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To: Poul-Henning Kamp <phk@critter.tfs.com>
cc: current@FreeBSD.org, Jim Fleming <JimFleming@unety.net>
Subject: Re: SLIP: Check IP Version (please test) 
In-reply-to: Your message of "Tue, 23 Apr 1996 20:05:54 -0000."
             <9458.830289954@critter.tfs.com> 
Date: Tue, 23 Apr 1996 18:47:05 -0700
From: Paul Traina <pst@shockwave.com>
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This patch seems to be irrelevant in any case.  Only IPv4 packets should
be passed to the SLIP driver.  SLIP is not a multiprotocol point-to-point
protocol, PPP is.

IPvX x!=4 is a different protocol.  SLIP is not supported in IPv6.  Please
don't slow down the code path by adding this change.

Paul

  From: Poul-Henning Kamp <phk@critter.tfs.com>
  Subject: SLIP: Check IP Version (please test)
  
  Somebody running slip with header compression please test this patch.
  
  Poul-Henning
  
  > I am starting to develop a substantialliy modified version of the IP protoc
>>ol
  .
  > As specified in the IP protocol the ip_v (IP Version) field of the IP heade
>>r
  > should be set to 4. (see /usr/src/sys/netinet/ip.h)
  > 
  > It is not desirable for new versions of IP to "break" existing code. I have
>> n
  ot
  > provide this but in studying the SLIP code I see that there is never really
  > a check done to see of the IP header is of version 4.
  
  Index: if_sl.c
  ===================================================================
  RCS file: /home/ncvs/src/sys/net/if_sl.c,v
  retrieving revision 1.37
  diff -u -r1.37 if_sl.c
  --- if_sl.c	1996/04/07 17:39:09	1.37
  +++ if_sl.c	1996/04/23 20:03:53
  @@ -561,7 +561,8 @@
   			} while (m1 = m1->m_next);
   		}
   #endif
  -		if ((ip = mtod(m, struct ip *))->ip_p == IPPROTO_TCP) {
  +		if ((ip = mtod(m, struct ip *))->ip_v == IPVERSION) &&
  +		    (ip = mtod(m, struct ip *))->ip_p == IPPROTO_TCP) {
   			if (sc->sc_if.if_flags & SC_COMPRESS)
   				*mtod(m, u_char *) |= sl_compress_tcp(m, ip,
   				    &sc->sc_comp, 1);
  --
  Poul-Henning Kamp           | phk@FreeBSD.ORG       FreeBSD Core-team.
  http://www.freebsd.org/~phk | phk@login.dknet.dk    Private mailbox.
  whois: [PHK]                | phk@ref.tfs.com       TRW Financial Systems, In
>>c.
  Future will arrive by its own means, progress not so.