Merge pull request #2231 from katiewasnothere/kabaldau/sort_endpoints

Sort the endpoints such that eth0 is first

internal/uvm/network.go

@@ -6,6 +6,8 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"slices"
+	"strings"
 
 	"github.com/Microsoft/go-winio"
 	"github.com/Microsoft/go-winio/pkg/guid"
@@ -36,6 +38,20 @@ var (
 	ErrNICNotFound = errors.New("NIC not found in network namespace")
 )
 
+func sortEndpoints(endpoints []*hns.HNSEndpoint) {
+	cmp := func(a, b *hns.HNSEndpoint) int {
+		if strings.HasSuffix(a.Name, "eth0") {
+			return -1
+		}
+		if strings.HasSuffix(b.Name, "eth0") {
+			return 1
+		}
+		return 0
+	}
+
+	slices.SortStableFunc(endpoints, cmp)
+}
+
 // In this function we take the namespace ID of the namespace that was created for this
 // UVM. We hot add the namespace. We get the endpoints associated with this namespace
 // and then hot add those endpoints.
@@ -59,6 +75,13 @@ func (uvm *UtilityVM) SetupNetworkNamespace(ctx context.Context, nsid string) er
 		return err
 	}
 
+	// Sort the endpoints.
+	// In some scenarios, multiple endpoints may be added to a pod. When this happens
+	// we need to know which endpoint to add first as the eth0 interface in the guest.
+	// Since we don't have CNI results here, instead look if any endpoints have the
+	// name eth0 at the end. If so, add that endpoint first. Otherwise this is a noop.
+	sortEndpoints(endpoints)
+
 	if err = uvm.AddEndpointsToNS(ctx, nsidInsideUVM, endpoints); err != nil {
 		// Best effort clean up the NS
 		if removeErr := uvm.RemoveNetNS(ctx, nsidInsideUVM); removeErr != nil {

internal/uvm/network_test.go

@@ -0,0 +1,69 @@
+//go:build windows
+
+package uvm
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/Microsoft/hcsshim/internal/hns"
+)
+
+func Test_SortEndpoints(t *testing.T) {
+	type config struct {
+		endpointNames []string
+		targetName    string
+	}
+	tests := []config{
+		{
+			endpointNames: []string{"eth1", "eth0"},
+			targetName:    "eth0",
+		},
+		{
+			endpointNames: []string{"eth0", "eth1"},
+			targetName:    "eth0",
+		},
+		{
+			endpointNames: []string{"eth1", "name-eth0"},
+			targetName:    "name-eth0",
+		},
+		{
+			endpointNames: []string{"name-eth098", "name-eth0"},
+			targetName:    "name-eth0",
+		},
+		{
+			endpointNames: []string{"name-eth0", "name-eth098"},
+			targetName:    "name-eth0",
+		},
+		{
+			endpointNames: []string{"random-ifname", "another-random-ifname"},
+			// ordering shouldn't change so the first entry should still be first
+			targetName: "random-ifname",
+		},
+		{
+			endpointNames: []string{"eth0-name", "name-eth0"},
+			targetName:    "name-eth0",
+		},
+		{
+			endpointNames: []string{},
+		},
+	}
+	for i, test := range tests {
+		t.Run(fmt.Sprint(t.Name(), i), func(st *testing.T) {
+			endpoints := []*hns.HNSEndpoint{}
+			for _, n := range test.endpointNames {
+				e := &hns.HNSEndpoint{
+					Name: n,
+				}
+				endpoints = append(endpoints, e)
+			}
+
+			sortEndpoints(endpoints)
+			if len(test.endpointNames) != 0 {
+				if endpoints[0].Name != test.targetName {
+					st.Fatalf("expected endpoint sorting to return endpoint with name %s first, instead got %s", test.targetName, endpoints[0].Name)
+				}
+			}
+		})
+	}
+}