1.. SPDX-License-Identifier: GPL-2.0 2 3======================================== 4Bare UDP Tunnelling Module Documentation 5======================================== 6 7There are various L3 encapsulation standards using UDP being discussed to 8leverage 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 for 12tunnelling different L3 protocols like MPLS, IP, NSH etc. inside a UDP tunnel. 13 14Special Handling 15---------------- 16 17The bareudp device supports special handling for MPLS & IP as they can have 18multiple ethertypes. 19The MPLS protocol can have ethertypes ETH_P_MPLS_UC (unicast) & ETH_P_MPLS_MC (multicast). 20IP protocol can have ethertypes ETH_P_IP (v4) & ETH_P_IPV6 (v6). 21This special handling can be enabled only for ethertypes ETH_P_IP & ETH_P_MPLS_UC 22with a flag called multiproto mode. 23 24Usage 25------ 26 271) Device creation & deletion 28 29 a) ip link add dev bareudp0 type bareudp dstport 6635 ethertype mpls_uc 30 31 This creates a bareudp tunnel device which tunnels L3 traffic with ethertype 32 0x8847 (MPLS traffic). The destination port of the UDP header will be set to 33 6635.The device will listen on UDP port 6635 to receive traffic. 34 35 b) ip link delete bareudp0 36 372) Device creation with multiproto mode enabled 38 39The multiproto mode allows bareudp tunnels to handle several protocols of the 40same family. It is currently only available for IP and MPLS. This mode has to 41be enabled explicitly with the "multiproto" flag. 42 43 a) ip link add dev bareudp0 type bareudp dstport 6635 ethertype ipv4 multiproto 44 45 For an IPv4 tunnel the multiproto mode allows the tunnel to also handle 46 IPv6. 47 48 b) ip link add dev bareudp0 type bareudp dstport 6635 ethertype mpls_uc multiproto 49 50 For MPLS, the multiproto mode allows the tunnel to handle both unicast 51 and multicast MPLS packets. 52 533) Device Usage 54 55The bareudp device could be used along with OVS or flower filter in TC. 56The OVS or TC flower layer must set the tunnel information in the SKB dst field before 57sending the packet buffer to the bareudp device for transmission. On reception, the 58bareUDP device extracts and stores the tunnel information in the SKB dst field before 59passing the packet buffer to the network stack. 60