[PATCH] udhcpc6 source address is null, should be link-local address
Ralf Friedl
Ralf.Friedl at online.de
Wed Aug 21 08:15:17 UTC 2013
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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