From 58864d889b55b7cf44ecc6fff245d4113cbe19e1 Mon Sep 17 00:00:00 2001
From: Davide D'Agostino <info@daddye.it>
Date: Mon, 1 May 2017 18:18:54 -0700
Subject: [PATCH 1/4] Avoid forever lock

If we close the connection two times the second time will hang forever waiting for a server code.
---
 ftp.go | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/ftp.go b/ftp.go
index 567e2fd..cafb986 100644
--- a/ftp.go
+++ b/ftp.go
@@ -47,8 +47,9 @@ type Entry struct {
 
 // Response represents a data-connection
 type Response struct {
-	conn net.Conn
-	c    *ServerConn
+	conn       net.Conn
+	c          *ServerConn
+	connClosed bool
 }
 
 // Connect is an alias to Dial, for backward compatibility
@@ -337,7 +338,7 @@ func (c *ServerConn) NameList(path string) (entries []string, err error) {
 		return
 	}
 
-	r := &Response{conn, c}
+	r := &Response{conn, c, false}
 	defer r.Close()
 
 	scanner := bufio.NewScanner(r)
@@ -368,7 +369,7 @@ func (c *ServerConn) List(path string) (entries []*Entry, err error) {
 		return
 	}
 
-	r := &Response{conn, c}
+	r := &Response{conn, c, false}
 	defer r.Close()
 
 	scanner := bufio.NewScanner(r)
@@ -445,7 +446,7 @@ func (c *ServerConn) RetrFrom(path string, offset uint64) (*Response, error) {
 		return nil, err
 	}
 
-	return &Response{conn, c}, nil
+	return &Response{conn, c, false}, nil
 }
 
 // Stor issues a STOR FTP command to store a file to the remote FTP server.
@@ -537,11 +538,15 @@ func (r *Response) Read(buf []byte) (int, error) {
 
 // Close implements the io.Closer interface on a FTP data connection.
 func (r *Response) Close() error {
+	if r.connClosed == true {
+		return nil
+	}
 	err := r.conn.Close()
 	_, _, err2 := r.c.conn.ReadResponse(StatusClosingDataConnection)
 	if err2 != nil {
 		err = err2
 	}
+	r.connClosed = true
 	return err
 }
 

From 7e3820b35dcf17f546d5d70d284f92bd12775f53 Mon Sep 17 00:00:00 2001
From: Davide D'Agostino <daddye@uber.com>
Date: Thu, 4 May 2017 13:03:00 -0700
Subject: [PATCH 2/4] Address comments

---
 ftp.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/ftp.go b/ftp.go
index cafb986..317002d 100644
--- a/ftp.go
+++ b/ftp.go
@@ -338,7 +338,7 @@ func (c *ServerConn) NameList(path string) (entries []string, err error) {
 		return
 	}
 
-	r := &Response{conn, c, false}
+	r := &Response{conn: conn, c: c}
 	defer r.Close()
 
 	scanner := bufio.NewScanner(r)
@@ -369,7 +369,7 @@ func (c *ServerConn) List(path string) (entries []*Entry, err error) {
 		return
 	}
 
-	r := &Response{conn, c, false}
+	r := &Response{conn: conn, c: c}
 	defer r.Close()
 
 	scanner := bufio.NewScanner(r)
@@ -446,7 +446,7 @@ func (c *ServerConn) RetrFrom(path string, offset uint64) (*Response, error) {
 		return nil, err
 	}
 
-	return &Response{conn, c, false}, nil
+	return &Response{conn: conn, c: c}, nil
 }
 
 // Stor issues a STOR FTP command to store a file to the remote FTP server.
@@ -538,7 +538,7 @@ func (r *Response) Read(buf []byte) (int, error) {
 
 // Close implements the io.Closer interface on a FTP data connection.
 func (r *Response) Close() error {
-	if r.connClosed == true {
+	if r.connClosed {
 		return nil
 	}
 	err := r.conn.Close()

From cb362c410118164e9c6f2db0e16d095525f9ef94 Mon Sep 17 00:00:00 2001
From: Davide D'Agostino <daddye@uber.com>
Date: Thu, 4 May 2017 17:46:29 -0700
Subject: [PATCH 3/4] Rename connClosed -> closed

---
 client_test.go |  1 +
 ftp.go         | 10 +++++-----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/client_test.go b/client_test.go
index 0409da0..8297e49 100644
--- a/client_test.go
+++ b/client_test.go
@@ -81,6 +81,7 @@ func testConn(t *testing.T, disableEPSV bool) {
 			t.Errorf("'%s'", buf)
 		}
 		r.Close()
+		r.Close() // test we can close two times
 	}
 
 	// Read with deadline
diff --git a/ftp.go b/ftp.go
index 317002d..17fe35a 100644
--- a/ftp.go
+++ b/ftp.go
@@ -47,9 +47,9 @@ type Entry struct {
 
 // Response represents a data-connection
 type Response struct {
-	conn       net.Conn
-	c          *ServerConn
-	connClosed bool
+	conn   net.Conn
+	c      *ServerConn
+	closed bool
 }
 
 // Connect is an alias to Dial, for backward compatibility
@@ -538,7 +538,7 @@ func (r *Response) Read(buf []byte) (int, error) {
 
 // Close implements the io.Closer interface on a FTP data connection.
 func (r *Response) Close() error {
-	if r.connClosed {
+	if r.closed {
 		return nil
 	}
 	err := r.conn.Close()
@@ -546,7 +546,7 @@ func (r *Response) Close() error {
 	if err2 != nil {
 		err = err2
 	}
-	r.connClosed = true
+	r.closed = true
 	return err
 }
 

From 980e2e09a582c080954c2c5a44627099fe3eea53 Mon Sep 17 00:00:00 2001
From: Davide D'Agostino <daddye@uber.com>
Date: Thu, 4 May 2017 19:03:56 -0700
Subject: [PATCH 4/4] Document that closing two times doesn't do anything

---
 ftp.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ftp.go b/ftp.go
index 17fe35a..c29cb38 100644
--- a/ftp.go
+++ b/ftp.go
@@ -537,6 +537,7 @@ func (r *Response) Read(buf []byte) (int, error) {
 }
 
 // Close implements the io.Closer interface on a FTP data connection.
+// After the first call, Close will do nothing and return nil.
 func (r *Response) Close() error {
 	if r.closed {
 		return nil