Why dos not supported inbound/outbound on linktype DLT_PPP?

[Petr Ostadal <postadal () suse cz>]

Hi,

we found in SUSE, that you removed support of inbound/outbound on linktype
DLT_PPP. See
http://cvs.tcpdump.org/cgi-bin/cvsweb/libpcap/gencode.c?r1=1.185&r2=1.186
with changelog "Feb 14, 2004: Unfortunately, there is no direction flag
for DLT_PPP."

Karsten Keil from SUSE investigated it and send me this informations:

Without inbound/outbound most of the filter rules for ppp is useless.
One goal of this filtering was to avoid that inbound traffic resets the
IDLE timer. And I don't beleave that this is really not supported, since
it did work in the past.  In kernel it looks like the first byte of the
data area is used as inbound/ outbound Flag 1:out 0:in, see the code in
ppp_generic bofore the sk_run_filter call, here are 2 bytes inserted
before the data area and the first is set to 1 in sendframe or to 0 in the
receive routine.

Is it any reason why support of inbound/outbound on linktype DLT_PPP was removed?

        Thnx in advance for any answers, Petr

--
Best Regards,

Petr Ostadal
Software Developer
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