Manual: dcb-rewr

DCB-REWR(8)						    Linux						 DCB-REWR(8)

NAME
       dcb-rewr - show / manipulate the rewrite table of the DCB (Data Center Bridging) subsystem

SYNOPSIS
       dcb [ OPTIONS ] rewr { COMMAND | help }

       dcb rewr	 {  show  |  flush  }  dev DEV [ prio-dscp ] [ prio-pcp ]

       dcb rewr	 {  add	 |  del	 |  replace  }	dev DEV [ prio-dscp DSCP-MAP ] [ prio-pcp PCP-MAP ]

       DSCP-MAP := [ DSCP-MAP ] DSCP-MAPPING

       DSCP-MAPPING := PRIO:{ DSCP | all }

       PCP-MAP := [ PCP-MAP ] PCP-MAPPING

       PCP-MAPPING := PRIO:PCP

       DSCP := { 0 .. 63 }

       PCP := { 0(nd/de) .. 7(nd/de) }

       PRIO := { 0 .. 7 }

DESCRIPTION
       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 enu‐
       meration 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.  dcb rewr tool allows low-level management of the rewrite table by
       adding and deleting individual rewrite 3-tuples through add and del commands. On the other hand, the command 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.

COMMANDS
       show   Display  all entries with a given selector. When no selector is given, shows all rewrite table entries catego‐
	      rized per selector.

       flush  Remove all entries with a given selector. When no selector is given, removes all rewrite table entries.

       add
       del    Add and, respectively, remove individual rewrite 3-tuples to and from the DCB rewrite table.

       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 ex‐
	      act 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.

PARAMETERS
       The following table shows parameters in a way that they would be used with add, del and replace	commands.  For	show
       and flush, the parameter name is to be used as a simple keyword without further arguments.

       prio-dscp DSCP-MAP
	      DSCP-MAP	uses the array parameter syntax, see 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 /etc/iproute2/rt_dsfield (however note that the file specifies full 8-bit dsfield
	      values, whereas dcb rewr will only use the higher six bits).  dcb rewr show will similarly format DSCP  values
	      as symbolic names if possible. The command line option -N turns the show translation off.

       prio-pcp PCP-MAP
	      PCP-MAP  uses  the array parameter syntax, see 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-eligi‐
	      ble), indicating that the DEI bit is 1 or 'nd' (not-drop-eligible), indicating that the DEI bit is 0.  In com‐
	      bination 1:2de translates to a mapping of priority 1 to PCP=2 and DEI=1.

EXAMPLE & USAGE
       Add a rule to rewrite DSCP to 0, 24 and 48 for traffic with priority 0, 3 and 6, respectively:

       # 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:

       # dcb rewr add dev eth0 prio-dscp 3:25
       # dcb rewr show dev eth0 prio-dscp
       prio-dscp 0:0 3:CS3 3:25 6:CS6
       # dcb -N rewr show dev eth0 prio-dscp
       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.

       # dcb rewr replace dev eth0 prio-dscp 3:26
       # dcb rewr -N show dev eth0 prio-dscp
       prio-dscp 0:0 3:26 6:48

       Flush all DSCP rules:

       # dcb rewr flush dev eth0 prio-dscp
       # dcb rewr show dev eth0 prio-dscp
       (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:

       # dcb rewr add dev eth0 prio-pcp 1:1nd 2:2de
       # dcb rewr show dev eth0 prio-pcp
       prio-pcp 1:1nd 2:2de

EXIT STATUS
       Exit status is 0 if command was successful or a positive integer upon failure.

SEE ALSO
       dcb(8) dcb-app(8) dcb-apptrust(8)

REPORTING BUGS
       Report any bugs to the Network Developers mailing list  where the development and maintenance
       is primarily done.  You do not have to be subscribed to the list to send a message there.

AUTHOR
       Daniel Machon 

iproute2						 15 may 2023						 DCB-REWR(8)