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1.. SPDX-License-Identifier: GPL-2.02 3========================================4Bare UDP Tunnelling Module Documentation5========================================6 7There are various L3 encapsulation standards using UDP being discussed to8leverage the UDP based load balancing capability of different networks.9MPLSoUDP (__ https://tools.ietf.org/html/rfc7510) is one among them.10 11The Bareudp tunnel module provides a generic L3 encapsulation support for12tunnelling different L3 protocols like MPLS, IP, NSH etc. inside a UDP tunnel.13 14Special Handling15----------------16The bareudp device supports special handling for MPLS & IP as they can have17multiple ethertypes.18MPLS procotcol can have ethertypes ETH_P_MPLS_UC (unicast) & ETH_P_MPLS_MC (multicast).19IP protocol can have ethertypes ETH_P_IP (v4) & ETH_P_IPV6 (v6).20This special handling can be enabled only for ethertypes ETH_P_IP & ETH_P_MPLS_UC21with a flag called multiproto mode.22 23Usage24------25 261) Device creation & deletion27 28 a) ip link add dev bareudp0 type bareudp dstport 6635 ethertype mpls_uc29 30 This creates a bareudp tunnel device which tunnels L3 traffic with ethertype31 0x8847 (MPLS traffic). The destination port of the UDP header will be set to32 6635.The device will listen on UDP port 6635 to receive traffic.33 34 b) ip link delete bareudp035 362) Device creation with multiproto mode enabled37 38The multiproto mode allows bareudp tunnels to handle several protocols of the39same family. It is currently only available for IP and MPLS. This mode has to40be enabled explicitly with the "multiproto" flag.41 42 a) ip link add dev bareudp0 type bareudp dstport 6635 ethertype ipv4 multiproto43 44 For an IPv4 tunnel the multiproto mode allows the tunnel to also handle45 IPv6.46 47 b) ip link add dev bareudp0 type bareudp dstport 6635 ethertype mpls_uc multiproto48 49 For MPLS, the multiproto mode allows the tunnel to handle both unicast50 and multicast MPLS packets.51 523) Device Usage53 54The bareudp device could be used along with OVS or flower filter in TC.55The OVS or TC flower layer must set the tunnel information in SKB dst field before56sending packet buffer to the bareudp device for transmission. On reception the57bareudp device extracts and stores the tunnel information in SKB dst field before58passing the packet buffer to the network stack.59