Version bump; new email address.

[tripe] / tun-slip.c

/* -*-c-*-
 *
 * $Id$
 *
 * Tunnel packets via SLIP
 *
 * (c) 2005 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Trivial IP Encryption (TrIPE).
 *
 * TrIPE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * TrIPE is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with TrIPE; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include "tripe.h"

/*----- Static variables --------------------------------------------------*/

static slipif *slipifs;			/* List of available interfaces */

/*----- Main code ---------------------------------------------------------*/

#if TUN_TYPE != TUN_SLIP
#  error "Tunnel type mismatch: fix the Makefile"
#endif

#define SL_END 0xc0
#define SL_ESC 0xdb
#define SL_ESCEND 0xdc
#define SL_ESCESC 0xdd

/* --- @t_read@ --- *
 *
 * Arguments:	@int fd@ = file descriptor to read
 *		@unsigned mode@ = what's happened
 *		@void *v@ = pointer to tunnel block
 *
 * Returns:	---
 *
 * Use:		Reads data from the tunnel.
 */

static void t_read(int fd, unsigned mode, void *v)
{
  tunnel *t = v;
  ssize_t n;
  const octet *p, *l, *ll;
  octet *q;
  unsigned st;
  octet o;
  buf b;

  /* --- Read the input data --- */

  n = read(fd, buf_t, sizeof(buf_t));
  if (n < 0) {
    if (errno == EINTR ||
#ifdef EWOULDBLOCK
	errno == EWOULDBLOCK ||
#endif
	errno == EAGAIN)
      return;
    a_warn("TUN %s read-error -- %s", t->sl->name, strerror(errno));
    return;
  }
  if (!n) {
    a_warn("TUN %s slip eof", t->sl->name);
    t->st = SLIPST_EOF;
    sel_rmfile(&t->f);
    return;
  }
  IF_TRACING(T_TUNNEL, {
    trace_block(T_PACKET, "tunnel: SLIP-encapsulated data",
		buf_t, n);
  })

  /* --- Decapsulate the packet --- */

  for (p = buf_t, l = p + n, st = t->st,
       q = t->buf + t->n, ll = t->buf + sizeof(t->buf);
       p < l;
       p++) {
    o = *p;
    switch (o) {
      case SL_END:
	if (st & SLIPST_BAD)
	  ;
	else if (st & SLIPST_ESC)
	  a_warn("TUN %s slip escape-end", t->sl->name);
	else if (q == t->buf) {
	  T( trace(T_TUNNEL, "tunnel: empty packet"); )
	} else {
	  IF_TRACING(T_TUNNEL, {
	    trace(T_TUNNEL, "tunnel: packet arrived");
	    trace_block(T_PACKET, "tunnel: packet contents",
			t->buf, q - t->buf);
	  })
	  buf_init(&b, t->buf, q - t->buf);
	  p_tun(t->p, &b);
	}
	q = t->buf;
	st &= ~(SLIPST_ESC | SLIPST_BAD);
	break;
      case SL_ESC:
	if ((st & SLIPST_ESC) && !(st & SLIPST_BAD)) {
	  a_warn("TUN %s slip bad-escape", t->sl->name);
	  st |= SLIPST_BAD;
	} else
	  st |= SLIPST_ESC;
	break;
      case SL_ESCEND:
	if (st & SLIPST_ESC)
	  o = SL_END;
	goto emit;
      case SL_ESCESC:
	if (st & SLIPST_ESC)
	  o = SL_ESC;
	goto emit;
      default:
	if ((st & SLIPST_ESC) && !(st & SLIPST_BAD)) {
	  a_warn("TUN %s slip bad-escape", t->sl->name);
	  st |= SLIPST_BAD;
	}
      emit:
	if (!(st & SLIPST_BAD)) {
	  if (q < ll)
	    *q++ = o;
	  else {
	    a_warn("TUN %s slip overflow", t->sl->name);
	    st |= SLIPST_BAD;
	  }
	}
	st &= ~SLIPST_ESC;
	break;
    }
  }

  t->n = q - t->buf;
  t->st = st;
}

/* --- @tun_init@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Initializes the tunneling system.  Maybe this will require
 *		opening file descriptors or something.
 */

void tun_init(void)
{
  char *p, *q;
  dstr d = DSTR_INIT;
  slipif *sl, **tail = &slipifs;
  unsigned long uli, ulo;
  size_t n;

