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

   1 /* -*-c-*-
   2  *
   3  * Channel management
   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 <sys/time.h>
  38 #include <unistd.h>
  39 #include <sys/uio.h>
  40
  41 #include <mLib/alloc.h>
  42 #include <mLib/conn.h>
  43 #include <mLib/sel.h>
  44
  45 #include "chan.h"
  46 #include "fw.h"
  47
  48 #ifdef CHAN_DEBUG
  49 #  define D(x) x
  50 #else
  51 #  define D(x)
  52 #endif
  53
  54 /*----- Main code ---------------------------------------------------------*/
  55
  56 /* --- @writechan@ --- *
  57  *
  58  * Arguments:   @int fd@ = file descriptor to write to
  59  *              @unsigned mode@ = what the descriptor is ready for
  60  *              @void *vp@ = pointer to channel block
  61  *
  62  * Returns:     ---
  63  *
  64  * Use:         Writes to a channel.
  65  */
  66
  67 static void writechan(int fd, unsigned mode, void *vp)
  68 {
  69   chan *c = vp;
  70   int w;
  71   unsigned base = c->base;
  72   unsigned len = c->len;
  73
  74   /* --- Write data from my buffer --- */
  75
  76   if (len) {
  77
  78     /* --- Do the write --- */
  79
  80     D( printf("writechan %d: base = %u, len = %u; ", fd, base, len); )
  81     if (base + len <= CHAN_BUFSZ) {
  82       D( printf("%u:%u", base, len); )
  83       w = write(fd, c->buf + base, len);
  84     } else {
  85       struct iovec iov[2];
  86       iov[0].iov_base = c->buf + base;
  87       iov[0].iov_len = CHAN_BUFSZ - base;
  88       iov[1].iov_base = c->buf;
  89       iov[1].iov_len = len - iov[0].iov_len;
  90       D( printf("%u:%u, %u:%u",
  91                 base, CHAN_BUFSZ - base,
  92                 0, len + base - CHAN_BUFSZ); )
  93       w = writev(fd, iov, 2);
  94     }
  95     D( printf("; returned %d\n", w); )
  96
  97     /* --- Sift through the results --- */
  98
  99     if (w < 0) {
 100       if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
 101         return;
 102       goto close;
 103     }
 104     else if (w == 0)
 105       goto close;
 106     else if (c->len == CHAN_BUFSZ && !(c->f & CHANF_CLOSE))
 107       sel_addfile(&c->r);
 108     c->len -= w;
 109     c->base += w;
 110   }
 111   if (c->len == 0)
 112     sel_rmfile(&c->w);
 113
 114   /* --- Close the output end if necessary --- */
 115
 116   if (c->len == 0) {
 117     c->base = 0;
 118     if (c->f & CHANF_CLOSE)
 119       c->func(c->p);
 120   }
 121   return;
 122
 123   /* --- Force a close if an error occurred --- */
 124
 125 close:
 126   chan_close(c);
 127   c->func(c->p);
 128 }
 129
 130 /* --- @readchan@ --- *
 131  *
 132  * Arguments:   @int fd@ = file descriptor to read from
 133  *              @unsigned mode@ = what the descriptor is ready for
 134  *              @void *vp@ = pointer to channel block
 135  *
 136  * Returns:     ---
 137  *
 138  * Use:         Reads from a channel.
