Lnd: Periodically resolve `externalip` if set to domain name

[gustavonalle]

Background

My lnd.conf is

[Application Options]
debuglevel=debug
minchansize=30000
maxpendingchannels=10
externalip=xxxxx.ddns.net:9735
alias=my-alias
restlisten=0.0.0.0:8081
listen=0.0.0.0:9735
maxlogfiles=0
maxlogfilesize=100
debuglevel=debug

[Bitcoin]
bitcoin.active=1
bitcoin.mainnet=1
bitcoin.node=bitcoind

[Bitcoind]
bitcoind.rpchost=localhost
bitcoind.rpcuser=xxxxx
bitcoind.rpcpass=xxxxx
bitcoind.zmqpubrawblock=tcp://127.0.0.1:29000
bitcoind.zmqpubrawtx=tcp://127.0.0.1:29001

Your environment

• version of lnd

lnd version 0.5.1-beta commit=v0.5.1-beta-rc3-2-g712fc3ebed1c9e0df6bad2b240acce1a0804b1d2

• which operating system (uname -a on *Nix)

Fedora release 28 (Twenty Eight)
Linux  4.19.2-200.fc28.x86_64 #1 SMP Wed Nov 14 20:58:35 UTC 2018 x86_64 x86_64 x86_64
 GNU/Linux

• version of btcd, bitcoind, or other backend

Bitcoin Core RPC client version v0.17.99.0-d26278988

Expected behaviour

lnd should detect external DNS changes periodically and send channel announcements automatically, without forcing me to use NAT traversal. Every X minutes, it should resolve the external domain name and compare with the last IP used and send updates in case needed.

Actual behaviour

External DNS changes, lnd does not send node announcement with the new IP unless I restart it manually.

[halseth]

Related: https://github.com/lightningnetwork/lnd/issues/274, https://github.com/lightningnetwork/lnd/issues/2005

[Roasbeef]

Every X minutes, it should resolve the external domain name and compare with the last IP used and send updates in case needed.

It has no awareness of DNS at all, we only advertise IP addresses on the network.

[gustavonalle]

@Roasbeef Currently it resolves the DNS configured in externalip to an ip, so we just need to do it periodically rather than on startup only

[gustavonalle]

I'd like to take a stab at this, seems a good issue for first time contributors?

[wpaulino]

Sure! Changed the title to better reflect the issue.

[jnaulty]

any progress on this?

[seth586]

+1, would like to use a VPN for inbound clearnet connections, VPN server constantly changes but their dns service would fix this!

[cfromknecht]

@jnaulty @seth586 i think this PR should cover it? https://github.com/lightningnetwork/lnd/pull/4281