bgpd: Ability to add/update unique extended communities

Certain extended communities cannot be repeated. An example is the
BGP link bandwidth extended community. Enhance the extended community
add function to ensure uniqueness, if requested.

Note: This commit does not change the lack of uniqueness for any of
the already-supported extended communities. Many of them such as the
BGP route target can obviously be present multiple times. Others like
the Router's MAC should most probably be present only once. The portions
of the code which add these may already be structured such that duplicates
do not arise.

Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>

1 files changed, 40 insertions, 14 deletions

diff --git a/bgpd/bgp_ecommunity.c b/bgpd/bgp_ecommunity.c
index dd97a3d213..0fbbc885b9 100644
--- a/bgpd/bgp_ecommunity.c
+++ b/bgpd/bgp_ecommunity.c
@@ -74,10 +74,16 @@ static void ecommunity_hash_free(struct ecommunity *ecom)
    Attribute structure.  When the value is already exists in the
    structure, we don't add the value.  Newly added value is sorted by
    numerical order.  When the value is added to the structure return 1
-   else return 0.  */
-bool ecommunity_add_val(struct ecommunity *ecom, struct ecommunity_val *eval)
+   else return 0.
+   The additional parameters 'unique' and 'overwrite' ensure a particular
+   extended community (based on type and sub-type) is present only
+   once and whether the new value should replace what is existing or
+   not.
+*/
+bool ecommunity_add_val(struct ecommunity *ecom, struct ecommunity_val *eval,
+			bool unique, bool overwrite)
 {
-	int c;
+	int c, ins_idx;
 
 	/* When this is fist value, just add it. */
 	if (ecom->val == NULL) {
@@ -88,25 +94,45 @@ bool ecommunity_add_val(struct ecommunity *ecom, struct ecommunity_val *eval)
 	}
 
 	/* If the value already exists in the structure return 0.  */
+	/* check also if the extended community itself exists. */
 	c = 0;
+	ins_idx = -1;
 	for (uint8_t *p = ecom->val; c < ecom->size;
 	     p += ECOMMUNITY_SIZE, c++) {
+		if (unique) {
+			if (p[0] == eval->val[0] &&
+			    p[1] == eval->val[1]) {
+				if (overwrite) {
+					memcpy(p, eval->val, ECOMMUNITY_SIZE);
+					return 1;
+				}
+				return 0;
+			}
+		}
 		int ret = memcmp(p, eval->val, ECOMMUNITY_SIZE);
 		if (ret == 0)
-			return false;
-		else if (ret > 0)
-			break;
+			return 0;
+		if (ret > 0) {
+			if (!unique)
+				break;
+			if (ins_idx == -1)
+				ins_idx = c;
+		}
 	}
 
+	if (ins_idx == -1)
+		ins_idx = c;
+
 	/* Add the value to the structure with numerical sorting.  */
 	ecom->size++;
 	ecom->val = XREALLOC(MTYPE_ECOMMUNITY_VAL, ecom->val,
 			     ecom->size * ECOMMUNITY_SIZE);
 
-	memmove(ecom->val + ((c + 1) * ECOMMUNITY_SIZE),
-		ecom->val + (c * ECOMMUNITY_SIZE),
-		(ecom->size - 1 - c) * ECOMMUNITY_SIZE);
-	memcpy(ecom->val + (c * ECOMMUNITY_SIZE), eval->val, ECOMMUNITY_SIZE);
+	memmove(ecom->val + ((ins_idx + 1) * ECOMMUNITY_SIZE),
+		ecom->val + (ins_idx * ECOMMUNITY_SIZE),
+		(ecom->size - 1 - ins_idx) * ECOMMUNITY_SIZE);
+	memcpy(ecom->val + (ins_idx * ECOMMUNITY_SIZE),
+	       eval->val, ECOMMUNITY_SIZE);
 
 	return true;
 }
@@ -128,7 +154,7 @@ struct ecommunity *ecommunity_uniq_sort(struct ecommunity *ecom)
 	for (i = 0; i < ecom->size; i++) {
 		eval = (struct ecommunity_val *)(ecom->val
 						 + (i * ECOMMUNITY_SIZE));
-		ecommunity_add_val(new, eval);
+		ecommunity_add_val(new, eval, false, false);
 	}
 	return new;
 }
@@ -543,7 +569,7 @@ struct ecommunity *ecommunity_str2com(const char *str, int type,
 			if (ecom == NULL)
 				ecom = ecommunity_new();
 			eval.val[1] = type;
-			ecommunity_add_val(ecom, &eval);
+			ecommunity_add_val(ecom, &eval, false, false);
 			break;
 		case ecommunity_token_unknown:
 		default:
@@ -927,8 +953,8 @@ extern struct ecommunity_val *ecommunity_lookup(const struct ecommunity *ecom,
 /* remove ext. community matching type and subtype
  * return 1 on success ( removed ), 0 otherwise (not present)
  */
-extern bool ecommunity_strip(struct ecommunity *ecom, uint8_t type,
-			     uint8_t subtype)
+bool ecommunity_strip(struct ecommunity *ecom, uint8_t type,
+		      uint8_t subtype)
 {
 	uint8_t *p, *q, *new;
 	int c, found = 0;