| .TH "Checksum action in tc" 8 "11 Jan 2015" "iproute2" "Linux" |
| |
| .SH NAME |
| csum - checksum update action |
| .SH SYNOPSIS |
| .in +8 |
| .ti -8 |
| .BR tc " ... " "action csum" |
| .I UPDATE |
| |
| .ti -8 |
| .IR UPDATE " := " TARGET " [ " UPDATE " ]" |
| |
| .ti -8 |
| .IR TARGET " := { " |
| .BR ip4h " |" |
| .BR icmp " |" |
| .BR igmp " |" |
| .BR tcp " |" |
| .BR udp " |" |
| .BR udplite " |" |
| .BR sctp " |" |
| .IR SWEETS " }" |
| |
| .ti -8 |
| .IR SWEETS " := { " |
| .BR and " | " or " | " + " }" |
| .SH DESCRIPTION |
| The |
| .B csum |
| action triggers checksum recalculation of specified packet headers. It is |
| commonly used to fix incorrect checksums after the |
| .B pedit |
| action has modified the packet content. |
| .SH OPTIONS |
| .TP |
| .I TARGET |
| Specify which headers to update: IPv4 header |
| .RB ( ip4h ), |
| ICMP header |
| .RB ( icmp ), |
| IGMP header |
| .RB ( igmp ), |
| TCP header |
| .RB ( tcp ), |
| UDP header |
| .RB ( udp ), |
| UDPLite header |
| .RB ( udplite ") or" |
| SCTP header |
| .RB ( sctp ). |
| .TP |
| .B SWEETS |
| These are merely syntactic sugar and ignored internally. |
| .SH 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: |
| |
| .RS |
| .EX |
| # 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 |
| .EE |
| .RE |
| |
| .SH SEE ALSO |
| .BR tc (8), |
| .BR tc-pedit (8) |