  /* --- Build the list of available interfaces --- */

  if ((p = getenv("TRIPE_SLIPIF")) == 0)
    die(1, "no slip interfaces listed: set TRIPE_SLIPIF");
  dstr_puts(&d, p);

  p = d.buf;
  for (;;) {
    uli = strtoul(p, &q, 0);
    if (uli > INT_MAX || q == p)
      goto whine;
    if (*q != ',')
      ulo = uli;
    else {
      p = q + 1;
      ulo = strtoul(p, &q, 0);
      if (ulo > INT_MAX || q == p)
	goto whine;
    }
    if (*q != '=' || (n = strcspn(q + 1, ":")) == 0)
      goto whine;
    sl = CREATE(slipif);
    sl->next = 0;
    sl->ifd = uli;
    sl->ofd = ulo;
    sl->name = xmalloc(n + 1);
    sl->f = 0;
    memcpy(sl->name, q + 1, n);
    sl->name[n] = 0;
    *tail = sl;
    tail = &sl->next;
    T( trace(T_TUNNEL, "tunnel: declared slipif %d,%d=%s",
	     sl->ifd, sl->ofd, sl->name); )
    p = q + n + 1;
    if (!*p)
      break;
    p++;
  }
  return;

whine:
  die(1, "bad slip interface list");
}

/* --- @tun_create@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *		@peer *p@ = pointer to peer block
 *
 * Returns:	Zero if it worked, nonzero on failure.
 *
 * Use:		Initializes a new tunnel.
 */

int tun_create(tunnel *t, peer *p)
{
  slipif *sl;
  static const char end[] = { SL_END, SL_END };

  for (sl = slipifs; sl; sl = sl->next) {
    if (!(sl->f & SLIPIFF_INUSE))
      goto found;
  }
  a_warn("TUN - slip no-slip-interfaces");
  return (-1);

found:
  t->p = p;
  t->sl = sl;
  t->st = 0;
  t->n = 0;
  sl->f |= SLIPIFF_INUSE;
  sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t);
  sel_addfile(&t->f);
  write(sl->ofd, end, sizeof(end));
  T( trace(T_TUNNEL, "tunnel: attached interface %s to peer `%s'",
	   sl->name, p_name(p)); )
  return (0);
}

/* --- @tun_ifname@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *
 * Returns:	A pointer to the tunnel's interface name.
 */

const char *tun_ifname(tunnel *t)
{
  return (t->sl->name);
}

/* --- @tun_inject@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *		@buf *b@ = buffer to send
 *
 * Returns:	---
 *
 * Use:		Injects a packet into the local network stack.
 */

void tun_inject(tunnel *t, buf *b)
{
  octet buf[PKBUFSZ * 2 + 2];
  const octet *p, *l;
  octet *q;

  IF_TRACING(T_TUNNEL, {
    trace(T_TUNNEL, "tunnel: inject decrypted packet");
    trace_block(T_PACKET, "tunnel: packet contents", BBASE(b), BLEN(b));
  })

  q = buf;
  *q++ = SL_END;
  for (p = BBASE(b), l = BCUR(b); p < l; p++) {
    switch (*p) {
      case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break;
      case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break;
      default: *q++ = *p; break;
    }
  }
  *q++ = SL_END;
  IF_TRACING(T_TUNNEL, {
    trace_block(T_PACKET, "tunnel: SLIP-encapsulated contents",
		buf, q - buf);
  })
  write(t->sl->ofd, buf, q - buf);
}

/* --- @tun_destroy@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *
 * Returns:	---
 *
 * Use:		Destroys a tunnel.
 */

void tun_destroy(tunnel *t)
{
  /* --- If it reported EOF, leave it out-of-action --- */

  if (!(t->st & SLIPST_EOF)) {
    sel_rmfile(&t->f);
    t->sl->f &= ~SLIPIFF_INUSE;
  }
}

/*----- That's all, folks -------------------------------------------------*/