416 |
} |
417 |
else |
418 |
{ |
419 |
int offs2 = ((len & 63) << 8) + (*this)[offs++]; |
420 |
|
421 |
data += decode_label (data, size, offs2); |
422 |
break; |
423 |
} |
424 |
} |
425 |
|
426 |
return data - orig; |
427 |
} |
428 |
|
429 |
///////////////////////////////////////////////////////////////////////////// |
430 |
|
431 |
struct dns_req |
432 |
{ |
433 |
dns_packet *pkt; |
434 |
tstamp next; |
435 |
int retry; |
436 |
connection *conn; |
437 |
int seqno; |
438 |
|
439 |
dns_req (connection *c); |
440 |
void gen_stream_req (int seqno, byte_stream *stream); |
441 |
}; |
442 |
|
443 |
static u16 dns_id = 12098; // TODO: should be per-vpn |
444 |
|
445 |
static u16 next_id () |
446 |
{ |
447 |
// the simplest lsfr with periodicity 65535 i could find |
448 |
dns_id = (dns_id << 1) |
449 |
| (((dns_id >> 1) |
450 |
^ (dns_id >> 2) |
451 |
^ (dns_id >> 4) |
452 |
^ (dns_id >> 15)) & 1); |
453 |
|
454 |
return dns_id; |
455 |
} |
456 |
|
457 |
dns_req::dns_req (connection *c) |
458 |
: conn (c) |
459 |
{ |
460 |
next = 0; |
461 |
retry = 0; |
462 |
|
463 |
pkt = new dns_packet; |
464 |
|
465 |
pkt->id = next_id (); |
466 |
} |
467 |
|
468 |
void dns_req::gen_stream_req (int seqno, byte_stream *stream) |
469 |
{ |
470 |
this->seqno = seqno; |
471 |
|
472 |
pkt->flags = htons (DEFAULT_CLIENT_FLAGS); |
473 |
pkt->qdcount = htons (1); |
474 |
|
475 |
int offs = 6*2; |
476 |
int dlen = MAX_DOMAIN_SIZE - (strlen (THISNODE->domain) + 2); |
477 |
// MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well, |
478 |
// so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra |
479 |
|
480 |
char enc[256], *encp = enc; |
481 |
encode_header (enc, THISNODE->id, seqno); |
482 |
|
483 |
int datalen = cdc62.decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE); |
484 |
|
485 |
if (datalen > stream->size ()) |
486 |
datalen = stream->size (); |
487 |
|
488 |
int enclen = cdc62.encode (enc + HDRSIZE, stream->begin (), datalen) + HDRSIZE; |
489 |
|
490 |
printf ("cdc62.encode %d->%d:%02x %02x %02x %02x\n", datalen, enclen, |
491 |
stream->begin ()[0], |
492 |
stream->begin ()[1], |
493 |
stream->begin ()[2], |
494 |
stream->begin ()[3]); |
495 |
|
496 |
stream->remove (datalen); |
497 |
|
498 |
while (enclen) |
499 |
{ |
500 |
int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; |
501 |
|
502 |
(*pkt)[offs++] = lbllen; |
503 |
memcpy (pkt->at (offs), encp, lbllen); |
504 |
|
505 |
offs += lbllen; |
506 |
encp += lbllen; |
507 |
|
508 |
enclen -= lbllen; |
509 |
} |
510 |
|
511 |
const char *suffix = THISNODE->domain; |
512 |
|
513 |
// add tunnel domain |
514 |
for (;;) |
515 |
{ |
516 |
const char *end = strchr (suffix, '.'); |
517 |
|
518 |
if (!end) |
519 |
end = suffix + strlen (suffix); |
520 |
|
521 |
int len = end - suffix; |
522 |
|
523 |
(*pkt)[offs++] = len; |
524 |
memcpy (&((*pkt)[offs]), suffix, len); |
525 |
offs += len; |
526 |
|
527 |
if (!*end) |
528 |
break; |
529 |
|
530 |
suffix = end + 1; |
531 |
} |
532 |
|
533 |
(*pkt)[offs++] = 0; |
