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