On Sat, 22 Feb 2020, Xin Long wrote:
> On Thu, Feb 20, 2020 at 5:18 PM Leppanen, Jere (Nokia - FI/Espoo)
> <jere.leppanen@xxxxxxxxx> wrote:
>>
>> Hello All,
>>
>> According to the RFC, a peeled-off socket is a one-to-one socket. But
>> in lksctp a peeled-off socket it not TCP style, it's UDP_HIGH_BANDWIDTH
>> style. Because of this, shutdown() doesn't work, linger probably
>> doesn't work, and so on.
>>
>> For example, in sctp_shutdown():
>>
>> static void sctp_shutdown(struct sock *sk, int how)
>> {
>> struct net *net = sock_net(sk);
>> struct sctp_endpoint *ep;
>>
>> if (!sctp_style(sk, TCP))
>> return;
>>
>> Here we just bail out, because a peeled-off socket is not TCP style.
>>
>> Is this just a bug, or am I missing something? Asking mostly out of
>> personal curiosity.
> I would say, it's because .shutdown is tcp_prot thing and udp_prot doesn't
> have. sctp doesn't have to implement it for UDP style socket. But for TCP-
> style socket, sctp is trying to be compatible with TCP protocol user API.
> But even though, sctp's .shutdown is still not fully compatible with TCP
> protocol due to sctp's 3-way shakehands for finishing a connection.
Thanks a bunch for replying, Xin Long. I'm not quite sure what you mean.
The actual association shutdown doesn't even come into play here, since
shutdown() doesn't do anything with peeled-off sockets.
If you mean that the current implementation of shutdown() might have
some problems with peeled-off sockets; well, that's true, but I suppose
that means that there's something to fix somewhere.
It looks like the reason for the peculiar socket style of peeled-off
sockets is that they're created by copying from a one-to-many socket and
modified a little to resemble a one-to-one socket. But this leads to
problems in several places in the code. Is this just implementation that
was never finalized?
