cifs: Improve establishing SMB connection with NetBIOS session

Function ip_rfc1001_connect() send NetBIOS session request but currently
does not read response. It even does not wait for the response. Instead it
just calls usleep_range(1000, 2000) and explain in comment that some
servers require short break before sending SMB negotiate packet. Response
is later handled in generic is_smb_response() function called from
cifs_demultiplex_thread().

That comment probably refers to the old DOS SMB server which cannot process
incoming SMB negotiate packet if it has not sent NetBIOS session response
packet. Note that current sleep timeout is too small when trying to
establish connection to DOS SMB server running in qemu virtual machine
connected over qemu user networking with guestfwd netcat options. So that
usleep_range() call is not useful at all.

NetBIOS session response packet contains useful error information, like
the server name specified NetBIOS session request packet is incorrect.
Old Windows SMB servers and even the latest SMB server on the latest
Windows Server 2022 version requires that the name is the correct server
name, otherwise they return error RFC1002_NOT_PRESENT. This applies for all
SMB dialects (old SMB1, and also modern SMB2 and SMB3).

Therefore read the reply of NetBIOS session request and implement parsing
of the reply. Log received error to dmesg to help debugging reason why
connection was refused. Also convert NetBIOS error to useful errno.

Note that ip_rfc1001_connect() function is used only when doing connection
over port 139. So the common SMB scenario over port 445 is not affected by
this change at all.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

0 files changed, 0 insertions, 0 deletions