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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: endpt.c,v 1.4 2004/04/08 01:36:25 mdw Exp $ |
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4 | * |
5 | * Generic endpoint abstraction |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of the `fw' port forwarder. |
13 | * |
14 | * `fw' is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * `fw' is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
25 | * along with `fw'; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
27 | */ |
28 | |
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29 | /*----- Header files ------------------------------------------------------*/ |
30 | |
31 | #include "config.h" |
32 | |
33 | #include <errno.h> |
34 | #include <stdio.h> |
35 | #include <stdlib.h> |
36 | #include <string.h> |
37 | |
38 | #include <sys/types.h> |
39 | #include <unistd.h> |
40 | #include <fcntl.h> |
41 | |
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42 | #include <mLib/alloc.h> |
43 | |
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44 | #include "chan.h" |
45 | #include "endpt.h" |
46 | |
47 | /*----- Data structures ---------------------------------------------------*/ |
48 | |
49 | /* --- Pairs of channels --- * |
50 | * |
51 | * Channels are always allocated and freed in pairs. It makes sense to keep |
52 | * the pair together. (It also wastes less memory.) |
53 | */ |
54 | |
55 | typedef struct chanpair { |
56 | struct chanpair *next; |
57 | chan ab, ba; |
58 | } chanpair; |
59 | |
60 | /* --- The `private data structure' --- * |
61 | * |
62 | * This is called a @tango@ because it takes two (endpoints). |
63 | */ |
64 | |
65 | typedef struct tango { |
66 | struct tango *next, *prev; /* A big list of all tangos */ |
67 | endpt *a, *b; /* The two endpoints */ |
68 | unsigned s; /* State of the connection */ |
69 | chanpair *c; /* The pair of channels */ |
70 | } tango; |
71 | |
72 | #define EPS_AB 1u |
73 | #define EPS_BA 2u |
74 | |
75 | /*----- Static variables --------------------------------------------------*/ |
76 | |
77 | static chanpair *chans = 0; /* List of spare channel pairs */ |
78 | static tango *tangos = 0; /* List of tangos */ |
79 | |
80 | /*----- Main code ---------------------------------------------------------*/ |
81 | |
82 | /* --- @doneab@, @doneba@ --- * |
83 | * |
84 | * Arguments: @void *p@ = pointer to a tango block |
85 | * |
86 | * Returns: --- |
87 | * |
88 | * Use: Handles completion of a channel. |
89 | */ |
90 | |
91 | static void doneab(void *p) |
92 | { |
93 | tango *t = p; |
94 | t->s &= ~EPS_AB; |
95 | t->b->ops->wclose(t->b); |
96 | if (!t->s) |
97 | endpt_kill(t->a); |
98 | } |
99 | |
100 | static void doneba(void *p) |
101 | { |
102 | tango *t = p; |
103 | t->s &= ~EPS_BA; |
104 | t->a->ops->wclose(t->a); |
105 | if (!t->s) |
106 | endpt_kill(t->a); |
107 | } |
108 | |
109 | /* --- @endpt_kill@ --- * |
110 | * |
111 | * Arguments: @endpt *a@ = an endpoint |
112 | * |
113 | * Returns: --- |
114 | * |
115 | * Use: Kills an endpoint. If the endpoint is joined to another, the |
116 | * other endpoint is also killed, as is the connection between |
117 | * them (and that's the tricky bit). |
118 | */ |
119 | |
120 | void endpt_kill(endpt *a) |
121 | { |
122 | tango *t; |
123 | endpt *b; |
124 | |
125 | /* --- If the endpont is unconnected, just close it --- */ |
126 | |
127 | if (!a->t) { |
128 | a->ops->close(a); |
129 | return; |
130 | } |
