From 48c2d8c458c2d911251d478885376b1906f215a0 Mon Sep 17 00:00:00 2001
From: Olli Janatuinen <olli.janatuinen@gmail.com>
Date: Mon, 20 Oct 2025 15:35:30 +0000
Subject: [PATCH] libnetwork: support custom DNS servers in Windows overlay
 driver

Signed-off-by: Olli Janatuinen <olli.janatuinen@gmail.com>
---
 .../windows/overlay/ov_endpoint_windows.go    |  6 +++++
 daemon/libnetwork/drivers/windows/windows.go  | 25 ++++++++++++-------
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/daemon/libnetwork/drivers/windows/overlay/ov_endpoint_windows.go b/daemon/libnetwork/drivers/windows/overlay/ov_endpoint_windows.go
index 14d5520fa5..706ea54539 100644
--- a/daemon/libnetwork/drivers/windows/overlay/ov_endpoint_windows.go
+++ b/daemon/libnetwork/drivers/windows/overlay/ov_endpoint_windows.go
@@ -124,12 +124,18 @@ func (d *driver) CreateEndpoint(ctx context.Context, nid, eid string, ifInfo dri
 
 	// Todo: Add port bindings and qos policies here
 
+	dnsServerList, err := windows.ParseDNSServers(epOptions)
+	if err != nil {
+		return err
+	}
+
 	hnsEndpoint := &hcsshim.HNSEndpoint{
 		Name:              eid,
 		VirtualNetwork:    n.hnsID,
 		IPAddress:         ep.addr.IP,
 		EnableInternalDNS: true,
 		GatewayAddress:    s.gwIP.String(),
+		DNSServerList:     dnsServerList,
 	}
 
 	if ep.mac != nil {
diff --git a/daemon/libnetwork/drivers/windows/windows.go b/daemon/libnetwork/drivers/windows/windows.go
index 361b9a48e5..73328b1e7c 100644
--- a/daemon/libnetwork/drivers/windows/windows.go
+++ b/daemon/libnetwork/drivers/windows/windows.go
@@ -610,14 +610,6 @@ func parseEndpointOptions(epOptions map[string]any) (*endpointOption, error) {
 		}
 	}
 
-	if opt, ok := epOptions[netlabel.DNSServers]; ok {
-		if dns, ok := opt.([]string); ok {
-			ec.DNSServers = dns
-		} else {
-			return nil, fmt.Errorf("Invalid endpoint configuration")
-		}
-	}
-
 	if opt, ok := epOptions[DisableICC]; ok {
 		if disableICC, ok := opt.(bool); ok {
 			ec.DisableICC = disableICC
@@ -637,6 +629,17 @@ func parseEndpointOptions(epOptions map[string]any) (*endpointOption, error) {
 	return ec, nil
 }
 
+func ParseDNSServers(epOptions map[string]any) (string, error) {
+	if opt, ok := epOptions[netlabel.DNSServers]; ok {
+		if dns, ok := opt.([]string); ok {
+			return strings.Join(dns, ","), nil
+		} else {
+			return "", fmt.Errorf("Invalid endpoint configuration")
+		}
+	}
+	return "", nil
+}
+
 // ParseEndpointConnectivity parses options passed to CreateEndpoint, specifically port bindings, and store in a endpointConnectivity object.
 func ParseEndpointConnectivity(epOptions map[string]any) (*EndpointConnectivity, error) {
 	if epOptions == nil {
@@ -729,7 +732,11 @@ func (d *driver) CreateEndpoint(ctx context.Context, nid, eid string, ifInfo dri
 		endpointStruct.IPAddress = ifInfo.Address().IP
 	}
 
-	endpointStruct.DNSServerList = strings.Join(epOption.DNSServers, ",")
+	dnsServerList, err := ParseDNSServers(epOptions)
+	if err != nil {
+		return err
+	}
+	endpointStruct.DNSServerList = dnsServerList
 
 	// overwrite the ep DisableDNS option if DisableGatewayDNS was set to true during the network creation option
 	if n.config.DisableGatewayDNS {