chain: add airstop soft fork

[rithvikvibhu]

This is a very simple PR to disable airdrops with a soft fork.

While it is currently functional and "works", everything is open to change (the name, scope, signalling threshold, duration, etc.)

It does not deal with name claims or non-airdrop faucet claims. It does not do any reallocation of funds. It only stops airdrops from being claimed if the soft fork is activated.

This should hopefully get some conversation going.

h/t to @nodech who wrote the icannlockup soft-fork, much of the test code is stolen from test/chain-icann-lockup-test.js

[coveralls]

coverage: 71.622% (+0.03%) from 71.588%
when pulling 4782714 on rithvikvibhu:end-airdrop
into f0a81da on handshake-org:master.

[AndreiChyrych]

«This is a very simple PR to disable airdrops with a soft fork»

is it possible to reintroduce airdrop with a new soft fork?

[Falci]

is it possible to reintroduce airdrop with a new soft fork?

No, that would require a hard fork.

[j9011303]

I support this proposal. Ending the airdrop makes sense at this stage of the project.
It can help reduce unnecessary token supply and move the project forward.

[smcki012]

My Father allows this. You can proceed.

[agaamin]

Lets do this.
Burn the damn spare tokens.

[HNSbroker]

Isn't there a way to actually burn the coins and permanently remove them from the supply, instead of just stopping the claims?

[Falci]

Isn't there a way to actually burn the coins and permanently remove them from the supply, instead of just stopping the claims?

These coins don't actually exist. The airdrop creates coins out of thin air when they're claimed. By stopping the airdrop, we prevent these coins from ever being created, removing them from the supply.

[faltrum]

Great Moment and great decision!. Congrats community involved in this step. Next steps:

1. Ensure miners awareness
2. Update the BIP9 dates
3. Merge
4. Wait the merge to be activated, or not.

Thanks @rithvikvibhu and @Falci for clarifications.

[rhymincymon]

I think this is the right way forward.

The supply looks as follows without and with the soft fork activated.

After the last subsidized block is mined, a total of 961,262,671.16 HNS would have been issued.

[nodech]

After the soft fork activates, miners may still accidentally use airdrops broadcasted in their blocks. This could potentially halt the network as those blocks are no longer valid. I believe miner code AND mempool code needs addressing.

Mempool on activation could drop all airdrops that are logged in it, to ensure miners don't include them in the blocks. And mempool also needs to not accept/propagate airdrops. Also in addition relevant miner code could be modified so it does not include it either way. I believe both changes are necessary.

[nodech]

After the soft fork activates, miners may still accidentally use airdrops broadcasted in their blocks. This could potentially halt the network as those blocks are no longer valid. I believe miner code AND mempool code needs addressing.

Mempool on activation could drop all airdrops that are logged in it, to ensure miners don't include them in the blocks. And mempool also needs to not accept/propagate airdrops. Also in addition relevant miner code could be modified so it does not include it either way. I believe both changes are necessary.

Okay, this is done.

[rithvikvibhu]

Thanks @nodech for review/changes! LGTM (apparently I can't "approve" my own PR)