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List:       openvswitch-discuss
Subject:    [ovs-discuss] issues on wildcard the matching fields
From:       blp () nicira ! com (Ben Pfaff)
Date:       2014-04-25 19:43:50
Message-ID: 20140425194350.GE26839 () nicira ! com
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On Thu, Apr 24, 2014 at 08:09:18PM +0000, Chenfei Gao wrote:
> I am a newbee to open vswitch community. I am interested on hot trending SDN and \
> OVS implementation. I have a question about wildcarding the match fields. ? 
> If we don't specify some match field (e.g. tcp_src_port), it will wildcard and \
> matching all flows on this field. However, is it possible to match the field, \
> tcp_src_port for instance, 
> for a range of numbers in one flowmod? I checked openflow specification and found \
> that there was only mask for eth_addr and ip_addr and no mask for other fields like \
> tcp_port. 
> Does it mean if i want to match tcp_port for a range of numbers, the only way is to \
> mod several rules?

Like so many questions about OVS, this is answered in the
documentation, in this case in ovs-ofctl(8):

       tp_src=port/mask
       tp_dst=port/mask
              Bitwise  match  on  TCP  (or  UDP or SCTP) source or destination
              port, respectively.  The port and mask are 16-bit numbers  writ-
              ten  in decimal or in hexadecimal prefixed by 0x.  Each 1-bit in
              mask requires that the corresponding bit  in  port  must  match.
              Each 0-bit in mask causes the corresponding bit to be ignored.

              Bitwise  matches  on transport ports are rarely useful in isola-
              tion, but a group of them can be used to reduce  the  number  of
              flows  required  to  match  on  a range of transport ports.  For
              example, suppose that the goal is to match TCP source ports 1000
              to  1999,  inclusive.   One way is to insert 1000 flows, each of
              which matches on a single source port.  Another way is  to  look
              at the binary representations of 1000 and 1999, as follows:
              01111101000
              11111001111
              and  then  to  transform  those into a series of bitwise matches
              that accomplish the same results:
              01111101xxx
              0111111xxxx
              10xxxxxxxxx
              110xxxxxxxx
              1110xxxxxxx
              11110xxxxxx
              1111100xxxx
              which become the following when written in the  syntax  required
              by ovs-ofctl:
              tcp,tp_src=0x03e8/0xfff8
              tcp,tp_src=0x03f0/0xfff0
              tcp,tp_src=0x0400/0xfe00
              tcp,tp_src=0x0600/0xff00
              tcp,tp_src=0x0700/0xff80
              tcp,tp_src=0x0780/0xffc0
              tcp,tp_src=0x07c0/0xfff0

              Only  Open  vSwitch  1.6  and later supports bitwise matching on
              transport ports.

              Like the exact-match forms of tp_src and tp_dst described above,
              the  bitwise  match  forms  apply only when dl_type and nw_proto
              specify TCP or UDP or SCTP.


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