Look clients up in the IPinfo Lite file with SWWAF_LOOKUP_SOURCE=file (closes #22)

SWWAF_LOOKUP_SOURCE=file looks every client up in the file
SWWAF_LOOKUP_DB_PATH names, without GeoJS. file without the path, the
path with another source, or a file that cannot be read stops the start.
The file is read whole into memory, so overwriting it in place cannot
disturb a lookup, and read again 2 seconds after its last change; a
replacement that cannot be read is logged, counted and sent as a
file_error alert, and the old one stays in use. Metrics give when it
was read and the failed reads. Tests write their databases through
internal/lookup/lookuptest.

Deviation: go.mod and go.sum written by hand; go runs only through make.
Judgement call: the 2-second wait, as the rule files have.

Model: opus-5-5

internal/proxy/lookup_test.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/netip"
+	"path/filepath"
 	"slices"
 	"sync"
 	"testing"
@@ -13,6 +14,7 @@ import (
 
 	"sneak.berlin/go/smallwebwaf/internal/alerts"
 	"sneak.berlin/go/smallwebwaf/internal/lookup"
+	"sneak.berlin/go/smallwebwaf/internal/lookup/lookuptest"
 	"sneak.berlin/go/smallwebwaf/internal/requestlog"
 )
 
@@ -166,6 +168,64 @@ func TestLookupSourceOffLooksNoClientUp(t *testing.T) {
 	}
 }
 
+func TestClientsAreLookedUpInTheLookupDatabaseAndGeoJSIsNotAsked(t *testing.T) {
+	t.Parallel()
+
+	geojsURL, asked := startGeoJS(t)
+	path := filepath.Join(t.TempDir(), "ipinfo_lite.mmdb")
+	lookuptest.Write(t, path, map[string]lookuptest.Network{
+		fromDE + "/32": {ASN: asnDE, ASName: asNameDE, Country: "DE"},
+		fromKP + "/32": {ASN: asnKP, ASName: asNameKP, Country: "KP"},
+	})
+	s, clk, server := startWithClock(t, geojsURL, map[string]string{
+		lookupSource:       "file",
+		lookupDBPath:       path,
+		allowedCountries:   "DE",
+		rateLimitPerMinute: "1",
+	})
+
+	// fromDE's second request breaks the limit and bans it. The list
+	// refuses fromKP, and unplaced, which the file does not hold.
+	de := asnAndCountry{asnDE, asNameDE, "DE"}
+
+	for _, tc := range []struct {
+		line logLine
+		want asnAndCountry
+	}{
+		{s.get(fromDE, http.StatusOK, requestlog.ActionForward), de},
+		{s.get(fromDE, http.StatusForbidden, requestlog.ActionRateLimited), de},
+		{
+			s.get(fromKP, http.StatusForbidden, requestlog.ActionCountryDenied),
+			asnAndCountry{asnKP, asNameKP, "KP"},
+		},
+		{
+			s.get(unplaced, http.StatusForbidden, requestlog.ActionCountryDenied),
+			asnAndCountry{},
+		},
+	} {
+		got := asnAndCountry{tc.line.ASN, tc.line.ASName, tc.line.Country}
+		if got != tc.want {
+			t.Errorf("log line has %+v, want %+v", got, tc.want)
+		}
+	}
+
+	h := historyOf(t, server, fromDE)
+	if got := (asnAndCountry{h.ASN, h.ASName, h.Country}); got != de ||
+		!h.LookedUp.Equal(clk.Now()) {
+		t.Errorf("history has %+v, looked up at %s; want %+v, at %s",
+			got, h.LookedUp, de, clk.Now())
+	}
+
+	notes := server.Ledger.Bans(netip.MustParsePrefix(fromDE + "/32"))[0].Notes
+	if got := (asnAndCountry{notes.ASN, notes.ASName, notes.Country}); got != de {
+		t.Errorf("the ban's notes have %+v, want %+v", got, de)
+	}
+
+	if len(asked()) != 0 {
+		t.Errorf("GeoJS was asked about %v, want nothing", asked())
+	}
+}
+
 func TestLookupHeadersArePassedToTheAppAndTheClientsOwnRemoved(t *testing.T) {
 	t.Parallel()