BIND 10 #334: message rendering problem in xfrout

[BIND 10 Development]

#334: message rendering problem in xfrout
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  Reporter:  jelte   |            Owner:  jelte
      Type:  defect  |           Status:  new  
  Priority:  major   |        Milestone:       
 Component:  xfrout  |         Keywords:       
 Sensitive:  0       |   Estimatedhours:  0    
     Hours:  0       |         Billable:  1    
Totalhours:  0       |         Internal:  0    
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 While tracking the cause of another bug, I noticed that the behaviour of
 xfrout is a bit weird;

 within the xfrout stream, messages are all < 512 octets, and have the TC
 bit set. Xfrout itself also does a 'test' render of the whole message for
 every RRset that is added, which is very inefficient. While the final
 renderer set the maximum size to 65535 octets, this check does not, hence
 the <512 octet messages. But if we change this test to check for <65535,
 the inefficiency gets really painful.

 My proposal is to render each rrset once, check the length of that (which
 will not have full compression) plus the length of the rrsets added so
 far, and if that reaches a certain limit, then do a full render on the
 packet. Still room for some more optimizations, but at least the
 complexity is bound :)

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Ticket URL: <https://bind10.isc.org/ticket/334>
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BIND 10 Development