Checksum action in tc
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
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)