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 the local
  15  *      system; <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  *      if `=' is specified then it's only allowed for the local
  25  *      endpoint address
  26  * or #...
  27  *      which is a comment
  28  * or /<config-file-name> or ./<config-file-name> or ../<config-file-name>
  29  *      which refers to a file which contains lines which
  30  *      are each <config>
  31  * or *
  32  *      which means that anything is permitted
  33  *
  34  * Should be run from userv with no-disconnect-hup.
  35  */
  36 /*
  37  * Copyright (C) 1999 Ian Jackson
  38  *
  39  * This is free software; you can redistribute it and/or modify it
  40  * under the terms of the GNU General Public License as published by
  41  * the Free Software Foundation; either version 2 of the License, or
  42  * (at your option) any later version.
  43  *
  44  * This program is distributed in the hope that it will be useful, but
  45  * WITHOUT ANY WARRANTY; without even the implied warranty of
  46  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  47  * General Public License for more details.
  48  *
  49  * You should have received a copy of the GNU General Public License
  50  * along with userv-utils; if not, write to the Free Software
  51  * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  52  *
  53  * $Id$
  54  */
  55
  56 #include <stdio.h>
  57 #include <string.h>
  58 #include <stdlib.h>
  59 #include <assert.h>
  60 #include <errno.h>
  61 #include <stdarg.h>
  62 #include <ctype.h>
  63 #include <limits.h>
  64 #include <signal.h>
  65 #include <unistd.h>
  66
  67 #include <sys/types.h>
  68 #include <sys/wait.h>
  69 #include <sys/stat.h>
  70
  71 #define NARGS 4
  72 #define MAXEXROUTES 5
  73 #define ATXTLEN 16
  74
  75 static const unsigned long gidmaxval= (unsigned long)((gid_t)-2);
  76 static const char *const protos_ok[]= { "slip", "cslip", "adaptive", 0 };
  77 static const int signals[]= { SIGHUP, SIGINT, SIGTERM, 0 };
  78
  79 static const char *configstr, *proto;
  80 static unsigned long localaddr, peeraddr, mtu;
  81 static int localallow, peerallow, allallow;
  82 static int nexroutes;
  83 static struct exroute {
  84   unsigned long prefix, mask;
  85   int allow;
  86   char prefixtxt[ATXTLEN], masktxt[ATXTLEN];
  87 } exroutes[MAXEXROUTES];
  88
  89 static char localtxt[ATXTLEN];
  90 static char peertxt[ATXTLEN];
  91
  92 static struct pplace {
  93   struct pplace *parent;
  94   const char *filename;
  95   int lineno;
  96 } *cpplace;
  97
  98
  99 static int slpipe[2], ptmaster, undoslattach;
 100 static const char *ifname;
 101 static const char *ptyname;
 102
 103 #define NPIDS 4
 104
 105 static union {
 106   struct { pid_t sl, cout, cin, task; } byname;
 107   pid_t bynumber[NPIDS];
 108 } pids;
 109 sigset_t emptyset, fullset;
 110
 111
 112 static int cleantask(void) {
 113   pid_t pid;
 114
 115   pid= fork();
 116   if (!pid) return 1;
 117   if (pid == (pid_t)-1)
 118     perror("userv-ipif: fork for undo slattach failed - cannot clean up properly");
 119   return 0;
 120 }
 121
 122 static void terminate(int estatus) {
 123   int i, status;
 124   pid_t pid;
 125
 126   for (i=0; i<NPIDS; i++)
 127     if (pids.bynumber[i]) kill(pids.bynumber[i], SIGTERM);
 128
 129   if (undoslattach) {
 130     if (cleantask()) {
 131       execlp("slattach", "slattach", "-p", "tty", ptyname, (char*)0);
 132       perror("userv-ipif: exec slattach for undo slattach failed");
 133       exit(-1);
 134     }
 135     if (ifname && cleantask()) {
 136       execlp("ifconfig", "ifconfig", ifname, "down", (char*)0);
 137       perror("userv-ipif: exec ifconfig for undo ifconfig failed");
 138       exit(-1);
 139     }
 140   }
 141
 142   for (;;) {
 143     pid= waitpid(-1,&status,0);
 144     if (pid == (pid_t)-1) break;
 145   }
 146   exit(estatus);
 147 }
 148
 149
 150 static void fatal(const char *fmt, ...)
