Z8 .conf file changes and connection issues?

str4d · August 23, 2016, 1:36am

We think we have identified the bug (not a DoS attack) causing the connection issues:

github.com/zcash/zcash

Decrease MAX_HEADERS_RESULTS

opened 01:31AM - 23 Aug 16 UTC

closed 06:15AM - 24 Aug 16 UTC

str4d

C-bug A-consensus network upgrade management A-networking

The Equihash parameters were changed in the z8 release (#1182), which increased …the solution size in the block header from 129 bytes to 2049 bytes, and thus the size of the block header from 269 bytes to 2189 bytes. This had an unintentional side-effect: once the block chain height passed 958, any newcomers to the network trying to download the whole blockchain (or anyone whose local blockchain was more than 958 blocks behind) would be sent messages that were too large, because of the following defined constants: - `MAX_HEADERS_RESULTS = 2000` - `MAX_PROTOCOL_MESSAGE_LENGTH = 2 * 1024 * 1024` This inability to download blocks was misinterpreted as a DoS attack (#1256). The solution is to reduce `MAX_HEADERS_RESULTS`. The problem will be somewhat mitigated by #1260 (which reduces the solution size to 1344 bytes), so we don't have to reduce it as far as the current testnet would require. In order to stay within `MAX_PROTOCOL_MESSAGE_LENGTH`, we should not have `MAX_HEADERS_RESULTS > 1400`. Note that reducing `MAX_HEADERS_RESULTS` does not require a hard fork (although #1260 does, so we will be resetting the testnet anyway). But _increasing_ `MAX_HEADERS_RESULTS` does require a hard fork, because peers are considered to be misbehaving if they send more than `MAX_HEADERS_RESULTS` headers in response to a `getheaders` request. We should take this into account when choosing `MAX_HEADERS_RESULTS`. Edit: Kudos for finding the bug goes to @ebfull (https://github.com/zcash/zcash/issues/1289#issuecomment-241809682)

Should be fixed in the z9 release

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Z8 .conf file changes and connection issues?

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