vendor that doesn't yet have any extension messages, then you will
also need to edit build-aux/extract-ofp-msgs.
+### 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. 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.)
+
+### Q: How do I add support for a new OpenFlow action?
+
+A: Add your new action to "enum ofp_raw_action_type" in
+ lib/ofp-actions.c, following the existing pattern. Then recompile
+ and fix all of the new warnings, implementing new functionality for
+ the new action as needed. (If you configure with --enable-Werror,
+ as described in [INSTALL.md], then it is impossible to miss any
+ warnings.)
+
+ If you need to add an OpenFlow vendor extension action for a vendor
+ that doesn't yet have any extension actions, then you will also
+ need to edit build-aux/extract-ofp-actions.
+
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