mdw@git.distorted.org.uk Git - secnet/blob - slip.c

   1 /* When dealing with SLIP (to a pty, or ipif) we have separate rx, tx
   2    and client buffers.  When receiving we may read() any amount, not
   3    just whole packets.  When transmitting we need to bytestuff anyway,
   4    and may be part-way through receiving. */
   5
   6 #include "secnet.h"
   7 #include "util.h"
   8 #include "netlink.h"
   9 #include "process.h"
  10 #include "unaligned.h"
  11 #include <stdio.h>
  12 #include <string.h>
  13 #include <unistd.h>
  14 #include <errno.h>
  15 #include <fcntl.h>
  16
  17 #define SLIP_END    192
  18 #define SLIP_ESC    219
  19 #define SLIP_ESCEND 220
  20 #define SLIP_ESCESC 221
  21
  22 struct slip {
  23     struct netlink nl;
  24     struct buffer_if *buff; /* We unstuff received packets into here
  25                                and send them to the netlink code. */
  26     bool_t pending_esc;
  27     bool_t ignoring_packet; /* If this packet was corrupt or overlong,
  28                                we ignore everything up to the next END */
  29     netlink_deliver_fn *netlink_to_tunnel;
  30     uint32_t local_address;
  31 };
  32
  33 /* Generic SLIP mangling code */
  34
  35 static void slip_stuff(struct slip *st, struct buffer_if *buf, int fd)
  36 {
  37     uint8_t txbuf[DEFAULT_BUFSIZE];
  38     uint8_t *i;
  39     int32_t j=0;
  40
  41     BUF_ASSERT_USED(buf);
  42
  43     /* There's probably a much more efficient way of implementing this */
  44     txbuf[j++]=SLIP_END;
  45     for (i=buf->start; i<(buf->start+buf->size); i++) {
  46         switch (*i) {
  47         case SLIP_END:
  48             txbuf[j++]=SLIP_ESC;
  49             txbuf[j++]=SLIP_ESCEND;
  50             break;
  51         case SLIP_ESC:
  52             txbuf[j++]=SLIP_ESC;
  53             txbuf[j++]=SLIP_ESCESC;
  54             break;
  55         default:
  56             txbuf[j++]=*i;
  57             break;
  58         }
  59         if ((j+2)>DEFAULT_BUFSIZE) {
  60             if (write(fd,txbuf,j)<0) {
  61                 fatal_perror("slip_stuff: write()");
  62             }
  63             j=0;
  64         }
  65     }
  66     txbuf[j++]=SLIP_END;
  67     if (write(fd,txbuf,j)<0) {
  68         fatal_perror("slip_stuff: write()");
  69     }
  70     BUF_FREE(buf);
  71 }
  72
  73 static void slip_unstuff(struct slip *st, uint8_t *buf, uint32_t l)
  74 {
  75     uint32_t i;
  76
  77     BUF_ASSERT_USED(st->buff);
  78     for (i=0; i<l; i++) {
  79         int outputchr;
  80         enum { OUTPUT_END = 256, OUTPUT_NOTHING = 257 };
  81
  82         if (st->pending_esc) {
  83             st->pending_esc=False;
  84             switch(buf[i]) {
  85             case SLIP_ESCEND:
  86                 outputchr=SLIP_END;
  87                 break;
  88             case SLIP_ESCESC:
  89                 outputchr=SLIP_ESC;
  90                 break;
  91             default:
  92                 if (!st->ignoring_packet) {
  93                     Message(M_WARNING, "userv_afterpoll: bad SLIP escape"
  94                             " character, dropping packet\n");
  95                 }
  96                 st->ignoring_packet=True;
  97                 outputchr=OUTPUT_NOTHING;
  98                 break;
  99             }
 100         } else {
 101             switch (buf[i]) {
 102             case SLIP_END:
 103                 outputchr=OUTPUT_END;
 104                 break;
 105             case SLIP_ESC:
 106                 st->pending_esc=True;
 107                 outputchr=OUTPUT_NOTHING;
 108                 break;
 109             default:
 110                 outputchr=buf[i];
 111                 break;
 112             }
 113         }
 114
 115         if (st->ignoring_packet) {
 116             if (outputchr == OUTPUT_END) {
