I have some comments on draft-chakrabarti-ipv6-addrselect-api-00.txt,
in addition to those already raised in this list (I'd apologize in
advance if there's any duplication).
1. Introduction
Currently IPv6 socket API extensions does not provide a
mechanism to choose a particular source address other than simple
bind() operation.
This is not really true. We can also specify the source address by
the IPV6_PKTINFO socket option or ancillary data item defined the
advanced API. This does not matter much, though, because we still
need to specify a particular source address.
Furthermore, the approach is to define two flags for each purpose,
so that an application can specify either that it prefers 'X' or
prefers 'not X', or it can choose not to set either of the flags
relating to 'X' and leave it up to the system default, perhaps while
specifing its preferences for some other attribute of the source
addresses.
Hmm, I'm not sure if this is really possible with the API described...
later the draft says (in Section 3):
The flags defined in this document are:
IPV6_PREFER_SRC_HOME
IPV6_PREFER_SRC_COA
IPV6_PREFER_SRC_TMP
IPV6_PREFER_SRC_PUBLIC
IPV6_PREFER_SRC_CGA
IPV6_PREFER_SRC_NONCGA
(...)
.... If the option is not set, the system selects
a default value. Setting conflicting flags at the same time results
in the error EINVAL.
I read this to mean unless IPV6_SRC_PREFERENCES is explicitly
specified, the kernel will choose the default values for all the
parameters. If my understanding is correct, how can I specify a
preference for HOME vs COA but keep the default for TMP vs PUBLIC?
Am I supposed to unset both IPV6_PREFER_SRC_TMP and
IPV6_PREFER_SRC_PUBLIC? But isn't it a conflicting configuration
since these two are exclusive flags?
The current specification is at least unclear to me on this, and
perhaps even contradicts itself. We could clarify this point, but I'm
afraid the result would be complicated and unintuitive...
5. IPv4-Mapped IPv6 Addresses
IPv4-Mapped IPv6 addresses are not supported for setting preference
on home, care-of-address, CGA, non-CGA, public or privacy auto-
configured addresses as source addresses.
"privacy auto-configured addresses" should just be "temporary
addresses" to be consistent with the rest of this draft.
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
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