Re: [PATCHv2 net-next] sctp: sctp should change socket state when shutdown is received

On Sat, Jun 4, 2016 at 1:49 AM, Marcelo Ricardo Leitner
[off-list ref] wrote:

On Fri, Jun 03, 2016 at 10:42:45PM +0800, Xin Long wrote:

quoted

Now sctp doesn't change socket state upon shutdown reception. It changes
just the assoc state, even though it's a TCP-style socket.

For some cases, if we really need to check sk->sk_state, it's necessary to
fix this issue, at least when we use ss or netstat to dump, we can get a
more exact information.

As an improvement, we will change sk->sk_state when we change asoc->state
to SHUTDOWN_RECEIVED, and also do it in sctp_shutdown to keep consistent with
sctp_close.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/sctp/sm_sideeffect.c | 4 +++-
 net/sctp/socket.c        | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index aa37122..12d4519 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c

@@ -806,8 +806,10 @@ static void sctp_cmd_new_state(sctp_cmd_seq_t *cmds,

              /* Set the RCV_SHUTDOWN flag when a SHUTDOWN is received. */
              if (sctp_state(asoc, SHUTDOWN_RECEIVED) &&
-                 sctp_sstate(sk, ESTABLISHED))
+                 sctp_sstate(sk, ESTABLISHED)) {
+                     sk->sk_state = SCTP_SS_CLOSING;
                      sk->sk_shutdown |= RCV_SHUTDOWN;
+             }
      }

      if (sctp_state(asoc, COOKIE_WAIT)) {

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 67154b8..91a460d 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -4193,6 +4193,7 @@ static void sctp_shutdown(struct sock *sk, int how)
              return;

      if (how & SEND_SHUTDOWN) {
+             sk->sk_state = SCTP_SS_CLOSING;
              ep = sctp_sk(sk)->ep;
              if (!list_empty(&ep->asocs)) {
                      asoc = list_entry(ep->asocs.next,

Oh but I think the removed chunk was important, it just needed fixing.

A comment in there said:
        /* If the association on the newsk is already closed before
         * accept() is called, set RCV_SHUTDOWN flag.
         */
Meaning that there is a way that it will create a socket in the state
you're trying to avoid here, which now is not handled.

agreed, but it's another problem
there, we'd better free newsk and assoc after sctp_sock_migrate,
and let sctp_accept return err. I will think more about it and see if
I cook another patch for it.

  Marcelo