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

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