BIND 10 #3279: DHCPv4 server should discard packets with non-matching server id

[BIND 10 Development]

#3279: DHCPv4 server should discard packets with non-matching server id
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            Reporter:  marcin        |                        Owner:  tmark
                Type:  defect        |                       Status:
            Priority:  medium        |  reviewing
           Component:  dhcp4         |                    Milestone:  DHCP-
            Keywords:                |  Kea1.0-alpha
           Sensitive:  0             |                   Resolution:
         Sub-Project:  DHCP          |                 CVSS Scoring:
Estimated Difficulty:  16            |              Defect Severity:
         Total Hours:  10.5          |  Medium
                                     |  Feature Depending on Ticket:
                                     |          Add Hours to Ticket:  .5
                                     |                    Internal?:  0
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Changes (by marcin):

 * owner:  marcin => tmark


Comment:

 Thankfully, before I merged this code I did some manual tests and it
 turned out that the ''acceptServerId'' function is not quite right. The
 server identifier function is in fact represented by !OptionCustom, not
 !Option4AddrLst. Therefore, when packet arrived from a client it was
 always dropped because the cast from Option to !Option4AddrLst failed.

 The unit test was wrong because it created the instance of !Option4AddrLst
 which made the cast to succeed. In the real world where the server
 identifier instance is created by the logic which parses incoming packet,
 server identifier is encapsulated by !OptionCustom.

 Please review the latest commit.

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Ticket URL: <http://bind10.isc.org/ticket/3279#comment:10>
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