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It appears there is no good way to decide whether or not broadcasts should be enabled,
there is hardware that must have broadcast, and there are networks that only allow
unicast. So we give up and make this configurable.
By default, unicast is used, but if the kernel were to inform us abotu certain
interfaces requiring broadcast, we could change this to opt-in by default in
those cases.
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Vendor Class Identifier be used by DHCP clients to identify
their vendor type and configuration. When using this option,
vendors can define their own specific identifier values, such
as to convey a particular hardware or operating system
configuration or other identifying information.
Vendor-specified DHCP options—features that let administrators assign
separate options to clients with similar configuration requirements.
For example, if DHCP-aware clients for example we want to separate
different gateway and option for different set of people
(dev/test/hr/finance) in a org or devices for example web/database
servers or let's say in a embedded device etc and require a different
default gateway or DNS server than the rest of clients.
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Check that received DHCP packets actually include our MAC address in
chaddr field. BPF interpreter has 32 bit wide registers but MAC address
is 48 bits long so we have to do check in two steps.
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Send hostname (option 12) in DISCOVER and REQUEST messages so the
DHCP server could use it to register with dynamic DNS and such.
To opt-out of this behaviour set SendHostname to false in [DHCP]
section of .network file
[tomegun: rebased, made sure a failing set_hostname is a noop and moved
config from DHCPv4 to DHCP]
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Even if we cannot renew the lease at T1, we will likely succeed at T2, so warn and ignore the failure.
This could happen if for whatever reason the received address is not yet configured, or it has
been lost.
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Note that /proc/sys/net/ipv4/ip_dynaddr needs to be non-zero.
[tomegun: hook up DHCP renew events to increase the lifetime when necessary]
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Let's keep this behavior consistent across our libraries.
In order to keep the refcounting working, a DONT_DESTROY macro similar
to the one in sd-bus was introduced.
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static int client_send_request(...) in
./src/libsystemd-network/sd-dhcp-client.c tries to initialize
"request" by calling client_message_init(...), which has atleast
5 error cases where it can return without that happening.
This leads to the function finishing without "request" being initialized.
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On systems which cannot receive unicast packets until its IP stack has been configured
we need to request broadcast packets. We are currently not able to reliably detect when
this is necessary, so set it unconditionally for now.
This is set on all packets, but the DHCP server will only broadcast the packets that are
necessary, and unicast the rest.
For more information please refer to this thread in CoreOS: https://github.com/coreos/bugs/issues/12
[tomegun: rephrased commit message]
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This fallback will anyway never get tested, so rip it out.
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Store a pointer to the options in the DHCPMessage struct, and pass
this together with an offset around, rather than a uint8_t**.
This avoids us having to (re)compute the pointer; and changes
dhcp_option_append from adjusting both the pointer to the next
option and the remaining size of the options, to just adjusting
the current offset.
This makes the code a bit simpler to follow IMHO, but there should
be no functional change.
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'Requested by user' was confusing, just drop it.
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close() is a blocking call, which may slow things down measurably when running many dhcp
clients in the same single-threaded main loop. Let's just use the asynchronous version
instead to avoid the problem.
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UDP sockets can anyway not be bound to specific netdev's. The packages would have to be filtered
when received instead.
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Log error no for such client_stop(client, DHCP_EVENT_STOP)
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- Also only allow positive ifindex on both dhcp and ipv4ll
[tomegun: the kernel always sets a positive ifindex, but some APIs accept
ifindex=0 with various meanings, so we should protect against
accidentally passing ifindex=0 along.]
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Also unref client objects in test code, and initalize logging,
to DEBUG by default.
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These are redundant now that the REQUEST messages contain the same information.
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Specify what kind of REQUEST we send, and distinguish between REBOOT and START.
Also log stop reasons as strings rather than numbers.
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Also reshuffle some code to make the correspondence with the RFC a bit more
obvious.
Small functional change: fail if we try to send a message from the wrong state.
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As we are now filtering the raw socket based on the transaction id, we must
reset the BPF when we reset the transaction id.
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Add an explicit stop state for the DHCP client so that the library
user can issue a stop at any time the callback has been called.
When returning from the callback, check also the stop state and
stop any further DHCP processing.
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The DHCP library user can decide to free the DHCP client any time
the callback is called. After the callback has been called, other
computations may still be needed - the best example being a full
restart of the DHCP procedure in case of lease expiry.
Fix this by introducing proper reference counting. Properly handle
a returned NULL from the notify and stop functions if the DHCP
client was freed.
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Try a bit harder to make the kernel drop packets not for us. This should reduce
the number of wakeups from n^2 to n in the number of dhcp clients, which admittedly
only makes a differenc in very extreme cases.
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If they are too small to fit the IP+UDP+DHCP headers they can be of no use, so
don't waste resources parsing them. This is at the cost of losing some verbosity
in the logging.
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Also move the checking of it to the main message handler, rather than the
options parser.
Fix a bug, so we now drop the packet if any of the magic bytes don't match.
Before we used to only drop the packet if they were all wrong.
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CLOCK_BOOTTIME_ALARM, too
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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.
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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.
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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.
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Also keep start_time in sync, but that shouldn't matter.
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The value is stored in the client object, so get it there when needed.
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Since the length used by options is known, send packets with no
extra padding.
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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.
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Otherwise we would fail with -EINVAL. Thanks to Brandon Philips
<brandon.philips@coreos.com>, for reporting the bug.
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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.
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This causes the DHCP client struct initialization and DHCP client
starting to be factored out into functions of their own.
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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.
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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...
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We are already assuming the close() will not fail, so make it explicit.
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This will be needed for sd-dhcp-server.
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