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dbfb17a67f
Signed-off-by: Phil Sutter <phil@nwl.cc> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
70 lines
1.4 KiB
Groff
70 lines
1.4 KiB
Groff
.TH "Checksum action in tc" 8 "11 Jan 2015" "iproute2" "Linux"
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.SH NAME
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csum - checksum update action
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.SH SYNOPSIS
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.in +8
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.ti -8
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.BR tc " ... " "action csum"
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.I UPDATE
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.ti -8
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.IR UPDATE " := " TARGET " [ " UPDATE " ]"
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.ti -8
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.IR TARGET " := { "
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.BR ip4h " |"
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.BR icmp " |"
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.BR igmp " |"
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.BR tcp " |"
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.BR udp " |"
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.BR udplite " |"
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.IR SWEETS " }"
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.ti -8
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.IR SWEETS " := { "
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.BR and " | " or " | " + " }"
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.SH DESCRIPTION
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The
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.B csum
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action triggers checksum recalculation of specified packet headers. It is
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commonly used after packet editing using the
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.B pedit
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action to fix for then incorrect checksums.
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.SH OPTIONS
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.TP
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.I TARGET
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Specify which headers to update: IPv4 header
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.RB ( ip4h ),
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ICMP header
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.RB ( icmp ),
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IGMP header
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.RB ( igmp ),
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TCP header
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.RB ( tcp ),
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UDP header
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.RB ( udp ") or"
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UDPLite header
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.RB ( udplite ).
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.TP
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.B SWEETS
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These are merely syntactic sugar and ignored internally.
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.SH EXAMPLES
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The following performs stateless NAT for incoming packets from 192.168.1.100 to
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new destination 18.52.86.120 (0x12345678 in hex). Assuming these are UDP
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packets, both IP and UDP checksums have to be recalculated:
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.RS
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.EX
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# tc qdisc add dev eth0 ingress handle ffff:
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# tc filter add eth0 prio 1 protocol ip parent ffff: \\
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u32 match ip src 192.168.1.100/32 flowid :1 \\
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action pedit munge ip dst set 0x12345678 pipe \\
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csum ip and udp
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.EE
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.RE
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.SH SEE ALSO
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.BR tc (8),
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.BR tc-pedit (8)
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