 151      __attribute__((format(printf,1,2)));
 152 static void fatal(const char *fmt, ...) {
 153   va_list al;
 154   va_start(al,fmt);
 155
 156   fputs("userv-ipif service: fatal error: ",stderr);
 157   vfprintf(stderr, fmt, al);
 158   putc('\n',stderr);
 159   terminate(8);
 160 }
 161
 162 static void sysfatal(const char *fmt, ...)
 163      __attribute__((format(printf,1,2)));
 164 static void sysfatal(const char *fmt, ...) {
 165   va_list al;
 166   int e;
 167
 168   e= errno;
 169   va_start(al,fmt);
 170
 171   fputs("userv-ipif service: fatal system error: ",stderr);
 172   vfprintf(stderr, fmt, al);
 173   fprintf(stderr,": %s\n", strerror(e));
 174   terminate(12);
 175 }
 176
 177
 178 static void badusage(const char *fmt, ...)
 179      __attribute__((format(printf,1,2)));
 180 static void badusage(const char *fmt, ...) {
 181   va_list al;
 182   struct pplace *cpp;
 183
 184   if (cpplace) {
 185     fprintf(stderr,
 186             "userv-ipif service: %s:%d: ",
 187             cpplace->filename, cpplace->lineno);
 188   } else {
 189     fputs("userv-ipif service: invalid usage: ",stderr);
 190   }
 191   va_start(al,fmt);
 192   vfprintf(stderr, fmt, al);
 193   putc('\n',stderr);
 194
 195   if (cpplace) {
 196     for (cpp=cpplace->parent; cpp; cpp=cpp->parent) {
 197       fprintf(stderr,
 198               "userv-ipif service: %s:%d: ... in file included from here\n",
 199               cpp->filename, cpp->lineno);
 200     }
 201   }
 202   terminate(16);
 203 }
 204
 205 static char *ip2txt(unsigned long addr, char *buf) {
 206   sprintf(buf, "%lu.%lu.%lu.%lu",
 207           (addr>>24) & 0x0ff,
 208           (addr>>16) & 0x0ff,
 209           (addr>>8) & 0x0ff,
 210           (addr) & 0x0ff);
 211   return buf;
 212 }
 213
 214 static unsigned long eat_number(const char **argp, const char *what,
 215                                 unsigned long min, unsigned long max,
 216                                 const char *endchars, int *endchar_r) {
 217   /* If !endchars then the endchar must be a nul, otherwise it may be
 218    * a nul (resulting in *argp set to 0) or something else (*argp set
 219    * to point to after delim, *endchar_r set to delim).
 220    * *endchar_r may be 0.
