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     uint32_t j=0;
  37
  38     BUF_ASSERT_USED(buf);
  39
  40     /* XXX crunchy bytestuff code */
  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     /* XXX really crude unstuff code */
  75     /* XXX check for buffer overflow */
  76     BUF_ASSERT_USED(st->buff);
  77     for (i=0; i<l; i++) {
  78         if (st->pending_esc) {
  79             st->pending_esc=False;
  80             switch(buf[i]) {
  81             case SLIP_ESCEND:
  82                 *(uint8_t *)buf_append(st->buff,1)=SLIP_END;
  83                 break;
  84             case SLIP_ESCESC:
  85                 *(uint8_t *)buf_append(st->buff,1)=SLIP_ESC;
  86                 break;
  87             default:
  88                 fatal("userv_afterpoll: bad SLIP escape character\n");
  89             }
  90         } else {
  91             switch (buf[i]) {
  92             case SLIP_END:
  93                 if (st->buff->size>0) {
  94                     st->netlink_to_tunnel(&st->nl,NULL,
  95                                           st->buff);
  96                     BUF_ALLOC(st->buff,"userv_afterpoll");
  97                 }
  98                 buffer_init(st->buff,st->nl.max_start_pad);
  99                 break;
 100             case SLIP_ESC:
 101                 st->pending_esc=True;
 102                 break;
 103             default:
 104                 *(uint8_t *)buf_append(st->buff,1)=buf[i];
 105                 break;
 106             }
 107         }
 108     }
 109 }
 110
 111 static void slip_init(struct slip *st, struct cloc loc, dict_t *dict,
 112                       string_t name, netlink_deliver_fn *to_host)
 113 {
 114     st->netlink_to_tunnel=
 115         netlink_init(&st->nl,st,loc,dict,
 116                      "netlink-userv-ipif",NULL,to_host);
 117     st->buff=find_cl_if(dict,"buffer",CL_BUFFER,True,"name",loc);
 118     st->local_address=string_to_ipaddr(
 119         dict_find_item(dict,"local-address", True, name, loc),"netlink");
 120     BUF_ALLOC(st->buff,"slip_init");
 121     st->pending_esc=False;
 122 }
 123
 124 /* Connection to the kernel through userv-ipif */
 125
 126 struct userv {
 127     struct slip slip;
 128     int txfd; /* We transmit to userv */
 129     int rxfd; /* We receive from userv */
 130     string_t userv_path;
 131     string_t service_user;
 132     string_t service_name;
 133     pid_t pid;
 134     bool_t expecting_userv_exit;
 135 };
 136
 137 static int userv_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
 138                             int *timeout_io, const struct timeval *tv_now,
 139                             uint64_t *now)
 140 {
 141     struct userv *st=sst;
 142
 143     if (st->rxfd!=-1) {
 144         *nfds_io=2;
 145         fds[0].fd=st->txfd;
 146         fds[0].events=POLLERR; /* Might want to pick up POLLOUT sometime */
 147         fds[1].fd=st->rxfd;
 148         fds[1].events=POLLIN|POLLERR|POLLHUP;
 149     } else {
 150         *nfds_io=0;
 151     }
 152     return 0;
 153 }
 154
 155 static void userv_afterpoll(void *sst, struct pollfd *fds, int nfds,
 156                             const struct timeval *tv_now, uint64_t *now)
 157 {
 158     struct userv *st=sst;
 159     uint8_t rxbuf[DEFAULT_BUFSIZE];
 160     int l;
 161
 162     if (nfds==0) return;
 163
 164     if (fds[1].revents&POLLERR) {
 165         Message(M_ERROR,"%s: userv_afterpoll: POLLERR!\n",st->slip.nl.name);
 166     }
 167     if (fds[1].revents&POLLIN) {
 168         l=read(st->rxfd,rxbuf,DEFAULT_BUFSIZE);
 169         if (l<0) {
 170             if (errno!=EINTR)
 171                 fatal_perror("%s: userv_afterpoll: read(rxfd)",
 172                              st->slip.nl.name);
 173         } else if (l==0) {
