From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: Re: [RFC PATCH 0/5] net: socket bind to file descriptor introduced Date: Tue, 4 Sep 2012 15:00:07 -0400 Message-ID: <20120904190007.GB29369@fieldses.org> References: <20120815161141.7598.16682.stgit@localhost.localdomain> <87y5lf7d37.fsf@xmission.com> <50320EE5.10307@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Eric W. Biederman" , "tglx@linutronix.de" , "mingo@redhat.com" , "davem@davemloft.net" , "hpa@zytor.com" , "thierry.reding@avionic-design.de" , "bfields@redhat.com" , "eric.dumazet@gmail.com" , Pavel Emelianov , "neilb@suse.de" , "netdev@vger.kernel.org" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "paul.gortmaker@windriver.com" , "viro@zeniv.linux.org.uk" , "gorcunov@openvz.org" , "akpm@linux-foundation.org" , "tim.c.chen@linux.intel.com" , "devel@ope To: Stanislav Kinsbursky Return-path: Content-Disposition: inline In-Reply-To: <50320EE5.10307@parallels.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Aug 20, 2012 at 02:18:13PM +0400, Stanislav Kinsbursky wrote: > 16.08.2012 07:03, Eric W. Biederman =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >Stanislav Kinsbursky writes: > > > >>This patch set introduces new socket operation and new system call: > >>sys_fbind(), which allows to bind socket to opened file. > >>File to bind to can be created by sys_mknod(S_IFSOCK) and opened by > >>open(O_PATH). > >> > >>This system call is especially required for UNIX sockets, which has= name > >>lenght limitation. > >> > >>The following series implements... > > > >Hmm. I just realized this patchset is even sillier than I thought. > > > >Stanislav is the problem you are ultimately trying to solve nfs clie= nts > >in a container connecting to the wrong user space rpciod? > > >=20 > Hi, Eric. > The problem you mentioned was the reason why I started to think about= this. > But currently I believe, that limitations in unix sockets connect or > bind should be removed, because it will be useful it least for CRIU > project. >=20 > >Aka net/sunrpc/xprtsock.c:xs_setup_local only taking an absolute pat= h > >and then creating a delayed work item to actually open the unix doma= in > >socket? > > > >The straight correct and straight forward thing to do appears to be: > >- Capture the root from current->fs in xs_setup_local. > >- In xs_local_finish_connect change current->fs.root to the captured > > version of root before kernel_connect, and restore current->fs.ro= ot > > after kernel_connect. > > > >It might not be a bad idea to implement open on unix domain sockets = in > >a filesystem as create(AF_LOCAL)+connect() which would allow you to > >replace __sock_create + kernel_connect with a simple file_open_root. > > >=20 > I like the idea of introducing new family (AF_LOCAL_AT for example) > and new sockaddr for connecting or binding from specified root. The > only thing I'm worrying is passing file descriptor to unix bind or > connect routine. Because this approach doesn't provide easy way to > use such family and sockaddr in kernel (like in NFS example). >=20 > >But I think the simple scheme of: > >struct path old_root; > >old_root =3D current->fs.root; > >kernel_connect(...); > >current->fs.root =3D old_root; > > > >Is more than sufficient and will remove the need for anything > >except a purely local change to get nfs clients to connect from > >containers. > > >=20 > That was my first idea. So is this what you're planning on doing now? > And probably it would be worth to change all > fs_struct to support sockets with relative path. > What do you think about it? I didn't understand the question. Are you suggesting that changes to fs_struct would be required to make this work? I don't see why. --b.