131 | t = a->t; |
132 | a = t->a; |
133 | b = t->b; |
134 | |
135 | /* --- See whether to close channels --- * |
136 | * |
137 | * I'll only have opened channels if both things are files. Also, the |
138 | * channel from @b@ to @a@ will only be open if @b@ is not pending. |
139 | */ |
140 | |
141 | if (a->f & b->f & EPF_FILE) { |
142 | if (t->s & EPS_AB) |
143 | chan_close(&t->c->ab); |
144 | if (!(b->f & EPF_PENDING) && (t->s & EPS_BA)) |
145 | chan_close(&t->c->ba); |
146 | t->c->next = chans; |
147 | chans = t->c; |
148 | } |
149 | |
150 | /* --- Now just throw the endpoints and tango block away --- */ |
151 | |
152 | a->ops->close(a); |
153 | b->ops->close(b); |
154 | if (t->next) |
155 | t->next->prev = t->prev; |
156 | if (t->prev) |
157 | t->prev->next = t->next; |
158 | else |
159 | tangos = t->next; |
160 | DESTROY(t); |
161 | } |
162 | |
163 | /* --- @endpt_killall@ --- * |
164 | * |
165 | * Arguments: --- |
166 | * |
167 | * Returns: --- |
168 | * |
169 | * Use: Destroys all current endpoint connections. Used when |
170 | * shutting down. |
171 | */ |
172 | |
173 | void endpt_killall(void) |
174 | { |
175 | tango *t = tangos; |
176 | while (t) { |
177 | tango *tt = t; |
178 | t = t->next; |
179 | endpt_kill(tt->a); |
180 | } |
181 | tangos = 0; |
182 | } |
183 | |
184 | /* --- @endpt_join@ --- * |
185 | * |
186 | * Arguments: @endpt *a@ = pointer to first endpoint |
187 | * @endpt *b@ = pointer to second endpoint |
188 | * |
189 | * Returns: --- |
190 | * |
191 | * Use: Joins two endpoints together. It's OK to join endpoints |
192 | * which are already joined; in fact, the the right thing to do |
193 | * when your endpoint decides that it's not pending any more is |
194 | * to join it to its partner again. |
195 | */ |
196 | |
197 | void endpt_join(endpt *a, endpt *b) |
198 | { |
199 | tango *t = a->t; |
200 | |
201 | /* --- If there is no tango yet, create one --- */ |
202 | |
203 | if (!t) { |
204 | t = CREATE(tango); |
205 | t->next = tangos; |
206 | t->prev = 0; |
207 | t->a = b->other = a; |
208 | t->b = a->other = b; |
209 | a->t = b->t = t; |
210 | t->s = EPS_AB | EPS_BA; |
211 | t->c = 0; |
212 | if (tangos) |
213 | tangos->prev = t; |
214 | tangos = t; |
215 | } |
216 | |
217 | /* --- If both endpoints are unfinished, leave them for a while --- */ |
218 | |
219 | if (a->f & b->f & EPF_PENDING) |
220 | return; |
221 | |
222 | /* --- At least one endpoint is ready --- * |
223 | * |
224 | * If both endpoints are files then I can speculatively create the |
225 | * channels, which will let data start flowing a bit. Otherwise, I'll just |
226 | * have to wait some more. |
227 | */ |
228 | |
229 | if ((a->f | b->f) & EPF_PENDING) { |
230 | |
231 | /* --- Only be interested if both things are files --- */ |
232 | |
233 | if (!t->c && (a->f & b->f & EPF_FILE)) { |
234 | |
235 | /* --- Allocate a pair of channels --- */ |
236 | |
237 | if (!chans) |
238 | t->c = xmalloc(sizeof(*t->c)); |
239 | else { |
240 | t->c = chans; |
241 | chans = chans->next; |
242 | } |
243 | |
244 | /* --- Make @a@ the endpoint which is ready --- */ |
245 | |
246 | if (a->f & EPF_PENDING) { |
247 | t->b = a; t->a = b; |
248 | a = t->a; b = t->b; |
249 | } |
250 | |
251 | /* --- Open one channel to read from @a@ --- */ |
252 | |
253 | chan_open(&t->c->ab, a->in->fd, -1, doneab, t); |
254 | } |
255 | return; |
256 | } |
257 | |
258 | /* --- Both endpoints are now ready --- * |
259 | * |
260 | * There are four cases to consider here. |
261 | */ |
262 | |
