search domain discovery: Increase test coverage

Randomly pick IP from address space
Update Go version to current scionproto master
Replace usage of deprecated package with math/rand/v2

Author: FR4NK-W

go.mod

@@ -27,4 +27,4 @@ require (
 
 replace github.com/insomniacslk/dhcp => github.com/stapelberg/dhcp v0.0.0-20190429172946-5244c0daddf0
 
-go 1.21
+go 1.22

hinting/dns.go

@@ -16,7 +16,7 @@
 package hinting
 
 import (
-	"math/rand"
+	"math/rand/v2"
 	"net"
 	"net/netip"
 	"sort"
@@ -214,10 +214,10 @@ func (s byPriority) Less(i, j int) bool {
 		return false
 	} else {
 		if s[i].Weight == 0 && s[j].Weight == 0 {
-			return rand.Intn(2) == 0
+			return rand.IntN(2) == 0
 		}
 		max := int(s[i].Weight) + int(s[j].Weight)
-		return rand.Intn(max) < int(s[i].Weight)
+		return rand.IntN(max) < int(s[i].Weight)
 	}
 }
 

hinting/dns_search_domain_fallbacks_reverse.go

@@ -3,7 +3,7 @@ package hinting
 import (
 	"context"
 	"errors"
-	"math/rand"
+	"math/rand/v2"
 	"net"
 	"net/netip"
 	"time"
@@ -37,13 +37,13 @@ func getAkaNS() (nameserver string, err error) {
 	defer cancel()
 	nameservers, err := resolver.LookupNS(ctx, akamaiDomain)
 	if err == nil {
-		return nameservers[rand.Intn(len(nameservers))].Host, err
+		return nameservers[rand.IntN(len(nameservers))].Host, err
 	}
 	if err, ok := err.(*net.DNSError); ok && err.IsNotFound {
 		// Do not attempt further fallback to a public resolver.
 		// We got a NXDOMAIN response or no NS type response. Since we know the NS record exists,
 		// it must have been intentionally shadowed by the system default resolver.
-		return nil, err
+		return "", err
 	}
 
 	m := new(dns.Msg)
@@ -57,7 +57,7 @@ func getAkaNS() (nameserver string, err error) {
 		err = errors.New("getAkaNS: No DNS RR answer")
 		return "", err
 	}
-	if ns, ok := in.Answer[rand.Intn(len(in.Answer))].(*dns.NS); ok {
+	if ns, ok := in.Answer[rand.IntN(len(in.Answer))].(*dns.NS); ok {
 		return ns.Ns, nil
 	}
 	return "", errors.New("getAkaNS: Invalid NS record")

hinting/dns_search_domain_fallbacks_test.go

@@ -1,9 +1,12 @@
 package hinting
 
 import (
-	"github.com/stretchr/testify/assert"
+	"crypto/rand"
+	"net"
 	"net/netip"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestReverseLookupDomains(t *testing.T) {
@@ -32,6 +35,8 @@ func TestReverseLookupDomains(t *testing.T) {
 				domain string
 			}{
 				{ip: netip.MustParseAddr("66.180.178.131"), domain: "princeton.edu"},
+				//{ip: randIPFromCIDR("128.112.0.0/16"), domain: "princeton.edu"},
+				{ip: randIPFromCIDR("128.112.66.0/23"), domain: "princeton.edu"},
 			},
 		},
 		{
@@ -42,6 +47,7 @@ func TestReverseLookupDomains(t *testing.T) {
 			}{
 				{ip: netip.MustParseAddr("128.143.33.137"), domain: "virginia.edu"},
 				{ip: netip.MustParseAddr("128.143.33.144"), domain: "virginia.edu"},
+				{ip: randIPFromCIDR("128.143.0.128/25"), domain: "virginia.edu"},
 			},
 		},
 		{
@@ -51,6 +57,7 @@ func TestReverseLookupDomains(t *testing.T) {
 				domain string
 			}{
 				{ip: netip.MustParseAddr("130.59.31.80"), domain: "switch.ch"},
+				{ip: randIPFromCIDR("130.59.2.128/25"), domain: "switch.ch"},
 			},
 		},
 		{
@@ -59,6 +66,7 @@ func TestReverseLookupDomains(t *testing.T) {
 				ip     netip.Addr
 				domain string
 			}{
+				//{ip: netip.MustParseAddr("203.250.215.48"), domain: "kreonet.net"},
 				{ip: netip.MustParseAddr("134.75.254.11"), domain: "kreonet.net"},
 				{ip: netip.MustParseAddr("134.75.254.12"), domain: "kreonet.net"},
 			},
@@ -70,6 +78,7 @@ func TestReverseLookupDomains(t *testing.T) {
 				domain string
 			}{
 				{ip: netip.MustParseAddr("163.152.6.10"), domain: "korea.ac.kr"},
+				{ip: randIPFromCIDR("163.152.6.16/29"), domain: "korea.ac.kr"},
 			},
 		},
 	}
@@ -124,3 +133,41 @@ func TestDomainsFromHostnamesDerivation(t *testing.T) {
 		}
 	}
 }
+
+// randIPFromCIDR returns a random host IP in the subnet specified by the CIDR
+func randIPFromCIDR(cidr string) (ip netip.Addr) {
+	_, ipNet, err := net.ParseCIDR(cidr)
+	if err != nil {
+		return
+	}
+	ip, ok := netip.AddrFromSlice(ipNet.IP)
+	if !ok {
+		return
+	}
+	var randBytes []byte
+	randBytes = make([]byte, net.IPv6len)
+	_, err = rand.Read(randBytes)
+	if err != nil {
+		return
+	}
+	if ip.Is4() {
+		randBytes = randBytes[:net.IPv4len]
+	}
+	randomIP := net.IP(randBytes)
+	maskedIP := randomIP.Mask(invertMask(ipNet.Mask))
+	if len(ipNet.IP) != len(maskedIP) {
+		return
+	}
+	for i := range ipNet.IP {
+		randomIP[i] = ipNet.IP[i] | maskedIP[i]
+	}
+	return netip.MustParseAddr(randomIP.String())
+}
+
+func invertMask(mask net.IPMask) (invertedMask net.IPMask) {
+	invertedMask = make(net.IPMask, len(mask))
+	for i, b := range mask {
+		invertedMask[i] = 0xff ^ b
+	}
+	return
+}