534 |
(*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; |
535 |
(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; |
536 |
|
537 |
pkt->len = offs; |
538 |
} |
539 |
|
540 |
struct dns_rcv |
541 |
{ |
542 |
int seqno; |
543 |
dns_packet *pkt; // reply packet |
544 |
u8 data [MAXSIZE]; // actually part of the reply packet... |
545 |
int datalen; |
546 |
|
547 |
dns_rcv (int seqno, u8 *data, int datalen); |
548 |
~dns_rcv (); |
549 |
}; |
550 |
|
551 |
dns_rcv::dns_rcv (int seqno, u8 *data, int datalen) |
552 |
: seqno (seqno), pkt (new dns_packet), datalen (datalen) |
553 |
{ |
554 |
memcpy (this->data, data, datalen); |
555 |
} |
556 |
|
557 |
dns_rcv::~dns_rcv () |
558 |
{ |
559 |
delete pkt; |
560 |
} |
561 |
|
562 |
///////////////////////////////////////////////////////////////////////////// |
563 |
|
564 |
struct dns_cfg |
565 |
{ |
566 |
u8 id1, id2, id3; |
567 |
u8 def_ttl; |
568 |
u8 unused1; |
569 |
u16 max_size; |
570 |
u8 flags1, flags2; |
571 |
}; |
572 |
|
573 |
void connection::dnsv4_receive_rep (struct dns_rcv *r) |
574 |
{ |
575 |
dns_rcvpq.push_back (r); |
576 |
|
577 |
printf ("%d got inketc %d (%02x %02x %02x %02x)\n", THISNODE->id, r->seqno |
578 |
,r->data[0] |
579 |
,r->data[1] |
580 |
,r->data[2] |
581 |
,r->data[3] |
582 |
); |
583 |
redo: |
584 |
|
585 |
// find next packet |
586 |
for (vector<dns_rcv *>::iterator i = dns_rcvpq.end (); i-- != dns_rcvpq.begin (); ) |
587 |
if (SEQNO_EQ (dns_rcvseq, (*i)->seqno)) |
588 |
{ |
589 |
// enter the packet into our input stream |
590 |
r = *i; |
591 |
|
592 |
printf ("%d checking for older packet %d\n", THISNODE->id, dns_rcvseq); |
593 |
// remove the oldest packet, look forward, as it's oldest first |
594 |
for (vector<dns_rcv *>::iterator j = dns_rcvpq.begin (); j != dns_rcvpq.end (); ++j) |
595 |
if (SEQNO_EQ ((*j)->seqno, dns_rcvseq - MAX_WINDOW)) |
596 |
{ |
597 |
printf ("%d removing %d\n", THISNODE->id, (*j)->seqno); |
598 |
delete *j; |
599 |
dns_rcvpq.erase (j); |
600 |
break; |
601 |
} |
602 |
|
603 |
dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK; |
604 |
|
605 |
if (!dns_snddq && !dns_rcvdq) |
606 |
{ |
607 |
dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); |
608 |
dns_snddq = new byte_stream (MAX_BACKLOG); |
609 |
|
610 |
dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); |
611 |
} |
612 |
|
613 |
if (!dns_rcvdq->put (r->data, r->datalen)) |
614 |
abort (); // MUST never overflow, can be caused by data corruption, TODO |
615 |
|
616 |
while (vpn_packet *pkt = dns_rcvdq->get ()) |
617 |
{ |
618 |
sockinfo si; |
619 |
si.host = 0; si.port = 0; si.prot = PROT_DNSv4; |
620 |
|
621 |
vpn->recv_vpn_packet (pkt, si); |
622 |
} |
623 |
|
624 |
// check for further packets |
625 |
goto redo; |
626 |
} |
627 |
} |
628 |
|
629 |
dns_packet * |
630 |
vpn::dnsv4_server (dns_packet *pkt) |
631 |
{ |
632 |
u16 flags = ntohs (pkt->flags); |
633 |
|
634 |
//memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len); |
635 |
int offs = 6 * 2; // skip header |
