Re: [PATCH net-next 10/10] mptcp: support TCP_CORK and TCP_NODELAY

On Mon, 2021-12-06 at 17:30 -0800, Jakub Kicinski wrote:

On Fri,  3 Dec 2021 14:35:41 -0800 Mat Martineau wrote:

quoted

+static int mptcp_setsockopt_sol_tcp_nodelay(struct mptcp_sock *msk, sockptr_t optval,
+					    unsigned int optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int val;
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&val, optval, sizeof(val)))
+		return -EFAULT;

Should we check that optval is not larger than sizeof(int) or if it is
that the rest of the buffer is zero? Or for the old school options we
should stick to the old school behavior?

I think it's useful if we keep the MPTCP socket options binary API as
close as possible to the plain TCP ones: that allows for seamless
switching existing TCP application to MPTCP with no code changes.

Old school, please ;)

Cheers,

Paolo