The RA's Retransmission Timer field was being ignored. This resolves the IPv6
Core Conformance test, v6LC.2.1.5 [1].
Retransmission Timer is a 32-bit unsigned integer. The time, in milliseconds,
between retransmitted Neighbor Solicitation messages. Used by the Address
Resolution and Neighbor Unreachability Detection (NUD) algorithm.
Support setting a default value for the neighbour retransmission timer value with:
[Network]
IPv6RetransmissionTimeSec=<int>
By default, upon receiving a Router Advertisement with the Retransmission Timer
field set to a non-zero value, it will update the kernel's retransmit timer value.
To disable this behaviour, configure the UseIPv6RetransmissionTime= under the
[IPv6AcceptRA] section.
[IPv6AcceptRA]
UseIPv6RetransmissionTime=<bool>
RFC4861: Neighbor Discovery in IPv6
* Section 4.2 RA Message Format.
* Section 6.3.4 Processing Received Router Advertisements
A Router Advertisement field (e.g., Cur Hop Limit, Reachable Time,
and Retrans Timer) may contain a value denoting that it is
unspecified. In such cases, the parameter should be ignored and the
host should continue using whatever value it is already using. In
particular, a host MUST NOT interpret the unspecified value as
meaning change back to the default value that was in use before the
first Router Advertisement was received.
The RetransTimer variable SHOULD be copied from the Retrans Timer
field, if the received value is non-zero.
References
[1] IPv6 Core Conformance Spec (PDF)
AllowList= and DenyList= filter only DHCPOFFER messages. So, if
RapidCommit= is enabled, then networkd unconditionally accepts a rapid
ACK message even if its sender is filtered out by the lists.
As AllowList=/DenyList= implemented earlier than RapidCommit=, so
enabling RapidCommit= unconditionally by default may break existing
setups that use AllowList=/DenyList=.
Let's disable RapidCommit= by default when AllowList=/DenyList= is
enabled. Still the setting can be enabled by setting explicitly even
AllowList=/DenyList= is also specified.
When an interface is being reconfigured with different bridge vlan
settings, this makes old vlan IDs on the interface removed.
This also makes the PVID= setting support negative boolean value, e.g. "no",
in which case, the currently assigned PVID (typically, assigned by the
kernel when an interface is joined to a bridge) is dropped.
This feature is requested by #15291.
Note, if a .network file has no settings about bridge vlan, networkd
keeps the currently assigned vlan IDs. That's intended, to make not
break existing setups.
When a .network file has only PVID=no line in [BridgeVLAN] section, then
all assigned vlan IDs are removed.
Fixes#29975.
Closes#15291.