 221    */
 222   unsigned long rv;
 223   char *ep;
 224   int endchar;
 225
 226   if (!*argp) { badusage("missing number %s",what); }
 227   rv= strtoul(*argp,&ep,0);
 228   if ((endchar= *ep)) {
 229     if (!endchars) badusage("junk after number %s",what);
 230     if (!strchr(endchars,endchar))
 231       badusage("invalid character or delimiter `%c' in or after number, %s:"
 232                " expected %s (or none?)", endchar,what,endchars);
 233     *argp= ep+1;
 234   } else {
 235     *argp= 0;
 236   }
 237   if (endchar_r) *endchar_r= endchar;
 238   if (rv < min || rv > max) badusage("number %s value %lu out of range %lu..%lu",
 239                                      what, rv, min, max);
 240   return rv;
 241 }
 242
 243 static void addrnet_mustdiffer(const char *w1, unsigned long p1, unsigned long m1,
 244                                const char *w2, unsigned long p2, unsigned long m2) {
 245   unsigned long mask;
 246
 247   mask= m1&m2;
 248   if ((p1 & mask) != (p2 & mask)) return;
 249   badusage("%s %08lx/%08lx overlaps/clashes with %s %08lx/%08lx",
 250            w1,p1,m1, w2,p2,m2);
 251 }
 252
 253 static unsigned long eat_addr(const char **argp, const char *what,
 254                               const char *endchars, int *endchar_r) {
 255   char whatbuf[100];
 256   unsigned long rv;
 257   int i;
 258
 259   for (rv=0, i=0;
 260        i<4;
 261        i++) {
 262     rv <<= 8;
 263     sprintf(whatbuf,"%s byte #%d",what,i);
 264     rv |= eat_number(argp,whatbuf, 0,255, i<3 ? "." : endchars, endchar_r);
 265   }
 266
 267   return rv;
 268 }
 269
 270 static void eat_prefixmask(const char **argp, const char *what,
 271                            const char *endchars, int *endchar_r,
 272                            unsigned long *prefix_r, unsigned long *mask_r, int *len_r) {
 273   /* mask_r and len_r may be 0 */
 274   char whatbuf[100];
 275   int len;
 276   unsigned long prefix, mask;
 277
 278   prefix= eat_addr(argp,what, "/",0);
 279   sprintf(whatbuf,"%s length",what);
 280   len= eat_number(argp,whatbuf, 0,32, endchars,endchar_r);
 281
 282   mask= (~0UL << (32-len));
 283   if (prefix & ~mask) badusage("%s prefix %08lx not fully contained in mask %08lx",
 284                                what,prefix,mask);
 285   *prefix_r= prefix;
 286   if (mask_r) *mask_r= mask;
 287   if (len_r) *len_r= len;
 288 }
 289
 290 static int addrnet_isin(unsigned long prefix, unsigned long mask,
 291                         unsigned long mprefix, unsigned long mmask) {
 292   return  !(~mask & mmask)  &&  (prefix & mmask) == mprefix;
 293 }
 294
 295
 296 static void permit(unsigned long pprefix, unsigned long pmask, int localonly) {
 297   int i, any;
 298
 299   assert(!(pprefix & ~pmask));
 300   any= 0;
 301
 302   if (!proto) fputs(localonly ? "permits-l" : "permits",stdout);
 303   if (addrnet_isin(localaddr,~0UL, pprefix,pmask)) {
 304     if (!proto) fputs(" local-addr",stdout);
 305     any= localallow= 1;
 306   }
 307   if (!localonly) {
 308     if (addrnet_isin(peeraddr,~0UL, pprefix,pmask)) {
 309       if (!proto) fputs(" peer-addr",stdout);
 310       any= peerallow= 1;
 311     }
 312     for (i=0; i<nexroutes; i++) {
 313       if (addrnet_isin(exroutes[i].prefix,exroutes[i].mask, pprefix,pmask)) {
 314         if (!proto) printf(" route#%d",i);
 315         any= exroutes[i].allow= 1;
 316       }
 317     }
 318   }
 319   if (!proto) {
 320     if (!any) fputs(" nothing",stdout);
