Channel pending / funds locked after lightningd failed to sendrawtransaction

[renepickhardt]

Recently a friend asked me to help out since he tried to open a channel but the funding transaction was never seen on chain. I assumed the channel open protocol was not complete and studied the logfile.

I was surprised that the funding_signed_message was received and signatures for the commitment tx were there. I also discovered in the log file that the the call sendrawtransaction ... exited without success.

It seems like afterwards lightningd did never again attempt to rebroadcast the funding transaction.

The situation became unluckily worse as my friend tried to force-close the channel hoping he would get his output back as he expected c-lightning would just forget about the open transaction (Meanwhile I understand that with dev-rescanoutputs and withdraw all I could have indeed created a double spend of the funding transaction to get the money back).

Anyway after I rebroadcasted the fundingtx which was stored in the logfile the same situation occurred with the commitment tx. It seems that the first time it was broadcasted the bitcoin network could not accept it as it was spending the funding tx which was not even in the mempool. Afterwards it was not broadcasted again. The command to force close the channel (in hope to trigger the broadcast again) aborted as lightning-cli said the channel was already unilaterally closed. (I was able to resolve this with dev-sign-last-tx and a manual broadcast)

suggestion / feature request

I suggest periodically broadcast transactions which are not in the mempool but which were supposed to be mined / broadcasted.

Issue and Steps to Reproduce

can't reproduce, was not able to figure out why sendrawtransaction failed

getinfo output

don't know: lightningd was updated and recompiled in developer mode to get the funds back. I would assume v0.7.

[SimonVrouwe]

If sendrawtransaction returns with non-zero exit code, then the fundchannelcommand fails and returns with error 303 and message that includes bitcoin-cli's exit code. From that point the user is supposed to investigate .. fix it (bitcoin?) .. and then maybe manually broadcast.

The log (debug) should contain a line
sendrawtx exit X, gave error code: Y
If you don't have a logfile and didn't restart CL, maybe lightning-cli getlog debug still has that line?

[cdecker]

The issue is a bit more subtle, since your own bitcoind may accept the transaction, but it may fail to propagate through the network, or it may be kicked out of the mempool due to other transactions crowding it out.

Regular broadcasts may handle the latter situation better.

[SimonVrouwe]

since your own bitcoind may accept the transaction

@cdecker From the description:

the call sendrawtransaction ... exited without success

@renepickhardt not entirely clear what is meant here, I guess
sendrawtx exit X, gave error code: Y
which means the tx wasn't accepted by bitcoind ?

EDIT: Maybe a users guide with a troubleshoot chapter or tips and tricks would be helpful, instead of users having to search in github issues to find solutions.

EDIT2: Aha, there is a helpme plugin!