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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