 321     putchar('\n');
 322   }
 323 }
 324
 325 static void pconfig(const char *configstr, int truncated);
 326
 327 static void pfile(const char *filename) {
 328   FILE *file;
 329   char buf[PATH_MAX];
 330   int l, truncated, c;
 331   struct pplace npp, *cpp;
 332
 333   for (cpp=cpplace; cpp; cpp=cpp->parent) {
 334     if (!strcmp(cpp->filename,filename))
 335       badusage("recursive configuration file `%s'",filename);
 336   }
 337
 338   file= fopen(filename,"r");
 339   if (!file)
 340     badusage("cannot open configuration file `%s': %s", filename, strerror(errno));
 341
 342   if (!proto) printf("config file `%s':\n",filename);
 343
 344   npp.parent= cpplace;
 345   npp.filename= filename;
 346   npp.lineno= 0;
 347   cpplace= &npp;
 348
 349   while (fgets(buf, sizeof(buf), file)) {
 350     npp.lineno++;
 351     l= strlen(buf);
 352     if (!l) continue;
 353
 354     truncated= (buf[l-1] != '\n');
 355     while (l>0 && isspace((unsigned char) buf[l-1])) l--;
 356     if (!l) continue;
 357     buf[l]= 0;
 358
 359     if (truncated) {
 360       while ((c= getc(file)) != EOF && c != '\n');
 361       if (c == EOF) break;
 362     }
 363
 364     pconfig(buf,truncated);
 365   }
 366   if (ferror(file))
 367     badusage("failed while reading configuration file: %s", strerror(errno));
 368
 369   cpplace= npp.parent;
 370 }
 371
 372 static void pconfig(const char *configstr, int truncated) {
 373   unsigned long fgid, tgid, pprefix, pmask;
 374   int plen, localonly;
 375   char ptxt[ATXTLEN];
 376   const char *gidlist;
 377
 378   switch (configstr[0]) {
 379   case '*':
 380     if (strcmp(configstr,"*")) badusage("`*' directive must be only thing on line");
 381     permit(0UL,0UL,0);
 382     return;
 383
 384   case '#':
 385     return;
 386
 387   case '/': case '.':
 388     if (truncated) badusage("filename too long (`%.100s...')",configstr);
 389     pfile(configstr);
 390     return;
 391
 392   default:
 393     if (!isdigit((unsigned char)configstr[0]))
 394       badusage("unknown configuration directive");
 395
 396     fgid= eat_number(&configstr,"gid", 0,gidmaxval, ",",0);
 397     if (configstr[0] == '=') {
 398       localonly= 1;
 399       configstr++;
 400     } else {
 401       localonly= 0;
 402     }
 403     eat_prefixmask(&configstr,"permitted-prefix", ",",0, &pprefix,&pmask,&plen);
 404     if (!configstr && truncated) badusage("gid,prefix/len,... spec too long");
 405
 406     if (!proto) printf(" %5lu,%s/%d: ", fgid, ip2txt(pprefix,ptxt), plen);
 407
 408     gidlist= getenv("USERV_GID");
 409     if (!gidlist) fatal("USERV_GID not set");
 410     for (;;) {
 411       if (!gidlist) {
 412         if (!proto) printf("no matching gid\n");
 413         return;
 414       }
 415       tgid= eat_number(&gidlist,"userv-gid", 0,gidmaxval, " ",0);
 416       if (tgid == fgid) break;
 417     }
 418     permit(pprefix,pmask,localonly);
 419     return;
 420   }
 421 }
 422
 423 static void checkallow(int allow, const char *what,
 424                        const char *prefixtxt, const char *masktxt) {
 425   if (allow) return;
 426   fprintf(stderr,"userv-ipif service: access denied for %s, %s/%s\n",
 427           what, prefixtxt, masktxt);
 428   allallow= 0;
 429 }
 430
 431 static void parseargs(int argc, const char *const *argv) {
 432   unsigned long routeaddr, routemask;
 433   const char *carg;
 434   const char *const *cprotop;
 435   int i;
