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)
 136 {
 137     struct userv *st=sst;
 138
 139     if (st->rxfd!=-1) {
 140         *nfds_io=2;
 141         fds[0].fd=st->txfd;
 142         fds[0].events=0; /* Might want to pick up POLLOUT sometime */
 143         fds[1].fd=st->rxfd;
 144         fds[1].events=POLLIN;
 145     } else {
 146         *nfds_io=0;
 147     }
 148     return 0;
 149 }
 150
 151 static void userv_afterpoll(void *sst, struct pollfd *fds, int nfds)
 152 {
 153     struct userv *st=sst;
 154     uint8_t rxbuf[DEFAULT_BUFSIZE];
 155     int l;
 156
 157     if (nfds==0) return;
 158
 159     if (fds[1].revents&POLLERR) {
 160         Message(M_ERR,"%s: userv_afterpoll: POLLERR!\n",st->slip.nl.name);
 161     }
 162     if (fds[1].revents&POLLIN) {
 163         l=read(st->rxfd,rxbuf,DEFAULT_BUFSIZE);
 164         if (l<0) {
 165             if (errno!=EINTR)
 166                 fatal_perror("%s: userv_afterpoll: read(rxfd)",
 167                              st->slip.nl.name);
 168         } else if (l==0) {
 169             fatal("%s: userv_afterpoll: read(rxfd)=0; userv gone away?",
 170                   st->slip.nl.name);
 171         } else slip_unstuff(&st->slip,rxbuf,l);
 172     }
 173 }
 174
 175 /* Send buf to the kernel. Free buf before returning. */
 176 static void userv_deliver_to_kernel(void *sst, struct buffer_if *buf)
 177 {
 178     struct userv *st=sst;
 179
 180     slip_stuff(&st->slip,buf,st->txfd);
 181 }
 182
 183 static void userv_userv_callback(void *sst, pid_t pid, int status)
 184 {
 185     struct userv *st=sst;
 186
 187     if (pid!=st->pid) {
 188         Message(M_WARNING,"userv_callback called unexpectedly with pid %d "
 189                 "(expected %d)\n",pid,st->pid);
 190         return;
 191     }
 192     if (!st->expecting_userv_exit) {
 193         if (WIFEXITED(status)) {
 194             fatal("%s: userv exited unexpectedly with status %d",
 195                   st->slip.nl.name,WEXITSTATUS(status));
 196         } else if (WIFSIGNALED(status)) {
 197             fatal("%s: userv exited unexpectedly: uncaught signal %d",
 198                   st->slip.nl.name,WTERMSIG(status));
 199         } else {
 200             fatal("%s: userv stopped unexpectedly");
 201         }
 202     }
 203     Message(M_WARNING,"%s: userv subprocess died with status %d\n",
 204             st->slip.nl.name,WEXITSTATUS(status));
 205     st->pid=0;
 206 }
 207
 208 struct userv_entry_rec {
 209     cstring_t path;
 210     const char **argv;
 211     int in;
 212     int out;
 213     /* XXX perhaps we should collect and log stderr? */
 214 };
 215
 216 static void userv_entry(void *sst)
 217 {
 218     struct userv_entry_rec *st=sst;
 219
 220     dup2(st->in,0);
 221     dup2(st->out,1);
 222
 223     /* XXX close all other fds */
 224     setsid();
 225     /* XXX We really should strdup() all of argv[] but because we'll just
 226        exit anyway if execvp() fails it doesn't seem worth bothering. */
 227     execvp(st->path,(char *const*)st->argv);
 228     perror("userv-entry: execvp()");
 229     exit(1);
 230 }
 231
 232 static void userv_invoke_userv(struct userv *st)
 233 {
 234     struct userv_entry_rec *er;
 235     int c_stdin[2];
 236     int c_stdout[2];
 237     string_t addrs;
 238     string_t nets;
 239     string_t s;
 240     struct netlink_client *r;
 241     struct ipset *allnets;
 242     struct subnet_list *snets;
 243     int i, nread;
 244     uint8_t confirm;
 245
 246     if (st->pid) {
 247         fatal("userv_invoke_userv: already running");
 248     }
 249
 250     /* This is where we actually invoke userv - all the networks we'll
 251        be using should already have been registered. */
 252
 253     addrs=safe_malloc(512,"userv_invoke_userv:addrs");
 254     snprintf(addrs,512,"%s,%s,%d,slip",
 255              ipaddr_to_string(st->slip.local_address),
 256              ipaddr_to_string(st->slip.nl.secnet_address),st->slip.nl.mtu);
 257
 258     allnets=ipset_new();
 259     for (r=st->slip.nl.clients; r; r=r->next) {
 260         if (r->link_quality > LINK_QUALITY_UNUSED) {
 261             struct ipset *nan;
 262             r->kup=True;
 263             nan=ipset_union(allnets,r->networks);
 264             ipset_free(allnets);
 265             allnets=nan;
 266         }
 267     }
 268     snets=ipset_to_subnet_list(allnets);
 269     ipset_free(allnets);
 270     nets=safe_malloc(20*snets->entries,"userv_invoke_userv:nets");
 271     *nets=0;
 272     for (i=0; i<snets->entries; i++) {
 273         s=subnet_to_string(snets->list[i]);
 274         strcat(nets,s);
 275         strcat(nets,",");
 276         free(s);
 277     }
 278     nets[strlen(nets)-1]=0;
