Add dns capabilities to allow for custom dns in Windows (#305)

* Add dns capabilities to allow for custom dns in Windows

Co-authored-by: James Sturtevant <[email protected]>

* Move customDNS logic for Windows into network_windows.go and update link for RuntimeDNSConfig

Co-authored-by: James Sturtevant <[email protected]>

* Concatenate the elements of DNS.Searches

Author: Michelle Cone

cni/azure-windows.conflist

@@ -7,7 +7,8 @@
             "mode": "bridge",
             "bridge": "azure0",
             "capabilities": {
-                "portMappings": true
+                "portMappings": true,
+                "dns": true
             },
             "ipam": {
                 "type": "azure-vnet-ipam"

cni/netconfig.go

@@ -28,9 +28,16 @@ type PortMapping struct {
 	Protocol      string `json:"protocol"`
 	HostIp        string `json:"hostIP,omitempty"`
 }
-
 type RuntimeConfig struct {
-	PortMappings []PortMapping `json:"portMappings,omitempty"`
+	PortMappings []PortMapping    `json:"portMappings,omitempty"`
+	DNS          RuntimeDNSConfig `json:"dns,omitempty"`
+}
+
+// https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/dockershim/network/cni/cni.go#L104
+type RuntimeDNSConfig struct {
+	Servers  []string `json:"servers,omitempty"`
+	Searches []string `json:"searches,omitempty"`
+	Options  []string `json:"options,omitempty"`
 }
 
 // NetworkConfig represents Azure CNI plugin network configuration.

cni/network/network_windows.go

@@ -134,6 +134,12 @@ func setupInfraVnetRoutingForMultitenancy(
 func getNetworkDNSSettings(nwCfg *cni.NetworkConfig, result *cniTypesCurr.Result, namespace string) (network.DNSInfo, error) {
 	var nwDNS network.DNSInfo
 
+	// use custom dns if present
+	nwDNS = getCustomDNS(nwCfg)
+	if len(nwDNS.Servers) > 0 || nwDNS.Suffix != "" {
+		return nwDNS, nil
+	}
+
 	if (len(nwCfg.DNS.Search) == 0) != (len(nwCfg.DNS.Nameservers) == 0) {
 		err := fmt.Errorf("Wrong DNS configuration: %+v", nwCfg.DNS)
 		return nwDNS, err
@@ -149,6 +155,12 @@ func getNetworkDNSSettings(nwCfg *cni.NetworkConfig, result *cniTypesCurr.Result
 func getEndpointDNSSettings(nwCfg *cni.NetworkConfig, result *cniTypesCurr.Result, namespace string) (network.DNSInfo, error) {
 	var epDNS network.DNSInfo
 
+	// use custom dns if present
+	epDNS = getCustomDNS(nwCfg)
+	if len(epDNS.Servers) > 0 || epDNS.Suffix != "" {
+		return epDNS, nil
+	}
+
 	if (len(nwCfg.DNS.Search) == 0) != (len(nwCfg.DNS.Nameservers) == 0) {
 		err := fmt.Errorf("Wrong DNS configuration: %+v", nwCfg.DNS)
 		return epDNS, err
@@ -192,3 +204,17 @@ func getPoliciesFromRuntimeCfg(nwCfg *cni.NetworkConfig) []policy.Policy {
 
 	return policies
 }
+
+func getCustomDNS(nwCfg *cni.NetworkConfig) network.DNSInfo {
+	log.Printf("[net] RuntimeConfigs: %+v", nwCfg.RuntimeConfig)
+
+	var search string
+	if len(nwCfg.RuntimeConfig.DNS.Searches) > 0 {
+		search = strings.Join(nwCfg.RuntimeConfig.DNS.Searches, ",")
+	}
+
+	return network.DNSInfo{
+		Servers: nwCfg.RuntimeConfig.DNS.Servers,
+		Suffix:  search,
+	}
+}