 436   char erwhatbuf[100], erwhatbuf2[100];
 437
 438   if (argc < NARGS+1) { badusage("too few arguments"); }
 439   if (argc > NARGS+1) { badusage("too many arguments"); }
 440
 441   configstr= *++argv;
 442
 443   carg= *++argv;
 444   if (strcmp(carg,"--")) badusage("separator argument `--' not found, got `%s'",carg);
 445
 446   carg= *++argv;
 447   localaddr= eat_addr(&carg,"local-addr", ",",0);
 448   peeraddr= eat_addr(&carg,"peer-addr", ",",0);
 449   mtu= eat_number(&carg,"mtu", 576,65536, ",",0);
 450   localallow= peerallow= 0;
 451
 452   if (!strcmp(carg,"debug")) {
 453     proto= 0;
 454   } else {
 455     for (cprotop= protos_ok;
 456          (proto= *cprotop) && strcmp(proto,carg);
 457          cprotop++);
 458     if (!proto) fatal("invalid protocol");
 459   }
 460
 461   addrnet_mustdiffer("local-addr",localaddr,~0UL, "peer-addr",peeraddr,~0UL);
 462
 463   carg= *++argv;
 464   if (strcmp(carg,"-")) {
 465     for (nexroutes=0;
 466          carg && *carg;
 467          nexroutes++) {
 468       if (nexroutes == MAXEXROUTES)
 469         fatal("too many extra routes (only %d allowed)",MAXEXROUTES);
 470       sprintf(erwhatbuf,"route#%d",nexroutes);
 471
 472       eat_prefixmask(&carg,erwhatbuf, ",",0, &routeaddr,&routemask,0);
 473       if (routemask == ~0UL) {
 474         addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "local-addr",localaddr,~0UL);
 475         addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "peer-addr",peeraddr,~0UL);
 476       }
 477       for (i=0; i<nexroutes; i++) {
 478         sprintf(erwhatbuf2,"route#%d",i);
 479         addrnet_mustdiffer(erwhatbuf,routeaddr,routemask,
 480                            erwhatbuf2,exroutes[i].prefix,exroutes[i].mask);
 481       }
 482       exroutes[nexroutes].prefix= routeaddr;
 483       exroutes[nexroutes].mask= routemask;
 484       exroutes[nexroutes].allow= 0;
 485       ip2txt(routeaddr,exroutes[nexroutes].prefixtxt);
 486       ip2txt(routemask,exroutes[nexroutes].masktxt);
 487     }
 488   }
 489
 490   ip2txt(localaddr,localtxt);
 491   ip2txt(peeraddr,peertxt);
 492 }
 493
 494 static void checkpermit(void) {
 495   int i;
 496   char erwhatbuf[100];
 497
 498   allallow= 1;
 499   checkallow(localallow,"local-addr", localtxt,"32");
 500   checkallow(peerallow,"peer-addr", peertxt,"32");
 501   for (i=0; i<nexroutes; i++) {
 502     sprintf(erwhatbuf, "route#%d", i);
 503     checkallow(exroutes[i].allow, erwhatbuf, exroutes[i].prefixtxt, exroutes[i].masktxt);
 504   }
 505   if (!allallow) fatal("access denied");
 506 }
 507
 508 static void dumpdebug(void) __attribute__((noreturn));
 509 static void dumpdebug(void) {
 510   int i;
 511   char erwhatbuf[100];
 512
 513   printf("protocol: debug\n"
 514          "local:    %08lx == %s\n"
 515          "peer:     %08lx == %s\n"
 516          "mtu:      %ld\n"
 517          "routes:   %d\n",
 518          localaddr, localtxt,
 519          peeraddr, peertxt,
 520          mtu,
 521          nexroutes);
 522   for (i=0; i<nexroutes; i++) {
 523     sprintf(erwhatbuf, "route#%d:", i);
 524     printf("%-9s %08lx/%08lx == %s/%s\n",
 525            erwhatbuf,
 526            exroutes[i].prefix, exroutes[i].mask,
 527            exroutes[i].prefixtxt, exroutes[i].masktxt);
 528   }
 529   if (ferror(stdout) || fclose(stdout)) sysfatal("flush stdout");
 530   exit(0);
 531 }
 532
 533
 534 static void setsigmask(const sigset_t *ss) {
 535   int r;
 536
