btcwallet: don't initialize wallet namespace if scrypt derivation fails due to low memory

[callebtc]

Background

lnd is killed at wallet creation.

Your environment

• Hardware: Raspberry Pi Zero 2 W
• version of lnd: Version: 0.14.1-beta commit=v0.14.1-beta,
• Linux 5.10.63-v7+ #\1459 SMP Wed Oct 6 16:41:10 BST 2021 armv7l GNU/Linu
• using neutrino backend

Steps to reproduce

I start with a fresh lnd with the Raspibolt config except that I use the neutrino backend. I use the ARMv7 binary since I'm running this on a Rpi Zero 2 W.

I start lnd and it does it's thing, waiting for me to create a wallet. In another session, I run lncli create. I see this:

x@y:~/.lnd $ lncli create
Input wallet password:
Confirm password:

Do you have an existing cipher seed mnemonic or extended master root key you want to use?
Enter 'y' to use an existing cipher seed mnemonic, 'x' to use an extended master root key
or 'n' to create a new seed (Enter y/x/n): n

Your cipher seed can optionally be encrypted.
Input your passphrase if you wish to encrypt it (or press enter to proceed without a cipher seed passphrase):

Generating fresh cipher seed...

!!!YOU MUST WRITE DOWN THIS SEED TO BE ABLE TO RESTORE THE WALLET!!!

---------------BEGIN LND CIPHER SEED---------------
 1. abandon    2. erupt   3. club       4. motion
 5. cabbage    6. leaf    7. build      8. fish
 9. enemy     10. basic  11. peanut    12. ski
13. slide     14. place  15. mechanic  16. fiction
17. crane     18. firm   19. chimney   20. rack
21. artefact  22. buyer  23. action    24. develop
---------------END LND CIPHER SEED-----------------

!!!YOU MUST WRITE DOWN THIS SEED TO BE ABLE TO RESTORE THE WALLET!!!

Around 10 seconds later, lncli terminates with:

[lncli] rpc error: code = Unavailable desc = error reading from server: EOF

At the same time, lnd gets killed only saying:

Killed

At this point I have created a wallet. I can try to run lnd again but I get

error creating wallet config: error unlocking wallet with password from file: missing address manager namespace

To check, I uncomment these lines in lnd.conf so I can enter the password manually:

wallet-unlock-password-file=/asd/password.txt
wallet-unlock-allow-create=true

I start lnd again, this time it runs but wants me to unlock the wallet manually:

2022-01-27 23:18:06.862 [INF] LTND: Waiting for wallet encryption password. Use `lncli create` to create a wallet, `lncli unlock` to unlock an existing wallet, or `lncli changepassword` to change the password of an existing wallet and unlock it.

I do that with lncli and now I get:

x@y:~/.lnd $ lncli unlock
Input wallet password: <I enter the pw here>
[lncli] rpc error: code = Unknown desc = missing address manager namespace
x@y:~/.lnd $

lnd keeps running. Can't unlock the wallet.

I delete everything in the .lnd directory except for my lnd.conf file and start over. Same thing happens.

:(

[Roasbeef]

Do you have any swap alloacted? I'm guessing the initial scrypt operation to encrypt the keys on disk is running out of memory. Depending on the type of telemetry you have on the machine, you can watch the memory usage.

There're some other settings you can use on the lnd front to reduce memory usage as well.

[Roasbeef]

Closing due to inactivity. The issue here seems to be lack of swap AFAICT, will re-open if we get any other information.

[joostjager]

I think I may have a repro for this scenario. Ran into it as well in a docker environment with insufficient memory. It isn't great, because wallet db seems to get into a state that lnd can't recover from. Restarting doesn't help.

Repro steps:

• Add a debug panic in btcwallet here: https://github.com/btcsuite/btcwallet/blob/79de92f527dcb810060c02848c62a906f7e0e394/wallet/wallet.go
• Build lnd with this patch
• Run lnd with noseedbackup=true
• It crashes on the debug panic. The bad state is created now
• Remove patch, re-run lnd:

2022-05-11 14:56:43.410 [ERR] LTND: unable to create wallet controller: missing address manager namespace
2022-05-11 14:56:43.410 [ERR] LTND: Shutting down because error in main method: error loading chain control: unable to create wallet controller: missing address manager namespace```

[joostjager]

The reason seems to be that an empty wallet file is already created, but not yet initialized. This will skip the initialization on the next run.

[joostjager]

@saubyk can this be re-opened? I've added a repro scenario above.