http://wiki.winehq.org/NamedPipes - documenting the samba / wine NamedPipes integration

[Luke Kenneth Casson Leighton]

On Sun, Feb 15, 2009 at 9:43 PM, Juan Lang <juan.lang at gmail.com> wrote:
> Hi Luke,
>
>> does this sound like a reasonable proposition - a mini SMB/wineserver
>> protocol - for use for inter-communication between wine and samba in
>> order to exchange named pipe traffic?
>
> Well, I think we have to crawl before we can walk.

 :)  that's why i said "mini" smb / wineserver protocol, comprising:

 [2-byte command] auth, waitnphs, setnphs, read, write
 [parameters]
 [variable-data]

 which is incredibly incredibly simple, and would take ... what... 200
lines of code, to write?

 setting the "auth" data blob to NULL _is_ "crawl before walk".


>  I think it's more
> important that we have a working local named pipe implementation
> before we start thinking about SMBs from Wine to a remote machine.

 follow the chain, here... :) not least, to make sure it sounds reasonable!

 well, the more i thought about how awful the "multiple socket-pair
queue" design is, and the more i think about what's on the MSDN
"CreateNamedPipe" page, the more i believe that a per-file-handle
Mutex is utterly utterly essential.

 and if you're going to do that [per-file-handle mutex], then you
_can_ use that to emulate blocking-read semantics correctly instead of
read(), select(), poll() etc.

_that_ means that you can do whatever you like - send headers down the
socket, send lengths down the socket, do
whatever-you-like-down-the-socket because there will be only one
reader.

_that_ means you can get away with sending quote commands quotes.

the combination of sending "commands" and exclusivity means you don't
have to have the multiple socketpair queue

and, while you're at it, it so happens that you can replace the
socketpair() with a sockaddr_un pair (hooray!)

so, you get to write a simplified design that meets the requirements
_and_ is well on the way to meeting the other requirements - being
able to interoperate with samba.

> Usually, having a specific app in mind really helps drive an
> implementation, too.

 i like to think ahead.  saves a lot of time and effort in the long run.

 l.