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

   1 /* -*-c-*-
   2  *
   3  * $Id: endpt.c,v 1.4 2004/04/08 01:36:25 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 /*----- 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
  42 #include <mLib/alloc.h>
  43
  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
 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      */
 326
 327     b->ops->attach(b, a->in, a->out);
 328     b->ops->file(b, a);
 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 -------------------------------------------------*/