From d2efb4b29b3b0be4daf700ffd803267f07f635ea Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Sat, 18 Jul 2020 09:52:22 +0100
Subject: [PATCH] ftp: add support for --dump bodies and --dump auth

See: https://forum.rclone.org/t/rclone-copy-gives-error-connection-reset-by-peer-using-ftp/17934/27
---
 backend/ftp/ftp.go  | 42 ++++++++++++++++++++++++++++++++++++++++++
 docs/content/ftp.md |  5 +++--
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/backend/ftp/ftp.go b/backend/ftp/ftp.go
index 2850229a7..0c4ba87ea 100644
--- a/backend/ftp/ftp.go
+++ b/backend/ftp/ftp.go
@@ -8,6 +8,8 @@ import (
 	"net/textproto"
 	"os"
 	"path"
+	"runtime"
+	"strings"
 	"sync"
 	"time"
 
@@ -160,6 +162,43 @@ func (f *Fs) Features() *fs.Features {
 	return f.features
 }
 
+// Enable debugging output
+type debugLog struct {
+	mu   sync.Mutex
+	auth bool
+}
+
+// Write writes len(p) bytes from p to the underlying data stream. It returns
+// the number of bytes written from p (0 <= n <= len(p)) and any error
+// encountered that caused the write to stop early. Write must return a non-nil
+// error if it returns n < len(p). Write must not modify the slice data, even
+// temporarily.
+//
+// Implementations must not retain p.
+//
+// This writes debug info to the log
+func (dl *debugLog) Write(p []byte) (n int, err error) {
+	dl.mu.Lock()
+	defer dl.mu.Unlock()
+	_, file, _, ok := runtime.Caller(1)
+	direction := "FTP Rx"
+	if ok && strings.Contains(file, "multi") {
+		direction = "FTP Tx"
+	}
+	lines := strings.Split(string(p), "\r\n")
+	if lines[len(lines)-1] == "" {
+		lines = lines[:len(lines)-1]
+	}
+	for _, line := range lines {
+		if !dl.auth && strings.HasPrefix(line, "PASS") {
+			fs.Debugf(direction, "PASS *****")
+			continue
+		}
+		fs.Debugf(direction, "%q", line)
+	}
+	return len(p), nil
+}
+
 // Open a new connection to the FTP server.
 func (f *Fs) ftpConnection() (*ftp.ServerConn, error) {
 	fs.Debugf(f, "Connecting to FTP server")
@@ -183,6 +222,9 @@ func (f *Fs) ftpConnection() (*ftp.ServerConn, error) {
 	if f.opt.DisableEPSV {
 		ftpConfig = append(ftpConfig, ftp.DialWithDisabledEPSV(true))
 	}
+	if fs.Config.Dump&(fs.DumpHeaders|fs.DumpBodies|fs.DumpRequests|fs.DumpResponses) != 0 {
+		ftpConfig = append(ftpConfig, ftp.DialWithDebugOutput(&debugLog{auth: fs.Config.Dump&fs.DumpAuth != 0}))
+	}
 	c, err := ftp.Dial(f.dialAddr, ftpConfig...)
 	if err != nil {
 		fs.Errorf(f, "Error while Dialing %s: %s", f.dialAddr, err)
diff --git a/docs/content/ftp.md b/docs/content/ftp.md
index 68ccffd1f..3e110a628 100644
--- a/docs/content/ftp.md
+++ b/docs/content/ftp.md
@@ -257,8 +257,9 @@ See: the [encoding section in the overview](/overview/#encoding) for more info.
 
 ### Limitations ###
 
-Note that since FTP isn't HTTP based the following flags don't work
-with it: `--dump-headers`, `--dump-bodies`, `--dump-auth`
+Note that FTP does have its own implementation of : `--dump headers`,
+`--dump bodies`, `--dump auth` for debugging which isn't the same as
+the HTTP based backends - it has less fine grained control.
 
 Note that `--timeout` isn't supported (but `--contimeout` is).