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     netlink_deliver_fn *netlink_to_tunnel;
  27     uint32_t local_address;
  28 };
  29
  30 /* Generic SLIP mangling code */
  31
  32 static void slip_stuff(struct slip *st, struct buffer_if *buf, int fd)
  33 {
  34     uint8_t txbuf[DEFAULT_BUFSIZE];
  35     uint8_t *i;
  36     int32_t j=0;
  37
  38     BUF_ASSERT_USED(buf);
  39
  40     /* There's probably a much more efficient way of implementing this */
  41     txbuf[j++]=SLIP_END;
  42     for (i=buf->start; i<(buf->start+buf->size); i++) {
  43         switch (*i) {
  44         case SLIP_END:
  45             txbuf[j++]=SLIP_ESC;
  46             txbuf[j++]=SLIP_ESCEND;
  47             break;
  48         case SLIP_ESC:
  49             txbuf[j++]=SLIP_ESC;
  50             txbuf[j++]=SLIP_ESCESC;
  51             break;
  52         default:
  53             txbuf[j++]=*i;
  54             break;
  55         }
  56         if ((j+2)>DEFAULT_BUFSIZE) {
  57             if (write(fd,txbuf,j)<0) {
  58                 fatal_perror("slip_stuff: write()");
  59             }
  60             j=0;
  61         }
  62     }
  63     txbuf[j++]=SLIP_END;
  64     if (write(fd,txbuf,j)<0) {
  65         fatal_perror("slip_stuff: write()");
  66     }
  67     BUF_FREE(buf);
  68 }
  69
  70 static void slip_unstuff(struct slip *st, uint8_t *buf, uint32_t l)
  71 {
  72     uint32_t i;
  73
  74     BUF_ASSERT_USED(st->buff);
  75     for (i=0; i<l; i++) {
  76         if (st->pending_esc) {
  77             st->pending_esc=False;
  78             switch(buf[i]) {
  79             case SLIP_ESCEND:
  80                 *(uint8_t *)buf_append(st->buff,1)=SLIP_END;
  81                 break;
  82             case SLIP_ESCESC:
  83                 *(uint8_t *)buf_append(st->buff,1)=SLIP_ESC;
  84                 break;
  85             default:
  86                 fatal("userv_afterpoll: bad SLIP escape character");
  87             }
  88         } else {
  89             switch (buf[i]) {
  90             case SLIP_END:
  91                 if (st->buff->size>0) {
  92                     st->netlink_to_tunnel(&st->nl,st->buff);
  93                     BUF_ALLOC(st->buff,"userv_afterpoll");
  94                 }
  95                 buffer_init(st->buff,st->nl.max_start_pad);
  96                 break;
  97             case SLIP_ESC:
  98                 st->pending_esc=True;
  99                 break;
 100             default:
 101                 *(uint8_t *)buf_append(st->buff,1)=buf[i];
 102                 break;
 103             }
 104         }
 105     }
 106 }
 107
 108 static void slip_init(struct slip *st, struct cloc loc, dict_t *dict,
 109                       cstring_t name, netlink_deliver_fn *to_host)
 110 {
 111     st->netlink_to_tunnel=
 112         netlink_init(&st->nl,st,loc,dict,
 113                      "netlink-userv-ipif",NULL,to_host);
 114     st->buff=find_cl_if(dict,"buffer",CL_BUFFER,True,"name",loc);
 115     st->local_address=string_item_to_ipaddr(
 116         dict_find_item(dict,"local-address", True, name, loc),"netlink");
 117     BUF_ALLOC(st->buff,"slip_init");
 118     st->pending_esc=False;
 119 }
 120
 121 /* Connection to the kernel through userv-ipif */
 122
 123 struct userv {
 124     struct slip slip;
 125     int txfd; /* We transmit to userv */
 126     int rxfd; /* We receive from userv */
 127     cstring_t userv_path;
 128     cstring_t service_user;
 129     cstring_t service_name;
 130     pid_t pid;
 131     bool_t expecting_userv_exit;
 132 };
 133
 134 static int userv_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
 135                             int *timeout_io, const struct timeval *tv_now,
 136                             uint64_t *now)
 137 {
 138     struct userv *st=sst;
 139
 140     if (st->rxfd!=-1) {
 141         *nfds_io=2;
 142         fds[0].fd=st->txfd;
 143         fds[0].events=0; /* Might want to pick up POLLOUT sometime */
 144         fds[1].fd=st->rxfd;
 145         fds[1].events=POLLIN;
 146     } else {
 147         *nfds_io=0;
 148     }
 149     return 0;
 150 }
 151
 152 static void userv_afterpoll(void *sst, struct pollfd *fds, int nfds,
 153                             const struct timeval *tv_now, uint64_t *now)
 154 {
 155     struct userv *st=sst;
 156     uint8_t rxbuf[DEFAULT_BUFSIZE];
 157     int l;
 158
 159     if (nfds==0) return;
