A userspace switch for virtual machines.

• Prerequisites

  sv3 currently only supports Linux on x86-64 with Qemu/KVM as virtualization layer. It also needs a relatively recent kernel, at least 3.6, but it hasn't been tested with anything older than 3.9.

• Building

** Qemu

The switch needs a patched qemu. Build it using:

#+BEGIN_SRC sh git submodule init git submodule update

cd contrib/qemu ./configure --target-list=x86_64-softmmu --enable-kvm --disable-fdt make #+END_SRC

** Switch

Execute =scons=. If you installed prerequisite libraries after you first scons run, you might have to do =scons --config=force= afterwards.

• Usage

** Starting a Guest

Start the switch and attach a guest using:

#+BEGIN_SRC sh ./sv3

Switch to another terminal

export PATH=$PWD/contrib/qemu/x86_64-softmmu:$PATH qemu-system-x86_64 -mem-path /tmp -net none -device externalpci,socket=/tmp/sv3 additional-args... #+END_SRC

Adding =-mem-path /tmp= to qemu is important, because it will create files there that serve as backing store for RAM. /tmp should be a tmpfs! If this is not the case, guest RAM will be periodically written to disk.

** Creating an Upstream Port

By default, the switch is not connected to the outside world. You need an upstream port to do this. sv3 is able to drive network cards itself, but needs some preparation. Currently, sv3 can drive a single upstream port at a time.

If the PCI ID of the desired network card is 0000:02:00.1 and the user that runs the switch is john, use =scripts/vfio-rebind.sh= like this:

#+BEGIN_SRC sh sudo ./scripts/vfio-rebind.sh 0000:02:00.1 john #+END_SRC

This will unload the device's driver and attach it to VFIO with access rights for john. The script might tell you to rebind unrelated devices as well to make the IOMMU happy.

Currently, sv3 supports Intel 82599 10G "Niantic" NICs (sold as x520).

• Known Bugs

• The switch will segfault, if passed file descriptors point to files that are too short.
• The switch sometimes segfaults when clients disappear unexpectedly.

L4 checksums are wrong in the presence of option headers. But this code is not used right now.