 174             fatal("%s: userv_afterpoll: read(rxfd)=0; userv gone away?\n",
 175                   st->slip.nl.name);
 176         } else slip_unstuff(&st->slip,rxbuf,l);
 177     }
 178 }
 179
 180 /* Send buf to the kernel. Free buf before returning. */
 181 static void userv_deliver_to_kernel(void *sst, void *cid,
 182                                     struct buffer_if *buf)
 183 {
 184     struct userv *st=sst;
 185
 186     slip_stuff(&st->slip,buf,st->txfd);
 187 }
 188
 189 static void userv_userv_callback(void *sst, pid_t pid, int status)
 190 {
 191     struct userv *st=sst;
 192
 193     if (pid!=st->pid) {
 194         Message(M_WARNING,"userv_callback called unexpectedly with pid %d "
 195                 "(expected %d)\n",pid,st->pid);
 196         return;
 197     }
 198     if (!st->expecting_userv_exit) {
 199         if (WIFEXITED(status)) {
 200             fatal("%s: userv exited unexpectedly with status %d\n",
 201                   st->slip.nl.name,WEXITSTATUS(status));
 202         } else if (WIFSIGNALED(status)) {
 203             fatal("%s: userv exited unexpectedly: uncaught signal %d\n",
 204                   st->slip.nl.name,WTERMSIG(status));
 205         } else {
 206             fatal("%s: userv stopped unexpectedly\n");
 207         }
 208     }
 209     Message(M_WARNING,"%s: userv subprocess died with status %d\n",
 210             st->slip.nl.name,WEXITSTATUS(status));
 211     st->pid=0;
 212 }
 213
 214 struct userv_entry_rec {
 215     string_t path;
 216     char **argv;
 217     int stdin;
 218     int stdout;
 219     /* XXX perhaps we should collect and log stderr? */
 220 };
 221
 222 static void userv_entry(void *sst)
 223 {
 224     struct userv_entry_rec *st=sst;
 225
 226     dup2(st->stdin,0);
 227     dup2(st->stdout,1);
 228
 229     /* XXX close all other fds */
 230     setsid();
 231     execvp(st->path,st->argv);
 232     perror("userv-entry: execvp()");
 233     exit(1);
 234 }
 235
 236 static void userv_invoke_userv(struct userv *st)
 237 {
 238     struct userv_entry_rec *er;
 239     int c_stdin[2];
 240     int c_stdout[2];
 241     string_t addrs;
 242     string_t nets;
 243     string_t s;
 244     struct netlink_route *r;
 245     int i;
 246     uint8_t confirm;
 247
 248     if (st->pid) {
 249         fatal("userv_invoke_userv: already running\n");
 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     nets=safe_malloc(1024,"userv_invoke_userv:nets");
 261     *nets=0;
 262     r=st->slip.nl.routes;
 263     for (i=0; i<st->slip.nl.n_routes; i++) {
 264         if (r[i].up) {
 265             r[i].kup=True;
 266             s=subnet_to_string(&r[i].net);
 267             strcat(nets,s);
 268             strcat(nets,",");
 269             free(s);
 270         }
 271     }
 272     nets[strlen(nets)-1]=0;
 273
 274     Message(M_INFO,"%s: about to invoke: %s %s %s %s %s\n",st->slip.nl.name,
 275             st->userv_path,st->service_user,st->service_name,addrs,nets);
 276
 277     st->slip.pending_esc=False;
 278
 279     /* Invoke userv */
 280     if (pipe(c_stdin)!=0) {
 281         fatal_perror("userv_invoke_userv: pipe(c_stdin)");
 282     }
 283     if (pipe(c_stdout)!=0) {
 284         fatal_perror("userv_invoke_userv: pipe(c_stdout)");
 285     }
 286     st->txfd=c_stdin[1];
 287     st->rxfd=c_stdout[0];
 288
 289     er=safe_malloc(sizeof(*r),"userv_invoke_userv: er");
 290
 291     er->stdin=c_stdin[0];
 292     er->stdout=c_stdout[1];
 293     /* The arguments are:
 294        userv
 295        service-user
 296        service-name
 297        local-addr,secnet-addr,mtu,protocol
 298        route1,route2,... */
 299     er->argv=safe_malloc(sizeof(*er->argv)*6,"userv_invoke_userv:argv");
 300     er->argv[0]=st->userv_path;
 301     er->argv[1]=st->service_user;
 302     er->argv[2]=st->service_name;
