Socket fs

Christian Helmuth christian.helmuth at ...1...
Mon Mar 27 13:25:43 CEST 2017

Hello Boris,

On Mon, Mar 13, 2017 at 03:48:54PM +0100, Boris Mulder wrote:
> 1. In the release notes you describe the support for async file I/O.
> However, it seems that while asynchronous I/O works now, synchronous I/O
> is no longer possible. When I remove the select() call in the echo
> scenario, the call to recvfrom() will fail saying the socket is not
> connected (even though it is an UDP socket and should not have the
> notion of connections at all).
> Of course this means it is not posix compatible; the intended behaviour
> is to block until data becomes available.

Thanks for your investigation. You're right the current state of
socket support has some rough edges (esp. POSIX-correct error
handling) that we plan to smoothen in near term. I'd like to invite
you to open an issue at Github to aggregate your findings.

> 2. Currently there are two ways an application can use tcp/ip sockets
> from the lxip stack: By using libc sockets, and by directly opening a
> file system session and writing to the right socket files. For any new
> Genode application that does not already depend on libc, the first way
> means you unnecessarily add the entirety of libc to your component. So
> the second way seems preferred. 
> However, when programming an application using a file system session 
> directly adds a lot of code with many open()s, read()s and write()s that
> could be abbreviated into single calls such as connect() and recv(). 
> Have you thought of providing a more convenient API (such an 
> object-oriented Socket class that hides the vfs calls from the 
> application programmer)? Or do you consider using the fs session
> interface to be better? If so, why?

We do not plan to implement an abstraction layer or object-oriented
Socket interface currently. The mere reason for our recent
developments was to enable more POSIX network applications to run on
Genode and to support those components to share one network stack.
Also, we imagine to mount the socket FS into Noux and use traditional
tools in shell scripts to interoperate with the network.

I must admit that we (the Genode Labs team) do not assess ourselves as
networking experts and, therefore, don't fancy to design and implement
such a library. But as always nothing is set in stone and priorities
may shift over time.

Christian Helmuth
Genode Labs · · /ˈdʒiː.nəʊd/

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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