 279     subnet_list_free(snets);
 280
 281     Message(M_INFO,"%s: about to invoke: %s %s %s %s %s\n",st->slip.nl.name,
 282             st->userv_path,st->service_user,st->service_name,addrs,nets);
 283
 284     st->slip.pending_esc=False;
 285
 286     /* Invoke userv */
 287     if (pipe(c_stdin)!=0) {
 288         fatal_perror("userv_invoke_userv: pipe(c_stdin)");
 289     }
 290     if (pipe(c_stdout)!=0) {
 291         fatal_perror("userv_invoke_userv: pipe(c_stdout)");
 292     }
 293     st->txfd=c_stdin[1];
 294     st->rxfd=c_stdout[0];
 295
 296     er=safe_malloc(sizeof(*r),"userv_invoke_userv: er");
 297
 298     er->in=c_stdin[0];
 299     er->out=c_stdout[1];
 300     /* The arguments are:
 301        userv
 302        service-user
 303        service-name
 304        local-addr,secnet-addr,mtu,protocol
 305        route1,route2,... */
 306     er->argv=safe_malloc(sizeof(*er->argv)*6,"userv_invoke_userv:argv");
 307     er->argv[0]=st->userv_path;
 308     er->argv[1]=st->service_user;
 309     er->argv[2]=st->service_name;
 310     er->argv[3]=addrs;
 311     er->argv[4]=nets;
 312     er->argv[5]=NULL;
 313     er->path=st->userv_path;
 314
 315     st->pid=makesubproc(userv_entry, userv_userv_callback,
 316                         er, st, st->slip.nl.name);
 317     close(er->in);
 318     close(er->out);
 319     free(er->argv);
 320     free(er);
 321     free(addrs);
 322     free(nets);
 323     Message(M_INFO,"%s: userv-ipif pid is %d\n",st->slip.nl.name,st->pid);
 324     /* Read a single character from the pipe to confirm userv-ipif is
 325        running. If we get a SIGCHLD at this point then we'll get EINTR. */
 326     if ((nread=read(st->rxfd,&confirm,1))!=1) {
 327         if (errno==EINTR) {
 328             Message(M_WARNING,"%s: read of confirmation byte was "
 329                     "interrupted\n",st->slip.nl.name);
 330         } else {
 331             if (nread<0) {
 332                 fatal_perror("%s: error reading confirmation byte",
 333                              st->slip.nl.name);
 334             } else {
 335                 fatal("%s: unexpected EOF instead of confirmation byte"
 336                       " - userv ipif failed?", st->slip.nl.name);
 337             }
 338         }
 339     } else {
 340         if (confirm!=SLIP_END) {
 341             fatal("%s: bad confirmation byte %d from userv-ipif",
 342                   st->slip.nl.name,confirm);
 343         }
 344     }
 345 }
 346
 347 static void userv_kill_userv(struct userv *st)
 348 {
 349     if (st->pid) {
 350         kill(-st->pid,SIGTERM);
 351         st->expecting_userv_exit=True;
 352     }
 353 }
 354
 355 static void userv_phase_hook(void *sst, uint32_t newphase)
 356 {
 357     struct userv *st=sst;
 358     /* We must wait until signal processing has started before forking
 359        userv */
 360     if (newphase==PHASE_RUN) {
 361         userv_invoke_userv(st);
 362         /* Register for poll() */
 363         register_for_poll(st, userv_beforepoll, userv_afterpoll, 2,
 364                           st->slip.nl.name);
 365     }
 366     if (newphase==PHASE_SHUTDOWN) {
 367         userv_kill_userv(st);
 368     }
 369 }
 370
 371 static list_t *userv_apply(closure_t *self, struct cloc loc, dict_t *context,
 372                            list_t *args)
 373 {
 374     struct userv *st;
 375     item_t *item;
 376     dict_t *dict;
 377
 378     st=safe_malloc(sizeof(*st),"userv_apply");
 379
 380     /* First parameter must be a dict */
 381     item=list_elem(args,0);
 382     if (!item || item->type!=t_dict)
 383         cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n");
 384
 385     dict=item->data.dict;
 386
 387     slip_init(&st->slip,loc,dict,"netlink-userv-ipif",
 388               userv_deliver_to_kernel);
 389
 390     st->userv_path=dict_read_string(dict,"userv-path",False,"userv-netlink",
 391                                     loc);
 392     st->service_user=dict_read_string(dict,"service-user",False,
 393                                       "userv-netlink",loc);
 394     st->service_name=dict_read_string(dict,"service-name",False,
 395                                       "userv-netlink",loc);
 396     if (!st->userv_path) st->userv_path="userv";
 397     if (!st->service_user) st->service_user="root";
 398     if (!st->service_name) st->service_name="ipif";
 399     st->rxfd=-1; st->txfd=-1;
 400     st->pid=0;
 401     st->expecting_userv_exit=False;
 402     add_hook(PHASE_RUN,userv_phase_hook,st);
 403     add_hook(PHASE_SHUTDOWN,userv_phase_hook,st);
 404
 405     return new_closure(&st->slip.nl.cl);
 406 }
 407
 408 void slip_module(dict_t *dict)
 409 {
 410     add_closure(dict,"userv-ipif",userv_apply);
 411 }