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List:       busybox
Subject:    Re: [PATCH] udhcpc6 source address is null, should be link-local address
From:       Ralf Friedl <Ralf.Friedl () online ! de>
Date:       2013-08-21 8:15:17
Message-ID: 52147715.9030105 () online ! de
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Denys Vlasenko wrote:
> But what if interface has no IPv6 addresses?
> Isn't the whole purpose of DHCP is to *acquire an address*?
> 
> For example, I don't use or need IPv6 for now.
> I just checked, and as expected, none of my interfaces have
> any IPv6 addresses.
> 
> What should happen in this case?
> Does an iface absolutely need a link-local address (and how
> to acquire one?).
> If not, what dhcp client should fill in - all zeros?
> If yes, why can't it just always do that?
 From RFC 4862:

link-local address -  an address having link-only scope that can be used to reach \
neighboring nodes attached to the same link.  All interfaces have a link-local \
unicast address.


 From RFC 4291:

   Links or Nodes with IEEE 802 48-bit MACs

EUI64  defines a method to create an IEEE EUI-64 identifier from an
    IEEE 48-bit MAC identifier.  This is to insert two octets, with
    hexadecimal values of 0xFF and 0xFE (see the Note at the end of
    appendix), in the middle of the 48-bit MAC (between the company_id
    and vendor-supplied id).  An example is the 48-bit IEEE MAC with
    Global scope:

    |0              1|1              3|3              4|
    |0              5|6              1|2              7|
    +----------------+----------------+----------------+
    |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|
    +----------------+----------------+----------------+


    where "c" is the bits of the assigned company_id, "0" is the value of
    the universal/local bit to indicate Global scope, "g" is
    individual/group bit, and "m" is the bits of the manufacturer-
    selected extension identifier.  The interface identifier would be of
    the form:

    |0              1|1              3|3              4|4              6|
    |0              5|6              1|2              7|8              3|
    +----------------+----------------+----------------+----------------+
    |cccccc1gcccccccc|cccccccc11111111|11111110mmmmmmmm|mmmmmmmmmmmmmmmm|
    +----------------+----------------+----------------+----------------+

    When IEEE 802 48-bit MAC addresses are available (on an interface or
    a node), an implementation may use them to create interface
    identifiers due to their availability and uniqueness properties.


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