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Unable to calculate offset #6

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marcbowes opened this issue Apr 14, 2014 · 3 comments
Closed

Unable to calculate offset #6

marcbowes opened this issue Apr 14, 2014 · 3 comments

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@marcbowes
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According to RFC 958, to calculate your offset, you need to use run a calculation that includes the timestamp of when the client received the packet.

Right now, this timestamp is being set in the constructor of Response - see

net-ntp/lib/net/ntp/ntp.rb

Line 103 in 234d8a1

@client_time_receive = Time.new.to_i
.

  1. it is private
  2. it is an integer

Would it be reasonable to:

  1. add the receive timestamp as a parameter to Response#initialize
  2. simply add an offset method which does the calculation as described in the RFC
offset = ( (response.receive_timestamp - response.originate_timestamp) + (response.transmit_timestamp - response.client_time_receive) ) / 2
@davispuh
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To me it looks like @client_time_receive is not used at all.

@marcbowes
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Not that I could see!

@brandonarbini
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That certainly seems reasonable.

marcbowes added a commit to marcbowes/net-ntp that referenced this issue Apr 15, 2014
@marcbowes
Add Response#offset and the start of a test that validates it
7d5def2 
The test is quite hard if your clock is in sync. I'm not sure the right
way to actually do this because we're using a pool of NTP servers and
ntpdate and Net::NTP could hit different servers.

I think this is good enough for now to verify that things actually
work and return reasonable results.

closes zencoder#6
@marcbowes marcbowes mentioned this issue Apr 15, 2014
Merged
brandonarbini pushed a commit that referenced this issue Apr 16, 2014
Merge pull request #7 from marcbowes/master
58a3f88 
Fix for 1.9, expose Response#offset. Fixes #5 and fixes #6.
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3 participants
@brandonarbini @marcbowes @davispuh