Neale Ranns
616447c392
Type: feature please see FEATURE.yaml for details. Signed-off-by: Neale Ranns <nranns@cisco.com> Signed-off-by: Matthew Smith <mgsmith@netgate.com> Signed-off-by: Jon Loeliger <jdl@netgate.com> Signed-off-by: Pim van Pelt <pim@ipng.nl> Signed-off-by: Neale Ranns <neale@graphiant.com> Change-Id: I6255fd9953d0b03e6b4fe75b67a6845a7c206f74 Signed-off-by: Pim van Pelt <pim@ipng.nl>
94 lines
3.4 KiB
ReStructuredText
94 lines
3.4 KiB
ReStructuredText
.. _Linux_control_plane:
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.. toctree::
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Linux Control Plane Integration
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===============================
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Overview
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________
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This plugin allows VPP to integrate with the Linux kernel. The
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general model is that Linux is the network stack, i.e. it has the
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control plane protocols, like ARP, IPv6 ND/MLD, ping, etc, and VPP
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provides a SW based ASIC for forwarding.
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Interfaces
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__________
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VPP owns the interfaces in the system; physical (.e.g PCI), quasi
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physical (e.g. vhost), or virtual (e.g. tunnel). However,
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for the Linux networking stack to function it needs a representation
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of these interfaces; it needs a mirror image in the kernel. For this
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mirror we use a TAP interface, if the VPP interface is multi-point, a
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TUN if it's point-to-point. A physical and its mirror form an
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interface 'pair'.
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The host interface has two identities; the sw_if_index of the TAP and
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the virtual interface index in the kernel. It may be in a Linux network
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namespace.
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The creation of the interface pairs is required from the control
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plane. It can be statically configured in the VPP startup
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configuration file. The intent here is to make the pair creation
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explicit, rather than have VPP guess which of the interfaces it owns
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require a mirror.
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Configuration
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_____________
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Linux will send and receive packets on the mirrored tap/tun
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interfaces. Any configuration that is made on these Linux interfaces,
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also needs to be applied on the corresponding physical interface in
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VPP.
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This is functionality is provided by the "linux_nl" plugin.
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Linux will own the [ARP/ND] neighbor tables (which will be copied via
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netlink to VPP also). This means that Linux will send packets with the
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peer's MAC address in the rewrite to VPP. The receiving TAP interface
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must therefore be in promiscuous mode.
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Forwarding
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__________
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The basic principle is to x-connect traffic from a Linux host interface
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(received on the tap/tun) to its paired the physical, and vice-versa.
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Host to Physical
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^^^^^^^^^^^^^^^^
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All packets sent by the host, and received by VPP on a tap/tun should
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be sent to its paired physical interface. However, they should be sent
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with the same consequences as if they had originated from VPP,
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i.e. they should be subject to all output features on the physical
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interface. To achieve this there is a per-IP-address-family (AF) node
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inserted in the per-AF input feature arc. The node must be per-AF,
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since it must be a sibling of a start node for the ipX-output feature
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arc. This node uses the packet's L2 rewrite to search for the
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adjacency that VPP would have used to send this packet; this adjacency
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is stored in the buffer's meta data so that it is available to all
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output features. Then the packet is sent through the physical
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interface's IP output feature arc.
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All ARP packets are x-connected from the tap to the physical.
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Physical to Host
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^^^^^^^^^^^^^^^^
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All ARP packets received on the physical are sent to the paired
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tap. This allows the Linux network stack to build the neighbor table.
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IP packets that are punted are sent to the host. They are sent on the
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tap that is paired with the physical on which they were originally
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received. The packet is sent on the tap/tun 'exactly' as it was
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received (i.e. with the L2 rewrite) but post any translations that
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input features may have made.
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Recommendations
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^^^^^^^^^^^^^^^
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When using this plugin disable the ARP, ND, IGMP plugins; this is the
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task for Linux. Disable ping plugin, since Linux will now respond.
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