[Xorp-hackers] [PIM] Setting a bit in the Encoded source address

[Pavlin Radoslavov]

> > > We have to set the bidirectional bit in the ENCODED GROUP ADDRESS
> > >
> > >
> > >  0                   1                   2                   3
> > >  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > > |  Addr Family  | Encoding Type |B| Reserved  |Z|  Mask Len     |
> > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > > |                Group multicast Address
> > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
> > >
> > > By using following function we can get octet but how can we set the
> > single
> > > bit ( B )?  :)
> > >
> > > i could not get the flow in the following code :
> > >
> > > #define GET_OCTET(val, cp, rcvlen)                      \
> > > do
> > {                                                                    \
> > >     if ((size_t)(rcvlen) < (size_t)1)                            \
> > >         goto rcvlen_error;                                         \
> > >     (rcvlen)--;
> > \
> > >     ((val) = *(cp)++);                                               \
> > > } while (0)
> > >
> > > thanking you in anticipation
> >
> > You could use the PUT_OCTET() macro.
> > I believe the remaining 7 bits in the Reserved field are suppose to
> > be 0. Hence you need to use PUT_OCTET() to set both Reserved and Z
> > at the same time (because they belong to the same octet).
> 
> 
> hello,
> we set that B bit but now we want to check that bit.
> we were able to see the BIDIR_CAPABLE Flag in hello messages using
> ethereal.How can we do the same for checking this B bit???
> 
> We made changes as follows
> in file
> ------------------------------------------------------
> -> pim_proto.hh
> #define EGADDR _B_BIT    0x80

The correct definition for the bit is 0x1, because it is the
least-significant bit in the Reserved octet.

> ------------------------------------------------------
> -> pim_proto_join_prune_message.cc
> group_addr_reserved_flag |= EGADDR _B_BIT
> --------------------------------------------------------------------
> i hope this will do the work!!!!

Yes, but make sure you remove the extra space between
EGADDR and _B_BIT :)
Also, the correct name of the variable is group_addr_reserved_flags
(used inside method PimJpHeader::network_send()).

Regards,
Pavlin

> 
> thanking you in anticipation
> Ashish
> Shamita
> Chintamani
> 
> 
> 
> 
> Regards,
> > Pavlin
> >
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