 160
 161     if (fds[1].revents&POLLERR) {
 162         Message(M_ERR,"%s: userv_afterpoll: POLLERR!\n",st->slip.nl.name);
 163     }
 164     if (fds[1].revents&POLLIN) {
 165         l=read(st->rxfd,rxbuf,DEFAULT_BUFSIZE);
 166         if (l<0) {
 167             if (errno!=EINTR)
 168                 fatal_perror("%s: userv_afterpoll: read(rxfd)",
 169                              st->slip.nl.name);
 170         } else if (l==0) {
 171             fatal("%s: userv_afterpoll: read(rxfd)=0; userv gone away?",
 172                   st->slip.nl.name);
 173         } else slip_unstuff(&st->slip,rxbuf,l);
 174     }
 175 }
 176
 177 /* Send buf to the kernel. Free buf before returning. */
 178 static void userv_deliver_to_kernel(void *sst, struct buffer_if *buf)
 179 {
 180     struct userv *st=sst;
 181
 182     slip_stuff(&st->slip,buf,st->txfd);
 183 }
 184
 185 static void userv_userv_callback(void *sst, pid_t pid, int status)
 186 {
 187     struct userv *st=sst;
 188
 189     if (pid!=st->pid) {
 190         Message(M_WARNING,"userv_callback called unexpectedly with pid %d "
 191                 "(expected %d)\n",pid,st->pid);
 192         return;
 193     }
 194     if (!st->expecting_userv_exit) {
 195         if (WIFEXITED(status)) {
 196             fatal("%s: userv exited unexpectedly with status %d",
 197                   st->slip.nl.name,WEXITSTATUS(status));
 198         } else if (WIFSIGNALED(status)) {
 199             fatal("%s: userv exited unexpectedly: uncaught signal %d",
 200                   st->slip.nl.name,WTERMSIG(status));
 201         } else {
 202             fatal("%s: userv stopped unexpectedly");
 203         }
 204     }
 205     Message(M_WARNING,"%s: userv subprocess died with status %d\n",
 206             st->slip.nl.name,WEXITSTATUS(status));
 207     st->pid=0;
 208 }
 209
 210 struct userv_entry_rec {
 211     cstring_t path;
 212     const char **argv;
 213     int in;
 214     int out;
 215     /* XXX perhaps we should collect and log stderr? */
 216 };
 217
 218 static void userv_entry(void *sst)
 219 {
 220     struct userv_entry_rec *st=sst;
 221
 222     dup2(st->in,0);
 223     dup2(st->out,1);
 224
 225     /* XXX close all other fds */
 226     setsid();
 227     /* XXX We really should strdup() all of argv[] but because we'll just
 228        exit anyway if execvp() fails it doesn't seem worth bothering. */
 229     execvp(st->path,(char *const*)st->argv);
 230     perror("userv-entry: execvp()");
 231     exit(1);
 232 }
 233
 234 static void userv_invoke_userv(struct userv *st)
 235 {
 236     struct userv_entry_rec *er;
 237     int c_stdin[2];
 238     int c_stdout[2];
 239     string_t addrs;
 240     string_t nets;
 241     string_t s;
 242     struct netlink_client *r;
 243     struct ipset *allnets;
 244     struct subnet_list *snets;
 245     int i, nread;
 246     uint8_t confirm;
 247
 248     if (st->pid) {
 249         fatal("userv_invoke_userv: already running");
 250     }
 251
 252     /* This is where we actually invoke userv - all the networks we'll
 253        be using should already have been registered. */
 254
 255     addrs=safe_malloc(512,"userv_invoke_userv:addrs");
 256     snprintf(addrs,512,"%s,%s,%d,slip",
 257              ipaddr_to_string(st->slip.local_address),
 258              ipaddr_to_string(st->slip.nl.secnet_address),st->slip.nl.mtu);
 259
 260     allnets=ipset_new();
 261     for (r=st->slip.nl.clients; r; r=r->next) {
 262         if (r->up) {
 263             struct ipset *nan;
 264             r->kup=True;
 265             nan=ipset_union(allnets,r->networks);
 266             ipset_free(allnets);
 267             allnets=nan;
 268         }
 269     }
 270     snets=ipset_to_subnet_list(allnets);
 271     ipset_free(allnets);
 272     nets=safe_malloc(20*snets->entries,"userv_invoke_userv:nets");
 273     *nets=0;
 274     for (i=0; i<snets->entries; i++) {
 275         s=subnet_to_string(snets->list[i]);
 276         strcat(nets,s);
 277         strcat(nets,",");
 278         free(s);
 279     }
 280     nets[strlen(nets)-1]=0;
 281     subnet_list_free(snets);
 282
 283     Message(M_INFO,"%s: about to invoke: %s %s %s %s %s\n",st->slip.nl.name,
 284             st->userv_path,st->service_user,st->service_name,addrs,nets);
 285
 286     st->slip.pending_esc=False;
 287
 288     /* Invoke userv */
 289     if (pipe(c_stdin)!=0) {
