11.08.2012 10:23, Pavel Emelyanov пишет:
On 08/11/2012 03:09 AM, H. Peter Anvin wrote:
On 08/10/2012 12:28 PM, Alan Cox wrote:
Explicitly for Linux yes - this is not generally true of the AF_UNIX
socket domain and even the permissions aspect isn't guaranteed to be
supported on some BSD environments !
Yes, but let's worry about what the Linux behavior should be.
The name is however just a proxy for the socket itself. You don't even
get a device node in the usual sense or the same inode in the file system
space.
No, but it is looked up the same way any other inode is (the difference
between FIFOs and sockets is that sockets have separate connections,
which is also why open() on sockets would be nice.)
However, there is a fundamental difference between AF_UNIX sockets and
open(), and that is how the pathname is delivered. It thus would make
more sense to provide the openat()-like information in struct
sockaddr_un, but that may be very hard to do in a sensible way. In that
sense it perhaps would be cleaner to be able to do an open[at]() on the
socket node with O_PATH (perhaps there should be an O_SOCKET option,
even?) and pass the resulting file descriptor to bind() or connect().
I vote for this (openat + O_WHATEVER on a unix socket) as well. It will
help us in checkpoint-restore, making handling of overmounted/unlinked
sockets much cleaner.
I have to notice, that it's not enough and doesn't solve the issue.
There should be some way how to connect/bind already existent unix
socket (from kernel, at least), because socket can be created in user space.
And this way (sock operation or whatever) have to provide an ability to
lookup UNIX socket starting from specified root to support containers.
-hpa
Thanks,
Pavel
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