1Checksum action in tc(8)             Linux            Checksum action in tc(8)
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NAME

6       csum - checksum update action
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SYNOPSIS

9       tc ... action csum UPDATE
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11       UPDATE := TARGET [ UPDATE ]
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13       TARGET := { ip4h | icmp | igmp | tcp | udp | udplite | sctp | SWEETS }
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15       SWEETS := { and | or | + }
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DESCRIPTION

18       The  csum  action  triggers  checksum recalculation of specified packet
19       headers. It is commonly used to fix incorrect checksums after the pedit
20       action has modified the packet content.
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OPTIONS

23       TARGET Specify which headers to update: IPv4 header (ip4h), ICMP header
24              (icmp), IGMP header (igmp), TCP header (tcp), UDP header  (udp),
25              UDPLite header (udplite) or SCTP header (sctp).
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27       SWEETS These are merely syntactic sugar and ignored internally.
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EXAMPLES

30       The   following  performs  stateless  NAT  for  incoming  packets  from
31       192.0.2.100 to new destination 198.51.100.1.  Assuming  these  are  UDP
32       packets, both IP and UDP checksums have to be recalculated:
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34              # tc qdisc add dev eth0 ingress handle ffff:
35              # tc filter add dev eth0 prio 1 protocol ip parent ffff: \
36                   u32 match ip src 192.0.2.100/32 flowid :1 \
37                   action pedit munge ip dst set 198.51.100.1 pipe \
38                   csum ip and udp
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SEE ALSO

42       tc(8), tc-pedit(8)
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46iproute2                          11 Jan 2015         Checksum action in tc(8)