 537   r= sigprocmask(SIG_SETMASK, ss, 0);
 538   if (r) sysfatal("[un]block signals");
 539 }
 540
 541 static void setsignals(void (*handler)(int), struct sigaction *sa, int chldflags) {
 542   const int *signalp;
 543   int r, sig;
 544
 545   sa->sa_handler= handler;
 546   sa->sa_flags= 0;
 547   for (signalp=signals; (sig=*signalp); signalp++) {
 548     r= sigaction(sig, sa, 0);  if (r) sysfatal("uncatch signal");
 549   }
 550   sa->sa_flags= chldflags;
 551   r= sigaction(SIGCHLD, sa, 0);  if (r) sysfatal("uncatch children");
 552 }
 553
 554 static void infork(void) {
 555   struct sigaction sa;
 556
 557   memset(&pids,0,sizeof(pids));
 558   sigemptyset(&sa.sa_mask);
 559   setsignals(SIG_DFL,&sa,0);
 560   setsigmask(&emptyset);
 561   undoslattach= 0;
 562 }
 563
 564 static pid_t makesubproc(void (*entry)(void)) {
 565   pid_t pid;
 566
 567   pid= fork();  if (pid == (pid_t)-1) sysfatal("fork for subprocess");
 568   if (pid) return pid;
 569
 570   infork();
 571   entry();
 572   abort();
 573 }
 574
 575 static int task(void) {
 576   pid_t pid;
 577
 578   pid= fork();
 579   if (pid == (pid_t)-1) sysfatal("fork for task");
 580   if (!pid) { infork(); return 1; }
 581
 582   pids.byname.task= pid;
 583   while (pids.byname.task) sigsuspend(&emptyset);
 584   return 0;
 585 }
 586
 587 static void mdup2(int fd1, int fd2, const char *what) {
 588   int r;
 589
 590   for (;;) {
 591     r= dup2(fd1,fd2); if (r==fd2) return;
 592     if (r!=-1) fatal("dup2 in %s gave wrong answer %d instead of %d",what,r,fd2);
 593     if (errno != EINTR) sysfatal("dup2 failed in %s",what);
 594   }
 595 }
 596
 597 static void sl_entry(void) {
 598   mdup2(slpipe[1],1,"slattach child");
 599   execlp("slattach", "slattach", "-v", "-L", "-p",proto, ptyname, (char*)0);
 600   sysfatal("cannot exec slattach");
 601 }
 602
 603 static void cin_entry(void) {
 604   mdup2(ptmaster,1,"cat input child");
 605   execlp("cat", "cat", (char*)0);
 606   sysfatal("cannot exec cat input");
 607 }
 608
 609 static void cout_entry(void) {
 610   mdup2(ptmaster,0,"cat output child");
 611   execlp("cat", "cat", (char*)0);
 612   sysfatal("cannot exec cat output");
 613 }
 614
 615 static void sighandler(int signum) {
 616   pid_t pid;
 617   int estatus, status;
 618   const char *taskfail;
 619
 620   estatus= 4;
 621
 622   if (signum == SIGCHLD) {
 623     for (;;) {
 624       pid= waitpid(-1,&status,WNOHANG);
 625       if (!pid || pid == (pid_t)-1) return;
 626
 627       if (pid == pids.byname.task) {
 628         pids.byname.task= 0;
 629         if (!status) return;
 630         taskfail= "task";
 631       } else if (pid == pids.byname.cin) {
 632         pids.byname.cin= 0;
 633         if (status) {
 634           taskfail= "input cat";
 635         } else {
 636           taskfail= 0;
 637           estatus= 0;
 638         }
 639       } else if (pid == pids.byname.cout) {
 640         pids.byname.cout= 0;
 641         taskfail= "output cat";
 642       } else if (pid == pids.byname.sl) {
 643         pids.byname.sl= 0;
 644         taskfail= "slattach";
 645       } else {
 646         continue;
 647       }
 648       break;
 649     }
 650     if (taskfail) {
 651       if (WIFEXITED(status)) {
 652         fprintf(stderr,
 653                 "userv-ipif service: %s unexpectedly exited with exit status %d\n",
 654                 taskfail, WEXITSTATUS(status));
 655       } else if (WIFSIGNALED(status)) {
