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authorAndrew Yourtchenko <ayourtch@gmail.com>2018-10-12 16:09:22 +0200
committerDamjan Marion <dmarion@me.com>2019-02-19 12:47:40 +0000
commit6a7cff7ec234af8529ff72a530076e191cc8d759 (patch)
treeea7a9bf447385172d0d3fda382aebf2d0203ecc8 /build-data
parentbe30fea370ed7cfe6a4a1b154a944411ec3eabd0 (diff)
tap gso: experimental support
This commit adds a "gso" parameter to existing "create tap..." CLI, and a "no-gso" parameter for the compatibility with the future, when/if defaults change. It makes use of the lowest bit of the "tap_flags" field in the API call in order to allow creation of GSO interfaces via API as well. It does the necessary syscalls to enable the GSO and checksum offload support on the kernel side and sets two flags on the interface: virtio-specific virtio_if_t.gso_enabled, and vnet_hw_interface_t.flags & VNET_HW_INTERFACE_FLAG_SUPPORTS_GSO. The first one, if enabled, triggers the marking of the GSO-encapsulated packets on ingress with VNET_BUFFER_F_GSO flag, and setting vnet_buffer2(b)->gso_size to the desired L4 payload size. VNET_HW_INTERFACE_FLAG_SUPPORTS_GSO determines the egress packet processing in interface-output for such packets: When the flag is set, they are sent out almost as usual (just taking care to set the vnet header for virtio). When the flag is not enabled (the case for most interfaces), the egress path performs the re-segmentation such that the L4 payload of the transmitted packets equals gso_size. The operations in the datapath are enabled only when there is at least one GSO-compatible interface in the system - this is done by tracking the count in interface_main.gso_interface_count. This way the impact of conditional checks for the setups that do not use GSO is minimized. "show tap" CLI shows the state of the GSO flag on the interface, and the total count of GSO-enabled interfaces (which is used to enable the GSO-related processing in the packet path). This commit lacks IPv6 extension header traversal support of any kind - the L4 payload is assumed to follow the IPv6 header. Also it performs the offloads only for TCP (TSO - TCP segmentation offload). The UDP fragmentation offload (UFO) is not part of it. For debug purposes it also adds the debug CLI: "set tap gso {<interface> | sw_if_index <sw_idx>} <enable|disable>" Change-Id: Ifd562db89adcc2208094b3d1032cee8c307aaef9 Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>
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