[FFmpeg-devel] [PATCH] FTP graceful close data connection to avoid server abort

[Lukasz Marek]

On 02.06.2016 14:29, Camille Gonnet wrote:
> When writing files to FTP, if the data connection is closed before the
> control connection, the server may handle it as an aborted file transfer
> and create and leave the file empty.
>
> ---
>   libavformat/ftp.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/ftp.c b/libavformat/ftp.c
> index 0663b47..00747bb 100644
> --- a/libavformat/ftp.c
> +++ b/libavformat/ftp.c
> @@ -220,15 +220,21 @@ static int ftp_send_command(FTPContext *s, const char
> *command,
>
>   static void ftp_close_data_connection(FTPContext *s)
>   {
> -    ffurl_closep(&s->conn_data);
> +static const int close_codes[] = {225, 226, 0};
> +
> +    if (s->conn_data) {
> +        ffurl_closep(&s->conn_data);
> +        // Need to wait for status, or file transfer might be aborted on
> server side
> +        ftp_status(s, NULL, close_codes);
> +    }
>       s->position = 0;
>       s->state = DISCONNECTED;
>   }

This is not working. ./ffplay ftp://user:pass@localhost/1.avi hangs at 
startup. It was working for you because (probably) your writing 
operation didn't perform seeking (did you enabled ftp-write-seekable?).
During seek operation, when seek is really done, ftp_abort is called and 
there is ftp_close_data_connection called with status check followed. So 
status is checked twice while sent by server just once.

I can work it out, but just tell what server has this issue. Perfectly 
setup some account for me. You can of course work it out yourself, but 
please test also other scenarios and other servers.

First thing to check is to revert patch completely and replace 
ftp_close_both_connections by ftp_abort inside ftp_close function.