636 |
|
637 |
pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); |
638 |
|
639 |
if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) |
640 |
&& pkt->qdcount == htons (1)) |
641 |
{ |
642 |
char qname[MAXSIZE]; |
643 |
int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); |
644 |
|
645 |
u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; |
646 |
u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; |
647 |
|
648 |
pkt->qdcount = htons (1); |
649 |
pkt->ancount = 0; |
650 |
pkt->nscount = 0; // should be self, as other nameservers reply like this |
651 |
pkt->arcount = 0; // a record for self, as other nameservers reply like this |
652 |
|
653 |
pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); |
654 |
|
655 |
int dlen = strlen (THISNODE->domain); |
656 |
|
657 |
if (qclass == RR_CLASS_IN |
658 |
&& (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT) |
659 |
&& qlen > dlen + 1 + HDRSIZE |
660 |
&& !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) |
661 |
{ |
662 |
// correct class, domain: parse |
663 |
int client, seqno; |
664 |
decode_header (qname, client, seqno); |
665 |
|
666 |
u8 data[MAXSIZE]; |
667 |
int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); |
668 |
|
669 |
printf ("cdc62.decode %d(%d): %02x %02x %02x %02x\n", |
670 |
qlen - (dlen + 1 + HDRSIZE), datalen |
671 |
,data[0] |
672 |
,data[1] |
673 |
,data[2] |
674 |
,data[3]); |
675 |
|
676 |
printf ("SRV got %d <%.*s>\n", seqno, qlen, qname + HDRSIZE);//D |
677 |
printf ("SRV got %d <%.*s>\n", seqno, qlen - (dlen + 1 + HDRSIZE), qname + HDRSIZE);//D |
678 |
|
679 |
if (0 < client && client <= conns.size ()) |
680 |
{ |
681 |
connection *c = conns [client - 1]; |
682 |
|
683 |
for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.end (); i-- != c->dns_rcvpq.begin (); ) |
684 |
if (SEQNO_EQ ((*i)->seqno, seqno)) |
685 |
{ |
686 |
// already seen that request: simply reply with the cached reply |
687 |
dns_rcv *r = *i; |
688 |
|
689 |
printf ("DUPLICATE %d\n", htons (r->pkt->id));//D |
690 |
|
691 |
memcpy (pkt->at (0), r->pkt->at (0), offs = r->pkt->len); |
692 |
pkt->id = r->pkt->id; |
693 |
goto duplicate_request; |
694 |
} |
695 |
|
696 |
// new packet, queue |
697 |
dns_rcv *rcv = new dns_rcv (seqno, data, datalen); |
698 |
c->dnsv4_receive_rep (rcv); |
699 |
|
700 |
// now generate reply |
701 |
pkt->ancount = htons (1); // one answer RR |
702 |
pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); |
703 |
|
704 |
(*pkt) [offs++] = 0xc0; |
705 |
(*pkt) [offs++] = 6 * 2; // same as in query section |
706 |
|
707 |
(*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; |
708 |
(*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; |
709 |
|
710 |
(*pkt) [offs++] = 0; (*pkt) [offs++] = 0; |
711 |
(*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL |
712 |
|
713 |
int dlen = MAX_PKT_SIZE - offs - 2; |
714 |
|
715 |
// bind doesn't compress well, so reduce further by one label length |
716 |
dlen -= qlen; |
717 |
