Internet exposure checks and response rate limiting

Jarl works out which views are reachable from the internet (match-clients
ending in a catch-all, not private-looking addresses: an internal view of a
global IPv6 prefix is still yours; a server without views: open allow-query
and a non-private listen address), with a per-view override (schema 9), and
checks public ones: rate limiting, open resolver, minimal-any, cache
snooping, open NOTIFY and transfers, version and host name, management
interfaces. Fixes are staged like any change, including rate limiting from
ISC's example in log-only mode with the secondaries exempt, then enforcing.
named logs what rate limiting limits (or would, in log-only mode, where its
counters don't move) as query-errors; Jarl routes those lines to its log
and counts them (rrl breakdown, ratelimited top lists, Prometheus
jarl_ratelimit_logged_total), shown on the new Exposure page.

A change that newly opens a public view up must be confirmed (accept_risk,
--accept-risk, a checkbox on the Changes page; 409 confirm_risk
otherwise). Findings can be acknowledged with a reason and stay visible as
info. GET /exposure, POST /exposure/fix|ack|unack, jarl exposure,
docs/exposure.md.

Also fixes query statistics skipping TSIG-signed queries ("IP#port/key
NAME" in named's log).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/stats/collector.go

@@ -26,10 +26,15 @@ const (
 	KindBlocked  = "blocked"  // names blocked (docs/blocking.md)
 	// KindBlockedClient: clients with the most blocked queries.
 	KindBlockedClient = "blocked_client"
+	// KindRateLimited: client networks whose responses rate limiting
+	// limited (or would have, in log-only mode); KindRateLimitedName: the
+	// names and types they asked for (docs/exposure.md).
+	KindRateLimited     = "ratelimited"
+	KindRateLimitedName = "ratelimited_name"
 )
 
 // Kinds lists the top-list kinds.
-var Kinds = []string{KindName, KindClient, KindNXDomain, KindServFail, KindRefused, KindBlocked, KindBlockedClient}
+var Kinds = []string{KindName, KindClient, KindNXDomain, KindServFail, KindRefused, KindBlocked, KindBlockedClient, KindRateLimited, KindRateLimitedName}
 
 // OtherZone is the zone key for names outside every local zone (answered
 // by recursion, or refused).
@@ -337,6 +342,8 @@ func (c *Collector) handleLine(line string) {
 	if !ok {
 		if rw, ok := ParseRewrite(line, c.opts.Location); ok {
 			c.handleRewrite(rw)
+		} else if rl, ok := ParseRateLimit(line, c.opts.Location); ok {
+			c.handleRateLimit(rl)
 		}
 		return
 	}
@@ -416,6 +423,30 @@ func (c *Collector) handleRewrite(rw Rewrite) {
 	hours[hour][KindBlockedClient][clientKey(rw.Client, c.opts.Anonymize)]++
 }
 
+// handleRateLimit counts a response rate limiting limited, or would have:
+// "rrl:drop", "rrl:slip", "rrl:would-drop" or "rrl:would-slip", and the
+// client network and name in the hour's top lists.
+func (c *Collector) handleRateLimit(rl RateLimit) {
+	for _, p := range c.opts.Exclude {
+		if p.Contains(rl.Client) {
+			return
+		}
+	}
+	key := "rrl:" + rl.Action
+	if rl.Would {
+		key = "rrl:would-" + rl.Action
+	}
+	minute, hour := c.minuteOf(rl.Time), c.hourOf(rl.Time)
+	c.count(minute, key, 1)
+	hours := c.hours
+	if hour < c.liveHour {
+		hours = c.late
+	}
+	hours[hour] = c.hourMaps(hours, hour)
+	hours[hour][KindRateLimited][rl.Prefix]++
+	hours[hour][KindRateLimitedName][rl.Name+" "+rl.Type]++
+}
+
 // policySource names what a rewrite came from: a blocklist's name, "rules"
 // for the rules entered in Jarl, or the policy zone for others.
 func policySource(via string) string {