Add support for tagging rules.

- in lua, look for a tags attribute to each rule. This is passed up in
  add_filter as a tags argument (as a lua table). If not present, an
  empty table is used. The tags table is iterated to populate a set
  of tags as strings, which is passed to add_filter().
- A new method falco_engine::enable_rule_by_tag is similar to
  enable_rule(), but is given a set of tag strings. Any rules containing
  one of the tags is enabled/disabled.
- The list of event types has been changed to a set to more accurately
  reflect its purpose.
- New argument to falco -T allows disabling all rules matching a given
  tag, via enable_rule_by_tag(). It can be provided multiple times.
- New argument to falco -t allows running those rules matching a given
  tag. If provided all rules are first disabled. It can be
  provided multiple times, but can not be combined with -T or
  -D (disable rules by name)
- falco_enging supports the notion of a ruleset. The idea is that you
  can choose a set of rules that are enabled/disabled by using
  enable_rule()/enable_rule_by_tag() in combination with a
  ruleset. Later, in process_event() you include that ruleset and the
  rules you had previously enabled will be run.
- rulsets are provided as strings in enable_rule()/enable_rule_by_tag()
  and as numbers in process_event()--this avoids the overhead of string
  lookups per-event. Ruleset ids are created on the fly as needed. A
  utility method find_ruleset_id() looks up the ruleset id for a given
  name. The default ruleset is NULL string/0 numeric if not provided.
- Although the ruleset is a useful falco engine feature, it isn't that
  important to the falco standalone program, so it's not
  documented. However, you can change the ruleset by providing
  FALCO_RULESET in the environment.

userspace/engine/falco_engine.h

@@ -20,6 +20,7 @@ along with falco.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <string>
 #include <memory>
+#include <set>
 
 #include "sinsp.h"
 #include "filter.h"
@@ -47,9 +48,18 @@ public:
 	void load_rules(const std::string &rules_content, bool verbose, bool all_events);
 
 	//
-	// Enable/Disable any rules matching the provided pattern (regex).
+	// Enable/Disable any rules matching the provided pattern
+	// (regex). If ruleset is non-NULL, enable/disable these
+	// rules in the context of the provided ruleset. The ruleset
+	// can later be passed as an argument to process_event(). This
+	// allows for different sets of rules being active at once.
 	//
-	void enable_rule(std::string &pattern, bool enabled);
+	void enable_rule(std::string &pattern, bool enabled, std::string *ruleset = NULL);
+
+	//
+	// Enable/Disable any rules with any of the provided tags (set, exact matches only)
+	//
+	void enable_rule_by_tag(std::set<std::string> &tags, bool enabled, std::string *ruleset = NULL);
 
 	struct rule_result {
 		sinsp_evt *evt;
@@ -58,13 +68,26 @@ public:
 		std::string format;
 	};
 
+	//
+	// Return the ruleset id corresponding to this ruleset name,
+	// creating a new one if necessary. If you provide any ruleset
+	// to enable_rule/enable_rule_by_tag(), you should look up the
+	// ruleset id and pass it to process_event().
+	//
+	uint16_t find_ruleset_id(std::string &ruleset);
+
 	//
 	// Given an event, check it against the set of rules in the
 	// engine and if a matching rule is found, return details on
 	// the rule that matched. If no rule matched, returns NULL.
 	//
-	// the reutrned rule_result is allocated and must be delete()d.
-	std::unique_ptr<rule_result> process_event(sinsp_evt *ev);
+	// If ruleset is non-NULL, use the enabled/disabled status
+	// associated with the provided ruleset. This is only useful
+	// when you have previously called enable_rule/enable_rule_by_tag
+	// with a non-NULL ruleset.
+	//
+	// the returned rule_result is allocated and must be delete()d.
+	std::unique_ptr<rule_result> process_event(sinsp_evt *ev, uint16_t ruleset_id = 0);
 
 	//
 	// Print details on the given rule. If rule is NULL, print
@@ -78,11 +101,12 @@ public:
 	void print_stats();
 
 	//
-	// Add a filter, which is related to the specified list of
+	// Add a filter, which is related to the specified set of
 	// event types, to the engine.
 	//
 	void add_evttype_filter(std::string &rule,
-				list<uint32_t> &evttypes,
+				std::set<uint32_t> &evttypes,
+				std::set<std::string> &tags,
 				sinsp_filter* filter);
 
 	// Clear all existing filters.
@@ -120,6 +144,8 @@ private:
 	inline bool should_drop_evt();
 
 	falco_rules *m_rules;
+	uint16_t m_next_ruleset_id;
+	std::map<string, uint16_t> m_known_rulesets;
 	std::unique_ptr<sinsp_evttype_filter> m_evttype_filter;
 
 	//