 290         fatal_perror("userv_invoke_userv: pipe(c_stdin)");
 291     }
 292     if (pipe(c_stdout)!=0) {
 293         fatal_perror("userv_invoke_userv: pipe(c_stdout)");
 294     }
 295     st->txfd=c_stdin[1];
 296     st->rxfd=c_stdout[0];
 297
 298     er=safe_malloc(sizeof(*r),"userv_invoke_userv: er");
 299
 300     er->in=c_stdin[0];
 301     er->out=c_stdout[1];
 302     /* The arguments are:
 303        userv
 304        service-user
 305        service-name
 306        local-addr,secnet-addr,mtu,protocol
 307        route1,route2,... */
 308     er->argv=safe_malloc(sizeof(*er->argv)*6,"userv_invoke_userv:argv");
 309     er->argv[0]=st->userv_path;
 310     er->argv[1]=st->service_user;
 311     er->argv[2]=st->service_name;
 312     er->argv[3]=addrs;
 313     er->argv[4]=nets;
 314     er->argv[5]=NULL;
 315     er->path=st->userv_path;
 316
 317     st->pid=makesubproc(userv_entry, userv_userv_callback,
 318                         er, st, st->slip.nl.name);
 319     close(er->in);
 320     close(er->out);
 321     free(er->argv);
 322     free(er);
 323     free(addrs);
 324     free(nets);
 325     Message(M_INFO,"%s: userv-ipif pid is %d\n",st->slip.nl.name,st->pid);
 326     /* Read a single character from the pipe to confirm userv-ipif is
 327        running. If we get a SIGCHLD at this point then we'll get EINTR. */
 328     if ((nread=read(st->rxfd,&confirm,1))!=1) {
 329         if (errno==EINTR) {
 330             Message(M_WARNING,"%s: read of confirmation byte was "
 331                     "interrupted\n",st->slip.nl.name);
 332         } else {
 333             if (nread<0) {
 334                 fatal_perror("%s: error reading confirmation byte",
 335                              st->slip.nl.name);
 336             } else {
 337                 fatal("%s: unexpected EOF instead of confirmation byte"
 338                       " - userv ipif failed?", st->slip.nl.name);
 339             }
 340         }
 341     } else {
 342         if (confirm!=SLIP_END) {
 343             fatal("%s: bad confirmation byte %d from userv-ipif",
 344                   st->slip.nl.name,confirm);
 345         }
 346     }
 347 }
 348
 349 static void userv_kill_userv(struct userv *st)
 350 {
 351     if (st->pid) {
 352         kill(-st->pid,SIGTERM);
 353         st->expecting_userv_exit=True;
 354     }
 355 }
 356
 357 static void userv_phase_hook(void *sst, uint32_t newphase)
 358 {
 359     struct userv *st=sst;
 360     /* We must wait until signal processing has started before forking
 361        userv */
 362     if (newphase==PHASE_RUN) {
 363         userv_invoke_userv(st);
 364         /* Register for poll() */
 365         register_for_poll(st, userv_beforepoll, userv_afterpoll, 2,
 366                           st->slip.nl.name);
 367     }
 368     if (newphase==PHASE_SHUTDOWN) {
 369         userv_kill_userv(st);
 370     }
 371 }
 372
 373 static list_t *userv_apply(closure_t *self, struct cloc loc, dict_t *context,
 374                            list_t *args)
 375 {
 376     struct userv *st;
 377     item_t *item;
 378     dict_t *dict;
 379
 380     st=safe_malloc(sizeof(*st),"userv_apply");
 381
 382     /* First parameter must be a dict */
 383     item=list_elem(args,0);
 384     if (!item || item->type!=t_dict)
 385         cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n");
 386
 387     dict=item->data.dict;
 388
 389     slip_init(&st->slip,loc,dict,"netlink-userv-ipif",
 390               userv_deliver_to_kernel);
 391
 392     st->userv_path=dict_read_string(dict,"userv-path",False,"userv-netlink",
 393                                     loc);
 394     st->service_user=dict_read_string(dict,"service-user",False,
 395                                       "userv-netlink",loc);
 396     st->service_name=dict_read_string(dict,"service-name",False,
 397                                       "userv-netlink",loc);
 398     if (!st->userv_path) st->userv_path="userv";
 399     if (!st->service_user) st->service_user="root";
 400     if (!st->service_name) st->service_name="ipif";
 401     st->rxfd=-1; st->txfd=-1;
 402     st->pid=0;
 403     st->expecting_userv_exit=False;
 404     add_hook(PHASE_RUN,userv_phase_hook,st);
 405     add_hook(PHASE_SHUTDOWN,userv_phase_hook,st);
 406
 407     return new_closure(&st->slip.nl.cl);
 408 }
 409
 410 void slip_module(dict_t *dict)
 411 {
 412     add_closure(dict,"userv-ipif",userv_apply);
 413 }