Re: [PATCH][RFC] tcp: fix ambiguity in the `before' relation

[Gerrit Renker <gerrit@erg.abdn.ac.uk>]

Hi David,

many thanks for taking the matter seriously and investigating
it further. 

|  I went over this patch and analysis a dozen times, because I
|  couldn't believe something like this has been broken for
|  so long :-)
It gave me some grief too, when I looked at DCCP sequence numbers %-)
RFC 1982 provides some definitions, but leaves the case a = (b + 2^31) % 2^32
open to the implementation (suggests `undefined').

I think the new definition is more conformant with RFC 1982 than the old one,
since the ambiguity is now removed with regard to a = (b + 2^31) % 32, and it
is not "unnecessarily burdensome to implement" (section 3.2 of RFC 1982).
  
|  Even BSD suffers of this issue, since the beginning.  See
|  SEQ_LT() in tcp_seq.h, and it seems that BSD's timestamp
|  sequence checking has the issue too (see TSTMP_LT() macro
|  in OpenBSD's tcp_input.c)
I didn't know about OpenBSD, but in Stevens vol 2 (sec. 24.7) it is
already defined in this way. 

Best regards & merry Christmas
Gerrit