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