Increase the chance of using the same link local address between reboots. The
pseudo random sequence of addresses we attempt is now seeded with data that is
very likely to stay the same between reboots, but at the same time be unique
to the specific machine/nic.
First we try to use the ID_NET_NAME_* data from the udev db combined with the
machin-id, which is guaranteed to be unique and persistent, if available. If
that is not possible (e.g., in containers where we don't have access to the
udev db) we fallback to using the MAC address of the interface, which is
guaranteed to be unique, and likely to be persistent.
[tomegun: three minor changes:
- don't expose HASH_KEY in the siphash24 header
- get rid of some compile-warnings (and some casts at the same time),
by using uint8_t[8] rather than uint64_t in the api
- added commit message]
If necessary, restart the clients to deal with a changing mac address
at runtime. This will solve the problem of starting clients on bridges
before they have received their final MAC address.
The DHCP RFC does not require the DHCP server to send a subnet mask, so if it
is missing, let's try to use the default subnet masks based on address class.
In case the class the address belongs to does not have a default subnet mask,
we fail as before.
Also improve logging when handling invalid dhcp messages, and simply ignore them
rather than stop the whole dhcp client.
Accept any lease lifetime greater than one second. Server should not
hand out extremely short leases, but let's not be the ones to fail.
Do not fail when arming a timer in the past, but also only arm one such
timer.
Avoid rounding errors when computing the default timeouts, this may be
an issue if we are handed a very short lease.
Also, don't pass 'time_now' around, as that can be found in the event
object when needed.
Even though client identifiers SHOULD be treated as opaque objects by
DHCP servers, follow the recommendation of a hardware type field with
value 0x01 (ethernet) followed by the hardware address as described in
RFC 2132.
Init-Reboot is tried if a client IP address has been given when
the DHCP client is started. In Init-Reboot, start by sending a
broadcast DHCP Request including the supplied client IP address
but without the server identifier. After sending the request,
enter Reboot state.
If a DHCP Ack is received, proceed to Bound state as usual. If a
DHCP Nak is received or the first timeout triggers, start the
address acquisition over from DHCP Init state.
See RFC 2131, sections 4.3.2, 4.4, 4.4.1 and 4.4.2 for details.
safe_close() automatically becomes a NOP when a negative fd is passed,
and returns -1 unconditionally. This makes it easy to write lines like
this:
fd = safe_close(fd);
Which will close an fd if it is open, and reset the fd variable
correctly.
By making use of this new scheme we can drop a > 200 lines of code that
was required to test for non-negative fds or to reset the closed fd
variable afterwards.
The default slack caused there to be a delay before timers fired. Solve it
by setting timers that should trigger immediately to trigger far in the past.
This brings down the ideal-case dhcp lease acquisition time from about 500ms to
about 50ms (over a veth pair, so no network latency involved).
All the rest of the time (except for ~0.5ms) is spent in the bind() call in,
dhcp_network_bind_raw_socket(). I don't know if there is anything to be done
about that though...
Implements IPv4LL with respect to RFC 3927
(http://tools.ietf.org/rfc/rfc3927.txt) and integrates it
with networkd. Majority of the IPv4LL state machine is
taken from avahi (http://avahi.org/) project's autoip.
IPv4LL can be enabled by IPv4LL=yes under [Network]
section of .network file.
IPv4LL works independent of DHCP but if DHCP lease is
aquired, then LL address will be dropped.
[tomegun: removed a trailing newline and a compiler warning]
