Keep the bans, the clients and GeoJS's answers in state files (closes #17)

smallwebwaf now copies its state to bans.json, clients.json and
lookups.json in SWWAF_STATE_DIR, as "Persistent state" in SPEC.md
describes, and reads them back at start, so a restart lifts no ban and
gives no client a fresh allowance. Each client gains a history, and a
ban's notes count the netblock's requests. bans.json is written
SWWAF_STATE_WRITE_DELAY after a ban, and every file every
SWWAF_STATE_COUNTER_INTERVAL and at the stop. A ban read back is masked
to its netblock and refuses every client in it. A file that does not
parse, an unknown version, an entry without a field it needs, or an
unwritable directory stops the start.

Deviation: no AS number or name, and no ban cause, reason or lifting yet.

Model: opus-5-5

internal/proxy/bans.go

@@ -14,10 +14,10 @@ func (rq *request) banResponse(action string) *refusal {
 	return &refusal{status: rq.h.config.BanResponse, action: action}
 }
 
-// banned reports whether a ban on the client's netblock refuses the
-// request at now, and notes for the log line when that ban ends.
+// banned reports whether a ban on a netblock the client is in refuses
+// the request at now, and notes for the log line when that ban ends.
 func (rq *request) banned(now time.Time) bool {
-	ban, banned := rq.h.ledger.Check(rq.netblock(), now)
+	ban, banned := rq.h.ledger.Check(rq.client, now)
 	if banned {
 		rq.line.BanExpires = banExpires(ban)
 	}
@@ -36,7 +36,8 @@ func (rq *request) limitBroken(now time.Time) bool {
 		return false
 	}
 
-	ban := rq.h.ledger.BanForLimit(rq.netblock(), now, bans.Notes{
+	netblock := rq.netblock()
+	ban := rq.h.ledger.BanForLimit(netblock, now, bans.Notes{
 		Country: rq.line.Country,
 		Limit:   hit.Limit,
 		Window:  hit.Window,
@@ -49,6 +50,8 @@ func (rq *request) limitBroken(now time.Time) bool {
 			Status:    rq.h.config.BanResponse,
 			UserAgent: rq.in.UserAgent(),
 		},
+		// The histories count this request only once it has ended.
+		Requests: rq.h.limiter.Requests(netblock) + 1,
 	})
 	rq.h.limiter.Reset(group)