mdw@git.distorted.org.uk Git - userv-utils/blob - ipif/service.c

   1 /*
   2  * userv service (or standalone program)
   3  * for per-user IP subranges.
   4  *
   5  * This is invoked as root, directly from userv.
   6  * Its arguments are supposed to be, in order:
   7  *  <config>
   8  *      Specifies address ranges and gids which own them.
   9  *  --  Indicates that the remaining arguments are user-supplied
  10  *      and therefore untrusted.
  11  *  <local-addr>,<peer-addr>,<mtu>,<proto>
  12  *      As for slattach.  Supported protocols are slip, cslip, and
  13  *      adaptive.  Alternatively, set to `debug' to print debugging
  14  *      info.  <local-addr> is address of the interface on chiark;
  15  *      <peer-addr> is the address of the point-to-point peer.
  16  *  <prefix>/<mask>,<prefix>/<mask>,...
  17  *      List of additional routes to add for this interface.
  18  *      May be the empty argument, or `-' if this is problematic.
  19  *
  20  * <config> is either
  21  *    <gid>,<prefix>/<len>[,<junk>]
  22  *      indicating that that gid may allocate addresses in
  23  *      the relevant subspace (<junk> is ignored)
  24  * or #...
  25  *      which is a comment
  26  * or /<config-file-name> or ./<config-file-name> or ../<config-file-name>
  27  *      which refers to a file which contains lines which
  28  *      are each <config>
  29  * or *
  30  *      which means that anything is permitted
  31  *
  32  * Should be run from userv with no-disconnect-hup.
  33  */
  34 /*
  35  * Copyright (C) 1999 Ian Jackson
  36  *
  37  * This is free software; you can redistribute it and/or modify it
  38  * under the terms of the GNU General Public License as published by
  39  * the Free Software Foundation; either version 2 of the License, or
  40  * (at your option) any later version.
  41  *
  42  * This program is distributed in the hope that it will be useful, but
  43  * WITHOUT ANY WARRANTY; without even the implied warranty of
  44  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  45  * General Public License for more details.
  46  *
  47  * You should have received a copy of the GNU General Public License
  48  * along with userv-utils; if not, write to the Free Software
  49  * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  50  *
  51  * $Id$
  52  */
  53
  54 #include <stdio.h>
  55 #include <string.h>
  56 #include <stdlib.h>
  57 #include <assert.h>
  58 #include <errno.h>
  59 #include <stdarg.h>
  60 #include <ctype.h>
  61 #include <limits.h>
  62 #include <signal.h>
  63 #include <unistd.h>
  64
  65 #include <sys/types.h>
  66 #include <sys/wait.h>
  67 #include <sys/stat.h>
  68
  69 #define NARGS 4
  70 #define MAXEXROUTES 5
  71 #define ATXTLEN 16
  72
  73 static const unsigned long gidmaxval= (unsigned long)((gid_t)-2);
  74 static const char *const protos_ok[]= { "slip", "cslip", "adaptive", 0 };
  75 static const int signals[]= { SIGHUP, SIGINT, SIGTERM, 0 };
  76
  77 static const char *configstr, *proto;
  78 static unsigned long localaddr, peeraddr, mtu;
  79 static int localallow, peerallow, allallow;
  80 static int nexroutes;
  81 static struct exroute {
  82   unsigned long prefix, mask;
  83   int allow;
  84   char prefixtxt[ATXTLEN], masktxt[ATXTLEN];
  85 } exroutes[MAXEXROUTES];
  86
  87 static char localtxt[ATXTLEN];
  88 static char peertxt[ATXTLEN];
  89
  90 static struct pplace {
  91   struct pplace *parent;
  92   const char *filename;
  93   int lineno;
  94 } *cpplace;
  95
  96
  97 static int slpipe[2], ptmaster, undoslattach;
