shared/cliconfig: Add keepalive proxy support

Signed-off-by: Stéphane Graber <stgraber@stgraber.org>

shared/cliconfig/keepalive.go

@@ -0,0 +1,60 @@
+//go:build !windows
+
+package cliconfig
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/lxc/incus/client"
+	"github.com/lxc/incus/shared/subprocess"
+	"github.com/lxc/incus/shared/util"
+)
+
+func (c *Config) handleKeepAlive(remote Remote, name string, args *incus.ConnectionArgs) (incus.InstanceServer, error) {
+	// Create the socker directory if missing.
+	socketDir := filepath.Join(c.ConfigDir, "keepalive")
+	err := os.Mkdir(socketDir, 0700)
+	if err != nil && !os.IsExist(err) {
+		return nil, err
+	}
+
+	// Attempt to use the existing socket.
+	socketPath := filepath.Join(socketDir, fmt.Sprintf("%s.socket", name))
+	d, err := incus.ConnectIncusUnix(socketPath, args)
+	if err != nil {
+		// Delete any existing sockets.
+		_ = os.Remove(socketPath)
+
+		// Spawn the proxy.
+		proc, err := subprocess.NewProcess("incus", []string{"remote", "proxy", name, socketPath, fmt.Sprintf("--timeout=%d", remote.KeepAlive)}, "", "")
+		if err != nil {
+			return nil, err
+		}
+
+		err = proc.Start(context.Background())
+		if err != nil {
+			return nil, err
+		}
+
+		// Try up to 10 times over 5s.
+		for i := 0; i < 10; i++ {
+			if util.PathExists(socketPath) {
+				break
+			}
+
+			time.Sleep(500 * time.Millisecond)
+		}
+
+		// Connect to the proxy.
+		d, err = incus.ConnectIncusUnix(socketPath, args)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return d, nil
+}

shared/cliconfig/keepalive_windows.go

@@ -0,0 +1,13 @@
+//go:build windows
+
+package cliconfig
+
+import (
+	"fmt"
+
+	"github.com/lxc/incus/client"
+)
+
+func (c *Config) handleKeepAlive(remote Remote, name string, args *incus.ConnectionArgs) (incus.InstanceServer, error) {
+	return nil, fmt.Errorf("Keepalive isn't supported on Windows")
+}

shared/cliconfig/remote.go

@@ -103,9 +103,21 @@ func (c *Config) GetInstanceServer(name string) (incus.InstanceServer, error) {
 		return nil, fmt.Errorf("Missing TLS client certificate and key")
 	}
 
-	d, err := incus.ConnectIncus(remote.Addr, args)
-	if err != nil {
-		return nil, err
+	var d incus.InstanceServer
+	if remote.KeepAlive > 0 {
+		d, err = c.handleKeepAlive(remote, name, args)
+		if err != nil {
+			// On proxy failure, just fallback to regular client.
+			d, err = incus.ConnectIncus(remote.Addr, args)
+			if err != nil {
+				return nil, err
+			}
+		}
+	} else {
+		d, err = incus.ConnectIncus(remote.Addr, args)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	if remote.Project != "" && remote.Project != "default" {