mdw@git.distorted.org.uk Git - fwd/blob - endpt.c

   1 /* -*-c-*-
   2  *
   3  * $Id: endpt.c,v 1.2 1999/10/22 22:46:17 mdw Exp $
   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
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: endpt.c,v $
  32  * Revision 1.2  1999/10/22 22:46:17  mdw
  33  * When a non-file endpoint is attached to a file, keep the file endpoint
  34  * open until the nonfile is done.  This stops socket sources from
  35  * resetting their connection limits too early.
  36  *
  37  * Revision 1.1  1999/07/26 23:33:01  mdw
  38  * Infrastructure for the new design.
  39  *
  40  */
  41
  42 /*----- Header files ------------------------------------------------------*/
  43
  44 #include "config.h"
  45
  46 #include <errno.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50
  51 #include <sys/types.h>
  52 #include <unistd.h>
  53 #include <fcntl.h>
  54
  55 #include "chan.h"
  56 #include "endpt.h"
  57
  58 /*----- Data structures ---------------------------------------------------*/
  59
  60 /* --- Pairs of channels --- *
  61  *
  62  * Channels are always allocated and freed in pairs.  It makes sense to keep
  63  * the pair together.  (It also wastes less memory.)
  64  */
  65
  66 typedef struct chanpair {
  67   struct chanpair *next;
  68   chan ab, ba;
  69 } chanpair;
  70
  71 /* --- The `private data structure' --- *
  72  *
  73  * This is called a @tango@ because it takes two (endpoints).
  74  */
  75
  76 typedef struct tango {
  77   struct tango *next, *prev;            /* A big list of all tangos */
  78   endpt *a, *b;                         /* The two endpoints */
  79   unsigned s;                           /* State of the connection */
  80   chanpair *c;                          /* The pair of channels */
  81 } tango;
  82
  83 #define EPS_AB 1u
  84 #define EPS_BA 2u
  85
  86 /*----- Static variables --------------------------------------------------*/
  87
  88 static chanpair *chans = 0;             /* List of spare channel pairs */
  89 static tango *tangos = 0;               /* List of tangos */
  90
  91 /*----- Main code ---------------------------------------------------------*/
  92
  93 /* --- @doneab@, @doneba@ --- *
  94  *
  95  * Arguments:   @void *p@ = pointer to a tango block
  96  *
  97  * Returns:     ---
  98  *
  99  * Use:         Handles completion of a channel.
 100  */
 101
 102 static void doneab(void *p)
 103 {
 104   tango *t = p;
 105   t->s &= ~EPS_AB;
 106   t->b->ops->wclose(t->b);
 107   if (!t->s)
 108     endpt_kill(t->a);
 109 }
 110
 111 static void doneba(void *p)
 112 {
 113   tango *t = p;
 114   t->s &= ~EPS_BA;
 115   t->a->ops->wclose(t->a);
 116   if (!t->s)
 117     endpt_kill(t->a);
 118 }
 119
 120 /* --- @endpt_kill@ --- *
 121  *
 122  * Arguments:   @endpt *a@ = an endpoint
 123  *
 124  * Returns:     ---
 125  *
 126  * Use:         Kills an endpoint.  If the endpoint is joined to another, the
 127  *              other endpoint is also killed, as is the connection between
 128  *              them (and that's the tricky bit).
 129  */
 130
 131 void endpt_kill(endpt *a)
 132 {
 133   tango *t;
 134   endpt *b;
 135
 136   /* --- If the endpont is unconnected, just close it --- */
 137
 138   if (!a->t) {
 139     a->ops->close(a);
 140     return;
 141   }
 142   t = a->t;
 143   a = t->a;
 144   b = t->b;
 145
 146   /* --- See whether to close channels --- *
 147    *
 148    * I'll only have opened channels if both things are files.  Also, the
 149    * channel from @b@ to @a@ will only be open if @b@ is not pending.
 150    */
 151
 152   if (a->f & b->f & EPF_FILE) {
 153     if (t->s & EPS_AB)
 154       chan_close(&t->c->ab);
 155     if (!(b->f & EPF_PENDING) && (t->s & EPS_BA))
 156       chan_close(&t->c->ba);
 157     t->c->next = chans;
 158     chans = t->c;
 159   }
 160
 161   /* --- Now just throw the endpoints and tango block away --- */
 162
 163   a->ops->close(a);
 164   b->ops->close(b);
 165   if (t->next)
 166     t->next->prev = t->prev;
 167   if (t->prev)
 168     t->prev->next = t->next;
 169   else
 170     tangos = t->next;
 171   DESTROY(t);
 172 }
 173
 174 /* --- @endpt_killall@ --- *
 175  *
 176  * Arguments:   ---
 177  *
 178  * Returns:     ---
 179  *
 180  * Use:         Destroys all current endpoint connections.  Used when
 181  *              shutting down.
 182  */
 183
 184 void endpt_killall(void)
 185 {
 186   tango *t = tangos;
 187   while (t) {
 188     tango *tt = t;
 189     t = t->next;
 190     endpt_kill(tt->a);
 191   }
 192   tangos = 0;
 193 }
 194
 195 /* --- @endpt_join@ --- *
 196  *
 197  * Arguments:   @endpt *a@ = pointer to first endpoint
 198  *              @endpt *b@ = pointer to second endpoint
 199  *
 200  * Returns:     ---
 201  *
 202  * Use:         Joins two endpoints together.  It's OK to join endpoints
 203  *              which are already joined; in fact, the the right thing to do
 204  *              when your endpoint decides that it's not pending any more is
 205  *              to join it to its partner again.