  98 static const char *ifname;
  99 static const char *ptyname;
 100
 101 #define NPIDS 4
 102
 103 static union {
 104   struct { pid_t sl, cout, cin, task; } byname;
 105   pid_t bynumber[NPIDS];
 106 } pids;
 107 sigset_t emptyset, fullset;
 108
 109
 110 static int cleantask(void) {
 111   pid_t pid;
 112
 113   pid= fork();
 114   if (!pid) return 1;
 115   if (pid == (pid_t)-1)
 116     perror("userv-ipif: fork for undo slattach failed - cannot clean up properly");
 117   return 0;
 118 }
 119
 120 static void terminate(int estatus) {
 121   int i, status;
 122   pid_t pid;
 123
 124   for (i=0; i<NPIDS; i++)
 125     if (pids.bynumber[i]) kill(pids.bynumber[i], SIGTERM);
 126
 127   if (undoslattach) {
 128     if (cleantask()) {
 129       execlp("slattach", "slattach", "-p", "tty", ptyname, (char*)0);
 130       perror("userv-ipif: exec slattach for undo slattach failed");
 131       exit(-1);
 132     }
 133     if (ifname && cleantask()) {
 134       execlp("ifconfig", "ifconfig", ifname, "down", (char*)0);
 135       perror("userv-ipif: exec ifconfig for undo ifconfig failed");
 136       exit(-1);
 137     }
 138   }
 139
 140   for (;;) {
 141     pid= waitpid(-1,&status,0);
 142     if (pid == (pid_t)-1) break;
 143   }
 144   exit(estatus);
 145 }
 146
 147
 148 static void fatal(const char *fmt, ...)
 149      __attribute__((format(printf,1,2)));
 150 static void fatal(const char *fmt, ...) {
 151   va_list al;
 152   va_start(al,fmt);
 153
 154   fputs("userv-ipif service: fatal error: ",stderr);
 155   vfprintf(stderr, fmt, al);
 156   putc('\n',stderr);
 157   terminate(8);
 158 }
 159
 160 static void sysfatal(const char *fmt, ...)
 161      __attribute__((format(printf,1,2)));
 162 static void sysfatal(const char *fmt, ...) {
 163   va_list al;
 164   int e;
 165
 166   e= errno;
 167   va_start(al,fmt);
 168
 169   fputs("userv-ipif service: fatal system error: ",stderr);
 170   vfprintf(stderr, fmt, al);
 171   fprintf(stderr,": %s\n", strerror(e));
 172   terminate(12);
 173 }
 174
 175
 176 static void badusage(const char *fmt, ...)
 177      __attribute__((format(printf,1,2)));
 178 static void badusage(const char *fmt, ...) {
 179   va_list al;
 180   struct pplace *cpp;
 181
 182   if (cpplace) {
 183     fprintf(stderr,
 184             "userv-ipif service: %s:%d: ",
 185             cpplace->filename, cpplace->lineno);
 186   } else {
 187     fputs("userv-ipif service: invalid usage: ",stderr);
 188   }
 189   va_start(al,fmt);
 190   vfprintf(stderr, fmt, al);
 191   putc('\n',stderr);
 192
 193   if (cpplace) {
 194     for (cpp=cpplace->parent; cpp; cpp=cpp->parent) {
 195       fprintf(stderr,
 196               "userv-ipif service: %s:%d: ... in file included from here\n",
 197               cpp->filename, cpp->lineno);
 198     }
 199   }
 200   terminate(16);
 201 }
 202
 203 static char *ip2txt(unsigned long addr, char *buf) {
 204   sprintf(buf, "%lu.%lu.%lu.%lu",
 205           (addr>>24) & 0x0ff,
 206           (addr>>16) & 0x0ff,
 207           (addr>>8) & 0x0ff,
 208           (addr) & 0x0ff);
 209   return buf;
 210 }
 211
 212 static unsigned long eat_number(const char **argp, const char *what,
 213                                 unsigned long min, unsigned long max,
 214                                 const char *endchars, int *endchar_r) {
 215   /* If !endchars then the endchar must be a nul, otherwise it may be
 216    * a nul (resulting in *argp set to 0) or something else (*argp set
 217    * to point to after delim, *endchar_r set to delim).
 218    * *endchar_r may be 0.
