connection to bad ftp server hangs whole connection most of the time

[boindil]

Describe the bug
The connection attempts to not abort properly

To Reproduce
I've set up an ftp server that can be reached somewhat, but is not fully functional (as tested via telnet)

package main

import (
	"log"
	"time"

	"github.com/jlaffaye/ftp"
)

func main() {
	c, err := ftp.Dial("10.0.2.2:21", ftp.DialWithTimeout(5*time.Second))
	if err != nil {
		log.Fatal(err)
	}

	err = c.Login("anonymous", "anonymous")
	if err != nil {
		log.Fatal(err)
	}

	// Do something with the FTP conn

	if err := c.Quit(); err != nil {
		log.Fatal(err)
	}
}

Expected behavior
dialing is aborted after timeout
p.s.: adding DialWithContext and adding a context that is cancelled after x seconds does not work either

FTP server

• Name and version: Windows 10 1909 integrated FTP via IIS services
• Public URL if applicable

Debug output
DialWithDebugOutput literally does nothing when it comes to the error. I guess that somethings waiting for more data to be submitted by the FTP server, but that never happens - thus its hanging.

Additional context
Go: go version go1.18.1 linux/amd64

sometime EOF error, sometimes not

corresponds to telnet tests, but this is still not a working FTP connection (command line FTP clients do not work either)
note the ^C in the lower left. The connection would stay open until I did something, while the first one aborts immediately (i guess thats the EOF case)

[jlaffaye]

Oh, yes, the timeout is for opening the TCP connection. It is not currently used for every read/write.

[glebteterin]

In my case it was an attempt to connect to freeSSHd: http://www.freesshd.com/ (identifies as SSH-2.0-WeOnlyDo 2.4.3)

In the Dial we expect to get a status code, but the freeSSHd replies with a single line SSH-2.0-WeOnlyDo 2.4.3, then the next ReadLine() hungs.

@jlaffaye does it make sense to set SetReadDeadline on the underlying network connection in the Dial ?

[lanyi1998]

I had the same problem

[sjakub]

Same problem here. This also happens when connecting to an HTTP server (which doesn't send anything on its own).
The Dial hangs until the remote server closes the connection.

EDIT:
For anybody else dealing with this, I came up with a different way of handling the timeout for the entire connection process.
Basically I use a custom DialFunc that stores all the connections generated:

var netCons []net.Conn

dialOpt := ftp.DialWithDialFunc(
  func(network, address string) (net.Conn, error) {
    dialer := net.Dialer{}
    c, err := dialer.Dial(network, address)
    if c != nil {
      netCons = append(netCons, c)
    }
    return c, err
})

Then I start a routine which, after some timeout delay, if the connection attempt hasn't completed yet, either closes all those connections, or uses SetDeadline with time in the past to get that 'timeout' error. This interrupts the connection attempt, no matter what state it is in.