- Open vSwitch currently assigns the OpenFlow port number for an - interface once, when the client first adds the interface. It does - not change the port number later if the client sets or changes or - clears . Therefore, to ensure that - takes effect, the client should set - it in the same database transaction that creates the interface. - (Future versions of Open vSwitch might honor changes to .) + A client should ideally set this column's value in the same + database transaction that it uses to create the interface. Open + vSwitch version 2.1 and later will honor a later request for a + specific port number, althuogh it might confuse some controllers: + OpenFlow does not have a way to announce a port number change, so + Open vSwitch represents it over OpenFlow as a port deletion + followed immediately by a port addition. +
+ ++ If is set or changed to some other + port's automatically assigned port number, Open vSwitch chooses a + new port number for the latter port.
@@ -2534,6 +2539,68 @@ column has no effect. + ++ This string set specifies which fields should be used for + address prefix tracking. Prefix tracking allows the + classifier to skip rules with longer than necessary prefixes, + resulting in better wildcarding for datapath flows. +
++ Prefix tracking may be beneficial when a flow table contains + matches on IP address fields with different prefix lengths. + For example, when a flow table contains IP address matches on + both full addresses and proper prefixes, the full address + matches will typically cause the datapath flow to un-wildcard + the whole address field (depending on flow entry priorities). + In this case each packet with a different address gets handed + to the userspace for flow processing and generates its own + datapath flow. With prefix tracking enabled for the address + field in question packets with addresses matching shorter + prefixes would generate datapath flows where the irrelevant + address bits are wildcarded, allowing the same datapath flow + to handle all the packets within the prefix in question. In + this case many userspace upcalls can be avoided and the + overall performance can be better. +
++ This is a performance optimization only, so packets will + receive the same treatment with or without prefix tracking. +
+
+ The supported fields are: tun_id,
+ tun_src, tun_dst,
+ nw_src, nw_dst (or aliases
+ ip_src and ip_dst),
+ ipv6_src, and ipv6_dst. (Using this
+ feature for tun_id would only make sense if the
+ tunnel IDs have prefix structure similar to IP addresses.)
+
+ For example, prefixes=ip_dst,ip_src instructs the
+ flow classifier to track the IP destination and source
+ addresses used by the rules in this specific flow table. To
+ set the prefix fields, the flow table record needs to exist:
+
ovs-vsctl set Bridge br0 flow_tables:0=@N1 -- --id=@N1 create Flow_Table name=table0ovs-vsctl set Flow_Table table0 prefixes=ip_dst,ip_src+ There is a maximum number of fields that can be enabled for any + one flow table. Currently this limit is 3. +
+