 219    */
 220   unsigned long rv;
 221   char *ep;
 222   int endchar;
 223
 224   if (!*argp) { badusage("missing number %s",what); }
 225   rv= strtoul(*argp,&ep,0);
 226   if ((endchar= *ep)) {
 227     if (!endchars) badusage("junk after number %s",what);
 228     if (!strchr(endchars,endchar))
 229       badusage("invalid character or delimiter `%c' in or after number, %s:"
 230                " expected %s (or none?)", endchar,what,endchars);
 231     *argp= ep+1;
 232   } else {
 233     *argp= 0;
 234   }
 235   if (endchar_r) *endchar_r= endchar;
 236   if (rv < min || rv > max) badusage("number %s value %lu out of range %lu..%lu",
 237                                      what, rv, min, max);
 238   return rv;
 239 }
 240
 241 static void addrnet_mustdiffer(const char *w1, unsigned long p1, unsigned long m1,
 242                                const char *w2, unsigned long p2, unsigned long m2) {
 243   unsigned long mask;
 244
 245   mask= m1&m2;
 246   if ((p1 & mask) != (p2 & mask)) return;
 247   badusage("%s %08lx/%08lx overlaps/clashes with %s %08lx/%08lx",
 248            w1,p1,m1, w2,p2,m2);
 249 }
 250
 251 static unsigned long eat_addr(const char **argp, const char *what,
 252                               const char *endchars, int *endchar_r) {
 253   char whatbuf[100];
 254   unsigned long rv;
 255   int i;
 256
 257   for (rv=0, i=0;
 258        i<4;
 259        i++) {
 260     rv <<= 8;
 261     sprintf(whatbuf,"%s byte #%d",what,i);
 262     rv |= eat_number(argp,whatbuf, 0,255, i<3 ? "." : endchars, endchar_r);
 263   }
 264
 265   return rv;
 266 }
 267
 268 static void eat_prefixmask(const char **argp, const char *what,
 269                            const char *endchars, int *endchar_r,
 270                            unsigned long *prefix_r, unsigned long *mask_r, int *len_r) {
 271   /* mask_r and len_r may be 0 */
 272   char whatbuf[100];
 273   int len;
 274   unsigned long prefix, mask;
 275
 276   prefix= eat_addr(argp,what, "/",0);
 277   sprintf(whatbuf,"%s length",what);
 278   len= eat_number(argp,whatbuf, 0,32, endchars,endchar_r);
 279
 280   mask= (~0UL << (32-len));
 281   if (prefix & ~mask) badusage("%s prefix %08lx not fully contained in mask %08lx",
 282                                what,prefix,mask);
 283   *prefix_r= prefix;
 284   if (mask_r) *mask_r= mask;
 285   if (len_r) *len_r= len;
 286 }
 287
 288 static int addrnet_isin(unsigned long prefix, unsigned long mask,
 289                         unsigned long mprefix, unsigned long mmask) {
 290   return  !(~mask & mmask)  &&  (prefix & mmask) == mprefix;
 291 }
 292
 293
 294 static void permit(unsigned long pprefix, unsigned long pmask) {
 295   int i, any;
 296
 297   assert(!(pprefix & ~pmask));
 298   any= 0;
 299
 300   if (!proto) fputs("permits",stdout);
 301   if (addrnet_isin(localaddr,~0UL, pprefix,pmask)) {
 302     if (!proto) fputs(" local-addr",stdout);
 303     any= localallow= 1;
 304   }
 305   if (addrnet_isin(peeraddr,~0UL, pprefix,pmask)) {
 306     if (!proto) fputs(" peer-addr",stdout);
 307     any= peerallow= 1;
 308   }
 309   for (i=0; i<nexroutes; i++) {
 310     if (addrnet_isin(exroutes[i].prefix,exroutes[i].mask, pprefix,pmask)) {
 311       if (!proto) printf(" route#%d",i);
 312       any= exroutes[i].allow= 1;
 313     }
 314   }
 315   if (!proto) {
 316     if (!any) fputs(" nothing",stdout);
 317     putchar('\n');
 318   }
