Additional field to RPC getpeerinfo output: addrlocal

[Krellan]

This simple patch gives user visibility to see the contents of the existing CNode::addrLocal member.
No existing behavior is changed, this is read-only.
If addrLocal is invalid (not filled in yet), the field will not be included in the output.

[Diapolo]

You should squash into one single commit.

[Krellan]

Thanks for the feedback! Done. Nicely squashed now.

[jgarzik]

ACK the code change... what is the use case? How is this useful?

[Krellan]

Thanks! Use case is to help network troubleshooting. In my example, I was having a tough time because I couldn't tell if my external IP address was being seen correctly by the outside world. Bitcoin exchanges this information during the "version" command handling, and stores it in the "addrLocal" member of CNode, but doesn't expose this to the user, so unless the user is lucky and sees the debug text scroll by at the moment a connection is made, the user won't be able to easily learn this information.

Also, it might be nice in the future to have a table of network connections in Bitcoin-Qt or something like that, and this would make it easy to have both local and remote addresses appear in the table (for completeness).

[sipa]

Nit: this can be a CService instead of a full CAddress, I suppose.

[sipa]

ACK

[Krellan]

Thanks. I found the methods worked the same when simply reusing the existing CService, so there's no need to construct a CAddress here.
I updated the commit, removing that CAddress.

[Krellan]

Found and removed a needless usage of c_str().

[Diapolo]

I'm not sure if an empty string, n/a or just to hide the addrlocal filed would be best...

[Krellan]

Thanks for the thought. I actually hide the addrlocal field from the output entirely, in the getpeerinfo handler, if it's blank. If local address is not known yet, the output is unchanged from upstream.

Thought about adding the field anyway but leaving it as an empty string, but that just added bloat to the output. Using n/a instead introduces a magic constant string that conveys no more information than an empty string.

[Krellan]

No change made, just rebased this branch to catch it up to the latest master.

[gavinandresen]

Rebase needed again.

[Krellan]

Rebased! Thanks for the reminder.

[BitcoinPullTester]

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