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comparison src/io/rx_packet.c @ 0:d39e1d0d75b6

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author paulo@hit-nxdomain.opendns.com
date Sat, 20 Feb 2010 21:18:28 -0800
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-1:000000000000 0:d3a1c2459d22
1 /*
2 * $Id: rx_packet.c,v 1.7 2004/02/15 04:53:38 hipnod Exp $
3 *
4 * Copyright (C) 2003 giFT project (gift.sourceforge.net)
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation; either version 2, or (at your option) any
9 * later version.
10 *
11 * This program is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * General Public License for more details.
15 */
16
17 #include "gt_gnutella.h"
18
19 #include "rx_stack.h"
20 #include "rx_layer.h"
21
22 #include "gt_packet.h"
23 #include "rx_packet.h"
24
25 /*****************************************************************************/
26
27 struct rx_packet
28 {
29 struct io_buf *partial;
30 rx_packet_handler_t handler;
31 void *udata;
32 };
33
34 /*****************************************************************************/
35
36 #define RX_PACKET(rx) \
37 ((struct rx_packet *) ((rx)->udata))
38
39 /*****************************************************************************/
40
41 static void null_packet_handler (void *udata, GtPacket *packet)
42 {
43 gt_packet_free (packet);
44 }
45
46 static BOOL rx_packet_init (struct rx_layer *rx, void *udata)
47 {
48 struct rx_packet *rx_packet;
49
50 if (!(rx_packet = NEW (struct rx_packet)))
51 return FALSE;
52
53 rx->udata = rx_packet;
54
55 /* discard the packets received */
56 rx_packet->handler = null_packet_handler;
57 return TRUE;
58 }
59
60 static void rx_packet_destroy (struct rx_layer *rx)
61 {
62 struct rx_packet *rx_packet = RX_PACKET(rx);
63
64 io_buf_free (rx_packet->partial);
65 FREE (rx_packet);
66 }
67
68 static void rx_packet_disable (struct rx_layer *rx)
69 {
70 /* NOP: lower layer will stop sending us data -- it'd better
71 * stop now */
72 }
73
74 static void rx_packet_enable (struct rx_layer *rx)
75 {
76 /* NOP: the lower layer will start sending us data again */
77 }
78
79 /*****************************************************************************/
80
81 static GtPacket *make_packet (struct rx_layer *rx, struct rx_packet *rx_packet,
82 size_t packet_size)
83 {
84 GtPacket *packet;
85 struct io_buf *pbuf = rx_packet->partial;
86
87 assert (io_buf_len (pbuf) == packet_size);
88 assert (packet_size < GT_PACKET_MAX);
89
90 /* construct a complete packet from the data in the binary buf */
91 packet = gt_packet_unserialize (pbuf->data, packet_size);
92
93 /*
94 * TODO: gt_packet_unserialize() currently copies the data, but should
95 * really take ownership of the data in place. That would also allow the
96 * null terminator in the io_buf to terminate the last string in the
97 * packet, if any.
98 */
99 io_buf_free (pbuf);
100 rx_packet->partial = NULL;
101
102 if (!packet)
103 {
104 gt_rx_stack_abort (rx->stack);
105 return NULL;
106 }
107
108 return packet;
109 }
110
111 static BOOL fill_up_to (struct rx_layer *rx, struct io_buf *dst,
112 struct io_buf *src, size_t fill_size)
113 {
114 size_t new_len;
115 size_t old_len;
116 size_t len_to_read;
117
118 old_len = io_buf_len (dst);
119 new_len = io_buf_len (src);
120
121 /* skip if we already have enough */
122 if (old_len >= fill_size)
123 return TRUE;
124
125 len_to_read = MIN (fill_size - old_len, new_len);
126
127 /* ensure the packet has enough room */
128 if (!io_buf_resize (dst, old_len + len_to_read))
129 {
130 gt_rx_stack_abort (rx->stack);
131 return FALSE;
132 }
133
134 io_buf_copy (dst, src, len_to_read);
135
136 if (io_buf_len (dst) >= fill_size)
137 return TRUE;
138
139 return FALSE;
140 }
141
142 static BOOL fill_header (struct rx_layer *rx, struct rx_packet *rx_packet,
143 struct io_buf *io_buf)
144 {
145 struct io_buf *dst = rx_packet->partial;
146 struct io_buf *src = io_buf;
147
148 if (!fill_up_to (rx, dst, src, GNUTELLA_HDR_LEN))
149 {
150 /* this would fail if there was an alloc failure */
151 assert (io_buf_read_avail (io_buf) == 0);
152 return FALSE;
153 }
154
155 return TRUE;
156 }
157
158 /*
159 * We must read all the data the lower layer has sent and buffer
160 * partial packets, because otherwise we would poll the CPU if the
161 * packet were bigger than the buffer size of one of the layer
162 * layers under this one.
