Lightning: Wallet blockchain hash does not match network blockchain hash

[Christewart]

Issue and Steps to Reproduce

I started lightningd in regtest mode once, stopped it, stopped bitcoind, switched bitcoind to testnet, and attempted to start lightningd in testnet mode and I get this error

$ bitcoind
Bitcoin server starting
chris@chris:~/dev/gentle-hollows-6489$ lightningd --network=testnet
2018-07-27T17:53:58.555Z lightningd(13152): Wallet blockchain hash does not match network blockchain hash: 0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206 != 000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943
lightningd: Wallet network check failed.
chris@chris:~/dev/gentle-hollows-6489$ bitcoin-cli getblockchaininfo
{
  "chain": "test",
  "blocks": 1355736,
  "headers": 1355736,
  "bestblockhash": "000000000000000a7719f13e8c9e67ca3250acb7ea9a3d442306f50d93197c97",
  "difficulty": 58358570.79038175,
  "mediantime": 1532710533,
  "verificationprogress": 0.9999985229509308,
  "initialblockdownload": false,
  "chainwork": "00000000000000000000000000000000000000000000007a32b106812aeeb631",
  "size_on_disk": 14448434319,
  "pruned": false,
  "softforks": [
    {
      "id": "bip34",
      "version": 2,
      "reject": {
        "status": true
      }
    },
    {
      "id": "bip66",
      "version": 3,
      "reject": {
        "status": true
      }
    },
    {
      "id": "bip65",
      "version": 4,
      "reject": {
        "status": true
      }
    }
  ],
  "bip9_softforks": {
    "csv": {
      "status": "active",
      "startTime": 1456790400,
      "timeout": 1493596800,
      "since": 770112
    },
    "segwit": {
      "status": "active",
      "startTime": 1462060800,
      "timeout": 1493596800,
      "since": 834624
    }
  },
  "warnings": "Warning: unknown new rules activated (versionbit 28)"
}

My lightning config file:

$ cat ~/.lightning/config 
alias=suredbits-client
rgb=008000
network=testnet
addr=localhost:9737

[cdecker]

That is because the wallet was created by starting lightningd --network=regtest (the blockhash 0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206 is the genesis hash for regtest). Either delete the lightningd.sqlite3 file, or specify another --lightning-dir where the new wallet will be created (don't forget to copy over the config).

[Christewart]

It would be nice if functionality was similar to bitcoin core's here, if someone wants to tackle this in the future! :-).

[cdecker]

We're a bit of unsure about this point: lightning nodes can technically be run on multiple currencies (which allows atomic swaps for example), but c-lightning currently doesn't support that. So if we split this up now, we'll have a hard time later. If we don't people will continue running into this issue.