.TH DCB-REWR 8 "15 may 2023" "iproute2" "Linux" .SH NAME dcb-rewr \- show / manipulate the rewrite table of the DCB (Data Center Bridging) subsystem .SH SYNOPSIS .sp .ad l .in +8 .ti -8 .B dcb .RI "[ " OPTIONS " ] " .B rewr .RI "{ " COMMAND " | " help " }" .sp .ti -8 .B dcb rewr " { " show " | " flush " } " dev .RI DEV .RB "[ " prio-dscp " ]" .RB "[ " prio-pcp " ]" .ti -8 .B dcb rewr " { " add " | " del " | " replace " } " dev .RI DEV .RB "[ " prio-dscp " " \fIDSCP-MAP\fB " ]" .RB "[ " prio-pcp " " \fIPCP-MAP\fB " ]" .ti -8 .IR DSCP-MAP " := [ " DSCP-MAP " ] " DSCP-MAPPING .ti -8 .IR DSCP-MAPPING " := " \fIPRIO \fB:\fR "{ " DSCP " | " \fBall\fR " }" .ti -8 .IR PCP-MAP " := [ " PCP-MAP " ] " PCP-MAPPING .ti -8 .IR PCP-MAPPING " := " \fIPRIO \fB:\fR PCP\fR .ti -8 .IR DSCP " := { " \fB0\fR " .. " \fB63\fR " }" .ti -8 .IR PCP " := { " \fB0(nd/de)\fR " .. " \fB7(nd/de)\fR " }" .ti -8 .IR PRIO " := { " \fB0\fR " .. " \fB7\fR " }" .SH DESCRIPTION .B dcb rewr is used to configure the rewrite table, in the DCB (Data Center Bridging) subsystem. The rewrite table is used to rewrite certain values in the packet headers, based on packet priority. DCB rewrite entries are, like DCB APP entries, 3-tuples of selector, protocol ID, and priority. Selector is an enumeration that picks one of the prioritization namespaces. Currently, only the DSCP and PCP selector namespaces are supported by dcb rewr. The rewrite table is a list of DCB rewrite rules, that applies to packets with matching priority. Notably, it is valid to have conflicting rewrite assignment for the same selector and priority. For example, the set of two rewrite entries (DSCP, 10, 1) and (DSCP, 11, 1), where packets with priority 1 should have its DSCP value rewritten to both 10 and 11, form a well-defined rewrite table. .B dcb rewr tool allows low-level management of the rewrite table by adding and deleting individual rewrite 3-tuples through .B add and .B del commands. On the other hand, the command .B replace does what one would typically want in this situation--first adds the new configuration, and then removes the obsolete one, so that only one rewrite rule is in effect for a given selector and priority. .SH COMMANDS .TP .B show Display all entries with a given selector. When no selector is given, shows all rewrite table entries categorized per selector. .TP .B flush Remove all entries with a given selector. When no selector is given, removes all rewrite table entries. .TP .B add .TQ .B del Add and, respectively, remove individual rewrite 3-tuples to and from the DCB rewrite table. .TP .B replace Take the list of entries mentioned as parameter, and add those that are not present in the rewrite table yet. Then remove those entries, whose selector and priority have been mentioned as parameter, but not with the exact same protocol ID. This has the effect of, for the given selector and priority, causing that the table only contains the protocol ID (or ID's) given as parameter. .SH PARAMETERS The following table shows parameters in a way that they would be used with \fBadd\fR, \fBdel\fR and \fBreplace\fR commands. For \fBshow\fR and \fBflush\fR, the parameter name is to be used as a simple keyword without further arguments. .TP .B prio-dscp \fIDSCP-MAP \fIDSCP-MAP\fR uses the array parameter syntax, see .BR dcb (8) for details. Keys are priorities, values are DSCP points for traffic with matching priority. DSCP points can be written either directly as numeric values, or using symbolic names specified in .B /etc/iproute2/rt_dsfield (however note that the file specifies full 8-bit dsfield values, whereas .B dcb rewr will only use the higher six bits). .B dcb rewr show will similarly format DSCP values as symbolic names if possible. The command line option .B -N turns the show translation off. .TP .B prio-pcp \fIPCP-MAP \fIPCP-MAP\fR uses the array parameter syntax, see .BR dcb (8) for details. Keys are priorities. Values are PCP/DEI for traffic with matching priority. PCP/DEI values are written as a combination of numeric- and symbolic values, to accommodate for both. PCP always in numeric form e.g 0 .. 7 and DEI in symbolic form e.g 'de' (drop-eligible), indicating that the DEI bit is 1 or 'nd' (not-drop-eligible), indicating that the DEI bit is 0. In combination 1:2de translates to a mapping of priority 1 to PCP=2 and DEI=1. .SH EXAMPLE & USAGE Add a rule to rewrite DSCP to 0, 24 and 48 for traffic with priority 0, 3 and 6, respectively: .P # dcb rewr add dev eth0 prio-dscp 0:0 3:24 6:48 Add a rule to rewrite DSCP to 25 for traffic with priority 3: .P # dcb rewr add dev eth0 prio-dscp 3:25 .br # dcb rewr show dev eth0 prio-dscp .br prio-dscp 0:0 3:CS3 3:25 6:CS6 .br # dcb -N rewr show dev eth0 prio-dscp .br prio-dscp 0:0 3:24 3:25 6:48 Reconfigure the table so that only one rule exists for rewriting traffic with priority 3. .P # dcb rewr replace dev eth0 prio-dscp 3:26 .br # dcb rewr -N show dev eth0 prio-dscp .br prio-dscp 0:0 3:26 6:48 Flush all DSCP rules: .P # dcb rewr flush dev eth0 prio-dscp .br # dcb rewr show dev eth0 prio-dscp .br (nothing) Add a rule to rewrite PCP to 1 and DEI to 0 for traffic with priority 1 and a rule to rewrite PCP to 2 and DEI to 1 for traffic with priority 2: .P # dcb rewr add dev eth0 prio-pcp 1:1nd 2:2de .br # dcb rewr show dev eth0 prio-pcp .br prio-pcp 1:1nd 2:2de .SH EXIT STATUS Exit status is 0 if command was successful or a positive integer upon failure. .SH SEE ALSO .BR dcb (8) .BR dcb-app (8) .BR dcb-apptrust (8) .SH REPORTING BUGS Report any bugs to the Network Developers mailing list .B where the development and maintenance is primarily done. You do not have to be subscribed to the list to send a message there. .SH AUTHOR Daniel Machon