On 8/17/20 6:56 PM, Christian Svensson wrote:
> [+linux-390 mailing list]
>
> On Mon, Aug 17, 2020 at 6:55 PM Christian Svensson <[email protected]> wrote:
>>
>> Hi,
>>
>> I am trying to call TCPIP service using IUCV.
>> I found AF_IUCV which seemed to do what I want, but reading
>> more into it it looks like AF_IUCV only ever implemented one-way
>> SEND operations.
>>
>> Is that correct?
>>

Yes, that's correct. The intention of the socket family AF_IUCV has been to
come up with a socket interface of types SOCK_STREAM and SOCK_SEQPACKET on top
of IUCV as transport layer. Later we added HiperSockets as another transport
layer.

>> There appears to exist a message_send and a message_send2way in
>> the Linux IUCV interface, however only message_send appears to be used
>> by AF_IUCV.
>>

There is a base IUCV layer in net/iucv/iucv.c offering message_send2way.
The base layer is used by several other kernel components, among them 
net/iucv/af_iucv.c.
But for the AF_IUCV socket family there has been no need to exploit 
message_send2way.

>> If my reading is correct, is there any way I can work around this
>> without writing a kernel module?
>>

Probably not: Either there is a good idea why to include message_send2way into
the standard socket interface AF_IUCV, or there is a new kernel module for
communication with the TCPIP service, built on top of net/iucv/iucv.c similar
to other specific IUCV exploiters like drivers/s390/char/vmlogrdr.c,
drivers/s390/net/netiucv.c, drivers/s390/net/smsgiucv.c, drivers/tty/hvc/...

>> Thanks
>
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