roachprod: add SSH config export

This change introduces a new option to `roachprod list` that exports an SSH
configuration file for the listed clusters. This configuration enables direct
SSH access to roachprod-created clusters using any SSH client, removing the need
to run `roachprod ssh`.

This feature is useful for tools, such as IDEs, that support remote SSH
connections.

Epic: None
Release note: None

Author: herkolategan

pkg/cmd/roachprod/cli/commands.go

@@ -12,6 +12,7 @@ import (
 	"net/url"
 	"os"
 	"path"
+	"path/filepath"
 	"runtime"
 	"sort"
 	"strconv"
@@ -556,6 +557,44 @@ hosts file.
 					}
 				}
 			}
+
+			// Optionally, export an SSH client config file for the clusters.
+			// Only export if a pattern is specified or if the --mine flag is set.
+			if exportSSHConfig != "" && (listPattern != "" || listMine) {
+				hostTemplate := `Host %[1]s
+    HostName %[2]s
+    User %[3]s
+    StrictHostKeyChecking no
+    UserKnownHostsFile /dev/null
+%[4]s
+`
+				var allKeys strings.Builder
+				paths := make([]string, len(config.DefaultPubKeyNames))
+				for idx, name := range config.DefaultPubKeyNames {
+					paths[idx] = filepath.Join(config.SSHDirectory, name)
+				}
+				for _, p := range paths {
+					if _, notFoundErr := os.Stat(p); notFoundErr == nil {
+						allKeys.WriteString(fmt.Sprintf("    IdentityFile %s\n", p))
+					}
+				}
+
+				var configBuf strings.Builder
+				for _, c := range filteredCloud.Clusters {
+					for _, cVM := range c.VMs {
+						if cVM.PublicIP == "" {
+							continue
+						}
+						configBuf.WriteString(
+							fmt.Sprintf(hostTemplate, cVM.Name, cVM.PublicIP, config.SharedUser, allKeys.String()),
+						)
+					}
+				}
+				err = os.WriteFile(filepath.Join(exportSSHConfig), []byte(configBuf.String()), 0600)
+				if err != nil {
+					return errors.Wrapf(err, "failed to write SSH config file to %s", exportSSHConfig)
+				}
+			}
 			return nil
 		}),
 	}

pkg/cmd/roachprod/cli/flags.go

@@ -53,6 +53,7 @@ var (
 	virtualClusterName    string
 	sqlInstance           int
 	extraSSHOptions       = ""
+	exportSSHConfig       string
 	nodeEnv               []string
 	tag                   string
 	external              = false
@@ -217,6 +218,8 @@ func initListCmdFlags(listCmd *cobra.Command) {
 		"mine", "m", false, "Show only clusters belonging to the current user")
 	listCmd.Flags().StringVar(&listPattern,
 		"pattern", "", "Show only clusters matching the regex pattern. Empty string matches everything.")
+	listCmd.Flags().StringVar(&exportSSHConfig,
+		"export-ssh-config", os.Getenv("ROACHPROD_EXPORT_SSH_CONFIG"), "export the SSH config for listed clusters (only when pattern or mine is specified")
 }
 
 func initAdminurlCmdFlags(adminurlCmd *cobra.Command) {
@@ -271,7 +274,6 @@ func initSyncCmdFlags(syncCmd *cobra.Command) {
 	syncCmd.Flags().BoolVar(&listOpts.IncludeVolumes, "include-volumes", false, "Include volumes when syncing")
 	syncCmd.Flags().StringArrayVarP(&listOpts.IncludeProviders, "clouds", "c",
 		make([]string, 0), "Specify the cloud providers when syncing. Important: Use this flag only if you are certain that you want to sync with a specific cloud. All DNS host entries for other clouds will be erased from the DNS zone.")
-
 }
 
 func initStageCmdFlags(stageCmd *cobra.Command) {