Fix CNAME

x/smart/cname.go

@@ -0,0 +1,71 @@
+// Copyright 2024 Jigsaw Operations LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package smart
+
+/*
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+*/
+import "C"
+
+import (
+	"context"
+	"fmt"
+	"unsafe"
+)
+
+func lookupCNAME(ctx context.Context, domain string) (string, error) {
+	type result struct {
+		cname string
+		err   error
+	}
+
+	results := make(chan result)
+	go func() {
+		cname, err := lookupCNAMEBlocking(domain)
+		results <- result{cname, err}
+	}()
+
+	select {
+	case r := <-results:
+		return r.cname, r.err
+	case <-ctx.Done():
+		return "", ctx.Err()
+	}
+}
+
+func lookupCNAMEBlocking(host string) (string, error) {
+	var hints C.struct_addrinfo
+	var result *C.struct_addrinfo
+
+	chost := C.CString(host)
+	defer C.free(unsafe.Pointer(chost))
+
+	hints.ai_family = C.AF_UNSPEC
+	hints.ai_flags = C.AI_CANONNAME
+
+	// Call getaddrinfo
+	res := C.getaddrinfo(chost, nil, &hints, &result)
+	if res != 0 {
+		return "", fmt.Errorf("getaddrinfo error: %s", C.GoString(C.gai_strerror(res)))
+	}
+	defer C.freeaddrinfo(result)
+
+	// Extract canonical name
+	cname := C.GoString(result.ai_canonname)
+	return cname, nil
+}

x/smart/stream_dialer.go

@@ -154,7 +154,7 @@ func fingerprint(pd transport.PacketDialer, sd transport.StreamDialer, testDomai
 
 func evaluateNetResolver(ctx context.Context, resolver *net.Resolver, testDomain string) ([]net.IP, error) {
 	requestDomain := mixCase(testDomain)
-	_, err := resolver.LookupCNAME(ctx, requestDomain)
+	_, err := lookupCNAME(ctx, requestDomain)
 	if err != nil {
 		return nil, fmt.Errorf("could not get cname: %w", err)
 	}