Addrman offline attempts #8065

1. 
   gmaxwell commented at 7:26 am on May 17, 2016: contributor

   If a node is offline failed outbound connection attempts will crank up the addrman counter and effectively blow away our state.

   This change reduces the problem by only counting attempts made while the node believes it has outbound connections to at least two netgroups.

   Connect and addnode connections are also not counted, as there is no reason to unequally penalize them for their more frequent connections – though there should be no real effect from this unless their addnode configureation is later removed.

   Wasteful repeated connection attempts while only a few connections are up are avoided via nLastTry.

   This is still somewhat incomplete protection because our outbound peers could be down but not timed out or might all be on ’local' networks (although the requirement for multiple netgroups helps).

   ( reopen of #6030 )

2. jonasschnelli added the label P2P on May 17, 2016
3. 
   pstratem commented at 10:07 pm on May 17, 2016: contributor

   This should probably be checking for connections to at least two netgroups outside of RFC1918 IP space, but this is certainly an improvement.
4. 
   gmaxwell commented at 9:17 am on May 18, 2016: contributor

   @pstratem checking connections is better than no check at all. This PR is from April 2015, so I’m not inclined to expand the scope any further right now. If this is accepted I’ll happily open a follow on PR to make it stronger.
5. 
   arowser commented at 8:43 am on May 25, 2016: contributor

   Can one of the admins verify this patch?
6. 
   sipa commented at 5:23 pm on May 25, 2016: member

   Needs rebase.
7. 
   sipa commented at 12:32 pm on May 26, 2016: member

   Did you accidentally include #7992?
8. 
   sipa commented at 12:35 pm on May 26, 2016: member

   utACK 66cefd47194a8aa7478dbea9a1b96640febeeda7
9. Avoid counting failed connect attempts when probably offline.

   If a node is offline failed outbound connection attempts will crank up
    the addrman counter and effectively blow away our state.
   
   This change reduces the problem by only counting attempts made while
    the node believes it has outbound connections to at least two
    netgroups.
   
   Connect and addnode connections are also not counted, as there is no
    reason to unequally penalize them for their more frequent
    connections -- though there should be no real effect from this
    unless their addnode configureation is later removed.
   
   Wasteful repeated connection attempts while only a few connections are
    up are avoided via nLastTry.
   
   This is still somewhat incomplete protection because our outbound
    peers could be down but not timed out or might all be on 'local'
    networks (although the requirement for multiple netgroups helps).

   c769c4af11
10. Do not increment nAttempts by more than one for every Good connection.

    This slows the increase of the nAttempts in addrman while partitioned,
     even if the node hasn't yet noticed the partitioning.

    6182d10503
11. 
    sipa commented at 10:27 pm on May 26, 2016: member

    Running a public node with #7960 #8007 #8065 #8080 #8082 #8084 #8086 for testing.
12. 
    sipa commented at 2:52 pm on June 7, 2016: member

    This should be easy to test manually: add a debug log entry above the info.nAttempts increment in CAddrMan::Attempt_(), and see how often it triggers with network connected and disconnected.
13. 
    laanwj commented at 10:58 am on June 8, 2016: member

    utACK 6182d10
14. laanwj merged this on Jun 8, 2016
15. laanwj closed this on Jun 8, 2016

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16. laanwj referenced this in commit 67c91f8c4c on Jun 8, 2016
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Contributors
gmaxwell pstratem arowser sipa laanwj

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