Re: [RFC PATCH] Introduce git-hive

From: Luke Kenneth Casson Leighton <luke.leighton@gmail.com>
Date: Aug 31, 2010, 15:08 UTC
Message-ID: <AANLkTinF1o0RZSKYEL9Qc=uwXx6fBBXh6wRx2CTULBSE@mail.gmail.com>
In-Reply-To: <20100831143839.GC16034@foucault.redhat.com>

On Tue, Aug 31, 2010 at 3:38 PM, Casey Dahlin <cdahlin@redhat.com> wrote:

Show 9 quoted lines

>        nguyen@host_b$ git config --add hive.uri http://myproject.org
>        nguyen@host_b$ git hive start host_a.com:21121
>
> So from host_b we specify host_a's address and listen port, and we join the
> network. From here on out anyone who also connects to host_a will get host_b's
> (randomly selected) listen port automatically and be able to connect to it as
> well.
>
> So now our two peers can see each other.

 ok - this only works if the two peers can see each other's ip
addresses.  i.e. if the two machines are either on a local subnet or
if the two machines are directly on the public internet.  ( or if
you've forced people to set up a firewall rule and/or UPnP rule, but
even then UPnP doesn't solve the entire problem - only one part of it)

 ... unless (and i haven't reviewed the code closely, i admit) you're
using the following protocol:

 * make tcp connection
 * send dedicated specific message "please tell me my public IP and port"
 * far end does sockaddr lookup of the incoming socket
 * far end returns IP and port as response to requestor

in this way, requestors can determine what the "apparent" IP address is as far as having been NAT'd through half a ton of ISP layers performing NAT, local routers performing NAT, laptops such as mine doing NAT sharing of a 3G connection over a netgear router and so on.

so it entirely depends on the scope / scale you're thinking of. if you are aiming hive at "local subnets", it's pretty much perfect, and, much as i hate to say it and you should not _remotely_ consider using it because of the vast and horrific dependencies, i can understand why you were considering avahi, because it is a good "local subnets" solution.

however for "global networking" - for putting hive out onto the public internet - there is one hell of a lot more involved, and all these "filesharing" applications have solved near as damnit every single one of the issues.

so, answering the question you were asking earlier: i believe that you really do need to consider taking the closest c-based bittorrent library/application apart, and use it as the basis for git-hive. if you don't, you will be here forever, reinventing everything that these fileshare-app-writers have spent nearly a decade perfecting.

l.