ofp-prop: Add support for putting and parsing nested properties.

It hadn't occurred to me before that any special support was actually
necessary or useful for nested properties, but the functions introduced in
this commit are nice wrappers to deal with the extra 4-byte padding that
ensures that the nested properties begin on 8-byte boundaries just like
the outer properties.

Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Jarno Rajahalme <jarno@ovn.org>

diff --git a/lib/ofp-prop.c b/lib/ofp-prop.c
index d6fd3a6..1512442 100644 (file)
--- a/lib/ofp-prop.c
+++ b/lib/ofp-prop.c
@@ -265,6 +265,27 @@ ofpprop_parse_uuid(const struct ofpbuf *property, struct uuid *uuid)
     return 0;
 }
 
+/* Attempts to parse 'property' as a property that contains nested properties.
+ * If successful, stores the nested data into '*nested' and returns 0;
+ * otherwise returns an OpenFlow error.
+ *
+ * The only thing special about nested properties is that the property header
+ * is followed by 4 bytes of padding, so that the nested properties begin at an
+ * 8-byte aligned offset.  This function can be used in other situations where
+ * this is the case. */
+enum ofperr
+ofpprop_parse_nested(const struct ofpbuf *property, struct ofpbuf *nested)
+{
+    size_t nested_offset = ROUND_UP(ofpbuf_headersize(property), 8);
+    if (property->size < nested_offset) {
+        return OFPERR_OFPBPC_BAD_LEN;
+    }
+
+    ofpbuf_use_const(nested, property->data, property->size);
+    ofpbuf_pull(nested, nested_offset);
+    return 0;
+}
+
 /* Adds a property with the given 'type' and 'len'-byte contents 'value' to
  * 'msg', padding the property out to a multiple of 8 bytes. */
 void
@@ -392,6 +413,18 @@ ofpprop_put_uuid(struct ofpbuf *msg, uint64_t type, const struct uuid *uuid)
     ofpprop_put(msg, type, uuid, sizeof *uuid);
 }
 
+/* Appends a property of type 'type' to 'msg' whose contents are padding to
+ * 8-byte alignment followed by 'nested'.  This is a suitable way to add nested
+ * properties to 'msg'. */
+void
+ofpprop_put_nested(struct ofpbuf *msg, uint64_t type,
+                   const struct ofpbuf *nested)
+{
+    size_t start = ofpprop_start_nested(msg, type);
+    ofpbuf_put(msg, nested->data, nested->size);
+    ofpprop_end(msg, start);
+}
+
 /* Appends a header for a property of type 'type' to 'msg'.  The caller should
  * add the contents of the property to 'msg', then finish it by calling
  * ofpprop_end().  Returns the offset of the beginning of the property (to pass
@@ -429,6 +462,22 @@ ofpprop_end(struct ofpbuf *msg, size_t start_ofs)
     ofpbuf_padto(msg, ROUND_UP(msg->size, 8));
 }
 
+/* Appends a header for a property of type 'type' to 'msg', followed by padding
+ * suitable for putting nested properties into the property; that is, padding
+ * to an 8-byte alignment.
+ *
+ * This otherwise works like ofpprop_start().
+ *
+ * There's no need for ofpprop_end_nested(), because ofpprop_end() works fine
+ * for this case. */
+size_t
+ofpprop_start_nested(struct ofpbuf *msg, uint64_t type)
+{
+    size_t start_ofs = ofpprop_start(msg, type);
+    ofpbuf_padto(msg, ROUND_UP(msg->size, 8));
+    return start_ofs;
+}
+
 enum ofperr
 ofpprop_unknown(struct vlog_module *module, bool loose, const char *msg,
                 uint64_t type)

diff --git a/lib/ofp-prop.h b/lib/ofp-prop.h
index 921b6c1..4f8e78d 100644 (file)
--- a/lib/ofp-prop.h
+++ b/lib/ofp-prop.h
@@ -85,6 +85,7 @@ enum ofperr ofpprop_parse_u16(const struct ofpbuf *, uint16_t *value);
 enum ofperr ofpprop_parse_u32(const struct ofpbuf *, uint32_t *value);
 enum ofperr ofpprop_parse_u64(const struct ofpbuf *, uint64_t *value);
 enum ofperr ofpprop_parse_uuid(const struct ofpbuf *, struct uuid *);
+enum ofperr ofpprop_parse_nested(const struct ofpbuf *, struct ofpbuf *);
 
 /* Serializing properties. */
 void ofpprop_put(struct ofpbuf *, uint64_t type,
@@ -100,10 +101,13 @@ void ofpprop_put_u64(struct ofpbuf *, uint64_t type, uint64_t value);
 void ofpprop_put_bitmap(struct ofpbuf *, uint64_t type, uint64_t bitmap);
 void ofpprop_put_flag(struct ofpbuf *, uint64_t type);
 void ofpprop_put_uuid(struct ofpbuf *, uint64_t type, const struct uuid *);
+void ofpprop_put_nested(struct ofpbuf *, uint64_t type, const struct ofpbuf *);
 
 size_t ofpprop_start(struct ofpbuf *, uint64_t type);
 void ofpprop_end(struct ofpbuf *, size_t start_ofs);
 
+size_t ofpprop_start_nested(struct ofpbuf *, uint64_t type);
+
 /* Logging errors while deserializing properties.
  *
  * The attitude that a piece of code should take when it deserializes an