 206  */
 207
 208 void endpt_join(endpt *a, endpt *b)
 209 {
 210   tango *t = a->t;
 211
 212   /* --- If there is no tango yet, create one --- */
 213
 214   if (!t) {
 215     t = CREATE(tango);
 216     t->next = tangos;
 217     t->prev = 0;
 218     t->a = b->other = a;
 219     t->b = a->other = b;
 220     a->t = b->t = t;
 221     t->s = EPS_AB | EPS_BA;
 222     t->c = 0;
 223     if (tangos)
 224       tangos->prev = t;
 225     tangos = t;
 226   }
 227
 228   /* --- If both endpoints are unfinished, leave them for a while --- */
 229
 230   if (a->f & b->f & EPF_PENDING)
 231     return;
 232
 233   /* --- At least one endpoint is ready --- *
 234    *
 235    * If both endpoints are files then I can speculatively create the
 236    * channels, which will let data start flowing a bit.  Otherwise, I'll just
 237    * have to wait some more.
 238    */
 239
 240   if ((a->f | b->f) & EPF_PENDING) {
 241
 242     /* --- Only be interested if both things are files --- */
 243
 244     if (!t->c && (a->f & b->f & EPF_FILE)) {
 245
 246       /* --- Allocate a pair of channels --- */
 247
 248       if (!chans)
 249         t->c = xmalloc(sizeof(*t->c));
 250       else {
 251         t->c = chans;
 252         chans = chans->next;
 253       }
 254
 255       /* --- Make @a@ the endpoint which is ready --- */
 256
 257       if (a->f & EPF_PENDING) {
 258         t->b = a; t->a = b;
 259         a = t->a; b = t->b;
 260       }
 261
 262       /* --- Open one channel to read from @a@ --- */
 263
 264       chan_open(&t->c->ab, a->in->fd, -1, doneab, t);
 265     }
 266     return;
 267   }
 268
 269   /* --- Both endpoints are now ready --- *
 270    *
 271    * There are four cases to consider here.
 272    */
 273
 274   /* --- Case 1 --- *
 275    *
 276    * Neither endpoint is a file.  I need to make a pair of pipes and tell
 277    * both endpoints to attach to them.  I can then close the pipes and
 278    * discard the tango.
 279    */
 280
 281   if (!((a->f | b->f) & EPF_FILE)) {
 282     int pab[2], pba[2];
 283     reffd *rab, *wab, *rba, *wba;
 284
 285     /* --- Create the pipes --- */
 286
 287     if (pipe(pab)) goto tidy_nofile_0;
 288     if (pipe(pba)) goto tidy_nofile_1;
 289
 290     /* --- Attach reference counters --- */
 291
 292     rab = reffd_init(pab[0]); wab = reffd_init(pab[1]);
 293     rba = reffd_init(pba[0]); wba = reffd_init(pba[1]);
 294     a->ops->attach(a, rba, wab);
 295     b->ops->attach(b, rab, wba);
 296     REFFD_DEC(rab); REFFD_DEC(wab);
 297     REFFD_DEC(rba); REFFD_DEC(wba);
 298     goto tidy_nofile_0;
 299
 300     /* --- Tidy up after a mess --- */
 301
 302   tidy_nofile_1:
 303     close(pab[0]); close(pab[1]);
 304   tidy_nofile_0:
 305     a->ops->close(a);
 306     b->ops->close(b);
 307     if (t->next)
 308       t->next->prev = t->prev;
 309     if (t->prev)
 310       t->prev->next = t->next;
 311     else
 312       tangos = t->next;
 313     DESTROY(t);
 314     return;
 315   }
 316
 317   /* --- Case 2 --- *
 318    *
 319    * One endpoint is a file, the other isn't.  I just attach the other
 320    * endpoint to the file and stand well back.
 321    */
 322
 323   if ((a->f ^ b->f) & EPF_FILE) {
 324
 325     /* --- Let @a@ be the endpoint with the file --- */
 326
 327     if (b->f & EPF_FILE) {
 328       endpt *e;
 329       e = a; a = b; b = e;
 330     }
 331
 332     /* --- Attach the non-file endpoint to the file and run away --- *
 333      *
 334      * Leave it as the non-file's responsibility to close the other endpoint
 335      * when it's ready.  It should also close itself at that time.
 336      */
 337
 338     b->ops->attach(b, a->in, a->out);
 339     b->ops->file(b, a);
 340     if (t->next)
 341       t->next->prev = t->prev;
 342     if (t->prev)
 343       t->prev->next = t->next;
 344     else
 345       tangos = t->next;
 346     DESTROY(t);
 347     return;
 348   }
 349
 350   /* --- Case 3 --- *
 351    *
 352    * Both endpoints are files and I have a partially created channel pair.  I
 353    * need to create the other channel and add a destination to the first one.
 354    * In this case, @t->b@ is the endpoint which has just finished setting
 355    * itself up.
 356    */
 357
 358   if (t->c) {
 359     a = t->a; b = t->b;
 360     chan_open(&t->c->ba, b->in->fd, a->out->fd, doneba, t);
 361     chan_dest(&t->c->ab, b->out->fd);
 362     return;
 363   }
 364
 365   /* --- Case 4 --- *
 366    *
 367    * Both endpoints are files and I don't have a partially created channel
 368    * pair.  I need to allocate a channel pair and create both channels.
 369    */
 370
 371   if (!chans)
 372     t->c = xmalloc(sizeof(*t->c));
 373   else {
 374     t->c = chans;
 375     chans = chans->next;
 376   }
 377   chan_open(&t->c->ab, a->in->fd, b->out->fd, doneab, t);
 378   chan_open(&t->c->ba, b->in->fd, a->out->fd, doneba, t);
 379   return;
 380 }
 381
 382 /*----- That's all, folks -------------------------------------------------*/