handle: use per-request sockets for VF-only configuration

handle_linux.go

@@ -58,8 +58,15 @@ type HandleOptions struct {
 	// [ErrDumpInterrupted].
 	RetryInterrupted bool
 
-	// NetNS specifies the network namespace to operate on. If not set, the
-	// current network namespace will be used.
+	// NetNS specifies the network namespace in which the Handle's persistent
+	// netlink sockets are created. A persistent socket remains bound to its
+	// creation namespace even if the calling OS thread later changes namespaces.
+	//
+	// When NetNS is non-nil, persistent sockets are created in that namespace.
+	// When NetNS is nil, persistent sockets are created in the calling OS thread's
+	// current namespace when the Handle is created. A socketless Handle instead
+	// creates a temporary socket for each operation in the calling OS thread's
+	// current namespace when the operation is executed.
 	NetNS *netns.NsHandle
 }
 
@@ -199,7 +206,13 @@ func NewHandleAtFrom(newNs, curNs netns.NsHandle) (*Handle, error) {
 }
 
 // NewHandleWithOptions returns a Handle created using the specified options.
+// If DisableVFInfoCollection is the only option set and no netlink families are
+// specified, the returned Handle creates a socket for each request in the
+// caller's current network namespace instead of keeping persistent sockets.
 func NewHandleWithOptions(opts HandleOptions, nlFamilies ...int) (*Handle, error) {
+	if opts.DisableVFInfoCollection && !opts.RetryInterrupted && opts.NetNS == nil && len(nlFamilies) == 0 {
+		return &Handle{options: opts}, nil
+	}
 	return newHandle(netns.None(), opts, nlFamilies...)
 }
 

handle_linux_test.go

@@ -5,6 +5,8 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/vishvananda/netns"
+	"golang.org/x/sys/unix"
 )
 
 func TestSetGetSocketTimeout(t *testing.T) {
@@ -34,3 +36,62 @@ func TestConfigureHandle(t *testing.T) {
 	assert.NoError(t, pkgHandle.Close())
 	assert.Error(t, ConfigureHandle(HandleOptions{}))
 }
+
+func TestNewHandleWithOptions(t *testing.T) {
+	none := netns.None()
+	tests := []struct {
+		name           string
+		opts           HandleOptions
+		nlFamilies     []int
+		wantSocketless bool
+	}{
+		{
+			name:           "disable VF only",
+			opts:           HandleOptions{DisableVFInfoCollection: true},
+			wantSocketless: true,
+		},
+		{
+			name: "retry interrupted",
+			opts: HandleOptions{
+				DisableVFInfoCollection: true,
+				RetryInterrupted:        true,
+			},
+		},
+		{
+			name: "explicit namespace",
+			opts: HandleOptions{
+				DisableVFInfoCollection: true,
+				NetNS:                   &none,
+			},
+		},
+		{
+			name:       "explicit netlink family",
+			opts:       HandleOptions{DisableVFInfoCollection: true},
+			nlFamilies: []int{unix.NETLINK_ROUTE},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			h, err := NewHandleWithOptions(tt.opts, tt.nlFamilies...)
+			if !assert.NoError(t, err) {
+				return
+			}
+			t.Cleanup(func() { assert.NoError(t, h.Close()) })
+
+			assert.True(t, h.options.DisableVFInfoCollection)
+			if tt.wantSocketless {
+				assert.Nil(t, h.sockets)
+			} else {
+				assert.NotNil(t, h.sockets)
+			}
+
+			req := h.newNetlinkRequest(unix.RTM_GETLINK, unix.NLM_F_DUMP)
+			if tt.wantSocketless {
+				assert.Nil(t, req.Sockets)
+			} else {
+				assert.NotNil(t, req.Sockets)
+			}
+		})
+	}
+}