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 };
  31
  32 /* Generic SLIP mangling code */
  33
  34 static void slip_write(int fd, const uint8_t *p, size_t l)
  35 {
  36     while (l) {
  37         ssize_t written=write(fd,p,l);
  38         if (written<0) {
  39             if (errno==EINTR) {
  40                 continue;
  41             } else if (iswouldblock(errno)) {
  42                 lg_perror(0,"slip",0,M_ERR,errno,"write() (packet(s) lost)");
  43                 return;
  44             } else {
  45                 fatal_perror("slip_stuff: write()");
  46             }
  47         }
  48         assert(written>0);
  49         assert((size_t)written<=l);
  50         p+=written;
  51         l-=written;
  52     }
  53 }
  54
  55 static void slip_stuff(struct slip *st, struct buffer_if *buf, int fd)
  56 {
  57     uint8_t txbuf[DEFAULT_BUFSIZE];
  58     uint8_t *i;
  59     int32_t j=0;
  60
  61     BUF_ASSERT_USED(buf);
  62
  63     /* There's probably a much more efficient way of implementing this */
  64     txbuf[j++]=SLIP_END;
  65     for (i=buf->start; i<(buf->start+buf->size); i++) {
  66         switch (*i) {
  67         case SLIP_END:
  68             txbuf[j++]=SLIP_ESC;
  69             txbuf[j++]=SLIP_ESCEND;
  70             break;
  71         case SLIP_ESC:
  72             txbuf[j++]=SLIP_ESC;
  73             txbuf[j++]=SLIP_ESCESC;
  74             break;
  75         default:
  76             txbuf[j++]=*i;
  77             break;
  78         }
  79         if ((j+2)>DEFAULT_BUFSIZE) {
  80             slip_write(fd,txbuf,j);
  81             j=0;
  82         }
  83     }
  84     txbuf[j++]=SLIP_END;
  85     slip_write(fd,txbuf,j);
  86     BUF_FREE(buf);
  87 }
  88
  89 static void slip_unstuff(struct slip *st, uint8_t *buf, uint32_t l)
  90 {
  91     uint32_t i;
  92
  93     BUF_ASSERT_USED(st->buff);
  94     for (i=0; i<l; i++) {
  95         int outputchr;
  96         enum { OUTPUT_END = 256, OUTPUT_NOTHING = 257 };
  97
  98         if (!st->buff->size)
  99             buffer_init(st->buff,calculate_max_start_pad());
 100
 101         if (st->pending_esc) {
 102             st->pending_esc=False;
 103             switch(buf[i]) {
 104             case SLIP_ESCEND:
 105                 outputchr=SLIP_END;
 106                 break;
 107             case SLIP_ESCESC:
 108                 outputchr=SLIP_ESC;
 109                 break;
 110             default:
 111                 if (!st->ignoring_packet) {
 112                     Message(M_WARNING, "userv_afterpoll: bad SLIP escape"
 113                             " character, dropping packet\n");
 114                 }
 115                 st->ignoring_packet=True;
 116                 outputchr=OUTPUT_NOTHING;
 117                 break;
 118             }
 119         } else {
 120             switch (buf[i]) {
 121             case SLIP_END:
 122                 outputchr=OUTPUT_END;
 123                 break;
 124             case SLIP_ESC:
 125                 st->pending_esc=True;
 126                 outputchr=OUTPUT_NOTHING;
 127                 break;
 128             default:
 129                 outputchr=buf[i];
 130                 break;
 131             }
 132         }
 133
 134         if (st->ignoring_packet) {
 135             if (outputchr == OUTPUT_END) {
 136                 st->ignoring_packet=False;
 137                 st->buff->size=0;
 138             }
 139         } else {
 140             if (outputchr == OUTPUT_END) {
 141                 if (st->buff->size>0) {
