bgpd: Ignore Prefix-SID attribute via EBGP

Also, allow filtering this attribute via `path-attribute discard/treat-as-widthraw`.

Signed-off-by: Donatas Abraitis <[email protected]>

bgpd/bgp_attr.c

@@ -3300,6 +3300,22 @@ enum bgp_attr_parse_ret bgp_attr_prefix_sid(struct bgp_attr_parser_args *args)
 	size_t headersz = sizeof(type) + sizeof(length);
 	size_t psid_parsed_length = 0;
 
+	/* A BGP speaker receiving a BGP Prefix-SID attribute from an
+	 * External BGP (EBGP) neighbor residing outside the boundaries
+	 * of the SR domain MUST discard the attribute unless it is
+	 * configured to accept the attribute from the EBGP neighbor.
+	 * A BGP speaker SHOULD log an error for further analysis when
+	 * discarding an attribute.
+	 */
+	if (peer->sort == BGP_PEER_EBGP && peer->sub_sort != BGP_PEER_EBGP_OAD) {
+		zlog_warn("%pBP received Prefix-SID attribute via eBGP, ignoring",
+			  peer);
+		goto prefix_sid_ignore;
+	}
+
+	if (peer->discard_attrs[args->type] || peer->withdraw_attrs[args->type])
+		goto prefix_sid_ignore;
+
 	while (STREAM_READABLE(peer->curr) > 0
 	       && psid_parsed_length < args->length) {
 
@@ -3346,7 +3362,10 @@ enum bgp_attr_parse_ret bgp_attr_prefix_sid(struct bgp_attr_parser_args *args)
 
 	SET_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_PREFIX_SID));
 
-	return BGP_ATTR_PARSE_PROCEED;
+prefix_sid_ignore:
+	stream_forward_getp(peer->curr, args->length);
+
+	return bgp_attr_ignore(peer, args->type);
 }
 
 /* PMSI tunnel attribute (RFC 6514)