Implement Reset{Req,Ack} properly, as per rfc 1962.

(I completely mis-read the rfc last time 'round!)

This means:
  o Better CCP/WARN Reset diagnostics.
  o After we've sent a REQ and before we've received an ACK, we drop
    incoming compressed data and send another REQ.
  o Before sending an ACK, re-sequence all pending PRI_NORMAL data in
    the modem queue so that pending packets won't get to the peer
    *after* the ResetAck.
  o Send ACKs with the `identifier' from the REQ frame.
  o After we've received a correct ACK, duplicate ACKs are ok (and will
    reset our history).
  o Incorrect ACKs (not matching the last REQ) are moaned about and dropped.

Also,

  o Calculate the correct FCS after compressing a packet.  DEFLATE
    *may* produce an mbuf with more than a single link in the chain,
    but HdlcOutput didn't know how to calculate the FCS :-(
  o Make `struct fsm'::reqid a u_char, not an int.
    This fix will prevent us from sending id `255' 2,000,000,000 times
    before wrapping to `0' for another 2,000,000,000 sends :-/
  o Bump the version number a little.

The end result:  DEFLATE now works over an unreliable link layer.
                 I can txfr a 1.5Mb kernel over a (rather bad) null-modem
                 cable at an average of 21679 bytes per second using rcp.
Repeat after me: Don't test compression using a loopback ppp/tcp setup as
                 we never lose packets and therefore never have to reset!

1 files changed, 12 insertions, 13 deletions

diff --git a/usr.sbin/ppp/deflate.c b/usr.sbin/ppp/deflate.c
index 3adf2e9..1897d3a 100644
--- a/usr.sbin/ppp/deflate.c
+++ b/usr.sbin/ppp/deflate.c
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: deflate.c,v 1.4 1997/12/21 12:11:04 brian Exp $
+ *	$Id: deflate.c,v 1.5 1997/12/28 02:17:06 brian Exp $
  */
 
 #include <sys/param.h>
@@ -50,7 +50,7 @@
 /* Our state */
 struct deflate_state {
     u_short seqno;
-    int dodgy_seqno;
+    int uncomp_rec;
     z_stream cx;
 };
 
@@ -66,7 +66,7 @@ static void
 DeflateResetOutput(void)
 {
   OutputState.seqno = 0;
-  OutputState.dodgy_seqno = 0;
+  OutputState.uncomp_rec = 0;
   deflateReset(&OutputState.cx);
   LogPrintf(LogCCP, "Deflate: Output channel reset\n");
 }
@@ -192,7 +192,7 @@ static void
 DeflateResetInput(void)
 {
   InputState.seqno = 0;
-  InputState.dodgy_seqno = 0;
+  InputState.uncomp_rec = 0;
   inflateReset(&InputState.cx);
   LogPrintf(LogCCP, "Deflate: Input channel reset\n");
 }
@@ -214,7 +214,12 @@ DeflateInput(u_short *proto, struct mbuf *mi)
   seq = (hdr[0] << 8) + hdr[1];
   LogPrintf(LogDEBUG, "DeflateInput: Seq %d\n", seq);
   if (seq != InputState.seqno) {
-    if (InputState.dodgy_seqno && seq < InputState.seqno)
+    if (seq <= InputState.uncomp_rec)
+      /*
+       * So the peer's started at zero again - fine !  If we're wrong,
+       * inflate() will fail.  This is better than getting into a loop
+       * trying to get a ResetReq to a busy sender.
+       */
       InputState.seqno = seq;
     else {
       LogPrintf(LogERROR, "DeflateInput: Seq error: Got %d, expected %d\n",
@@ -225,7 +230,7 @@ DeflateInput(u_short *proto, struct mbuf *mi)
     }
   }
   InputState.seqno++;
-  InputState.dodgy_seqno = 0;
+  InputState.uncomp_rec = 0;
 
   /* Allocate an output mbuf */
   mo_head = mo = mballoc(DEFLATE_CHUNK_LEN, MB_IPIN);
@@ -420,6 +425,7 @@ DeflateDictSetup(u_short proto, struct mbuf *mi)
   CcpInfo.uncompin += len;
 
   InputState.seqno++;
+  InputState.uncomp_rec++;
   mbfree(mi_head);		/* lose our allocated ``head'' buf */
 }
 
@@ -533,13 +539,6 @@ DeflateInitInput(void)
   if (inflateInit2(&InputState.cx, -iWindowSize) != Z_OK)
     return 0;
   DeflateResetInput();
-  /*
-   * When we begin, we may start adding to our dictionary before the
-   * peer does.  If `dodgy_seqno' is set, we'll allow the peer to send
-   * us a seqno that's too small and just adjust seqno accordingly -
-   * deflate is a sliding window compressor !
-   */
-  InputState.dodgy_seqno = 1;
   return 1;
 }