 142                     st->netlink_to_tunnel(&st->nl,st->buff);
 143                     BUF_ALLOC(st->buff,"userv_afterpoll");
 144                 }
 145                 st->buff->size=0;
 146             } else if (outputchr != OUTPUT_NOTHING) {
 147                 if (buf_remaining_space(st->buff)) {
 148                     buf_append_uint8(st->buff,outputchr);
 149                 } else {
 150                     Message(M_WARNING, "userv_afterpoll: dropping overlong"
 151                             " SLIP packet\n");
 152                     st->ignoring_packet=True;
 153                 }
 154             }
 155         }
 156     }
 157 }
 158
 159 static void slip_init(struct slip *st, struct cloc loc, dict_t *dict,
 160                       cstring_t name, netlink_deliver_fn *to_host)
 161 {
 162     st->netlink_to_tunnel=
 163         netlink_init(&st->nl,st,loc,dict,
 164                      "netlink-userv-ipif",NULL,to_host);
 165     st->buff=find_cl_if(dict,"buffer",CL_BUFFER,True,"name",loc);
 166     BUF_ALLOC(st->buff,"slip_init");
 167     st->pending_esc=False;
 168     st->ignoring_packet=False;
 169 }
 170
 171 /* Connection to the kernel through userv-ipif */
 172
 173 struct userv {
 174     struct slip slip;
 175     int txfd; /* We transmit to userv */
 176     int rxfd; /* We receive from userv */
 177     cstring_t userv_path;
 178     cstring_t service_user;
 179     cstring_t service_name;
 180     pid_t pid;
 181     bool_t expecting_userv_exit;
 182 };
 183
 184 static int userv_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
 185                             int *timeout_io)
 186 {
 187     struct userv *st=sst;
 188
 189     if (st->rxfd!=-1) {
 190         BEFOREPOLL_WANT_FDS(2);
 191         fds[0].fd=st->txfd;
 192         fds[0].events=0; /* Might want to pick up POLLOUT sometime */
 193         fds[1].fd=st->rxfd;
 194         fds[1].events=POLLIN;
 195     } else {
 196         BEFOREPOLL_WANT_FDS(0);
 197     }
 198     return 0;
 199 }
 200
 201 static void userv_afterpoll(void *sst, struct pollfd *fds, int nfds)
 202 {
 203     struct userv *st=sst;
 204     uint8_t rxbuf[DEFAULT_BUFSIZE];
 205     int l;
 206
 207     if (nfds==0) return;
 208
 209     if (fds[1].revents&POLLERR) {
 210         Message(M_ERR,"%s: userv_afterpoll: POLLERR!\n",st->slip.nl.name);
 211     }
 212     if (fds[1].revents&POLLIN) {
 213         l=read(st->rxfd,rxbuf,DEFAULT_BUFSIZE);
 214         if (l<0) {
 215             if (errno!=EINTR && !iswouldblock(errno))
 216                 fatal_perror("%s: userv_afterpoll: read(rxfd)",
 217                              st->slip.nl.name);
 218         } else if (l==0) {
 219             fatal("%s: userv_afterpoll: read(rxfd)=0; userv gone away?",
 220                   st->slip.nl.name);
 221         } else slip_unstuff(&st->slip,rxbuf,l);
 222     }
 223 }
 224
 225 /* Send buf to the kernel. Free buf before returning. */
 226 static void userv_deliver_to_kernel(void *sst, struct buffer_if *buf)
 227 {
 228     struct userv *st=sst;
 229
 230     if (buf->size > st->slip.nl.mtu) {
 231         Message(M_ERR,"%s: packet of size %"PRIu32" exceeds mtu %"PRIu32":"
 232                 " cannot be injected into kernel, dropped\n",
 233                 st->slip.nl.name, buf->size, st->slip.nl.mtu);
 234         BUF_FREE(buf);
 235         return;
 236     }
 237
 238     slip_stuff(&st->slip,buf,st->txfd);
 239 }
 240
 241 static void userv_userv_callback(void *sst, pid_t pid, int status)
 242 {
