Re: [PATCH mptcp-net] mptcp: Do not return EINPROGRESS when subflow creation succeeds

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Fri, 15 Jul 2022, Mat Martineau wrote:

> New subflows are created within the kernel using O_NONBLOCK, so
> EINPROGRESS is the expected return value from kernel_connect().
> __mptcp_subflow_connect() has the correct logic to consider EINPROGRESS
> to be a successful case, but it has also used that error code as its
> return value.
>
> Before v5.19 this was benign: all the callers ignored the return
> value. Starting in v5.19 there is a MPTCP_PM_CMD_SUBFLOW_CREATE generic
> netlink command that does use the return value, so the EINPROGRESS gets
> propagated to userspace.
>
> Make __mptcp_subflow_connect() always return 0 on success instead.
>
> Fixes: ec3edaa7ca6c ("mptcp: Add handling of outgoing MP_JOIN requests")
> Fixes: 702c2f646d42 ("mptcp: netlink: allow userspace-driven subflow establishment")
> Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

Noting here for the lore.kernel.org records: Paolo acked this patch today 
on IRC (#mptcp / irc.libera.chat).

Given that ack, the simplicity of the change, and the timeline for this 
week's -net pull request, I'm sending this patch to netdev today.

Thanks,

Mat

> ---
> net/mptcp/subflow.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index 63e8892ec807..af28f3b60389 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -1533,7 +1533,7 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
> 	mptcp_sock_graft(ssk, sk->sk_socket);
> 	iput(SOCK_INODE(sf));
> 	WRITE_ONCE(msk->allow_infinite_fallback, false);
> -	return err;
> +	return 0;
>
> failed_unlink:
> 	list_del(&subflow->node);
> -- 
> 2.37.1
>
>

--
Mat Martineau
Intel