 117                 st->ignoring_packet=False;
 118                 buffer_init(st->buff,st->nl.max_start_pad);
 119             }
 120         } else {
 121             if (outputchr == OUTPUT_END) {
 122                 if (st->buff->size>0) {
 123                     st->netlink_to_tunnel(&st->nl,st->buff);
 124                     BUF_ALLOC(st->buff,"userv_afterpoll");
 125                 }
 126                 buffer_init(st->buff,st->nl.max_start_pad);
 127             } else if (outputchr != OUTPUT_NOTHING) {
 128                 if (st->buff->size < st->buff->len) {
 129                     buf_append_uint8(st->buff,outputchr);
 130                 } else {
 131                     Message(M_WARNING, "userv_afterpoll: dropping overlong"
 132                             " SLIP packet\n");
 133                     st->ignoring_packet=True;
 134                 }
 135             }
 136         }
 137     }
 138 }
 139
 140 static void slip_init(struct slip *st, struct cloc loc, dict_t *dict,
 141                       cstring_t name, netlink_deliver_fn *to_host)
 142 {
 143     st->netlink_to_tunnel=
 144         netlink_init(&st->nl,st,loc,dict,
 145                      "netlink-userv-ipif",NULL,to_host);
 146     st->buff=find_cl_if(dict,"buffer",CL_BUFFER,True,"name",loc);
 147     st->local_address=string_item_to_ipaddr(
 148         dict_find_item(dict,"local-address", True, name, loc),"netlink");
 149     BUF_ALLOC(st->buff,"slip_init");
 150     st->pending_esc=False;
 151     st->ignoring_packet=False;
 152 }
 153
 154 /* Connection to the kernel through userv-ipif */
 155
 156 struct userv {
 157     struct slip slip;
 158     int txfd; /* We transmit to userv */
 159     int rxfd; /* We receive from userv */
 160     cstring_t userv_path;
 161     cstring_t service_user;
 162     cstring_t service_name;
 163     pid_t pid;
 164     bool_t expecting_userv_exit;
 165 };
 166
 167 static int userv_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
 168                             int *timeout_io)
 169 {
 170     struct userv *st=sst;
 171
 172     if (st->rxfd!=-1) {
 173         *nfds_io=2;
 174         fds[0].fd=st->txfd;
 175         fds[0].events=0; /* Might want to pick up POLLOUT sometime */
 176         fds[1].fd=st->rxfd;
 177         fds[1].events=POLLIN;
 178     } else {
 179         *nfds_io=0;
 180     }
 181     return 0;
 182 }
 183
 184 static void userv_afterpoll(void *sst, struct pollfd *fds, int nfds)
 185 {
 186     struct userv *st=sst;
 187     uint8_t rxbuf[DEFAULT_BUFSIZE];
 188     int l;
 189
 190     if (nfds==0) return;
 191
 192     if (fds[1].revents&POLLERR) {
 193         Message(M_ERR,"%s: userv_afterpoll: POLLERR!\n",st->slip.nl.name);
 194     }
 195     if (fds[1].revents&POLLIN) {
 196         l=read(st->rxfd,rxbuf,DEFAULT_BUFSIZE);
 197         if (l<0) {
 198             if (errno!=EINTR)
 199                 fatal_perror("%s: userv_afterpoll: read(rxfd)",
 200                              st->slip.nl.name);
 201         } else if (l==0) {
 202             fatal("%s: userv_afterpoll: read(rxfd)=0; userv gone away?",
 203                   st->slip.nl.name);
 204         } else slip_unstuff(&st->slip,rxbuf,l);
 205     }
 206 }
 207
 208 /* Send buf to the kernel. Free buf before returning. */
 209 static void userv_deliver_to_kernel(void *sst, struct buffer_if *buf)
 210 {
 211     struct userv *st=sst;
 212
 213     slip_stuff(&st->slip,buf,st->txfd);
 214 }
 215
 216 static void userv_userv_callback(void *sst, pid_t pid, int status)
 217 {
 218     struct userv *st=sst;
 219
 220     if (pid!=st->pid) {
 221         Message(M_WARNING,"userv_callback called unexpectedly with pid %d "
 222                 "(expected %d)\n",pid,st->pid);
 223         return;
 224     }
 225     if (!st->expecting_userv_exit) {
