DNS seeder 'options'

Question

I've seen various 'options' that the different DNS seeders support, for example x1, x5, x9, and xd:

vSeeds.emplace_back("seed.bitcoin.sipa.be", true); // Pieter Wuille, only supports x1, x5, x9, and xd
vSeeds.emplace_back("dnsseed.bluematt.me", true); // Matt Corallo, only supports x9
vSeeds.emplace_back("dnsseed.bitcoin.dashjr.org", false); // Luke Dashjr
vSeeds.emplace_back("seed.bitcoinstats.com", true); // Christian Decker, supports x1 - xf
vSeeds.emplace_back("seed.bitcoin.jonasschnelli.ch", true); // Jonas Schnelli, only supports x1, x5, x9, and xd
vSeeds.emplace_back("seed.btc.petertodd.org", true); // Peter Todd, only supports x1, x5, x9, and xd

(from chainparams.cpp)

But I can't find anything which actually explains what these options are. What do these options do and why do only some seeders offer some of the options?

score 5 · Accepted Answer · answered Oct 07 '17 at 03:55

5

This is 'service bit filtering.'

You can run nslookup seed.bitcoin.sipa.be, and get a list of bitcoin nodes.

You can also run nslookup x1.seed.bitcoin.sipa.be, and get a list of nodes with NODE_NETWORK set.

(source 1. source 2.)

answered Oct 07 '17 at 03:55

Nick ODell

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So the number following the X is like a bitmask for the service bits? Makes sense, thanks :) – meshcollider Oct 07 '17 at 06:50
1

Exactly, it sets what bits are required in the result. – Pieter Wuille Oct 07 '17 at 09:57

DNS seeder 'options'

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