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Add the tun mounting with vhost is requested #394

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Nov 16, 2021
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Add the tun mounting with vhost is requested #394

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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -232,7 +232,7 @@ This selector is applicable when "deviceType" is "netDevice"(note: this is defau
| "linkTypes" | N | The link type of the net device associated with the PCI device | `string` list Default: `null` | "linkTypes": ["ether"] |
| "ddpProfiles" | N | A map of device selectors | `string` list Default: `null` | "ddpProfiles": ["GTPv1-C/U IPv4/IPv6 payload"] |
| "isRdma" | N | Mount RDMA resources | `bool` values `true` or `false` Default: `false` | "isRdma": `true` |
| "needVhostNet"| N | Share /dev/vhost-net | `bool` values `true` or `false` Default: `false` | "needVhostNet": `true` |
| "needVhostNet"| N | Share /dev/vhost-net and /dev/net/tun | `bool` values `true` or `false` Default: `false` | "needVhostNet": `true` |


[//]: # (The tables above generated using: https://ozh.github.io/ascii-tables/)
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10 changes: 9 additions & 1 deletion pkg/netdevice/netInfoProviders.go
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Expand Up @@ -76,7 +76,15 @@ func (rip *vhostNetInfoProvider) GetDeviceSpecs() []*pluginapi.DeviceSpec {
glog.Errorf("GetDeviceSpecs(): /dev/vhost-net doesn't exist")
return nil
}
return GetVhostNetDeviceSpec()
deviceSpec := GetVhostNetDeviceSpec()

if !TunDeviceExist() {
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@adrianchiris adrianchiris Nov 2, 2021 •
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This means we now require /dev/net/tun to exist when needVhostNet is set to true in resource config.

is there no use-case for vhost-net without tun device ? (there must be because that how it was working before :))

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Thanks for the comment!

That was my question I am not aware from our side of any use case that we use vhost until now.
Now we have a use-case (dpdk slow path/ vpp) there is a need to create a tap device and for that, the tun device should be available inside the pod.

The other solution is to have a new flag for the tun device but I will like to know if there is a use-case for only vhost-net mount if not I don't see a reason to create another flag to will be always equal to the vhost one

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With our use case, we also need /dev/net/tun, it is exported to via:
volumes:
- hostPath:
path: /dev/net/tun
type: ""
name: net

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@amorenoz I see you also participated in discussions on the original vhostNet support PR #228
any thoughts on this ? do you see a case where we need vhost but not /dev/net/tun ?

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Not with upstream DPDK. The vhost-net (virtio-user) PMD creates a tap device and configures it as the backend of the vhost-net device.

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ack, thanks for the input. if all use-cases sift down to needing tun as well, to me it makes sense to provide it as a mount when needVhostNet is specified.

lets see if we get additional inputs, maybe raise this in one of the NPWG network resource mgmt meeting ?

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I will do it at the next meeting thanks everyone for the inputs!

glog.Errorf("GetDeviceSpecs(): /dev/net/tun doesn't exist")
return nil
}
deviceSpec = append(deviceSpec, GetTunDeviceSpec()...)

return deviceSpec
}

func (rip *vhostNetInfoProvider) GetEnvVal() string {
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2 changes: 1 addition & 1 deletion pkg/netdevice/pciNetDevice_test.go
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Expand Up @@ -247,7 +247,7 @@ var _ = Describe("PciNetDevice", func() {
Expect(dev.GetDriver()).To(Equal("vfio-pci"))
Expect(dev.GetNetName()).To(Equal(""))
Expect(dev.GetEnvVal()).To(Equal("0000:00:00.1"))
Expect(dev.GetDeviceSpecs()).To(HaveLen(3)) // /dev/vfio/vfio0 and default /dev/vfio/vfio + vhost-net
Expect(dev.GetDeviceSpecs()).To(HaveLen(4)) // /dev/vfio/vfio0 and default /dev/vfio/vfio + vhost-net + tun
Expect(dev.GetRdmaSpec().IsRdma()).To(BeFalse())
Expect(dev.GetRdmaSpec().GetRdmaDeviceSpec()).To(HaveLen(0))
Expect(dev.GetLinkType()).To(Equal(""))
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18 changes: 18 additions & 0 deletions pkg/netdevice/vhostNet.go
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Expand Up @@ -23,3 +23,21 @@ func GetVhostNetDeviceSpec() []*pluginapi.DeviceSpec {

return deviceSpec
}

// TunDeviceExist returns true if /dev/net/tun exists
func TunDeviceExist() bool {
_, err := os.Stat("/dev/net/tun")
return err == nil
}

// GetTunDeviceSpec returns an instance of DeviceSpec for Tun
func GetTunDeviceSpec() []*pluginapi.DeviceSpec {
deviceSpec := make([]*pluginapi.DeviceSpec, 0)
deviceSpec = append(deviceSpec, &pluginapi.DeviceSpec{
HostPath: "/dev/net/tun",
ContainerPath: "/dev/net/tun",
Permissions: "mrw",
})

return deviceSpec
}