Tests if addresses are online or offline by briefly connecting to them. These short lived connections are referred to as feeler connections. Feeler connections are designed to increase the number of fresh online addresses in tried by selecting and connecting to addresses in new. One feeler connection is attempted on average once every two minutes.
This change was suggested as Countermeasure 4 in
Eclipse Attacks on Bitcoin’s Peer-to-Peer Network, Ethan Heilman,
Alison Kendler, Aviv Zohar, Sharon Goldberg. ePrint Archive Report
2015/263. March 2015.
When processing a headers message that looks like a block announcement,
send peer a getheaders if the headers message won't connect.
Apply DoS points after too many consecutive unconnecting headers messages.
Moves the IsStandard check to happen after the premature-witness check,
so that adding a witness to a transaction can't prevent mempool acceptance.
Note that this doesn't address the broader category of potential mempool DoS
issues that affect transactions after segwit activation.
Changes in tinyformat, recently imported from upstream have made the
zero-argument versions of formatting functions unnecessary. Remove them.
This is a slight semantic change: `%` characters in the zero-argument
call are now regarded and need to be escaped. As for as I know, the only
use of this is in `main.cpp`.
An orphan whos parents were rejected is never going to connect, so there
is little utility in keeping it.
Orphans also helpfully tell us what we're missing, so go ahead and treat
it as INVed.
This prevents higher order orphans and other junk from
holding positions in the orphan map. Parents delayed
twenty minutes are more are unlikely to ever arrive.
The freed space will improve the orphan matching success rate for
other transactions.
As per meeting 2016-03-31
https://bitcoincore.org/en/meetings/2016/03/31/#bad-chain-alerts
The partition checker was producing huge number of false-positives
and was disabled in 0.12.1 on the understanding it would either be
fixed in 0.13 or removed entirely from master if not.
Ethan Heilman