[PATCH] ChromiumOS DHCPv6 support

Cherry-picked from
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/
master/net-misc/dhcpcd/files/patches/dhcpcd-6.8.2-ChromiumOS-DHCPv6-
support.patch.

Add support to emit DHCPv6 configuration/status updates through
DBus, and prevent the daemon from updating IPv6 system configurations.

Add command line option "-a" to enable ia options for shill usage,
since ia options can only be specified through the config file by
default.  When "-a" option is enabled, the daemon will request ia_na
(Non-temporary Address) and ia_pd (Prefix Delegation) options from
the DHCPv6 server.

BUG: 22956197
Change-Id: I12ba8e72ec4f2e8aa1cede6c717f477be2df20ea

Reviewed-on: https://chromium-review.googlesource.com/275700
9 files changed