Fix: dhcp client should request special interface

dns/client.go

@@ -15,9 +15,10 @@ import (
 
 type client struct {
 	*D.Client
-	r    *Resolver
-	port string
-	host string
+	r     *Resolver
+	port  string
+	host  string
+	iface string
 }
 
 func (c *client) Exchange(m *D.Msg) (*D.Msg, error) {
@@ -45,7 +46,11 @@ func (c *client) ExchangeContext(ctx context.Context, m *D.Msg) (*D.Msg, error)
 		network = "tcp"
 	}
 
-	conn, err := dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), c.port))
+	options := []dialer.Option{}
+	if c.iface != "" {
+		options = append(options, dialer.WithInterface(c.iface))
+	}
+	conn, err := dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), c.port), options...)
 	if err != nil {
 		return nil, err
 	}

dns/dhcp.go

@@ -68,8 +68,11 @@ func (d *dhcpClient) resolve(ctx context.Context) (*Resolver, error) {
 			dns, err := dhcp.ResolveDNSFromDHCP(ctx, d.ifaceName)
 			if err == nil {
 				nameserver := make([]NameServer, 0, len(dns))
-				for _, d := range dns {
-					nameserver = append(nameserver, NameServer{Addr: net.JoinHostPort(d.String(), "53")})
+				for _, item := range dns {
+					nameserver = append(nameserver, NameServer{
+						Addr:      net.JoinHostPort(item.String(), "53"),
+						Interface: d.ifaceName,
+					})
 				}
 
 				res = NewResolver(Config{

dns/resolver.go

@@ -302,8 +302,9 @@ func (r *Resolver) asyncExchange(ctx context.Context, client []dnsClient, msg *D
 }
 
 type NameServer struct {
-	Net  string
-	Addr string
+	Net       string
+	Addr      string
+	Interface string
 }
 
 type FallbackFilter struct {

dns/util.go

@@ -138,9 +138,10 @@ func transform(servers []NameServer, resolver *Resolver) []dnsClient {
 				UDPSize: 4096,
 				Timeout: 5 * time.Second,
 			},
-			port: port,
-			host: host,
-			r:    resolver,
+			port:  port,
+			host:  host,
+			iface: s.Interface,
+			r:     resolver,
 		})
 	}
 	return ret