Get darwin local DNS server from libresolv

dns/transport/local/resolv_darwin_cgo.go

@@ -0,0 +1,53 @@
+//go:build darwin && cgo
+
+package local
+
+/*
+#include <stdlib.h>
+#include <stdio.h>
+#include <resolv.h>
+#include <arpa/inet.h>
+*/
+import "C"
+
+import (
+	"time"
+
+	E "github.com/sagernet/sing/common/exceptions"
+
+	"github.com/miekg/dns"
+)
+
+func dnsReadConfig(_ string) *dnsConfig {
+	if C.res_init() != 0 {
+		return &dnsConfig{
+			servers:  defaultNS,
+			search:   dnsDefaultSearch(),
+			ndots:    1,
+			timeout:  5 * time.Second,
+			attempts: 2,
+			err:      E.New("libresolv initialization failed"),
+		}
+	}
+	conf := &dnsConfig{
+		ndots:    1,
+		timeout:  5 * time.Second,
+		attempts: int(C._res.retry),
+	}
+	for i := 0; i < int(C._res.nscount); i++ {
+		ns := C._res.nsaddr_list[i]
+		addr := C.inet_ntoa(ns.sin_addr)
+		if addr == nil {
+			continue
+		}
+		conf.servers = append(conf.servers, C.GoString(addr))
+	}
+	for i := 0; ; i++ {
+		search := C._res.dnsrch[i]
+		if search == nil {
+			break
+		}
+		conf.search = append(conf.search, dns.Fqdn(C.GoString(search)))
+	}
+	return conf
+}