 243     struct userv *st=sst;
 244
 245     if (pid!=st->pid) {
 246         Message(M_WARNING,"userv_callback called unexpectedly with pid %d "
 247                 "(expected %d)\n",pid,st->pid);
 248         return;
 249     }
 250     if (!(st->expecting_userv_exit &&
 251           (!status ||
 252            (WIFSIGNALED(status) && WTERMSIG(status)==SIGTERM)))) {
 253         lg_exitstatus(0,st->slip.nl.name,0,
 254                       st->expecting_userv_exit ? M_WARNING : M_FATAL,
 255                       status,"userv");
 256     }
 257     st->pid=0;
 258 }
 259
 260 struct userv_entry_rec {
 261     cstring_t path;
 262     const char **argv;
 263     int in;
 264     int out;
 265     /* XXX perhaps we should collect and log stderr? */
 266 };
 267
 268 static void userv_entry(void *sst)
 269 {
 270     struct userv_entry_rec *st=sst;
 271
 272     dup2(st->in,0);
 273     dup2(st->out,1);
 274
 275     setsid();
 276     execvp(st->path,(char *const*)st->argv);
 277     perror("userv-entry: execvp()");
 278     exit(1);
 279 }
 280
 281 static void userv_invoke_userv(struct userv *st)
 282 {
 283     struct userv_entry_rec er[1];
 284     int c_stdin[2];
 285     int c_stdout[2];
 286     string_t nets;
 287     string_t s;
 288     struct netlink_client *r;
 289     struct ipset *allnets;
 290     struct subnet_list *snets;
 291     int i, nread;
 292     uint8_t confirm;
 293
 294     if (st->pid) {
 295         fatal("userv_invoke_userv: already running");
 296     }
 297
 298     /* This is where we actually invoke userv - all the networks we'll
 299        be using should already have been registered. */
 300
 301     char addrs[512];
 302     snprintf(addrs,sizeof(addrs),"%s,%s,%d,slip",
 303              ipaddr_to_string(st->slip.nl.local_address),
 304              ipaddr_to_string(st->slip.nl.secnet_address),st->slip.nl.mtu);
 305
 306     allnets=ipset_new();
 307     for (r=st->slip.nl.clients; r; r=r->next) {
 308         if (r->link_quality > LINK_QUALITY_UNUSED) {
 309             struct ipset *nan;
 310             r->kup=True;
 311             nan=ipset_union(allnets,r->networks);
 312             ipset_free(allnets);
 313             allnets=nan;
 314         }
 315     }
 316     snets=ipset_to_subnet_list(allnets);
 317     ipset_free(allnets);
 318     nets=safe_malloc(20*snets->entries,"userv_invoke_userv:nets");
 319     *nets=0;
 320     for (i=0; i<snets->entries; i++) {
 321         s=subnet_to_string(snets->list[i]);
 322         strcat(nets,s);
 323         strcat(nets,",");
 324     }
 325     nets[strlen(nets)-1]=0;
 326     subnet_list_free(snets);
 327
 328     Message(M_INFO,"%s: about to invoke: %s %s %s %s %s\n",st->slip.nl.name,
 329             st->userv_path,st->service_user,st->service_name,addrs,nets);
 330
 331     st->slip.pending_esc=False;
 332
 333     /* Invoke userv */
 334     pipe_cloexec(c_stdin);
 335     pipe_cloexec(c_stdout);
 336     st->txfd=c_stdin[1];
 337     st->rxfd=c_stdout[0];
 338
 339     er->in=c_stdin[0];
 340     er->out=c_stdout[1];
 341     /* The arguments are:
 342        userv
 343        service-user
 344        service-name
 345        local-addr,secnet-addr,mtu,protocol
 346        route1,route2,... */
 347     const char *er_argv[6];
 348     er->argv=er_argv;
 349     er->argv[0]=st->userv_path;
 350     er->argv[1]=st->service_user;
 351     er->argv[2]=st->service_name;
 352     er->argv[3]=addrs;
 353     er->argv[4]=nets;
 354     er->argv[5]=NULL;
 355     er->path=st->userv_path;
 356
