Re: XP + cygwin version 1.7: problem with /proc/net/if_inet6 format and if_indextoname

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Jun  8 22:03, Deti Fliegl wrote:
> Hi,
>
> according to http://tldp.org/HOWTO/Linux+IPv6-HOWTO/proc-net.html the 
> format of /proc/net/if_inet6 contains scope and interface flags in position 
> 4 and 5.
>
> In Windows XP it looks like this (excerpt):
> fe80000000000000020b5dfffea4902b 08 40 08 01 
> {8C302852-0093-4ED1-8BBD-BAEA630C3A2A}
> fe8000000000000002ffa4fffe224702 06 40 06 01 
> {A4224702-1783-4CE5-B0BE-E02885C29AA1}
> fe80000000000000020000fffe000001 05 40 05 04 
> {2C2F83B8-BEF7-4B7B-AED6-E87A8B4252D2}
> fe80000000000000020b5dfffe96a55c 04 40 04 01 
> {AB80DBF9-46A7-463C-933C-5CD48E9B583E}
> fe8000000000000000005efec0a80266 02 40 02 04 
> {48FCE3FC-EC30-E50E-F1A7-71172AEEE3AE}
> 00000000000000000000000000000001 01 80 00 04 
> {6BD113CC-5EC2-7638-B953-0B889DA72014}
>
> In Windows Vista it looks like this (full):
> 20014c50fffe000589223b7d1c32bf30 08 40 00 04 
> {92F7E3A1-A7C4-4D89-A80F-C62EF31CE0DE}
> 20014c50fffe00058c77167371f63d08 08 80 00 04 
> {92F7E3A1-A7C4-4D89-A80F-C62EF31CE0DE}
> fe8000000000000089223b7d1c32bf30 08 40 08 04 
> {92F7E3A1-A7C4-4D89-A80F-C62EF31CE0DE}
> 00000000000000000000000000000001 01 80 00 04 
> {3D4E88D4-6A70-11DB-B1BA-806E6F6E6963}
> fe8000000000000000000100007ffffe 0A 40 0A 03 
> {B3B050EF-8A68-4ECC-8FEB-7E6C0EDB93F2}
>
> As you can see in XP the interface index (netlink device number) in 
> position 2 is equal to the scope value in position 4.
> Vista shows different values for index and scope - this seems to be 
> correct.

The scope values are not always equal to the index, as you can see in your
above output as well for the loopback.  It's also 0 for the addresses
with global scope.  The values are taken from the sin6_scope_id field
returned by the Win32 function GetAdaptersAddresses.  Compare with the
scope values printed by `ipconfig /all'.  Apparently the v6 stack in
XP uses (not quite) arbitrary numbers for local interfaces.  I don't
know the rules behind the choice, but apparently it has been fixed in
Vista.

> My question: Did I hit a bug? Is there any documentation what's the meaning 
> of the values for scope and interface flags (they don't seem to follow the 
> referenced definitions of the Linux kernel).

The flags field is the DAD state right now.  I'm looking through what I
did when I implemented that but I can't figure out anymore why I put the
DAD state into this field.  It looks like it should actually contain the
interface flags (IFF_* values).  Can somebody confirm or deny that?  If
that's correct, it's probably not a big deal to change that.

> Further it seems that if_indextoname(...) does not work for XP while it  
> works for Vista. Don't know if this problem is related. Did I miss 
> something? I would appreciate any hint.

*How* does it not work.  A *very* simply testcase in plain C might
be helpful...


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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