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Tunnel metadata manipulation action in tc

Section: Linux (8)
Updated: 10 Nov 2016
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NAME

tunnel_key - Tunnel metadata manipulation

SYNOPSIS

tc ... action tunnel_key { unset | SET }

SET := set src_ip ADDRESS dst_ip ADDRESS id KEY_ID dst_port UDP_PORT [ csum | nocsum ]

DESCRIPTION

The tunnel_key action combined with a shared IP tunnel device, allows to perform IP tunnel en- or decapsulation on a packet, reflected by the operation modes UNSET and SET. The UNSET mode is optional - even without using it, the metadata information will be released automatically when packet processing will be finished. UNSET function could be used in cases when traffic is forwarded between two tunnels, where the metadata from the first tunnel will be used for encapsulation done by the second tunnel. SET mode requires the source and destination ip ADDRESS and the tunnel key id KEY_ID which will be used by the ip tunnel shared device to create the tunnel header. The tunnel_key action is useful only in combination with a mirred redirect action to a shared IP tunnel device which will use the metadata (for SET ) and unset the metadata created by it (for UNSET ).

OPTIONS

unset

Unset the tunnel metadata created by the IP tunnel device. This function is not mandatory and might be used only in some specific use cases (as explained above).

set

Set tunnel metadata to be used by the IP tunnel device. Requires id , src_ip and dst_ip options. dst_port is optional.

id: Tunnel ID (for example VNI in VXLAN tunnel)
src_ip: Outer header source IP address (IPv4 or IPv6)
dst_ip: Outer header destination IP address (IPv4 or IPv6)
dst_port: Outer header destination UDP port
[no]csum: Controlls outer UDP checksum. When set to csum (which is default), the outer UDP checksum is calculated and included in the packets. When set to nocsum, outer UDP checksum is zero. Note that when using zero UDP checksums with IPv6, the other tunnel endpoint must be configured to accept such packets. In Linux, this would be the udp6zerocsumrx option for the VXLAN tunnel interface.
: If using nocsum with IPv6, be sure you know what you are doing. Zero UDP checksums provide weaker protection against corrupted packets. See RFC6935 for details.

EXAMPLES

The following example encapsulates incoming ICMP packets on eth0 into a vxlan tunnel, by setting metadata to VNI 11, source IP 11.11.0.1 and destination IP 11.11.0.2, and by redirecting the packet with the metadata to device vxlan0, which will do the actual encapsulation using the metadata:

: #tc qdisc add dev eth0 handle ffff: ingress #tc filter add dev eth0 protocol ip parent ffff: \
  flower \
    ip_proto icmp \
  action tunnel_key set \
    src_ip 11.11.0.1 \
    dst_ip 11.11.0.2 \
    id 11 \
  action mirred egress redirect dev vxlan0

Here is an example of the unset function: Incoming VXLAN traffic with outer IP's and VNI 11 is decapsulated by vxlan0 and metadata is unset before redirecting to tunl1 device:

: #tc qdisc add dev eth0 handle ffff: ingress #tc filter add dev vxlan0 protocol ip parent ffff:
flower \ enc_src_ip 11.11.0.2 enc_dst_ip 11.11.0.1 enc_key_id 11 action tunnel_key unset action mirred egress redirect dev tunl1