Add synchronization around endpoint modification on RS1 - RS4

Server versions before 2019 (RS5), including Server 2016 (RS1) do not
support concurrent add/delete of endpoints. Therefore, we need to use
a mutex to serialize the add/delete of endpoints on those versions.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

internal/hns/hnsendpoint.go

@@ -6,7 +6,9 @@ import (
 	"encoding/json"
 	"net"
 	"strings"
+	"sync"
 
+	"github.com/Microsoft/hcsshim/osversion"
 	"github.com/sirupsen/logrus"
 )
 
@@ -36,7 +38,7 @@ type HNSEndpoint struct {
 	SharedContainers   []string          `json:",omitempty"`
 }
 
-//SystemType represents the type of the system on which actions are done
+// SystemType represents the type of the system on which actions are done
 type SystemType string
 
 // SystemType const
@@ -46,6 +48,14 @@ const (
 	HostType           SystemType = "Host"
 )
 
+var (
+	// Server versions before 2019 (RS5), including Server 2016 (RS1) do not
+	// support concurrent add/delete of endpoints. Therefore, we need to use
+	// this mutex and serialize the add/delete of endpoints on those versions.
+	endpointMu   sync.RWMutex
+	windowsBuild = osversion.Build()
+)
+
 // EndpointAttachDetachRequest is the structure used to send request to the container to modify the system
 // Supported resource types are Network and Request Types are Add/Remove
 type EndpointAttachDetachRequest struct {
@@ -76,6 +86,16 @@ type EndpointStats struct {
 // HNSEndpointRequest makes a HNS call to modify/query a network endpoint
 func HNSEndpointRequest(method, path, request string) (*HNSEndpoint, error) {
 	endpoint := &HNSEndpoint{}
+	if windowsBuild < osversion.RS5 {
+		switch method {
+		case "GET":
+			endpointMu.RLock()
+			defer endpointMu.RUnlock()
+		case "DELETE", "POST":
+			endpointMu.Lock()
+			defer endpointMu.Unlock()
+		}
+	}
 	err := hnsCall(method, "/endpoints/"+path, request, &endpoint)
 	if err != nil {
 		return nil, err
@@ -87,6 +107,10 @@ func HNSEndpointRequest(method, path, request string) (*HNSEndpoint, error) {
 // HNSListEndpointRequest makes a HNS call to query the list of available endpoints
 func HNSListEndpointRequest() ([]HNSEndpoint, error) {
 	var endpoint []HNSEndpoint
+	if windowsBuild < osversion.RS5 {
+		endpointMu.RLock()
+		defer endpointMu.RUnlock()
+	}
 	err := hnsCall("GET", "/endpoints/", "", &endpoint)
 	if err != nil {
 		return nil, err
@@ -181,6 +205,10 @@ func (endpoint *HNSEndpoint) Update() (*HNSEndpoint, error) {
 	if err != nil {
 		return nil, err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	err = hnsCall("POST", "/endpoints/"+endpoint.Id, string(jsonString), &endpoint)
 
 	return endpoint, err
@@ -244,6 +272,10 @@ func (endpoint *HNSEndpoint) ContainerAttach(containerID string, compartmentID u
 	if err != nil {
 		return err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	return hnsCall("POST", "/endpoints/"+endpoint.Id+"/attach", string(jsonString), &response)
 }
 
@@ -263,6 +295,10 @@ func (endpoint *HNSEndpoint) ContainerDetach(containerID string) error {
 	if err != nil {
 		return err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	return hnsCall("POST", "/endpoints/"+endpoint.Id+"/detach", string(jsonString), &response)
 }
 
@@ -281,6 +317,10 @@ func (endpoint *HNSEndpoint) HostAttach(compartmentID uint16) error {
 	if err != nil {
 		return err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	return hnsCall("POST", "/endpoints/"+endpoint.Id+"/attach", string(jsonString), &response)
 }
 
@@ -298,6 +338,10 @@ func (endpoint *HNSEndpoint) HostDetach() error {
 	if err != nil {
 		return err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	return hnsCall("POST", "/endpoints/"+endpoint.Id+"/detach", string(jsonString), &response)
 }
 
@@ -316,6 +360,10 @@ func (endpoint *HNSEndpoint) VirtualMachineNICAttach(virtualMachineNICName strin
 	if err != nil {
 		return err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	return hnsCall("POST", "/endpoints/"+endpoint.Id+"/attach", string(jsonString), &response)
 }
 
@@ -334,5 +382,9 @@ func (endpoint *HNSEndpoint) VirtualMachineNICDetach() error {
 	if err != nil {
 		return err
 	}
+	if windowsBuild < osversion.RS5 {
+		endpointMu.Lock()
+		defer endpointMu.Unlock()
+	}
 	return hnsCall("POST", "/endpoints/"+endpoint.Id+"/detach", string(jsonString), &response)
 }