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Comparing gvpe/src/vpn_dns.C (file contents):
Revision 1.1 by pcg, Fri Apr 2 14:42:45 2004 UTC vs.
Revision 1.2 by pcg, Tue Mar 1 04:38:21 2005 UTC

… …
52 52
53/* 53/*
54 54
55protocol, in shorthand :) 55protocol, in shorthand :)
56 56
57<cseqno> ANY? poll for more data 57client -> server <req> ANY?
58 => TXT <sseqno><data> 58server -> client <req> TXT <rep>
59<cseqno><data> TXT? send more data
60 => TXT <empty>
61 59
62sequence numbers are 12 bit, 9 bit packet-number and 3 bit fragment id (7 60<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
63- id, actually) last fragment is sent first, however 61<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
62
63if <client-id> is zero, the connection will be configured:
64
65<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
64 66
65*/ 67*/
68
69#define MAX_LBL_SIZE 63
70#define MAX_PKT_SIZE 512
71
72#define RR_TYPE_TXT 16
73#define RR_TYPE_ANY 255
74#define RR_CLASS_IN 1
75
76// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)
77struct dns64
78{
79 static const char encode_chars[64 + 1];
80 static s8 decode_chars[256];
81
82 static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }
83 static int decode_len (int bytes) { return (bytes * 6) / 8; }
84 static void encode (char *dst, u8 *src, int len);
85 static void decode (u8 *dst, char *src, int len);
86
87 dns64 ();
88} dns64;
89
90const char dns64::encode_chars[64 + 1] = "0123456789-abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ";
91s8 dns64::decode_chars[256];
92
93dns64::dns64 ()
94{
95 for (int i = 0; i < 64; i++)
96 decode_chars [encode_chars [i]] = i + 1;
97}
98
99void dns64::encode (char *dst, u8 *src, int len)
100{
101 // slow, but easy to debug
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
121void dns64::decode (u8 *dst, char *src, int len)
122{
123 // slow, but easy to debug
124 unsigned int accum, bits = 0;
125
126 while (len--)
127 {
128 s8 chr = decode_chars [(u8)*src++];
129
130
131 if (!chr)
132 break;
133
134 accum <<= 6;
135 accum |= chr - 1;
136 bits += 6;
137
138 while (bits >= 8)
139 {
140 *dst++ = accum >> (bits - 8);
141 bits -= 8;
142 }
143 }
144}
145
146#define FLAG_QUERY ( 0 << 15)
147#define FLAG_RESPONSE ( 1 << 15)
148#define FLAG_OP_MASK (15 << 14)
149#define FLAG_OP_QUERY ( 0 << 11)
150#define FLAG_AA ( 1 << 10)
151#define FLAG_TC ( 1 << 9)
152#define FLAG_RD ( 1 << 8)
153#define FLAG_RA ( 1 << 7)
154#define FLAG_RCODE_MASK (15 << 0)
155#define FLAG_RCODE_OK ( 0 << 0)
156#define FLAG_RCODE_FORMERR ( 1 << 0)
157#define FLAG_RCODE_SERVFAIL ( 2 << 0)
158#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
159#define FLAG_RCODE_REFUSED ( 5 << 0)
160
161#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)
162#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD)
163
164struct dns_packet : net_packet
165{
166 u16 id;
167 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
168 u16 qdcount, ancount, nscount, arcount;
169
170 u8 data[MAXSIZE - 6 * 2];
171
172 int decode_label (char *data, int size, int &offs);
173};
174
175int dns_packet::decode_label (char *data, int size, int &offs)
176{
177 char *orig = data;
178
179 memset (data, 0, size);
180
181 while (offs < size - 1)
182 {
183 u8 len = (*this)[offs++];
184
185 if (!len)
186 break;
187 else if (len < 64)
188 {
189 if (size < len + 1 || offs + len >= MAXSIZE - 1)
190 break;
191
192 memcpy (data, &((*this)[offs]), len);
193
194 data += len; size -= len; offs += len;
195 *data++ = '.'; size--;
196 }
197 else
198 {
199 int offs2 = ((len & 63) << 8) + (*this)[offs++];
200
201 data += decode_label (data, size, offs2);
202 break;
203 }
204 }
205
206 return data - orig;
207}
208
209struct dns_cfg
210{
211 u8 id1, id2, id3;
212 u8 def_ttl;
213 u8 unused1;
214 u16 max_size;
215 u8 flags1, flags2;
216};
217
218// reply to client-poll
219void dnsv4_poll (dns_packet *pkt, int &offs)
220{
221 int dlen = MAX_PKT_SIZE - offs - 2;
222
223 (*pkt) [offs++] = 0;
224 (*pkt) [offs++] = 5;
225 memcpy (&((*pkt)[offs]), "\01H\02\xff\x00", 5);
226 offs += 5;
227
228 pkt->ancount = htons (1);
229 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
230
231 printf ("we have room for %d bytes\n", dlen);
232}
66 233
67void 234void
68vpn::dnsv4_ev (io_watcher &w, short revents) 235vpn::dnsv4_ev (io_watcher &w, short revents)
69{ 236{
70 if (revents & EVENT_READ) 237 if (revents & EVENT_READ)
71 { 238 {
239 dns_packet *pkt = new dns_packet;
72 struct sockaddr_in sa; 240 struct sockaddr_in sa;
73 socklen_t sa_len = sizeof (sa); 241 socklen_t sa_len = sizeof (sa);
74 int len; 242
243 int len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
244 pkt->len = len;
245
246 u16 flags = ntohs (pkt->flags);
247
248 if (THISNODE->dns_port)
249 {
250 // server
251 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
252
253 int offs = 6 * 2; // skip header
254
255 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC))
256 && pkt->qdcount == htons (1))
257 {
258 char qname[MAXSIZE];
259 int qlen = pkt->decode_label ((char *)qname, MAXSIZE, offs);
260
261 printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", len,
262 pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D
263
264 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++];
265 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++];
266
267 pkt->qdcount = htons (1);
268 pkt->ancount = 0;
269 pkt->nscount = 0; // should be self, as other nameservers reply like this
270 pkt->arcount = 0; // a record for self, as other nameservers reply like this
271
272 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN);
273
274 int dlen = strlen (THISNODE->domain);
275
276 if (qclass == RR_CLASS_IN
277 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
278 && qlen > dlen + 1
279 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))
280 {
281 // correct class, now generate reply
282 pkt->ancount = htons (1); // one answer RR
283
284 (*pkt) [offs++] = 0xc0;
285 (*pkt) [offs++] = 6 * 2; // same as in query section
286
287 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT;
288 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN;
289
290 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0;
291 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL
292
293 dnsv4_poll (pkt, offs);
294 printf ("correct class\n");
295 }
296 }
297
298 sendto (w.fd, &((*pkt)[0]), offs, 0, (sockaddr *)&sa, sa_len);
299 }
300 else
301 {
302 // client
303 }
75 } 304 }
76} 305}
77 306
78bool 307bool
79vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) 308vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)

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