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 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.  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 categorized 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 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.


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-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.


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
       <netdev@vger.kernel.org> 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 <daniel.machon@microchip.com>

iproute2			  15 may 2023			   DCB-REWR(8)