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Some DHCP servers will not work correctly if secs == 0, so round up
to at least 1.
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This allows us users of the library to keep copies of old leases. This is
used by networkd to know what addresses to drop (if any) when the lease
expires.
In the future this may be used by DNAv4 and sd-dhcp-server.
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Compute the 'secs' field as seconds since start of lease acquisition
procedure. Start off with a value of zero and increase it only for
each resent DHCP discover message. See the discussion before and
after http://www.ietf.org/mail-archive/web/dhcwg/current/msg05836.html
and Section 3.1 of RFC 2131.
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Go back to Init state independent of the current state the client
is in.
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A checksum field with value zero means no UDP checksum has been
computed for the packet.
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This was originally included in the dhcp-client at my request, but it is not
really dhcp-specific and useful outside of it, so let's pull it out.
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Unlike the other merged libs, the rest of libsystemd will never depend on
sd-dhcp-client, so there is no reason not to keep it separate.
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My original patch only returned the first DNS server, but we might
want all of them.
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We need to be able to stop the dhcp client at any time, and the function appears to be written to handle this.
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GREEDY_REALLOC needs to have two size variables: one for the
allocated size, and a second one for the used size. Using
the allocated size only lead to leaving some elements unitialized
and assigning some more than once.
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SipHash appears to be the new gold standard for hashing smaller strings
for hashtables these days, so let's make use of it.
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Reuse existing functionality when adding T2 Rebinding support.
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Factor out common code from timeout T1 handling and starting of
the DHCP client.
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Expiration of T1 timeout takes the client to the Rebinding state,
where it attempts to renew its lease. Start by opening a DCHP unicast
socket as there now is a proper IP address set.
Compute the resend timer as half of the remaining time down to a
minimum of 60 seconds (RFC2131). Modify DHCP Request sending to send
only UDP DHCP data when unicasting. Also modify DHCP Ack/Nak
receiving such that the client_receive_ack() takes care of using
either the full IP, UDP, DHCP packet or only the DHCP payload
depending whether the client is in Requesting or Renewing state.
Finally always report DHCP_EVENT_IP_ACQUIRE from Requesting state
and only DHCP_EVENT_IP_CHANGE if the IP address was modified when
the lease was renewed.
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Create a helper functions setting up an unicast DHCP UDP socket and
sending data. Add function stubs for the test program.
[tomegun: initialize structs when allocating, and drop unneccesary 'err']
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Fix off-by-one error and notice that summing may need more than one
round for the result to be in the lower 16 bits.
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When a DHCP Nak is received, return a DHCP_EVENT_NO_LEASE event. If
some other DHCP message is received or an error happens when parsing
options, return -ENOMSG in order to ignore the packet. There may be
more than one server serving the same subnet, each server will send
its Offer to the client.
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This also fixes a minor indentation damage.
[tomegun: use close_noint_nofail() instead and drop 'err' variables]
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Ignore DHCP Ack packets if they are found to be erroneous or have
an unexpected xid by setting the result to zero instead of propagating
an error. Also remember to report a DHCP Nak and stop the DHCP client.
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test-fileio/test-strv:
Use the streq_ptr to make build-scan not worry about passing in a null
to a nonnull function.
test-dhcp-option:
Prevent a theoretical null pointer dereference
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Define a notification callback and events for stopping and client
lease expiry. Add functions to fetch IP parameters from a lease.
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Compute the default T1 and T2 timer values if they were not set by
the DHCP server. Verify that the values are reasonable.
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Process a DHCP Ack/Nak in much the same way as an DHCP Offer. Factor
out header verification and process options sent. Add notification
functionality with discrete values for the outcome of the DHCP Ack/
Nak processing.
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Add maximum message size option to keep some DHCP server implementations
from sending too big messages. See ConnMan commit
0c5c862749c05193cf4c513628328c6db02b5222.
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Create and send a DHCP Request message reusing already existing parts
of the code. This causes factoring out IP and UDP header creation and
moving next timeout calculation to be done every time in the timer
callback function independent of DHCP state. Also add an exponential
part to the timer calculation, bail out if there are errors while
resending the DHCP message for the sixth or more times.
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Create a function for handling the full IP, UDP and DHCP packet
and tie it to the main loop. Verify IP and UDP headers and checksum.
Creat a new lease structure with using the values supplied in the
DHCP message. Free the lease structure when client is stopped.
Split out socket handling into a creation and a sending part. As a
result modify the test code.
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Require a main loop to be set when creating a DHCP client. Set up
a timer to resend DHCP Discover messages and add a 0-2 second
delay to the timeout value. Move to state Selecting after successful
sending of a Discover message.
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The client is stopped and brought back to its initial state.
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It was noticed by Grant Erickson in ConnMan commit
95e15c09350acf58d4707056ae2614570883ef66 that:
"Certain DHCP servers, such as that implemented in Mac OS X
(< 10.7) for its "Internet Sharing" feature, refuse to issue
a DHCP lease to clients that have not set a non-zero value
in their DISCOVER or REQUEST packets."
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Set a fake MAC address and emulate raw packet sending. When the buffer
containing the Discover message is received, check selected IP and
UDP headers and compute IP header and UDP message checksums. Also
send the DHCP message for option parsing and expect a successful
outcome.
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On starting the client, use the supplied interface mac address and create
a transaction id. Puzzle together an IP/UDP/DHCP Discover message, compute
checksums and send it out as a raw packet.
Create an additional function that constructs default options common to
all DHCP messages.
Set the DHCP Client ID option as noticed by Grant Erickson in ConnMan
commit b18d9798b3a0ae46ed87d6d2be8d5a474bf3ab1e:
"Some Internet gateways and Wi-Fi access points are unhappy when the
DHCPv4 client-id option (61) is missing and will refuse to issue a
DHCP lease."
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Open a packet socket, create a link level header, send packet and
close socket. Adding it to a separate file makes testing of the
DHCP sending much easier, as the test program can supply any socket
to the DHCP client code.
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Add checks for invalid lengths and parameters when using the option
appending function. Add also checks for adding options, see to it
that the resulting array is identical to the array of options added.
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Add a structure describing the DHCP file, sname and trailing options
fields. Create a messge holding these fields and call the internal
option parsing function.
In the test callback function verify that only regular options are
passed and figure out which part of the DHCP message is the one that
is being processed. As the test program knows the full contents of
the test options in the test structure, skip all non-regular fields
and verify that the option provided to the callback indeed is the
one expected. Check also if non-regular option fields are to be
ignored in the end of the option field as the callback is not called
again and the final check when the whole message has been processed
needs to be successful.
Add a boolean flag for pretty-printing, anticipate there will be a
nice option to toggle it in the future.
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Create an initial simple test program for these two cases.
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Add functions to append and parse DHCP options. Not all options
are passed to the callback function, the ones not exposed are
pad, end, message type and overload. If indicated by the overload
option, file and sname fields will be examined for more options.
The option functions are internal to DHCP, add a new header files
for interal function prototypes.
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The client test program is the only one to be built so far.
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