 357     st->pid=makesubproc(userv_entry, userv_userv_callback,
 358                         er, st, st->slip.nl.name);
 359     close(er->in);
 360     close(er->out);
 361     free(nets);
 362     Message(M_INFO,"%s: userv-ipif pid is %d\n",st->slip.nl.name,st->pid);
 363     /* Read a single character from the pipe to confirm userv-ipif is
 364        running. If we get a SIGCHLD at this point then we'll get EINTR. */
 365     if ((nread=read(st->rxfd,&confirm,1))!=1) {
 366         if (errno==EINTR) {
 367             Message(M_WARNING,"%s: read of confirmation byte was "
 368                     "interrupted\n",st->slip.nl.name);
 369         } else {
 370             if (nread<0) {
 371                 fatal_perror("%s: error reading confirmation byte",
 372                              st->slip.nl.name);
 373             } else {
 374                 fatal("%s: unexpected EOF instead of confirmation byte"
 375                       " - userv ipif failed?", st->slip.nl.name);
 376             }
 377         }
 378     } else {
 379         if (confirm!=SLIP_END) {
 380             fatal("%s: bad confirmation byte %d from userv-ipif",
 381                   st->slip.nl.name,confirm);
 382         }
 383     }
 384     setnonblock(st->txfd);
 385     setnonblock(st->rxfd);
 386 }
 387
 388 static void userv_kill_userv(struct userv *st)
 389 {
 390     if (st->pid) {
 391         kill(-st->pid,SIGTERM);
 392         st->expecting_userv_exit=True;
 393     }
 394 }
 395
 396 static void userv_phase_hook(void *sst, uint32_t newphase)
 397 {
 398     struct userv *st=sst;
 399     /* We must wait until signal processing has started before forking
 400        userv */
 401     if (newphase==PHASE_RUN) {
 402         userv_invoke_userv(st);
 403         /* Register for poll() */
 404         register_for_poll(st, userv_beforepoll, userv_afterpoll,
 405                           st->slip.nl.name);
 406     }
 407     if (newphase==PHASE_SHUTDOWN) {
 408         userv_kill_userv(st);
 409     }
 410 }
 411
 412 static list_t *userv_apply(closure_t *self, struct cloc loc, dict_t *context,
 413                            list_t *args)
 414 {
 415     struct userv *st;
 416     item_t *item;
 417     dict_t *dict;
 418
 419     st=safe_malloc(sizeof(*st),"userv_apply");
 420
 421     /* First parameter must be a dict */
 422     item=list_elem(args,0);
 423     if (!item || item->type!=t_dict)
 424         cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n");
 425
 426     dict=item->data.dict;
 427
 428     slip_init(&st->slip,loc,dict,"netlink-userv-ipif",
 429               userv_deliver_to_kernel);
 430
 431     st->userv_path=dict_read_string(dict,"userv-path",False,"userv-netlink",
 432                                     loc);
 433     st->service_user=dict_read_string(dict,"service-user",False,
 434                                       "userv-netlink",loc);
 435     st->service_name=dict_read_string(dict,"service-name",False,
 436                                       "userv-netlink",loc);
 437     if (!st->userv_path) st->userv_path="userv";
 438     if (!st->service_user) st->service_user="root";
 439     if (!st->service_name) st->service_name="ipif";
 440     st->rxfd=-1; st->txfd=-1;
 441     st->pid=0;
 442     st->expecting_userv_exit=False;
 443     add_hook(PHASE_RUN,userv_phase_hook,st);
 444     add_hook(PHASE_SHUTDOWN,userv_phase_hook,st);
 445
 446     return new_closure(&st->slip.nl.cl);
 447 }
 448
 449 void slip_module(dict_t *dict)
 450 {
 451     add_closure(dict,"userv-ipif",userv_apply);
 452 }