Checksum action in tc(8)					       Linux						  Checksum action in tc(8)

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)

iproute2							    11 Jan 2015 					  Checksum action in tc(8)