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Re: [Xen-devel] [patch] xen udev rule interfering with openvpn
El 17/04/2012, a las 11:26, Ian Campbell escribió:
> On Mon, 2012-04-16 at 20:03 +0100, M A Young wrote:
>> There is a Fedora bug report
>> https://bugzilla.redhat.com/show_bug.cgi?id=812421 reporting that openvpn
>> is having problems because of the line
>> SUBSYSTEM=="net", KERNEL=="tap*", ACTION=="add",
>> RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
>> in /etc/udev/rules.d/xen-backend.rules which is causing the xen script to
>> run when openvpn tries to use a tap device, causing it to fail. I have
>> used the attached patch to solve this problem, by matching the form of the
>> tap device that xen uses more exactly to avoid to openvpn case. A better
>> long-term solution (suggested in one of the comments in the bug) might be
>> to use a more specific name instead of "tap" so we have less chance of
>> interfering with another application.
>
> This is a good start, I think we should do this for 4.2.
>
> Changing the name might be pretty simple though e.g. the following.
> Works for me with xl but I didn't try xend (seems "obviously correct"?)
>
> I noticed that when vifname is set xend prepends "tap-" (presumably to
> distinguish it from the vif device) whereas libxl does not, so I suspect
> named vifs for HVM guests don't work so well, I fixed that while I was
> there...
>
> Also at least for the libxl case we will likely not be running these
> hotplug scripts via udev any more in 4.2, however I don't think there is
> any harm in making this change first (iff we decide it is suitable for
> 4.2).
>
> Ian.
>
> # HG changeset patch
> # User Ian Campbell <ian.campbell@xxxxxxxxxx>
> # Date 1334658366 -3600
> # Node ID de3e65d804cceab7291e2accc18d50ae8b816433
> # Parent 8d92d1f34921c8675d85c74aa36e319c9451f68f
> libxl/xend: name tap devices with a xentap prefix
>
> This prevents the udev scripts from operating on other tap devices (e.g.
> openvpn etc)
>
> Also add "xentap-" prefix to the tap device when an explicit name is given to
> avoid a conflict with the vif device, which would otherwise have the same
> name.
> Likewise correct the documentation for this option which suggested it applied
> to HVM tap devices only.
>
> Reported by Michael Young.
>
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Acked-by: Roger Pau Monne <roger.pau@xxxxxxxxxx>
I've already changed my hotplug series to match this change in the udev rules,
so this has to go in before mine.
>
> diff -r 8d92d1f34921 -r de3e65d804cc
> docs/misc/xl-network-configuration.markdown
> --- a/docs/misc/xl-network-configuration.markdown Mon Apr 16 17:57:00
> 2012 +0100
> +++ b/docs/misc/xl-network-configuration.markdown Tue Apr 17 11:26:06
> 2012 +0100
> @@ -93,11 +93,14 @@ are:
>
> ### vifname
>
> -This keyword is valid for HVM guest devices with `type=ioemu` only.
> +Specifies the backend device name for the virtual device.
>
> -Specifies the backend device name for an emulated device. The default
> -is `tapDOMID.DEVID` where `DOMID` is the guest domain ID and `DEVID`
> -is the device number.
> +If the domain is an HVM domain then the associated emulated (tap)
> +device will have a "xentap-" prefix added.
> +
> +The default name for the virtual device is `vifDOMID.DEVID` where
> +`DOMID` is the guest domain ID and `DEVID` is the device
> +number. Likewise the default tap name is `xentapDOMID.DEVID`.
>
> ### script
>
> diff -r 8d92d1f34921 -r de3e65d804cc tools/hotplug/Linux/vif-common.sh
> --- a/tools/hotplug/Linux/vif-common.sh Mon Apr 16 17:57:00 2012 +0100
> +++ b/tools/hotplug/Linux/vif-common.sh Tue Apr 17 11:26:06 2012 +0100
> @@ -85,8 +85,8 @@ elif [ "$type_if" = tap ]; then
> : ${INTERFACE:?}
>
> # Get xenbus_path from device name.
> - # The name is built like that: "tap${domid}.${devid}".
> - dev_=${dev#tap}
> + # The name is built like that: "xentap${domid}.${devid}".
> + dev_=${dev#xentap}
> domid=${dev_%.*}
> devid=${dev_#*.}
>
> diff -r 8d92d1f34921 -r de3e65d804cc tools/hotplug/Linux/xen-backend.rules
> --- a/tools/hotplug/Linux/xen-backend.rules Mon Apr 16 17:57:00 2012 +0100
> +++ b/tools/hotplug/Linux/xen-backend.rules Tue Apr 17 11:26:06 2012 +0100
> @@ -13,4 +13,4 @@ KERNEL=="blktap-control", NAME="xen/blkt
> KERNEL=="gntdev", NAME="xen/%k", MODE="0600"
> KERNEL=="pci_iomul", NAME="xen/%k", MODE="0600"
> KERNEL=="tapdev[a-z]*", NAME="xen/blktap-2/tapdev%m", MODE="0600"
> -SUBSYSTEM=="net", KERNEL=="tap*", ACTION=="add",
> RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
> +SUBSYSTEM=="net", KERNEL=="xentap*", ACTION=="add",
> RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
> diff -r 8d92d1f34921 -r de3e65d804cc tools/libxl/libxl_dm.c
> --- a/tools/libxl/libxl_dm.c Mon Apr 16 17:57:00 2012 +0100
> +++ b/tools/libxl/libxl_dm.c Tue Apr 17 11:26:06 2012 +0100
> @@ -212,9 +212,9 @@ static char ** libxl__build_device_model
> char *ifname;
> if (!vifs[i].ifname)
> ifname = libxl__sprintf(gc,
> - "tap%d.%d", domid,
> vifs[i].devid);
> + "xentap%d.%d", domid,
> vifs[i].devid);
> else
> - ifname = vifs[i].ifname;
> + ifname = libxl__sprintf(gc, "xentap-%s", vifs[i].ifname);
> flexarray_vappend(dm_args,
> "-net", libxl__sprintf(gc,
> "nic,vlan=%d,macaddr=%s,model=%s",
> vifs[i].devid, smac,
> vifs[i].model),
> @@ -451,10 +451,10 @@ static char ** libxl__build_device_model
> LIBXL_MAC_FMT, LIBXL_MAC_BYTES(vifs[i].mac));
> char *ifname;
> if (!vifs[i].ifname) {
> - ifname = libxl__sprintf(gc, "tap%d.%d",
> + ifname = libxl__sprintf(gc, "xentap%d.%d",
> guest_domid, vifs[i].devid);
> } else {
> - ifname = vifs[i].ifname;
> + ifname = libxl__sprintf(gc, "xentap-%s", vifs[i].ifname);
> }
> flexarray_append(dm_args, "-device");
> flexarray_append(dm_args,
> diff -r 8d92d1f34921 -r de3e65d804cc tools/python/xen/xend/image.py
> --- a/tools/python/xen/xend/image.py Mon Apr 16 17:57:00 2012 +0100
> +++ b/tools/python/xen/xend/image.py Tue Apr 17 11:26:06 2012 +0100
> @@ -921,7 +921,7 @@ class HVMImageHandler(ImageHandler):
> if vifname:
> vifname = "tap-" + vifname
> else:
> - vifname = "tap%d.%d" % (self.vm.getDomid(), nics-1)
> + vifname = "xentap%d.%d" % (self.vm.getDomid(), nics-1)
> ret.append("-net")
> ret.append("tap,vlan=%d,ifname=%s,bridge=%s" %
> (nics, vifname, bridge))
>
>
>
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