263 | /* --- Case 1 --- * |
264 | * |
265 | * Neither endpoint is a file. I need to make a pair of pipes and tell |
266 | * both endpoints to attach to them. I can then close the pipes and |
267 | * discard the tango. |
268 | */ |
269 | |
270 | if (!((a->f | b->f) & EPF_FILE)) { |
271 | int pab[2], pba[2]; |
272 | reffd *rab, *wab, *rba, *wba; |
273 | |
274 | /* --- Create the pipes --- */ |
275 | |
276 | if (pipe(pab)) goto tidy_nofile_0; |
277 | if (pipe(pba)) goto tidy_nofile_1; |
278 | |
279 | /* --- Attach reference counters --- */ |
280 | |
281 | rab = reffd_init(pab[0]); wab = reffd_init(pab[1]); |
282 | rba = reffd_init(pba[0]); wba = reffd_init(pba[1]); |
283 | a->ops->attach(a, rba, wab); |
284 | b->ops->attach(b, rab, wba); |
285 | REFFD_DEC(rab); REFFD_DEC(wab); |
286 | REFFD_DEC(rba); REFFD_DEC(wba); |
287 | goto tidy_nofile_0; |
288 | |
289 | /* --- Tidy up after a mess --- */ |
290 | |
291 | tidy_nofile_1: |
292 | close(pab[0]); close(pab[1]); |
293 | tidy_nofile_0: |
294 | a->ops->close(a); |
295 | b->ops->close(b); |
296 | if (t->next) |
297 | t->next->prev = t->prev; |
298 | if (t->prev) |
299 | t->prev->next = t->next; |
300 | else |
301 | tangos = t->next; |
302 | DESTROY(t); |
303 | return; |
304 | } |
305 | |
306 | /* --- Case 2 --- * |
307 | * |
308 | * One endpoint is a file, the other isn't. I just attach the other |
309 | * endpoint to the file and stand well back. |
310 | */ |
311 | |
312 | if ((a->f ^ b->f) & EPF_FILE) { |
313 | |
314 | /* --- Let @a@ be the endpoint with the file --- */ |
315 | |
316 | if (b->f & EPF_FILE) { |
317 | endpt *e; |
318 | e = a; a = b; b = e; |
319 | } |
320 | |
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321 | /* --- Attach the non-file endpoint to the file and run away --- * |
322 | * |
323 | * Leave it as the non-file's responsibility to close the other endpoint |
324 | * when it's ready. It should also close itself at that time. |
325 | */ |
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326 | |
327 | b->ops->attach(b, a->in, a->out); |
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328 | b->ops->file(b, a); |
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329 | if (t->next) |
330 | t->next->prev = t->prev; |
331 | if (t->prev) |
332 | t->prev->next = t->next; |
333 | else |
334 | tangos = t->next; |
335 | DESTROY(t); |
336 | return; |
337 | } |
338 | |
339 | /* --- Case 3 --- * |
340 | * |
341 | * Both endpoints are files and I have a partially created channel pair. I |
342 | * need to create the other channel and add a destination to the first one. |
343 | * In this case, @t->b@ is the endpoint which has just finished setting |
344 | * itself up. |
345 | */ |
346 | |
347 | if (t->c) { |
348 | a = t->a; b = t->b; |
349 | chan_open(&t->c->ba, b->in->fd, a->out->fd, doneba, t); |
350 | chan_dest(&t->c->ab, b->out->fd); |
351 | return; |
352 | } |
353 | |
354 | /* --- Case 4 --- * |
355 | * |
356 | * Both endpoints are files and I don't have a partially created channel |
357 | * pair. I need to allocate a channel pair and create both channels. |
358 | */ |
359 | |
360 | if (!chans) |
361 | t->c = xmalloc(sizeof(*t->c)); |
362 | else { |
363 | t->c = chans; |
364 | chans = chans->next; |
365 | } |
366 | chan_open(&t->c->ab, a->in->fd, b->out->fd, doneab, t); |
367 | chan_open(&t->c->ba, b->in->fd, a->out->fd, doneba, t); |
368 | return; |
369 | } |
370 | |
371 | /*----- That's all, folks -------------------------------------------------*/ |