|
718 |
int rdlen_offs = offs += 2; |
719 |
|
720 |
while (c->dns_snddq |
721 |
&& !c->dns_snddq->empty () |
722 |
&& dlen > 1) |
723 |
{ |
724 |
int txtlen = dlen <= 255 ? dlen - 1 : 255; |
725 |
|
726 |
if (txtlen > c->dns_snddq->size ()) |
727 |
txtlen = c->dns_snddq->size (); |
728 |
|
729 |
(*pkt)[offs++] = txtlen; |
730 |
memcpy (pkt->at (offs), c->dns_snddq->begin (), txtlen); |
731 |
offs += txtlen; |
732 |
c->dns_snddq->remove (txtlen); |
733 |
|
734 |
dlen -= txtlen + 1; |
735 |
} |
736 |
|
737 |
// avoid empty TXT rdata |
738 |
if (offs == rdlen_offs) |
739 |
(*pkt)[offs++] = 0; |
740 |
|
741 |
int rdlen = offs - rdlen_offs; |
742 |
|
743 |
(*pkt) [rdlen_offs - 2] = rdlen >> 8; |
744 |
(*pkt) [rdlen_offs - 1] = rdlen; |
745 |
|
746 |
// now update dns_rcv copy |
747 |
rcv->pkt->len = offs; |
748 |
memcpy (rcv->pkt->at (0), pkt->at (0), offs); |
749 |
|
750 |
duplicate_request: ; |
751 |
} |
752 |
else |
753 |
pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); |
754 |
} |
755 |
|
756 |
pkt->len = offs; |
757 |
} |
758 |
|
759 |
return pkt; |
760 |
} |
761 |
|
762 |
void |
763 |
vpn::dnsv4_client (dns_packet *pkt) |
764 |
{ |
765 |
u16 flags = ntohs (pkt->flags); |
766 |
int offs = 6 * 2; // skip header |
767 |
|
768 |
pkt->qdcount = ntohs (pkt->qdcount); |
769 |
pkt->ancount = ntohs (pkt->ancount); |
770 |
|
771 |
// go through our request list and find the corresponding request |
772 |
for (vector<dns_req *>::iterator i = dns_sndpq.begin (); |
773 |
i != dns_sndpq.end (); |
774 |
++i) |
775 |
if ((*i)->pkt->id == pkt->id) |
776 |
{ |
777 |
connection *c = (*i)->conn; |
778 |
int seqno = (*i)->seqno; |
779 |
u8 data[MAXSIZE], *datap = data; |
780 |
|
781 |
delete *i; |
782 |
dns_sndpq.erase (i); |
783 |
|
784 |
if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) |
785 |
{ |
786 |
char qname[MAXSIZE]; |
787 |
|
788 |
while (pkt->qdcount-- && offs < MAXSIZE - 4) |
789 |
{ |
790 |
int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); |
791 |
offs += 4; // skip qtype, qclass |
792 |
} |
793 |
|
794 |
while (pkt->ancount-- && offs < MAXSIZE - 10) |
795 |
{ |
796 |
int qlen = //D |
797 |
pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); |
798 |
|
799 |
printf ("got reply to <%.*s>\n", qlen, qname);//D |
800 |
|
801 |
u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; |
802 |
u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; |
803 |
u32 ttl = (*pkt) [offs++] << 24; |
804 |
ttl |= (*pkt) [offs++] << 16; |
805 |
ttl |= (*pkt) [offs++] << 8; |
806 |
ttl |= (*pkt) [offs++]; |
807 |
|
808 |
u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; |
809 |
|
810 |
if (rdlen <= MAXSIZE - offs) |
811 |
{ |
812 |
// decode bytes, finally |
813 |
|
814 |
while (rdlen) |
815 |
{ |
816 |
int txtlen = (*pkt) [offs++]; |
817 |
|
818 |
assert (txtlen + offs < MAXSIZE - 1); |
819 |
|
820 |
memcpy (datap, pkt->at (offs), txtlen); |
821 |
datap += txtlen; offs += txtlen; |
822 |
|
823 |
rdlen -= txtlen + 1; |
824 |
} |
825 |
|
826 |
