confd: extend syslogd support with property-based filtering

This is the last commit in the series that extend syslog matching and sorting
to the level of sysklogd 2.7.0 and later.  Like hostname filtering, property
based filtering is not supported natively in the IETF RFC, and the modeling is
unfortunately a bit clunky.  The most confusing part is probably 'negate'
which is the '!' operator that inverts the matching, e.g., !icase_regex match
everthing *not* in the regexp.

Fixes #1091

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/confd/src/ietf-syslog.c

@@ -118,6 +118,40 @@ static size_t selector(sr_session_ctx_t *session, struct action *act)
 		count = 0;
 	}
 
+	/* Check for property-filter (infix-syslog augment) */
+	char *property = srx_get_str(session, "%s/infix-syslog:property-filter/property", act->xpath);
+	if (property) {
+		char *operator = srx_get_str(session, "%s/infix-syslog:property-filter/operator", act->xpath);
+		char *value = srx_get_str(session, "%s/infix-syslog:property-filter/value", act->xpath);
+		char *case_str = srx_get_str(session, "%s/infix-syslog:property-filter/case-insensitive", act->xpath);
+		char *negate_str = srx_get_str(session, "%s/infix-syslog:property-filter/negate", act->xpath);
+
+		if (operator && value) {
+			/* Build operator prefix: [!][icase_]operator */
+			char op_prefix[32] = "";
+
+			/* Only apply negate if explicitly set to true */
+			if (negate_str && !strcmp(negate_str, "true"))
+				strlcat(op_prefix, "!", sizeof(op_prefix));
+
+			/* Only apply icase_ if explicitly set to true */
+			if (case_str && !strcmp(case_str, "true"))
+				strlcat(op_prefix, "icase_", sizeof(op_prefix));
+
+			strlcat(op_prefix, operator, sizeof(op_prefix));
+
+			/* Property-based filter: :property, [!][icase_]operator, "value" */
+			fprintf(act->fp, ":%s, %s, \"%s\"\n", property, op_prefix, value);
+			has_pattern = true;
+		}
+
+		free(property);
+		free(operator);
+		free(value);
+		free(case_str);
+		free(negate_str);
+	}
+
 	/* Check for pattern-match (select-match feature) */
 	pattern = srx_get_str(session, "%s/pattern-match", act->xpath);
 	if (pattern) {

src/confd/yang/confd/infix-syslog.yang

@@ -175,6 +175,83 @@ module infix-syslog {
       description "Filter messages by hostname. Messages from the listed
                    hostnames will be logged to this file.";
     }
+
+    container property-filter {
+      presence "Enable property-based filtering";
+      description "Advanced property-based message filtering. Allows filtering
+                   on specific message fields with various comparison operators.";
+
+      leaf property {
+        type enumeration {
+          enum msg {
+            description "The message body (SYSLOG-MSG field).";
+          }
+          enum msgid {
+            description "The RFC5424 message identifier (MSGID field).";
+          }
+          enum programname {
+            description "The originating program or tag name.";
+          }
+          enum hostname {
+            description "The message source hostname.";
+          }
+          enum source {
+            description "The message source (alias for hostname).";
+          }
+          enum data {
+            description "The RFC5424 structured data (SD field).";
+          }
+        }
+        mandatory true;
+        description "The message property to match against.";
+      }
+
+      leaf operator {
+        type enumeration {
+          enum contains {
+            description "Substring match (case-sensitive).";
+          }
+          enum isequal {
+            description "Exact equality match.";
+          }
+          enum startswith {
+            description "Prefix match.";
+          }
+          enum regex {
+            description "Basic regular expression match.";
+          }
+          enum ereregex {
+            description "Extended regular expression match (POSIX ERE).";
+          }
+        }
+        mandatory true;
+        description "The comparison operator to use.";
+      }
+
+      leaf value {
+        type string;
+        mandatory true;
+        description "The value to compare against.";
+      }
+
+      leaf case-insensitive {
+        type boolean;
+        description "Perform case-insensitive comparison.";
+      }
+
+      leaf negate {
+        type boolean;
+        description "Negate the comparison result. When set to true, the
+                     filter matches messages that do NOT satisfy the
+                     specified condition.
+
+                     For example:
+                     - operator: contains, value: 'ERROR', negate: false
+                       → matches messages containing 'ERROR'
+                     - operator: contains, value: 'ERROR', negate: true
+                       → matches messages NOT containing 'ERROR'";
+      }
+    }
   }
 
   augment "/syslog:syslog/syslog:actions/syslog:remote/syslog:destination" {