Provided by: iproute2_4.15.0-2ubuntu1.3_amd64 
NAME
csum - checksum update action
SYNOPSIS
tc ... action csum UPDATE
UPDATE := TARGET [ UPDATE ]
TARGET := { ip4h | icmp | igmp | tcp | udp | udplite | sctp | SWEETS }
SWEETS := { and | or | + }
DESCRIPTION
The csum action triggers checksum recalculation of specified packet headers. It is commonly used to fix
incorrect checksums after the pedit action has modified the packet content.
OPTIONS
TARGET Specify which headers to update: IPv4 header (ip4h), ICMP header (icmp), IGMP header (igmp), TCP
header (tcp), UDP header (udp), UDPLite header (udplite) or SCTP header (sctp).
SWEETS These are merely syntactic sugar and ignored internally.
EXAMPLES
The following performs stateless NAT for incoming packets from 192.0.2.100 to new destination
198.51.100.1. Assuming these are UDP packets, both IP and UDP checksums have to be recalculated:
# tc qdisc add dev eth0 ingress handle ffff:
# tc filter add dev eth0 prio 1 protocol ip parent ffff: \
u32 match ip src 192.0.2.100/32 flowid :1 \
action pedit munge ip dst set 198.51.100.1 pipe \
csum ip and udp
SEE ALSO
tc(8), tc-pedit(8)