 303     er->argv[3]=addrs;
 304     er->argv[4]=nets;
 305     er->argv[5]=NULL;
 306     er->path=st->userv_path;
 307
 308     st->pid=makesubproc(userv_entry, userv_userv_callback,
 309                         er, st, st->slip.nl.name);
 310     close(er->stdin);
 311     close(er->stdout);
 312     free(er->argv);
 313     free(er);
 314     free(addrs);
 315     free(nets);
 316     Message(M_INFO,"%s: userv-ipif pid is %d\n",st->slip.nl.name,st->pid);
 317     /* Read a single character from the pipe to confirm userv-ipif is
 318        running. If we get a SIGCHLD at this point then we'll get EINTR. */
 319     if (read(st->rxfd,&confirm,1)!=1) {
 320         if (errno==EINTR) {
 321             Message(M_WARNING,"%s: read of confirmation byte was "
 322                     "interrupted\n",st->slip.nl.name);
 323         } else {
 324             fatal_perror("%s: read() of confirmation byte",st->slip.nl.name);
 325         }
 326     } else {
 327         if (confirm!=SLIP_END) {
 328             fatal("%s: bad confirmation byte %d from userv-ipif\n",
 329                   st->slip.nl.name,confirm);
 330         }
 331     }
 332     /* Mark rxfd non-blocking */
 333     if (fcntl(st->rxfd, F_SETFL, fcntl(st->rxfd, F_GETFL)|O_NONBLOCK)==-1) {
 334         fatal_perror("%s: fcntl(O_NONBLOCK)",st->slip.nl.name);
 335     }
 336 }
 337
 338 static void userv_kill_userv(struct userv *st)
 339 {
 340     if (st->pid) {
 341         kill(-st->pid,SIGTERM);
 342         st->expecting_userv_exit=True;
 343     }
 344 }
 345
 346 static void userv_phase_hook(void *sst, uint32_t newphase)
 347 {
 348     struct userv *st=sst;
 349     /* We must wait until signal processing has started before forking
 350        userv */
 351     if (newphase==PHASE_RUN) {
 352         userv_invoke_userv(st);
 353         /* Register for poll() */
 354         register_for_poll(st, userv_beforepoll, userv_afterpoll, 2,
 355                           st->slip.nl.name);
 356     }
 357     if (newphase==PHASE_SHUTDOWN) {
 358         userv_kill_userv(st);
 359     }
 360 }
 361
 362 static list_t *userv_apply(closure_t *self, struct cloc loc, dict_t *context,
 363                            list_t *args)
 364 {
 365     struct userv *st;
 366     item_t *item;
 367     dict_t *dict;
 368
 369     st=safe_malloc(sizeof(*st),"userv_apply");
 370
 371     /* First parameter must be a dict */
 372     item=list_elem(args,0);
 373     if (!item || item->type!=t_dict)
 374         cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n");
 375
 376     dict=item->data.dict;
 377
 378     slip_init(&st->slip,loc,dict,"netlink-userv-ipif",
 379               userv_deliver_to_kernel);
 380
 381     st->userv_path=dict_read_string(dict,"userv-path",False,"userv-netlink",
 382                                     loc);
 383     st->service_user=dict_read_string(dict,"service-user",False,
 384                                       "userv-netlink",loc);
 385     st->service_name=dict_read_string(dict,"service-name",False,
 386                                       "userv-netlink",loc);
 387     if (!st->userv_path) st->userv_path="userv";
 388     if (!st->service_user) st->service_user="root";
 389     if (!st->service_name) st->service_name="ipif";
 390     st->rxfd=-1; st->txfd=-1;
 391     st->pid=0;
 392     st->expecting_userv_exit=False;
 393     add_hook(PHASE_RUN,userv_phase_hook,st);
 394     add_hook(PHASE_SHUTDOWN,userv_phase_hook,st);
 395
 396     return new_closure(&st->slip.nl.cl);
 397 }
 398
 399 init_module slip_module;
 400 void slip_module(dict_t *dict)
 401 {
 402     add_closure(dict,"userv-ipif",userv_apply);
 403 #if 0
 404     /* TODO */
 405     add_closure(dict,"pty-slip",ptyslip_apply);
 406     add_closure(dict,"slipd",slipd_apply);
 407 #endif /* 0 */
 408 }