BIND 10 #3207: per-client option values (hook lib extension)

[BIND 10 Development]

#3207: per-client option values (hook lib extension)
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            Reporter:  tomek         |                        Owner:
                Type:  enhancement   |  UnAssigned
            Priority:  medium        |                       Status:
           Component:  dhcp          |  reviewing
            Keywords:                |                    Milestone:
           Sensitive:  0             |  Sprint-DHCP-20131016
         Sub-Project:  DHCP          |                   Resolution:
Estimated Difficulty:  0             |                 CVSS Scoring:
         Total Hours:  0             |              Defect Severity:  N/A
                                     |  Feature Depending on Ticket:
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Changes (by tmark):

 * owner:  tmark => UnAssigned
 * status:  assigned => reviewing


Comment:

 This submission extends the user check hook library with the ability to
 set
 options in a DHCP response packet based upon the user registry. If the
 DHCP
 query is from a registered user, then that user's properties may be used
 to
 populate options in the response.  If the user is not registered, default
 users
  may be defined which supply default values for the desired properties.

 Currently, which options are supported is hard-coded (see pkt_send_co.cc)
 and
 those two options are boot file and tftp server.

 This implementation builds upon 3186, but adds callouts for pkt_receive
 and
 pkt_send, and supports the same overall logic for both IPv4 an IPv6. The
 callouts and their respective tasks are as follows:

 1.pkt_receive:
  a. Refresh the user registry,
  b. Extract user id from DHCP query, store it to context
  c. Look up user id in registry, store result to context

 2.subnet_select:
  a. Retrieve user pointer from context
  b. If pointer is null (i.e. user not registered), replace subnet
 selection
  with restricted subnet

 3.pkt_send:
  a. Retrieve user id and user pointer from context
  b. If user is not null add options based on user, otherwise use default
 user
  c. Generate user check outcome


 Note, that much of the actual callout code is not currently unit tested as
 it relies on a good deal of setup.  This could be expanded.  Additionally,
 the code to extract lease value (address or prefix) from the response
 packet
 is fairly involved as it must navigate packet options and account for
 various
 permutations.  It would be more efficient to add lease_select callout
 logic to
 grab and store the lease value to the context and use that in pkt_send to
 generate the outcome output.  Lastly, there should be some thought perhaps
 given to packet type checks.  For instance, not all response should have
 options added or outcome records generated.

-- 
Ticket URL: <http://bind10.isc.org/ticket/3207#comment:3>
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