 319 }
 320
 321 static void pconfig(const char *configstr, int truncated);
 322
 323 static void pfile(const char *filename) {
 324   FILE *file;
 325   char buf[PATH_MAX];
 326   int l, truncated, c;
 327   struct pplace npp, *cpp;
 328
 329   for (cpp=cpplace; cpp; cpp=cpp->parent) {
 330     if (!strcmp(cpp->filename,filename))
 331       badusage("recursive configuration file `%s'",filename);
 332   }
 333
 334   file= fopen(filename,"r");
 335   if (!file)
 336     badusage("cannot open configuration file `%s': %s", filename, strerror(errno));
 337
 338   if (!proto) printf("config file `%s':\n",filename);
 339
 340   npp.parent= cpplace;
 341   npp.filename= filename;
 342   npp.lineno= 0;
 343   cpplace= &npp;
 344
 345   while (fgets(buf, sizeof(buf), file)) {
 346     npp.lineno++;
 347     l= strlen(buf);
 348     if (!l) continue;
 349
 350     truncated= (buf[l-1] != '\n');
 351     while (l>0 && isspace((unsigned char) buf[l-1])) l--;
 352     if (!l) continue;
 353     buf[l]= 0;
 354
 355     if (truncated) {
 356       while ((c= getc(file)) != EOF && c != '\n');
 357       if (c == EOF) break;
 358     }
 359
 360     pconfig(buf,truncated);
 361   }
 362   if (ferror(file))
 363     badusage("failed while reading configuration file: %s", strerror(errno));
 364
 365   cpplace= npp.parent;
 366 }
 367
 368 static void pconfig(const char *configstr, int truncated) {
 369   unsigned long fgid, tgid, pprefix, pmask;
 370   int plen;
 371   char ptxt[ATXTLEN];
 372   const char *gidlist;
 373
 374   switch (configstr[0]) {
 375   case '*':
 376     if (strcmp(configstr,"*")) badusage("`*' directive must be only thing on line");
 377     permit(0UL,0UL);
 378     return;
 379
 380   case '#':
 381     return;
 382
 383   case '/': case '.':
 384     if (truncated) badusage("filename too long (`%.100s...')",configstr);
 385     pfile(configstr);
 386     return;
 387
 388   default:
 389     if (!isdigit((unsigned char)configstr[0]))
 390       badusage("unknown configuration directive");
 391
 392     fgid= eat_number(&configstr,"gid", 0,gidmaxval, ",",0);
 393     eat_prefixmask(&configstr,"permitted-prefix", ",",0, &pprefix,&pmask,&plen);
 394     if (!configstr && truncated) badusage("gid,prefix/len,... spec too long");
 395
 396     if (!proto) printf(" %5lu,%s/%d: ", fgid, ip2txt(pprefix,ptxt), plen);
 397
 398     gidlist= getenv("USERV_GID");
 399     if (!gidlist) fatal("USERV_GID not set");
 400     for (;;) {
 401       if (!gidlist) {
 402         if (!proto) printf("no matching gid\n");
 403         return;
 404       }
 405       tgid= eat_number(&gidlist,"userv-gid", 0,gidmaxval, " ",0);
 406       if (tgid == fgid) break;
 407     }
 408     permit(pprefix,pmask);
 409     return;
 410   }
 411 }
 412
 413 static void checkallow(int allow, const char *what,
 414                        const char *prefixtxt, const char *masktxt) {
 415   if (allow) return;
 416   fprintf(stderr,"userv-ipif service: access denied for %s, %s/%s\n",
 417           what, prefixtxt, masktxt);
 418   allallow= 0;
 419 }
 420
 421 static void parseargs(int argc, const char *const *argv) {
 422   unsigned long routeaddr, routemask;
 423   const char *carg;
 424   const char *const *cprotop;
 425   int i;
 426   char erwhatbuf[100], erwhatbuf2[100];
 427
 428   if (argc < NARGS+1) { badusage("too few arguments"); }
 429   if (argc > NARGS+1) { badusage("too many arguments"); }
