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| -rw-r--r-- | man/man8/tc-skbmod.8 | 160 |
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diff --git a/man/man8/tc-skbmod.8 b/man/man8/tc-skbmod.8 new file mode 100644 index 0000000..646a7e6 --- /dev/null +++ b/man/man8/tc-skbmod.8 @@ -0,0 +1,160 @@ +.TH "skbmod action in tc" 8 "21 Sep 2016" "iproute2" "Linux" + +.SH NAME +skbmod - user-friendly packet editor action +.SH SYNOPSIS +.in +8 +.ti -8 +.BR tc " ... " "action skbmod " "{ " "set " +.IR SETTABLE " | " +.BI swap " SWAPPABLE" +.RB " | " ecn +.RI "} [ " CONTROL " ] [ " +.BI index " INDEX " +] + +.ti -8 +.IR SETTABLE " := " +.RB " [ " dmac +.IR DMAC " ] " +.RB " [ " smac +.IR SMAC " ] " +.RB " [ " etype +.IR ETYPE " ] " + +.ti -8 +.IR SWAPPABLE " := " +.B mac +.ti -8 + +.IR CONTROL " := {" +.BR reclassify " | " pipe " | " drop " | " shot " | " continue " | " pass " }" +.SH DESCRIPTION +The +.B skbmod +action is intended as a usability upgrade to the existing +.B pedit +action. Instead of having to manually edit 8-, 16-, or 32-bit chunks of an +ethernet header, +.B skbmod +allows complete substitution of supported elements. +Action must be one of +.BR set ", " swap " and " ecn "." +.BR set " and " swap +only affect Ethernet packets, while +.B ecn +only affects IP packets. +.SH OPTIONS +.TP +.BI dmac " DMAC" +Change the destination mac to the specified address. +.TP +.BI smac " SMAC" +Change the source mac to the specified address. +.TP +.BI etype " ETYPE" +Change the ethertype to the specified value. +.TP +.BI mac +Used to swap mac addresses. +.TP +.B ecn +Used to mark ECN Capable Transport (ECT) IP packets as Congestion Encountered (CE). +Does not affect Non ECN-Capable Transport (Non-ECT) packets. +.TP +.I CONTROL +The following keywords allow one to control how the tree of qdisc, classes, +filters and actions is further traversed after this action. +.RS +.TP +.B reclassify +Restart with the first filter in the current list. +.TP +.B pipe +Continue with the next action attached to the same filter. +.TP +.B drop +.TQ +.B shot +Drop the packet. +.TP +.B continue +Continue classification with the next filter in line. +.TP +.B pass +Finish classification process and return to calling qdisc for further packet +processing. This is the default. +.RE +.SH EXAMPLES +To start, observe the following filter with a pedit action: + +.RS +.EX +tc filter add dev eth1 parent 1: protocol ip prio 10 \\ + u32 match ip protocol 1 0xff flowid 1:2 \\ + action pedit munge offset -14 u8 set 0x02 \\ + munge offset -13 u8 set 0x15 \\ + munge offset -12 u8 set 0x15 \\ + munge offset -11 u8 set 0x15 \\ + munge offset -10 u16 set 0x1515 \\ + pipe +.EE +.RE + +Using the skbmod action, this command can be simplified to: + +.RS +.EX +tc filter add dev eth1 parent 1: protocol ip prio 10 \\ + u32 match ip protocol 1 0xff flowid 1:2 \\ + action skbmod set dmac 02:15:15:15:15:15 \\ + pipe +.EE +.RE + +Complexity will increase if source mac and ethertype are also being edited +as part of the action. If all three fields are to be changed with skbmod: + +.RS +.EX +tc filter add dev eth5 parent 1: protocol ip prio 10 \\ + u32 match ip protocol 1 0xff flowid 1:2 \\ + action skbmod \\ + set etype 0xBEEF \\ + set dmac 02:12:13:14:15:16 \\ + set smac 02:22:23:24:25:26 +.EE +.RE + +To swap the destination and source mac addresses in the Ethernet header: + +.RS +.EX +tc filter add dev eth3 parent 1: protocol ip prio 10 \\ + u32 match ip protocol 1 0xff flowid 1:2 \\ + action skbmod \\ + swap mac +.EE +.RE + +Finally, to mark the CE codepoint in the IP header for ECN Capable Transport (ECT) packets: + +.RS +.EX +tc filter add dev eth0 parent 1: protocol ip prio 10 \\ + u32 match ip protocol 1 0xff flowid 1:2 \\ + action skbmod \\ + ecn +.EE +.RE + +Only one of +.BR set ", " swap " and " ecn +shall be used in a single command. +Trying to use more than one of them in a single command is considered undefined behavior; pipe +multiple commands together instead. + +.SH SEE ALSO +.BR tc (8), +.BR tc-u32 (8), +.BR tc-pedit (8) |