VirtualBox

Opened 12 years ago

Closed 10 years ago

#11670 closed defect (fixed)

Double data socket connection when FTP passive through NAT

Reported by: bripatand Owned by:
Component: network/NAT Version: VirtualBox 4.2.10
Keywords: NAT FTP extra connection Cc:
Guest type: Windows Host type: Windows

Description

When transferring files through FTP passive mode from a Windows 7 64 bits Guest in NAT network mode on a Windows 7 64 bits Host to a FTP server, an extra FTP data connection seems to be created by Virtualbox for each file transfer. For instance, if the TCP data connection is created from FTP Client in Guest port N to port S on FTP server, we can see 2 TCP data connections are created in the Host:

  • Host port M to port S on server (N is mapped to M by the NAT)
  • Host port M-1 to another random port T on server.

Most of the time there is no effect as no process is listening to port T on the server but randomly T = S which mess up the FTP data connection resulting in zero file size being created on the server without any error or the connection is reset. This was seen with both a Filezilla client or a .Net client.

In attachment, you can see the Wireshark trace for Guest, Host, and Server. After each frame in FTP Cmd connection "Entering Passive mode", you can see this extra TCP Data connection in the Host (and server) which is not found in the Guest.

Attachments (4)

Host.png (149.5 KB ) - added by bripatand 12 years ago.
Guest.png (147.4 KB ) - added by bripatand 12 years ago.
Server1.png (111.2 KB ) - added by bripatand 12 years ago.
Server2.png (105.2 KB ) - added by bripatand 12 years ago.

Download all attachments as: .zip

Change History (6)

by bripatand, 12 years ago

Attachment: Host.png added

by bripatand, 12 years ago

Attachment: Guest.png added

by bripatand, 12 years ago

Attachment: Server1.png added

by bripatand, 12 years ago

Attachment: Server2.png added

comment:1 by Valery Ushakov, 10 years ago

This should have been fixed in 4.3.12

comment:2 by Valery Ushakov, 10 years ago

Resolution: fixed
Status: newclosed

Marking as fixed. Please, reopen if necessary.

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