 430
 431   configstr= *++argv;
 432
 433   carg= *++argv;
 434   if (strcmp(carg,"--")) badusage("separator argument `--' not found, got `%s'",carg);
 435
 436   carg= *++argv;
 437   localaddr= eat_addr(&carg,"local-addr", ",",0);
 438   peeraddr= eat_addr(&carg,"peer-addr", ",",0);
 439   mtu= eat_number(&carg,"mtu", 576,65536, ",",0);
 440   localallow= peerallow= 0;
 441
 442   if (!strcmp(carg,"debug")) {
 443     proto= 0;
 444   } else {
 445     for (cprotop= protos_ok;
 446          (proto= *cprotop) && strcmp(proto,carg);
 447          cprotop++);
 448     if (!proto) fatal("invalid protocol");
 449   }
 450
 451   addrnet_mustdiffer("local-addr",localaddr,~0UL, "peer-addr",peeraddr,~0UL);
 452
 453   carg= *++argv;
 454   if (strcmp(carg,"-")) {
 455     for (nexroutes=0;
 456          carg && *carg;
 457          nexroutes++) {
 458       if (nexroutes == MAXEXROUTES)
 459         fatal("too many extra routes (only %d allowed)",MAXEXROUTES);
 460       sprintf(erwhatbuf,"route#%d",nexroutes);
 461
 462       eat_prefixmask(&carg,erwhatbuf, ",",0, &routeaddr,&routemask,0);
 463       if (routemask == ~0UL) {
 464         addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "local-addr",localaddr,~0UL);
 465         addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "peer-addr",peeraddr,~0UL);
 466       }
 467       for (i=0; i<nexroutes; i++) {
 468         sprintf(erwhatbuf2,"route#%d",i);
 469         addrnet_mustdiffer(erwhatbuf,routeaddr,routemask,
 470                            erwhatbuf2,exroutes[i].prefix,exroutes[i].mask);
 471       }
 472       exroutes[nexroutes].prefix= routeaddr;
 473       exroutes[nexroutes].mask= routemask;
 474       exroutes[nexroutes].allow= 0;
 475       ip2txt(routeaddr,exroutes[nexroutes].prefixtxt);
 476       ip2txt(routemask,exroutes[nexroutes].masktxt);
 477     }
 478   }
 479
 480   ip2txt(localaddr,localtxt);
 481   ip2txt(peeraddr,peertxt);
 482 }
 483
 484 static void checkpermit(void) {
 485   int i;
 486   char erwhatbuf[100];
 487
 488   allallow= 1;
 489   checkallow(localallow,"local-addr", localtxt,"32");
 490   checkallow(peerallow,"peer-addr", peertxt,"32");
 491   for (i=0; i<nexroutes; i++) {
 492     sprintf(erwhatbuf, "route#%d", i);
 493     checkallow(exroutes[i].allow, erwhatbuf, exroutes[i].prefixtxt, exroutes[i].masktxt);
 494   }
 495   if (!allallow) fatal("access denied");
 496 }
 497
 498 static void dumpdebug(void) __attribute__((noreturn));
 499 static void dumpdebug(void) {
 500   int i;
 501   char erwhatbuf[100];
 502
 503   printf("protocol: debug\n"
 504          "local:    %08lx == %s\n"
 505          "peer:     %08lx == %s\n"
 506          "mtu:      %ld\n"
 507          "routes:   %d\n",
 508          localaddr, localtxt,
 509          peeraddr, peertxt,
 510          mtu,
 511          nexroutes);
 512   for (i=0; i<nexroutes; i++) {
 513     sprintf(erwhatbuf, "route#%d:", i);
 514     printf("%-9s %08lx/%08lx == %s/%s\n",
 515            erwhatbuf,
 516            exroutes[i].prefix, exroutes[i].mask,
 517            exroutes[i].prefixtxt, exroutes[i].masktxt);
 518   }
 519   if (ferror(stdout) || fclose(stdout)) sysfatal("flush stdout");
 520   exit(0);
 521 }
 522
 523
 524 static void setsigmask(const sigset_t *ss) {
 525   int r;
 526
 527   r= sigprocmask(SIG_SETMASK, ss, 0);
 528   if (r) sysfatal("[un]block signals");
 529 }
 530
