net/dns/publicdns: remove additional information in DOH URL passed to IPv6 address generation for controlD.

This commit truncates any additional information (mainly hostnames) that's passed to controlD via DOH URL in DoHIPsOfBase.
This change is to make sure only resolverID is passed to controlDv6Gen but not the additional information.

Updates: #7946
Signed-off-by: KevinLiang10 <37811973+KevinLiang10@users.noreply.github.com>

net/dns/publicdns/publicdns.go

@@ -10,6 +10,7 @@ import (
 	"encoding/binary"
 	"encoding/hex"
 	"fmt"
+	"log"
 	"math/big"
 	"net/netip"
 	"sort"
@@ -122,6 +123,9 @@ func DoHIPsOfBase(dohBase string) []netip.Addr {
 		}
 	}
 	if pathStr, ok := strings.CutPrefix(dohBase, controlDBase); ok {
+		if i := strings.IndexFunc(pathStr, isSlashOrQuestionMark); i != -1 {
+			pathStr = pathStr[:i]
+		}
 		return []netip.Addr{
 			controlDv4One,
 			controlDv4Two,
@@ -318,7 +322,10 @@ func nextDNSv6Gen(ip netip.Addr, id []byte) netip.Addr {
 // e.g. https://dns.controld.com/hyq3ipr2ct
 func controlDv6Gen(ip netip.Addr, id string) netip.Addr {
 	b := make([]byte, 8)
-	decoded, _ := strconv.ParseUint(id, 36, 64)
+	decoded, err := strconv.ParseUint(id, 36, 64)
+	if err != nil {
+		log.Printf("controlDv6Gen: failed to parse id %q: %v", id, err)
+	}
 	binary.BigEndian.PutUint64(b, decoded)
 	a := ip.AsSlice()
 	copy(a[6:14], b)

net/dns/publicdns/publicdns_test.go

@@ -134,6 +134,15 @@ func TestDoHIPsOfBase(t *testing.T) {
 				"2606:1a40:1:ffff:ffff:ffff:ffff:0",
 			),
 		},
+		{
+			base: "https://dns.controld.com/hyq3ipr2ct/test-host-name",
+			want: ips(
+				"76.76.2.22",
+				"76.76.10.22",
+				"2606:1a40:0:6:7b5b:5949:35ad:0",
+				"2606:1a40:1:6:7b5b:5949:35ad:0",
+			),
+		},
 	}
 	for _, tt := range tests {
 		got := DoHIPsOfBase(tt.base)