realip: Add null check for netvc

[maskit]

Apparently, client netvc is not always available on READ_REQUEST_HDR_HOOK.

[brbzull0]

looks good.

[bneradt]

Looks fine, approving as is. But would a debug log for the else case be helpful potentially? If you want to add that, I can give you a quick approval after another commit. Otherwise feel free to merge with these changes as is.

[bryancall]

I would like to see the implementation being safer by doing null check on the input arguments and return TS_ERROR.

[maskit]

Looks fine, approving as is. But would a debug log for the else case be helpful potentially?

There's a debug log on the caller side, and that works for all address sources.

I would like to see the implementation being safer by doing null check on the input arguments and return TS_ERROR.

I do not think that is a good idea. If we took that way, null check would be done again and again by all functions that receive vconn on every call. So redundant.