 531 static void setsignals(void (*handler)(int), struct sigaction *sa, int chldflags) {
 532   const int *signalp;
 533   int r, sig;
 534
 535   sa->sa_handler= handler;
 536   sa->sa_flags= 0;
 537   for (signalp=signals; (sig=*signalp); signalp++) {
 538     r= sigaction(sig, sa, 0);  if (r) sysfatal("uncatch signal");
 539   }
 540   sa->sa_flags= chldflags;
 541   r= sigaction(SIGCHLD, sa, 0);  if (r) sysfatal("uncatch children");
 542 }
 543
 544 static void infork(void) {
 545   struct sigaction sa;
 546
 547   memset(&pids,0,sizeof(pids));
 548   sigemptyset(&sa.sa_mask);
 549   setsignals(SIG_DFL,&sa,0);
 550   setsigmask(&emptyset);
 551   undoslattach= 0;
 552 }
 553
 554 static pid_t makesubproc(void (*entry)(void)) {
 555   pid_t pid;
 556
 557   pid= fork();  if (pid == (pid_t)-1) sysfatal("fork for subprocess");
 558   if (pid) return pid;
 559
 560   infork();
 561   entry();
 562   abort();
 563 }
 564
 565 static int task(void) {
 566   pid_t pid;
 567
 568   pid= fork();
 569   if (pid == (pid_t)-1) sysfatal("fork for task");
 570   if (!pid) { infork(); return 1; }
 571
 572   pids.byname.task= pid;
 573   while (pids.byname.task) sigsuspend(&emptyset);
 574   return 0;
 575 }
 576
 577 static void mdup2(int fd1, int fd2, const char *what) {
 578   int r;
 579
 580   for (;;) {
 581     r= dup2(fd1,fd2); if (r==fd2) return;
 582     if (r!=-1) fatal("dup2 in %s gave wrong answer %d instead of %d",what,r,fd2);
 583     if (errno != EINTR) sysfatal("dup2 failed in %s",what);
 584   }
 585 }
 586
 587 static void sl_entry(void) {
 588   mdup2(slpipe[1],1,"slattach child");
 589   execlp("slattach", "slattach", "-v", "-L", "-p",proto, ptyname, (char*)0);
 590   sysfatal("cannot exec slattach");
 591 }
 592
 593 static void cin_entry(void) {
 594   mdup2(ptmaster,1,"cat input child");
 595   execlp("cat", "cat", (char*)0);
 596   sysfatal("cannot exec cat input");
 597 }
 598
 599 static void cout_entry(void) {
 600   mdup2(ptmaster,0,"cat output child");
 601   execlp("cat", "cat", (char*)0);
 602   sysfatal("cannot exec cat output");
 603 }
 604
 605 static void sighandler(int signum) {
 606   pid_t pid;
 607   int estatus, status;
 608   const char *taskfail;
 609
 610   estatus= 4;
 611
 612   if (signum == SIGCHLD) {
 613     for (;;) {
 614       pid= waitpid(-1,&status,WNOHANG);
 615       if (!pid || pid == (pid_t)-1) return;
 616
 617       if (pid == pids.byname.task) {
 618         pids.byname.task= 0;
 619         if (!status) return;
 620         taskfail= "task";
 621       } else if (pid == pids.byname.cin) {
 622         pids.byname.cin= 0;
 623         if (status) {
 624           taskfail= "input cat";
 625         } else {
 626           taskfail= 0;
 627           estatus= 0;
 628         }
 629       } else if (pid == pids.byname.cout) {
 630         pids.byname.cout= 0;
 631         taskfail= "output cat";
 632       } else if (pid == pids.byname.sl) {
 633         pids.byname.sl= 0;
 634         taskfail= "slattach";
 635       } else {
 636         continue;
 637       }
 638       break;
 639     }
 640     if (taskfail) {
 641       if (WIFEXITED(status)) {
 642         fprintf(stderr,
 643                 "userv-ipif service: %s unexpectedly exited with exit status %d\n",
 644                 taskfail, WEXITSTATUS(status));
 645       } else if (WIFSIGNALED(status)) {
 646         fprintf(stderr,
