[Samba] smbsrv_reply_printwrite not returning a response causing the print job to be truncated to 124 bytes

[Jeremy Allison]

On Thu, Apr 29, 2021 at 01:38:04AM +0200, Mateusz Mikołajczyk via samba wrote:
>Hello. I am investigating a weird issue with an old MS Net client for DOS
>(v 3.0). I have used wireshark in order to inspect the packets and see the
>difference between samba and windows xp server responses. this question is
>only about printing capabilities as file sharing works flawlessly.
>
>when the client negotiates protocol it is settled as 2 / Greater than CORE
>PROTOCOL and up to LANMAN2.1
>
>the start of print request seems to be OK, the server (in both
>implementations) returns a file ID in the response that's labeled as 'Open
>Print File Response / 0xC0'. Then the client sends print job (packet id:
>0xc1) (124 bytes of it in fact - I suppose that's either due to some buffer
>size or a maximum packet length) and that's when the servers differ in
>terms of response.
>
>windows xp responds with 0xc1 and the data section contains 3 zero bytes
>(0x00, 0x00, 0x00). Wireshark describes this as 'Write Print File
>Response'. Samba does not respond at all which makes the client simply
>hang. Then, after couple of seconds samba simply puts the print job to cups
>which makes the output truncated. By inspecting samba source code for 0xc1
>I saw a reference to smbsrv_reply_printwrite. I've read the source code for
>that function and I can't understand why it would not return a response at
>all. I would understand if it would return an error packet or something but
>there's simply no response at all.
>
>here's what I tried so far:
>
>   ntvfs handler = print
>   aio read size = 0
>   aio write size = 0
>
>   strict sync = yes
>   sync always = yes
>
>but somethinig tells me that because at the very beginning of the function
>there's a hardcoded NTVFS_ASYNC_STATE_MAY_ASYNC then I am simply out of
>luck?

Looks like you're using the (unsupported code) ntvfs file
server. That's legacy code only used for testing.

You need to be talking to smbd, not the samba binary.

Please ensure you have smbd running, and as I'm sure
Rowland will ask, please submit your smb.conf :-).