refactor: spin geoipx off geolocate (#893)

A bunch of packages (including oohelperd) just need the ability to
use MaxMind-like databases. They don't need the additional functionality
implemented by the geolocate package. Such a package, in fact, is
mostly (if not only) needed by the engine package.

Therefore, move code to query MaxMind-like databases to a separate
package, and avoid depending on geolocate in all the packages for
which it's sufficient to use geoipx.

Part of https://github.com/ooni/probe/issues/2240

internal/geoipx/geoipx.go

@@ -0,0 +1,50 @@
+// Package geoipx contains code to use the embedded MaxMind-like databases.
+package geoipx
+
+import (
+	"net"
+
+	"github.com/ooni/probe-assets/assets"
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/runtimex"
+	"github.com/oschwald/geoip2-golang"
+)
+
+// TODO(bassosimone): this would be more efficient if we'd open just
+// once the database and then reuse it for every address.
+
+// LookupASN maps [ip] to an AS number and an AS organization name.
+func LookupASN(ip string) (asn uint, org string, err error) {
+	asn, org = model.DefaultProbeASN, model.DefaultProbeNetworkName
+	db, err := geoip2.FromBytes(assets.ASNDatabaseData())
+	runtimex.PanicOnError(err, "cannot load embedded geoip2 ASN database")
+	defer db.Close()
+	record, err := db.ASN(net.ParseIP(ip))
+	if err != nil {
+		return
+	}
+	asn = record.AutonomousSystemNumber
+	if record.AutonomousSystemOrganization != "" {
+		org = record.AutonomousSystemOrganization
+	}
+	return
+}
+
+// LookupCC maps [ip] to a country code.
+func LookupCC(ip string) (cc string, err error) {
+	cc = model.DefaultProbeCC
+	db, err := geoip2.FromBytes(assets.CountryDatabaseData())
+	runtimex.PanicOnError(err, "cannot load embedded geoip2 country database")
+	defer db.Close()
+	record, err := db.Country(net.ParseIP(ip))
+	if err != nil {
+		return
+	}
+	// With MaxMind DB we used record.RegisteredCountry.IsoCode but that does
+	// not seem to work with the db-ip.com database. The record is empty, at
+	// least for my own IP address in Italy. --Simone (2020-02-25)
+	if record.Country.IsoCode != "" {
+		cc = record.Country.IsoCode
+	}
+	return
+}

internal/geoipx/geoipx_test.go

@@ -0,0 +1,59 @@
+package geoipx
+
+import (
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/model"
+)
+
+const ipAddr = "8.8.8.8"
+
+func TestLookupASN(t *testing.T) {
+	t.Run("with valid IP address", func(t *testing.T) {
+		asn, org, err := LookupASN(ipAddr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if asn != 15169 {
+			t.Fatal("unexpected ASN value", asn)
+		}
+		if org != "Google LLC" {
+			t.Fatal("unexpected org value", org)
+		}
+	})
+
+	t.Run("with invalid IP address", func(t *testing.T) {
+		asn, org, err := LookupASN("xxx")
+		if err == nil {
+			t.Fatal("expected an error here")
+		}
+		if asn != model.DefaultProbeASN {
+			t.Fatal("expected a zero ASN")
+		}
+		if org != model.DefaultProbeNetworkName {
+			t.Fatal("expected an empty org")
+		}
+	})
+}
+
+func TestLookupCC(t *testing.T) {
+	t.Run("with valid IP address", func(t *testing.T) {
+		cc, err := LookupCC(ipAddr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if cc != "US" {
+			t.Fatal("invalid country code", cc)
+		}
+	})
+
+	t.Run("with invalid IP address", func(t *testing.T) {
+		cc, err := LookupCC("xxx")
+		if err == nil {
+			t.Fatal("expected an error here")
+		}
+		if cc != model.DefaultProbeCC {
+			t.Fatal("expected an empty cc")
+		}
+	})
+}