Re: [PATCH net] kcm: Fix splice support

[Jakub Kicinski]

On Fri, 25 Jul 2025 12:33:04 +0200 Michal Luczaj wrote:
> Flags passed in for splice() syscall should not end up in
> skb_recv_datagram(). As SPLICE_F_NONBLOCK == MSG_PEEK, kernel gets
> confused: skb isn't unlinked from a receive queue, while strp_msg::offset
> and strp_msg::full_len are updated.
> 
> Unbreak the logic a bit more by mapping both O_NONBLOCK and
> SPLICE_F_NONBLOCK to MSG_DONTWAIT. This way we align with man splice(2) in
> regard to errno EAGAIN:
> 
>    SPLICE_F_NONBLOCK was specified in flags or one of the file descriptors
>    had been marked as nonblocking (O_NONBLOCK), and the operation would
>    block.

Coincidentally looks like we're not honoring

	sock->file->f_flags & O_NONBLOCK 

in TLS..