 139  */
 140
 141 static void readchan(int fd, unsigned mode, void *vp)
 142 {
 143   chan *c = vp;
 144   int r;
 145   unsigned base = c->base;
 146   unsigned len = c->len;
 147
 148   /* --- Do the read --- */
 149
 150   D( printf("readchan %d: base = %u, len = %u; ", fd, base, len); )
 151   if (base == 0) {
 152     D( printf("%u:%u", len, CHAN_BUFSZ - len); )
 153     r = read(fd, c->buf + len, CHAN_BUFSZ - len);
 154   } else if (base + len >= CHAN_BUFSZ) {
 155     D( printf("%u:%u", base + len - CHAN_BUFSZ, CHAN_BUFSZ - len); )
 156     r = read(fd, c->buf + base + len - CHAN_BUFSZ, CHAN_BUFSZ - len);
 157   } else {
 158     struct iovec iov[2];
 159     iov[0].iov_base = c->buf + base + len;
 160     iov[0].iov_len = CHAN_BUFSZ - base - len;
 161     iov[1].iov_base = c->buf;
 162     iov[1].iov_len = base;
 163     D( printf("%u:%u, %u:%u",
 164               base + len, CHAN_BUFSZ - base - len,
 165               0, base); )
 166     r = readv(fd, iov, 2);
 167   }
 168   D( printf("; returned %d\n", r); )
 169
 170   /* --- Sift through the results --- */
 171
 172   if (r < 0) {
 173     if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
 174       return;
 175     goto close;
 176   }
 177   else if (r == 0)
 178     goto close;
 179   else if (c->len == 0 && (c->f & CHANF_READY)) {
 180     sel_addfile(&c->w);
 181     sel_force(&c->w);
 182   }
 183   c->len += r;
 184   if (c->len == CHAN_BUFSZ)
 185     sel_rmfile(&c->r);
 186   return;
 187
 188   /* --- Close the read end of the channel --- */
 189
 190 close:
 191   c->f |= CHANF_CLOSE;
 192   if (!c->len && (c->f & CHANF_READY)) {
 193     sel_addfile(&c->w);
 194     sel_force(&c->w);
 195   }
 196   sel_rmfile(&c->r);
 197 }
 198
 199 /* --- @chan_close@ --- *
 200  *
 201  * Arguments:   @chan *c@ = pointer to channel
 202  *
 203  * Returns:     ---
 204  *
 205  * Use:         Closes down a channel prematurely.
 206  */
 207
 208 void chan_close(chan *c)
 209 {
 210   if (!(c->f & CHANF_CLOSE) && c->len != CHAN_BUFSZ)
 211     sel_rmfile(&c->r);
 212   if ((c->f & CHANF_READY) && c->len != 0)
 213     sel_rmfile(&c->w);
 214 }
 215
 216 /* --- @chan_dest@ --- *
 217  *
 218  * Arguments:   @chan *c@ = pointer to channel
 219  *              @int fd@ = destination file descriptor for channel
 220  *
 221  * Returns:     ---
 222  *
 223  * Use:         Sets the channel's destination so it knows where to put
 224  *              data.
 225  */
 226
 227 void chan_dest(chan *c, int fd)
 228 {
 229   if (c->f & CHANF_READY)
 230     return;
 231   sel_initfile(sel, &c->w, fd, SEL_WRITE, writechan, c);
 232   if (c->len || (c->f & CHANF_CLOSE)) {
 233     sel_addfile(&c->w);
 234     sel_force(&c->w);
 235   }
 236   c->f |= CHANF_READY;
 237 }
 238
 239 /* --- @chan_open@ --- *
 240  *
 241  * Arguments:   @chan *c@ = pointer to channel to open
 242  *              @int from, to@ = source and destination file descriptors
 243  *              @void (*func)(void *p)@ = function to call on closure
 244  *              @void *p@ = argument to pass to function
 245  *
 246  * Returns:     ---
 247  *
 248  * Use:         Opens a channel.  Data is copied from the source to the
 249  *              destination.  The @to@ argument may be @-1@ if the file
 250  *              descriptor isn't known yet.
 251  */
 252
 253 void chan_open(chan *c, int from, int to,
 254                void (*func)(void */*p*/), void *p)
 255 {
 256   c->func = func;
 257   c->p = p;
 258
 259   c->base = 0;
 260   c->len = 0;
 261   c->f = 0;
 262
 263   sel_initfile(sel, &c->r, from, SEL_READ, readchan, c);
 264   sel_addfile(&c->r);
 265
 266   if (to != -1)
 267     chan_dest(c, to);
 268 }
 269
 270 /*----- That's all, folks -------------------------------------------------*/