 226         if (WIFEXITED(status)) {
 227             fatal("%s: userv exited unexpectedly with status %d",
 228                   st->slip.nl.name,WEXITSTATUS(status));
 229         } else if (WIFSIGNALED(status)) {
 230             fatal("%s: userv exited unexpectedly: uncaught signal %d",
 231                   st->slip.nl.name,WTERMSIG(status));
 232         } else {
 233             fatal("%s: userv stopped unexpectedly");
 234         }
 235     }
 236     Message(M_WARNING,"%s: userv subprocess died with status %d\n",
 237             st->slip.nl.name,WEXITSTATUS(status));
 238     st->pid=0;
 239 }
 240
 241 struct userv_entry_rec {
 242     cstring_t path;
 243     const char **argv;
 244     int in;
 245     int out;
 246     /* XXX perhaps we should collect and log stderr? */
 247 };
 248
 249 static void userv_entry(void *sst)
 250 {
 251     struct userv_entry_rec *st=sst;
 252
 253     dup2(st->in,0);
 254     dup2(st->out,1);
 255
 256     /* XXX close all other fds */
 257     setsid();
 258     /* XXX We really should strdup() all of argv[] but because we'll just
 259        exit anyway if execvp() fails it doesn't seem worth bothering. */
 260     execvp(st->path,(char *const*)st->argv);
 261     perror("userv-entry: execvp()");
 262     exit(1);
 263 }
 264
 265 static void userv_invoke_userv(struct userv *st)
 266 {
 267     struct userv_entry_rec *er;
 268     int c_stdin[2];
 269     int c_stdout[2];
 270     string_t addrs;
 271     string_t nets;
 272     string_t s;
 273     struct netlink_client *r;
 274     struct ipset *allnets;
 275     struct subnet_list *snets;
 276     int i, nread;
 277     uint8_t confirm;
 278
 279     if (st->pid) {
 280         fatal("userv_invoke_userv: already running");
 281     }
 282
 283     /* This is where we actually invoke userv - all the networks we'll
 284        be using should already have been registered. */
 285
 286     addrs=safe_malloc(512,"userv_invoke_userv:addrs");
 287     snprintf(addrs,512,"%s,%s,%d,slip",
 288              ipaddr_to_string(st->slip.local_address),
 289              ipaddr_to_string(st->slip.nl.secnet_address),st->slip.nl.mtu);
 290
 291     allnets=ipset_new();
 292     for (r=st->slip.nl.clients; r; r=r->next) {
 293         if (r->link_quality > LINK_QUALITY_UNUSED) {
 294             struct ipset *nan;
 295             r->kup=True;
 296             nan=ipset_union(allnets,r->networks);
 297             ipset_free(allnets);
 298             allnets=nan;
 299         }
 300     }
 301     snets=ipset_to_subnet_list(allnets);
 302     ipset_free(allnets);
 303     nets=safe_malloc(20*snets->entries,"userv_invoke_userv:nets");
 304     *nets=0;
 305     for (i=0; i<snets->entries; i++) {
 306         s=subnet_to_string(snets->list[i]);
 307         strcat(nets,s);
 308         strcat(nets,",");
 309         free(s);
 310     }
 311     nets[strlen(nets)-1]=0;
 312     subnet_list_free(snets);
 313
 314     Message(M_INFO,"%s: about to invoke: %s %s %s %s %s\n",st->slip.nl.name,
 315             st->userv_path,st->service_user,st->service_name,addrs,nets);
 316
 317     st->slip.pending_esc=False;
 318
 319     /* Invoke userv */
 320     if (pipe(c_stdin)!=0) {
 321         fatal_perror("userv_invoke_userv: pipe(c_stdin)");
 322     }
 323     if (pipe(c_stdout)!=0) {
 324         fatal_perror("userv_invoke_userv: pipe(c_stdout)");
 325     }
 326     st->txfd=c_stdin[1];
 327     st->rxfd=c_stdout[0];
 328
 329     er=safe_malloc(sizeof(*r),"userv_invoke_userv: er");
 330
 331     er->in=c_stdin[0];
 332     er->out=c_stdout[1];
 333     /* The arguments are:
 334        userv
 335        service-user
 336        service-name
 337        local-addr,secnet-addr,mtu,protocol
 338        route1,route2,... */
 339     er->argv=safe_malloc(sizeof(*er->argv)*6,"userv_invoke_userv:argv");
