[backport#15558] Do not query all DNS seed at once
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Authored by PiRK on Oct 22 2020, 15:18.

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rABC30f2e10ee7a7: [backport#15558] Do not query all DNS seed at once

Summary

Before this PR, when we don't have enough connections after 11 seconds, we proceed to query all DNS seeds in a fixed order, loading responses from all of them.

Change this to to only query three randomly-selected DNS seed. If 11 seconds later we still don't have enough connections, try again with another one, and so on.

This reduces the amount of information DNS seeds can observe about the requesters by spreading the load over all of them.

This is a backport of Core PR15558

Test Plan

ninja all check-all

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PiRK created this revision.Oct 22 2020, 15:18

Owners added a reviewer: Restricted Owners Package.Oct 22 2020, 15:18

Herald added a reviewer: Restricted Project. · View Herald TranscriptOct 22 2020, 15:18

PiRK requested review of this revision.Oct 22 2020, 15:18

teamcity edited the summary of this revision. (Show Details)Oct 22 2020, 15:18

PiRK added inline comments.Oct 22 2020, 15:29

src/net.cpp
1682 ↗	(On Diff #24952)	Not sure about this one. In some other part of the file we use `config->GetChainParams().DNSSeeds()

Harbormaster completed remote builds in B13599: Diff 24952.Oct 22 2020, 15:36

jasonbcox requested changes to this revision.Oct 22 2020, 17:38

jasonbcox added a subscriber: jasonbcox.

jasonbcox added inline comments.

src/net.cpp
1682 ↗	(On Diff #24952)	Please use the config. It helps us get a small step closer to removing global state. I see a couple other places in this file that could use it as well, but those can go in a separate diff.