 647                 "userv-ipif service: %s unexpectedly killed by signal %s%s\n",
 648                 taskfail, strsignal(WTERMSIG(status)),
 649                 WCOREDUMP(status) ? " (core dumped)" : "");
 650       } else {
 651         fprintf(stderr, "userv-ipif service: %s unexpectedly terminated"
 652                 " with unknown status code %d\n", taskfail, status);
 653       }
 654     }
 655   } else {
 656     fprintf(stderr,
 657             "userv-ipif service: received signal %d, terminating\n",
 658             signum);
 659   }
 660
 661   terminate(estatus);
 662 }
 663
 664 static void startup(void) {
 665   int r;
 666   struct sigaction sa;
 667
 668   sigfillset(&fullset);
 669   sigemptyset(&emptyset);
 670
 671   ptmaster= getpt();  if (ptmaster==-1) sysfatal("allocate pty master");
 672   r= grantpt(ptmaster);  if (r) sysfatal("grab/grant pty slave");
 673   ptyname= ptsname(ptmaster);  if (!ptyname) sysfatal("get pty slave name");
 674   r= chmod(ptyname,0600);  if (r) sysfatal("chmod pty slave");
 675   r= unlockpt(ptmaster);  if (r) sysfatal("unlock pty");
 676
 677   sigfillset(&sa.sa_mask);
 678   setsignals(sighandler,&sa,SA_NOCLDSTOP);
 679   setsigmask(&fullset);
 680 }
 681
 682 static void startslattach(void) {
 683   static char ifnbuf[200];
 684
 685   FILE *piper;
 686   int r, l, k;
 687
 688   r= pipe(slpipe);  if (r) sysfatal("create pipe");
 689   piper= fdopen(slpipe[0],"r");  if (!piper) sysfatal("fdopen pipe");
 690
 691   undoslattach= 1;
 692   pids.byname.sl= makesubproc(sl_entry);
 693
 694   close(slpipe[1]);
 695   setsigmask(&emptyset);
 696   if (!fgets(ifnbuf,sizeof(ifnbuf),piper)) {
 697     if (ferror(piper)) sysfatal("cannot read ifname from slattach");
 698     else fatal("cannot read ifname from slattach");
 699   }
 700   setsigmask(&fullset);
 701   l= strlen(ifnbuf);
 702   if (l<=0 || ifnbuf[l-1] != '\n') fatal("slattach gave strange output `%s'",ifnbuf);
 703   ifnbuf[l-1]= 0;
 704   for (k=l; k>0 && ifnbuf[k-1]!=' '; k--);
 705   ifname= ifnbuf+k;
 706 }
 707
 708 static void netconfigure(void) {
 709   char mtutxt[100];
 710   int i;
 711
 712   if (task()) {
 713     sprintf(mtutxt,"%lu",mtu);
 714
 715     execlp("ifconfig", "ifconfig", ifname, localtxt,
 716            "netmask","255.255.255.255", "-broadcast", "pointopoint",peertxt,
 717            "mtu",mtutxt, "up", (char*)0);
 718     sysfatal("cannot exec ifconfig");
 719   }
 720
 721   for (i=0; i<nexroutes; i++) {
 722     if (task()) {
 723       execlp("route","route", "add", "-net",exroutes[i].prefixtxt,
 724              "netmask",exroutes[i].masktxt,
 725              "gw",peertxt, "dev",ifname, (char*)0);
 726       sysfatal("cannot exec route (for route)");
 727     }
 728   }
 729 }
 730
 731 static void copydata(void) __attribute__((noreturn));
 732 static void copydata(void) {
 733   int r;
 734
 735   pids.byname.cin= makesubproc(cin_entry);
 736   for (;;) {
 737     r= write(1, "\300", 1); if (r==1) break;
 738     assert(r==-1);  if (errno != EINTR) sysfatal("send initial delim to confirm");
 739   }
 740   pids.byname.cout= makesubproc(cout_entry);
 741
 742   for (;;) sigsuspend(&emptyset);
 743 }
 744
 745 int main(int argc, const char *const *argv) {
 746   parseargs(argc,argv);
 747   pconfig(configstr,0);
 748   checkpermit();
 749   if (!proto) dumpdebug();
 750
 751   startup();
 752   startslattach();
 753   netconfigure();
 754   copydata();
 755 }