[sshutil] Add a total timeout to SSH client creation
ssh.Dial can hang during authentication, the 'timeout' being set in the config only applying to establishment of the initial connection. This function is effectively ssh.Dial with the ability to set a deadline on the underlying connection.
See https://github.com/golang/go/issues/21941 for more details on the hang.
Change-Id: Ie5b51dad23ac44bed5f98c322a5da8c06cd93f45
diff --git a/sshutil/sshutil.go b/sshutil/sshutil.go
index afc6f45..271c923 100644
--- a/sshutil/sshutil.go
+++ b/sshutil/sshutil.go
@@ -27,8 +27,10 @@
// Default RSA key size.
RSAKeySize = 2048
- // The default timeout for IO operations.
- defaultIOTimeout = 5 * time.Second
+ // The allowed timeout to establish an SSH connection.
+ connTimeout = 5 * time.Second
+ // The total allowed timeout to establish an SSH connection and complete an auth handshake.
+ totalDialTimeout = 10 * time.Second
sshUser = "fuchsia"
)
@@ -58,7 +60,7 @@
// TODO: figure out optimal backoff time and number of retries
if err := retry.Retry(ctx, retry.WithMaxDuration(&retry.ZeroBackoff{}, time.Minute), func() error {
var err error
- client, err = ssh.Dial(network, address.String(), config)
+ client, err = dialWithTimeout(network, address.String(), config, totalDialTimeout)
return err
}, nil); err != nil {
return nil, fmt.Errorf("cannot connect to address %q: %v", address, err)
@@ -67,6 +69,32 @@
return client, nil
}
+// ssh.Dial can hang during authentication, the 'timeout' being set in the config only
+// applying to establishment of the initial connection. This function is effectively
+// ssh.Dial with the ability to set a deadline on the underlying connection.
+//
+// See https://github.com/golang/go/issues/21941 for more details on the hang.
+func dialWithTimeout(network, addr string, config *ssh.ClientConfig, timeout time.Duration) (*ssh.Client, error) {
+ conn, err := net.DialTimeout(network, addr, config.Timeout)
+ if err != nil {
+ return nil, err
+ }
+ if err := conn.SetDeadline(time.Now().Add(timeout)); err != nil {
+ conn.Close()
+ return nil, err
+ }
+ c, chans, reqs, err := ssh.NewClientConn(conn, addr, config)
+ if err != nil {
+ conn.Close()
+ return nil, err
+ }
+ if err := conn.SetDeadline(time.Time{}); err != nil {
+ c.Close()
+ return nil, err
+ }
+ return ssh.NewClient(c, chans, reqs), nil
+}
+
// ConnectToNode connects to the device with the given nodename.
func ConnectToNode(ctx context.Context, nodename string, config *ssh.ClientConfig) (*ssh.Client, error) {
addr, err := netutil.GetNodeAddress(ctx, nodename, true)
@@ -91,7 +119,7 @@
return &ssh.ClientConfig{
User: sshUser,
Auth: []ssh.AuthMethod{ssh.PublicKeys(signers...)},
- Timeout: defaultIOTimeout,
+ Timeout: connTimeout,
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}, nil
}
