netdev - TCP/IPv4 sending using MSG_ZEROCOPY and closing the socket

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Date:   Mon, 28 Jan 2019 07:44:37 +0000
From:   mathias_koehrer@...or.de
To:     netdev@...r.kernel.org, willemb@...gle.com
Subject: TCP/IPv4 sending using MSG_ZEROCOPY and closing the socket

Hi all,

I have one question on the behavior of TCP/IPv4 sending using the MSG_ZEROCOPY flag,
the kernel version is 4.19.18.

What happens if I close the sending socket immediately after performing a socket 
send() or sendmsg() call (called with the MSG_ZEROCOPY flag)?
I.e. in this situation not all messages have been sent yet, however - as the 
socket is closed - it is no longer possible to retrieve the completion 
notification via the error channel.

Is it fine for the user space program to free all outstanding messages after the
socket close() has returned?
Or is there anything else that has to be considered?

Thanks for any help

Best regards

Mathias