datapath-windows: Data structures and functions for dump state

Signed-off-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Saurabh Shah <ssaurabh@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
datapath-windows: make NL version a UIN8 and add a validateDp arg

I didn't realize earlier that version in a netlink message was a
UINT8. So, fixing that here.

Also, some of the commands don't pass a valid DP value. Hence adding
a field to identify such commands.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Saurabh Shah <ssaurabh@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
datapath-windows: add a context structure for user parameters

In this patch we add a context structure for collecting all the parameters
passed from usersapce in one place. The idea is to reduce the number of
parameters being passed to the netlink command handler functions.

It can be argued that not all functions require all the arguments, but this
approach keeps the code clean, IMO.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Saurabh Shah <ssaurabh@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
datapath-windows: add support for GET_DP command to dump datpaths

In this patch, we add support for the GET_DP netlink command to dump
the datpaaths. The userspace workflow to get this to work is the same
as on Linux. dpif-linux.c initiates a dump start by writing a netlink
message, and after that continues to read data from the kernel while
the kernel has data. The state is maintained in the kernel, and not in
userspace. This approach was taken since there was not great benefit
of maintaining state in userspace, and also to avoid userspace changes
specific to Windows.

This hopefully serves as a template to base the other dump commands on.

validation:
- With a hacked up dpif-linux.c to work on Windows,
  dpif_linux_enumerate() successfully enumerated the datapaths in the
  kernel.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Saurabh Shah <ssaurabh@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>