 656         fprintf(stderr,
 657                 "userv-ipif service: %s unexpectedly killed by signal %s%s\n",
 658                 taskfail, strsignal(WTERMSIG(status)),
 659                 WCOREDUMP(status) ? " (core dumped)" : "");
 660       } else {
 661         fprintf(stderr, "userv-ipif service: %s unexpectedly terminated"
 662                 " with unknown status code %d\n", taskfail, status);
 663       }
 664     }
 665   } else {
 666     fprintf(stderr,
 667             "userv-ipif service: received signal %d, terminating\n",
 668             signum);
 669   }
 670
 671   terminate(estatus);
 672 }
 673
 674 static void startup(void) {
 675   int r;
 676   struct sigaction sa;
 677
 678   sigfillset(&fullset);
 679   sigemptyset(&emptyset);
 680
 681   ptmaster= getpt();  if (ptmaster==-1) sysfatal("allocate pty master");
 682   r= grantpt(ptmaster);  if (r) sysfatal("grab/grant pty slave");
 683   ptyname= ptsname(ptmaster);  if (!ptyname) sysfatal("get pty slave name");
 684   r= chmod(ptyname,0600);  if (r) sysfatal("chmod pty slave");
 685   r= unlockpt(ptmaster);  if (r) sysfatal("unlock pty");
 686
 687   sigfillset(&sa.sa_mask);
 688   setsignals(sighandler,&sa,SA_NOCLDSTOP);
 689   setsigmask(&fullset);
 690 }
 691
 692 static void startslattach(void) {
 693   static char ifnbuf[200];
 694
 695   FILE *piper;
 696   int r, l, k;
 697
 698   r= pipe(slpipe);  if (r) sysfatal("create pipe");
 699   piper= fdopen(slpipe[0],"r");  if (!piper) sysfatal("fdopen pipe");
 700
 701   undoslattach= 1;
 702   pids.byname.sl= makesubproc(sl_entry);
 703
 704   close(slpipe[1]);
 705   setsigmask(&emptyset);
 706   if (!fgets(ifnbuf,sizeof(ifnbuf),piper)) {
 707     if (ferror(piper)) sysfatal("cannot read ifname from slattach");
 708     else fatal("cannot read ifname from slattach");
 709   }
 710   setsigmask(&fullset);
 711   l= strlen(ifnbuf);
 712   if (l<=0 || ifnbuf[l-1] != '\n') fatal("slattach gave strange output `%s'",ifnbuf);
 713   ifnbuf[l-1]= 0;
 714   for (k=l; k>0 && ifnbuf[k-1]!=' '; k--);
 715   ifname= ifnbuf+k;
 716 }
 717
 718 static void netconfigure(void) {
 719   char mtutxt[100];
 720   int i;
 721
 722   if (task()) {
 723     sprintf(mtutxt,"%lu",mtu);
 724
 725     execlp("ifconfig", "ifconfig", ifname, localtxt,
 726            "netmask","255.255.255.255", "-broadcast", "pointopoint",peertxt,
 727            "mtu",mtutxt, "up", (char*)0);
 728     sysfatal("cannot exec ifconfig");
 729   }
 730
 731   for (i=0; i<nexroutes; i++) {
 732     if (task()) {
 733       execlp("route","route", "add", "-net",exroutes[i].prefixtxt,
 734              "netmask",exroutes[i].masktxt,
 735              "gw",peertxt, "dev",ifname, (char*)0);
 736       sysfatal("cannot exec route (for route)");
 737     }
 738   }
 739 }
 740
 741 static void copydata(void) __attribute__((noreturn));
 742 static void copydata(void) {
 743   int r;
 744
 745   pids.byname.cin= makesubproc(cin_entry);
 746   for (;;) {
 747     r= write(1, "\300", 1); if (r==1) break;
 748     assert(r==-1);  if (errno != EINTR) sysfatal("send initial delim to confirm");
 749   }
 750   pids.byname.cout= makesubproc(cout_entry);
 751
 752   for (;;) sigsuspend(&emptyset);
 753 }
 754
 755 int main(int argc, const char *const *argv) {
 756   parseargs(argc,argv);
 757   pconfig(configstr,0);
 758   checkpermit();
 759   if (!proto) dumpdebug();
 760
 761   startup();
 762   startslattach();
 763   netconfigure();
 764   copydata();
 765 }