bacon-message-connection (was Re: Shipping Vera with 2.4)

[Bastien Nocera <hadess hadess net>]

On Thu, 2003-02-27 at 14:51, Michael Meeks wrote:
> Hi Bastien,
> 
> On Thu, 2003-02-27 at 14:14, Bastien Nocera wrote:
> > > 	It's very hard to compare a system that exists, and works
> > > with one that does not.
> > 
> > I've also got my very own thingo to do simple IPC, that I use in totem:
> > $ cat bacon-message-connection.[ch] | wc -l
> >     271
> > 
> > And that replaces the whole of CORBA for simple IPC purposes.
> 
> 	Well yes it's small. The facts that again it's a type-unsafe, "send
> string" API, with no way of ascertaining what the interfaces are, are
> rather unfavourable.

It's simple, and only sends strings. The server is an existing instance
of the application. That's why the protocol is so simple.

There are also a lot of your comments that would really need to be taken
into account if this was a communication protocol used remotely. It is
local only, thus the risk of errors is minimised.

> 	There are also the following bugs/mis-features I saw with a brief
> glance, correct me if I'm wrong:
> 
> 	* missing syscall error handling

I check the return values of all the syscalls. What did I miss exactly?

> 	* blocking accept

No, it's in a different loop, thanks to the usage of GIOChannel.

> 	* not handling EINTR

See Havoc's mail

> 	* assuming non-blocking / short reads [ possibly in-spec, 
> 	  perhaps better to use NON_BLOCK ].

It is assumed that short reads are enough.

> 	* blocking connection write

Usually the client's only purpose is to send messages to the server
(already running instance) and exit. So it is appropriate.

> 	* no error checking / short write handling on write

That needs fixing.

> 	* server_cb locks in a tight loop on 'read' error

That needs a test for EIO which is the only error that could really
happen in this case.

> 	* looks like it creates an insecure, world writable /tmp
> 	  Unix domain socket -> instant, huge security hazard

As I said, it's user writable only. I'm not *that* stupid.

> 	* doesn't do collision checking => instant DOS attack.

If the user wants to DOS his own application, well, that's his right. He
could also load a 500 megs TIFF image in the GIMP and lock his machine
up. That's his problem.

Thank you for the comments.

Cheers

-- 
/Bastien Nocera
http://hadess.net

#2  0x4205a2cc in printf ("Oh my %s\n", preferred_deity) from
/lib/i686/libc.so.6 printf ("Oh my %s\n", preferred_deity);
Segmentation fault