dnsdist: Add local ComboAddress parameter for SBind() at TeeAction()

[FredericDT]

Short description

In my prod env, I need to Tee queries from specific ip address, since there are multiple ip addresses on a single interface and the receiver has source address based ACLs and Views.

So I proposed an optional parameter in TeeAction to set the socket bind address.

Usage:
addAction(AllRule(), TeeAction("192.0.2.54", false, "192.0.2.53"))

In which case, "192.0.2.54" is the ComboAddress of receiver, "192.0.2.53" is the ComboAddress of sender.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[omoerbeek]

I think there is need to have an extra boolean flag, a boost::optional<X> already has that flag in itself.

[FredericDT]

I think there is need to have an extra boolean flag, a boost::optional<X> already has that flag in itself.

Sounds good,

I think there are two options:

1. Pass that boost::optional<std:string> to TeeAction class, build ComboAddress in the constructor.
2. Pass boost::optional<ComboAddress> as parameter local.

I prefer the second way.

[rgacogne]

Thanks for that pull request! I have made a few suggestions but nothing big, the code looks good.

[rgacogne]

Looks good, thanks!