[ovs-discuss] Deep Packet Inspection possible?

[Jesse Gross]

On Fri, Aug 14, 2015 at 5:29 PM, Dave Waters <davewaters1970 at gmail.com> wrote:
> I took a look at P4 and i thought it was primarily for HW devices. Let me
> see how i can use that with OVS.
>
> Can you give me the function in the code that i could start looking at if i
> want to make custom changes to deep inspect the packet in OVS. Some starting
> point would help.

>From the FAQ:

### Q: How do I add support for a new field or header?

A: Add new members for your field to "struct flow" in lib/flow.h, and
   add new enumerations for your new field to "enum mf_field_id" in
   lib/meta-flow.h, following the existing pattern.  Also, add support
   to miniflow_extract() in lib/flow.c for extracting your new field
   from a packet into struct miniflow.  Then recompile and fix all of
   the new warnings, implementing new functionality for the new field
   or header as needed.  (If you configure with --enable-Werror, as
   described in [INSTALL.md], then it is impossible to miss any
   warnings.)

   If you want kernel datapath support for your new field, you also
   need to modify the kernel module for the operating systems you are
   interested in.  This isn't mandatory, since fields understood only
   by userspace work too (with a performance penalty), so it's
   reasonable to start development without it.  If you implement
   kernel module support for Linux, then the Linux kernel "netdev"
   mailing list is the place to submit that support first; please read
   up on the Linux kernel development process separately.  The Windows
   datapath kernel module support, on the other hand, is maintained
   within the OVS tree, so patches for that can go directly to
   ovs-dev.