 340     er->argv[0]=st->userv_path;
 341     er->argv[1]=st->service_user;
 342     er->argv[2]=st->service_name;
 343     er->argv[3]=addrs;
 344     er->argv[4]=nets;
 345     er->argv[5]=NULL;
 346     er->path=st->userv_path;
 347
 348     st->pid=makesubproc(userv_entry, userv_userv_callback,
 349                         er, st, st->slip.nl.name);
 350     close(er->in);
 351     close(er->out);
 352     free(er->argv);
 353     free(er);
 354     free(addrs);
 355     free(nets);
 356     Message(M_INFO,"%s: userv-ipif pid is %d\n",st->slip.nl.name,st->pid);
 357     /* Read a single character from the pipe to confirm userv-ipif is
 358        running. If we get a SIGCHLD at this point then we'll get EINTR. */
 359     if ((nread=read(st->rxfd,&confirm,1))!=1) {
 360         if (errno==EINTR) {
 361             Message(M_WARNING,"%s: read of confirmation byte was "
 362                     "interrupted\n",st->slip.nl.name);
 363         } else {
 364             if (nread<0) {
 365                 fatal_perror("%s: error reading confirmation byte",
 366                              st->slip.nl.name);
 367             } else {
 368                 fatal("%s: unexpected EOF instead of confirmation byte"
 369                       " - userv ipif failed?", st->slip.nl.name);
 370             }
 371         }
 372     } else {
 373         if (confirm!=SLIP_END) {
 374             fatal("%s: bad confirmation byte %d from userv-ipif",
 375                   st->slip.nl.name,confirm);
 376         }
 377     }
 378 }
 379
 380 static void userv_kill_userv(struct userv *st)
 381 {
 382     if (st->pid) {
 383         kill(-st->pid,SIGTERM);
 384         st->expecting_userv_exit=True;
 385     }
 386 }
 387
 388 static void userv_phase_hook(void *sst, uint32_t newphase)
 389 {
 390     struct userv *st=sst;
 391     /* We must wait until signal processing has started before forking
 392        userv */
 393     if (newphase==PHASE_RUN) {
 394         userv_invoke_userv(st);
 395         /* Register for poll() */
 396         register_for_poll(st, userv_beforepoll, userv_afterpoll, 2,
 397                           st->slip.nl.name);
 398     }
 399     if (newphase==PHASE_SHUTDOWN) {
 400         userv_kill_userv(st);
 401     }
 402 }
 403
 404 static list_t *userv_apply(closure_t *self, struct cloc loc, dict_t *context,
 405                            list_t *args)
 406 {
 407     struct userv *st;
 408     item_t *item;
 409     dict_t *dict;
 410
 411     st=safe_malloc(sizeof(*st),"userv_apply");
 412
 413     /* First parameter must be a dict */
 414     item=list_elem(args,0);
 415     if (!item || item->type!=t_dict)
 416         cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n");
 417
 418     dict=item->data.dict;
 419
 420     slip_init(&st->slip,loc,dict,"netlink-userv-ipif",
 421               userv_deliver_to_kernel);
 422
 423     st->userv_path=dict_read_string(dict,"userv-path",False,"userv-netlink",
 424                                     loc);
 425     st->service_user=dict_read_string(dict,"service-user",False,
 426                                       "userv-netlink",loc);
 427     st->service_name=dict_read_string(dict,"service-name",False,
 428                                       "userv-netlink",loc);
 429     if (!st->userv_path) st->userv_path="userv";
 430     if (!st->service_user) st->service_user="root";
 431     if (!st->service_name) st->service_name="ipif";
 432     st->rxfd=-1; st->txfd=-1;
 433     st->pid=0;
 434     st->expecting_userv_exit=False;
 435     add_hook(PHASE_RUN,userv_phase_hook,st);
 436     add_hook(PHASE_SHUTDOWN,userv_phase_hook,st);
 437
 438     return new_closure(&st->slip.nl.cl);
 439 }
 440
 441 void slip_module(dict_t *dict)
 442 {
 443     add_closure(dict,"userv-ipif",userv_apply);
 444 }