On 23.01.2017 16:35, Laine Stump wrote: > This has been requested several times in #virt on IRC, and on > libvirt-users, and a comment posted to > https://bugzilla.redhat.com/1224348 reminded me that there's even an > open BZ for it, so I finally sat down and wrote the patches for it. > > The idea of the patches is that an *empty* bridge device can't have > its MTU directly set to anything higher than 1500, but once there are > any devices on the bridge, its MTU is limited to the smallest of the > MTUs of any attached devices. However, when the very first device is > attached to the bridge, the bridge will *increase* its own MTU to > match if needed. So the trick to setting a high MTU is to set the MTU > of every device to the desired value before it is added (especially > the first). libvirt already sets the MTU of every device to the MTU of > the bridge, so all we need to do is make it so the first device is set > from the network config's "mtu" attribute instead - the bridge will > get the larger MTU, and all future devices added will get the higher > MTU as well. > > This doesn't take care of setting the MTU on the guest side of the tap > device; for now that must be done manually, but qemu has recently > added a commandline parameter to send the desired MTU to the guest, > and the virtio-net guest driver at least honors this. An upcoming > patch to libvirt will automatically set this qemu commandline option > so that no intervention will be required (beyond setting the MTU once > in the network config). > > > > Laine Stump (3): > util: add MTU arg to virNetDevTapCreateInBridgePort() > conf: support mtu attribute in a network's <bridge> element > network: honor mtu setting when creating network > > docs/formatnetwork.html.in | 8 +++++++- > docs/news.xml | 6 +++++- > docs/schemas/network.rng | 6 ++++++ > src/bhyve/bhyve_command.c | 2 +- > src/conf/network_conf.c | 20 ++++++++++++++++++-- > src/conf/network_conf.h | 1 + > src/network/bridge_driver.c | 1 + > src/qemu/qemu_interface.c | 2 +- > src/uml/uml_conf.c | 2 +- > src/util/virnetdevtap.c | 20 +++++++++++++++----- > src/util/virnetdevtap.h | 1 + > tests/bhyvexml2argvmock.c | 1 + > tests/networkxml2xmlin/set-mtu.xml | 11 +++++++++++ > tests/networkxml2xmlout/set-mtu.xml | 11 +++++++++++ > tests/networkxml2xmltest.c | 1 + > 15 files changed, 81 insertions(+), 12 deletions(-) > create mode 100644 tests/networkxml2xmlin/set-mtu.xml > create mode 100644 tests/networkxml2xmlout/set-mtu.xml > ACK series. I've given it some basic testing and it worked just fine. Incidentally, I've started working on this very same feature. But from the other side - from domain's POV. Michal -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