} |
827 |
|
828 |
} |
829 |
} |
830 |
|
831 |
// todo: pkt now used |
832 |
c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data)); |
833 |
|
834 |
break; |
835 |
} |
836 |
|
837 |
delete pkt; |
838 |
} |
839 |
|
840 |
void |
841 |
vpn::dnsv4_ev (io_watcher &w, short revents) |
842 |
{ |
843 |
if (revents & EVENT_READ) |
844 |
{ |
845 |
dns_packet *pkt = new dns_packet; |
846 |
struct sockaddr_in sa; |
847 |
socklen_t sa_len = sizeof (sa); |
848 |
|
849 |
pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); |
850 |
|
851 |
if (pkt->len > 0) |
852 |
{ |
853 |
if (pkt->flags & htons (FLAG_TC)) |
854 |
{ |
855 |
slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); |
856 |
//TODO connection reset |
857 |
} |
858 |
|
859 |
if (THISNODE->dns_port) |
860 |
{ |
861 |
pkt = dnsv4_server (pkt); |
862 |
sendto (w.fd, &((*pkt)[0]), pkt->len, 0, (sockaddr *)&sa, sa_len); |
863 |
} |
864 |
else |
865 |
dnsv4_client (pkt); |
866 |
} |
867 |
} |
868 |
} |
869 |
|
870 |
bool |
871 |
connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) |
872 |
{ |
873 |
// never initialized |
874 |
if (!dns_snddq && !dns_rcvdq) |
875 |
{ |
876 |
dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); |
877 |
dns_snddq = new byte_stream (MAX_BACKLOG); |
878 |
|
879 |
//dns_rcvseq = dns_sndseq = 0; |
880 |
|
881 |
dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); |
882 |
} |
883 |
|
884 |
if (!dns_snddq->put (pkt)) |
885 |
return false; |
886 |
|
887 |
// start timer if neccessary |
888 |
if (!THISNODE->dns_port && !dnsv4_tw.active) |
889 |
dnsv4_cb (dnsv4_tw); |
890 |
|
891 |
return true; |
892 |
} |
893 |
|
894 |
void |
895 |
connection::dnsv4_cb (time_watcher &w) |
896 |
{ |
897 |
// check for timeouts and (re)transmit |
898 |
tstamp next = NOW + 60; |
899 |
dns_req *send = 0; |
900 |
|
901 |
for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin (); |
902 |
i != vpn->dns_sndpq.end (); |
903 |
++i) |
904 |
{ |
905 |
dns_req *r = *i; |
906 |
|
907 |
if (r->next <= NOW) |
908 |
{ |
909 |
if (!send) |
910 |
{ |
911 |
send = r; |
912 |
|
913 |
if (r->retry)//D |
914 |
printf ("req %d:%d, retry %d\n", r->seqno, r->pkt->id, r->retry); |
915 |
r->retry++; |
916 |
r->next = NOW + r->retry; |
917 |
} |
918 |
} |
919 |
|
920 |
if (r->next < next) |
921 |
next = r->next; |
922 |
} |
923 |
|
924 |
if (!send |
925 |
&& vpn->dns_sndpq.size () < MAX_OUTSTANDING) |
926 |
{ |
927 |
send = new dns_req (this); |
928 |
send->gen_stream_req (dns_sndseq, dns_snddq); |
929 |
vpn->dns_sndpq.push_back (send); |
930 |
|
931 |
dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK; |
932 |
} |
933 |
|
934 |
tstamp min_next = NOW + (1. / (tstamp)MAX_RATE); |
935 |
|
936 |
if (send) |
937 |
{ |
938 |
dns_packet *pkt = send->pkt; |
939 |
|
940 |
next = min_next; |
941 |
|
942 |
sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ()); |
943 |
} |
944 |
else if (next < min_next) |
945 |
next = min_next; |
946 |
|
947 |
w.start (next); |
948 |
} |
949 |
|
950 |
#endif |
951 |
|