163 */
164 static BOOL read_packet (struct rx_layer *rx, struct rx_packet *rx_packet,
165 struct io_buf *io_buf, GtPacket **ret)
166 {
167 uint32_t payload_len;
168 size_t partial_len;
169 uint32_t packet_size;
170 struct io_buf *partial = rx_packet->partial;
171 GtPacket *pkt;
172
173 *ret = NULL;
174
175 partial_len = io_buf_len (partial);
176 assert (partial_len >= GNUTELLA_HDR_LEN);
177
178 /*
179 * The partial packet is now at least 23 bytes. Look in the header for
180 * the payload length so we know how much we need to read before the
181 * packet is complete.
182 */
183 payload_len = get_payload_len (partial->data);
184 packet_size = payload_len + GNUTELLA_HDR_LEN;
185
186 /*
187 * Check for wraparound, and reset the packet size to its payload len.
188 * Its likely we've experienced a protocol de-sync here. Set the size so
189 * the connection will be closed.
190 */
191 if (packet_size < GNUTELLA_HDR_LEN)
192 packet_size = GT_PACKET_MAX;
193
194 if (packet_size >= GT_PACKET_MAX)
195 {
196 if (IO_DEBUG)
197 GT->dbg (GT, "received too large packet(%d)", packet_size);
198
199 /* TODO: should send a BYE message here */
200 gt_rx_stack_abort (rx->stack);
201 return FALSE;
202 }
203
204 if (!fill_up_to (rx, partial, io_buf, packet_size))
205 {
206 /* this would fail if there was an alloc failure */
207 assert (io_buf_read_avail (io_buf) == 0);
208 return FALSE;
209 }
210
211 /* yay, read a packet */
212 pkt = make_packet (rx, rx_packet, packet_size);
213 *ret = pkt;
214
215 return (pkt == NULL ? FALSE : TRUE);
216 }
217
218 /*
219 * Receive a message buffer from the lower layer, parse it into as many
220 * packets as it contains, and pass those to our handler function.
221 *
222 * This is meant to be the top layer of the rx stack only.
223 *
224 * TODO: A handler could be implemented as another layer, should think
225 * about this approach instead.
226 */
227 static void rx_packet_recv (struct rx_layer *rx, struct io_buf *io_buf)
228 {
229 GtPacket *packet = NULL;
230 struct rx_packet *rx_packet;
231
232 rx_packet = RX_PACKET(rx);
233
234 while (rx->enabled && io_buf_read_avail (io_buf) > 0)
235 {
236 /* allocate a new partial buffer, if one is not present yet */
237 if (!rx_packet->partial &&
238 !(rx_packet->partial = io_buf_new (GNUTELLA_HDR_LEN)))
239 {
240 gt_rx_stack_abort (rx->stack);
241 break;
242 }
243
244 /* try to read the first 23 bytes */
245 if (!fill_header (rx, rx_packet, io_buf))
246 break;
247
248 /*
249 * Read the payload. If there arent enough bytes to complete the
250 * packet, we finish it later.
251 */
252 if (!read_packet (rx, rx_packet, io_buf, &packet))
253 {
254 assert (packet == NULL);
255 break;
256 }
257
258 assert (packet != NULL);
259 (*rx_packet->handler) (rx_packet->udata, packet);
260
261 /* freeing the packet here means the callback must make its own
262 * provisions for storing the packet's data */
263 gt_packet_free (packet);
264 packet = NULL;
265 }
266
267 io_buf_free (io_buf);
268 }
269
270 /*****************************************************************************/
271
272 struct rx_layer_ops gt_rx_packet_ops =
273 {
274 rx_packet_init,
275 rx_packet_destroy,
276 rx_packet_enable,
277 rx_packet_disable,
278 rx_packet_recv,
279 };
280
281 void gt_rx_packet_set_handler (struct rx_layer *rx,
282 rx_packet_handler_t handler,
283 void *udata)
284 {
285 struct rx_packet *rx_packet = RX_PACKET(rx);
286
287 rx_packet->handler = handler;
288 rx_packet->udata = udata;
289 }