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Message-ID: <20150608210247.GB27887@fieldses.org> Date: Mon, 8 Jun 2015 17:02:47 -0400 From: "J. Bruce Fields" <bfields@...ldses.org> To: Stefan Hajnoczi <stefanha@...hat.com> Cc: linux-nfs@...r.kernel.org, Anna Schumaker <anna.schumaker@...app.com>, Trond Myklebust <trond.myklebust@...marydata.com>, asias.hejun@...il.com, netdev@...r.kernel.org, Daniel Berrange <berrange@...hat.com>, "David S. Miller" <davem@...emloft.net> Subject: Re: [RFC 00/10] NFS: add AF_VSOCK support to NFS client On Thu, Jun 04, 2015 at 05:45:43PM +0100, Stefan Hajnoczi wrote: > This patch series enables AF_VSOCK address family support in the NFS client. > Please use the https://github.com/stefanha/linux.git vsock-nfs branch, which > contains the dependencies for this series. > > The AF_VSOCK address family provides dgram and stream socket communication > between virtual machines and hypervisors. A VMware VMCI transport is currently > available in-tree (see net/vmw_vsock) and I have posted virtio-vsock patches > for use with QEMU/KVM: http://thread.gmane.org/gmane.linux.network/365205 > > The goal of this work is sharing files between virtual machines and > hypervisors. AF_VSOCK is well-suited to this because it requires no > configuration inside the virtual machine, making it simple to manage and > reliable. > > Why NFS over AF_VSOCK? > ---------------------- > It is unusual to add a new NFS transport, only TCP, RDMA, and UDP are currently > supported. Here is the rationale for adding AF_VSOCK. > > Sharing files with a virtual machine can be configured manually: > 1. Add a dedicated network card to the virtual machine. It will be used for > NFS traffic. > 2. Configure a local subnet and assign IP addresses to the virtual machine and > hypervisor > 3. Configure an NFS export on the hypervisor and start the NFS server > 4. Mount the export inside the virtual machine > > Automating these steps poses a problem: modifying network configuration inside > the virtual machine is invasive. It's hard to add a network interface to an > arbitrary running system in an automated fashion, considering the network > management tools, firewall rules, IP address usage, etc. > > Furthermore, the user may disrupt file sharing by accident when they add > firewall rules, restart networking, etc because the NFS network interface is > visible alongside the network interfaces managed by the user. > > AF_VSOCK is a zero-configuration network transport that avoids these problems. > Adding it to a virtual machine is non-invasive. It also avoids accidental > misconfiguration by the user. This is why "guest agents" and other services in > various hypervisors (KVM, Xen, VMware, VirtualBox) do not use regular network > interfaces. > > This is why AF_VSOCK is appropriate for providing shared files as a hypervisor > service. > > The approach in this series > --------------------------- > AF_VSOCK stream sockets can be used for NFSv4.1 much in the same way as TCP. > RFC 1831 record fragments divide messages since SOCK_STREAM semantics are > present. The backchannel shares the connection just like the default TCP > configuration. So the NFSv4 backchannel isn't handled for now, I assume. And I guess NFSv2/v3 is out too thanks to rpcbind? Which maybe is fine. Do we need an IETF draft or similar to document how NFS should work over AF_VSOCK? NFS developers rely heavily on wireshark (and similar tools) for debugging. Is that still possible over AF_VSOCK? > Addresses are <Context ID, Port Number> pairs. These patches use "vsock:<cid>" > string representation to distinguish AF_VSOCK addresses from IPv4 and IPv6 > numeric addresses. > > The patches cover the following areas: > > Patch 1 - support struct sockaddr_vm in sunrpc addr.h > > Patch 2-4 - make sunrpc TCP record fragment parser reusable for any stream > socket > > Patch 5 - add tcp_read_sock()-like interface to AF_VSOCK sockets > > Patch 6 - extend sunrpc xprtsock.c for AF_VSOCK RPC clients > > Patch 7-9 - AF_VSOCK backchannel support > > Patch 10 - add AF_VSOCK support to NFS client > > The following example mounts /export from the hypervisor (CID 2) inside the > virtual machine (CID 3): > > # /sbin/mount.nfs 2:/export /mnt -o clientaddr=3,proto=vsock > > Status > ------ > I am looking for feedback on this approach. There are TODOs remaining in the code. > > Hopefully the way I add AF_VSOCK support to sunrpc is reasonable and something > that can be standardized (a netid assigned and the uaddr string format decided). > > See below for the nfs-utils patch. It can be made nice once glibc > getnameinfo()/getaddrinfo() support AF_VSOCK. > > The vsock_read_sock() implementation is dumb. Less of a NFS/SUNRPC issue and > more of a vsock issue, but perhaps virtio_transport.c should use skbs for its > receive queue instead of a custom packet struct. That would eliminate memory > allocation and copying in vsock_read_sock(). > > The next step is tackling NFS server. In the meantime, I have tested the > patches using the nc-vsock netcat-like utility that is available in my Linux > kernel repo below. So by a netcat-like utility, you mean it's proxying between client and a server so the client thinks the server is communicating over AF_VSOCK and the server thinks the client is using TCP? (Sorry, I haven't looked at the code.) Once we have a server and client, how will you recommend testing them? (Will the server side need to run on real hardware?) I guess if it works then the main question is whether it's worth supporting another transport type in order to get the zero-configuration host<->guest NFS setup. Or whether there's another way to get the same gains. Seems like a useful thing to have. --b. > > Repositories > ------------ > * Linux kernel: https://github.com/stefanha/linux.git vsock-nfs > * QEMU virtio-vsock device: https://github.com/stefanha/qemu.git vsock > * nfs-utils vsock: https://github.com/stefanha/nfs-utils.git vsock > > Stefan Hajnoczi (10): > SUNRPC: add AF_VSOCK support to addr.h > SUNRPC: rename "TCP" record parser to "stream" parser > SUNRPC: abstract tcp_read_sock() in record fragment parser > SUNRPC: extract xs_stream_reset_state() > VSOCK: add tcp_read_sock()-like vsock_read_sock() function > SUNRPC: add AF_VSOCK support to xprtsock.c > SUNRPC: restrict backchannel svc IPPROTO_TCP check to IP > SUNRPC: add vsock-bc backchannel > SUNRPC: add AF_VSOCK support to svc_xprt.c > NFS: add AF_VSOCK support to NFS client > > drivers/vhost/vsock.c | 1 + > fs/nfs/callback.c | 7 +- > fs/nfs/client.c | 16 + > fs/nfs/super.c | 10 + > include/linux/sunrpc/addr.h | 6 + > include/linux/sunrpc/svc_xprt.h | 12 + > include/linux/sunrpc/xprt.h | 1 + > include/linux/sunrpc/xprtsock.h | 37 +- > include/linux/virtio_vsock.h | 4 + > include/net/af_vsock.h | 5 + > include/trace/events/sunrpc.h | 30 +- > net/sunrpc/addr.c | 57 +++ > net/sunrpc/svc.c | 13 +- > net/sunrpc/svc_xprt.c | 13 + > net/sunrpc/svcsock.c | 48 ++- > net/sunrpc/xprtsock.c | 693 +++++++++++++++++++++++++------- > net/vmw_vsock/af_vsock.c | 15 + > net/vmw_vsock/virtio_transport.c | 1 + > net/vmw_vsock/virtio_transport_common.c | 55 +++ > net/vmw_vsock/vmci_transport.c | 8 + > 20 files changed, 825 insertions(+), 207 deletions(-) > > -- > 2.4.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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