Re: [PATCH] af_unix: Allow Unix sockets to raise SIGURG

[Jakub Kicinski]

On Fri, 29 Jan 2021 11:48:15 -0800 Shoaib Rao wrote:
> >> SO_OOBINLINE does not control the delivery of signal, It controls how
> >> OOB Byte is delivered. It may not be obvious but this change does not
> >> deliver any Byte, just a signal. So, as long as sendmsg flag contains
> >> MSG_OOB, signal will be delivered just like it happens for TCP.  
> > Not as far as I can read this code. If MSG_OOB is set the data from the
> > message used to be discarded, and EOPNOTSUPP returned. Now the data gets
> > queued to the socket, and will be read inline.  
> 
> Data was discarded because the flag was not supported, this patch 
> changes that but does not support any urgent data.

When you say it does not support any urgent data do you mean the
message len must be == 0 because something is checking it, or that 
the code does not support its handling?

I'm perfectly fine with the former, just point me at the check, please.

> OOB data has some semantics that would have to be followed and if we 
> support SO_OOBINLINE we would have to support NOT SO_OOBINLINE.
> 
> One can argue that we add a socket option to allow this OR just do what 
> TCP does.