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

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,

-- 
2.1.0

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

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.

  Marcelo

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

Em 04-06-2016 06:45, Xin Long escreveu:

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

quoted

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.

Return error? Please don't. Adam Endrodi asked in May (linux-sctp@) a 
way to return the addresses used on such attempts and currently this 
address returned by accept() is the only one we can get.

   Marcelo

From: Xin Long <lucien.xin@gmail.com>
Date: Fri,  3 Jun 2016 22:42:45 +0800

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>

It looks like some changes are still needed for this.

On Sat, Jun 4, 2016 at 8:22 PM, Marcelo Ricardo Leitner
[off-list ref] wrote:

Return error? Please don't. Adam Endrodi asked in May (linux-sctp@) a way to
return the addresses used on such attempts and currently this address
returned by accept() is the only one we can get.

[1] I've checked Adam's email, what he asked  was different case,  in
his case, the assoc
closed *after* sctp_accept, that's why he can catch the SCTP_COMM_UP event on
accept_sk but asoc is freed already.

[2] if assoc close *before* sctp_accept return, I mean asoc close
during sctp_accept schedule out.
listen sk will be the assoc's parent sk, in sctp_cmd_delete_tcb
(SCTP_CMD_DELETE_TCB):

        if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING) &&
            (!asoc->temp) && (sk->sk_shutdown != SHUTDOWN_MASK))
                return;

assoc can't be freed. and the event skb will be appended to
listen_sk->sk_receive_queue
when sctp_accept schedule back, it will transfer to
accept_sk->sk_receive_queue. we can
still get the closed assoc information. until we call sctp_close:
                        if (sctp_state(asoc, CLOSED)) {
                                sctp_association_free(asoc);
                                continue;
                        }

and your suggestion to improve for his case [1] is to not schedule
SCTP_CMD_DELETE_TCB
(only for tcp style). right ?

if so, in the case [2] that assoc close *before* sctp_accept return,
we should also update
the newsk->sk_state, like:

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -7565,10 +7565,12 @@ static void sctp_sock_migrate(struct sock

*oldsk, struct sock *newsk,
        /* If the association on the newsk is already closed before accept()
         * is called, set RCV_SHUTDOWN flag.
         */
-       if (sctp_state(assoc, CLOSED) && sctp_style(newsk, TCP))
+       if (sctp_state(assoc, CLOSED) && sctp_style(newsk, TCP)) {
+               newsk->sk_state = SCTP_SS_CLOSING;
                newsk->sk_shutdown |= RCV_SHUTDOWN;
+       } else
+               newsk->sk_state = SCTP_SS_ESTABLISHED;

-       newsk->sk_state = SCTP_SS_ESTABLISHED;

so that this two cases have the similar process, and wait for
sctp_close to clean assoc.
what do you think ?

  Marcelo

On Tue, Jun 07, 2016 at 07:03:55PM +0800, Xin Long wrote:

On Sat, Jun 4, 2016 at 8:22 PM, Marcelo Ricardo Leitner
[off-list ref] wrote:

quoted

Return error? Please don't. Adam Endrodi asked in May (linux-sctp@) a way to
return the addresses used on such attempts and currently this address
returned by accept() is the only one we can get.

[1] I've checked Adam's email, what he asked  was different case,  in
his case, the assoc
closed *after* sctp_accept, that's why he can catch the SCTP_COMM_UP event on
accept_sk but asoc is freed already.

It doesn't have to be after sctp_accept because we will queue
SCTP_COMM_UP as reactions to COOKIE_ECHO and COOKIE_ACK, and then such
event will be moved to the new socket upon sctp_accept() call (which
calls sctp_sock_migrate()).

[2] if assoc close *before* sctp_accept return, I mean asoc close
during sctp_accept schedule out.
listen sk will be the assoc's parent sk, in sctp_cmd_delete_tcb
(SCTP_CMD_DELETE_TCB):

        if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING) &&
            (!asoc->temp) && (sk->sk_shutdown != SHUTDOWN_MASK))
                return;

assoc can't be freed. and the event skb will be appended to
listen_sk->sk_receive_queue
when sctp_accept schedule back, it will transfer to
accept_sk->sk_receive_queue. we can
still get the closed assoc information. until we call sctp_close:
                        if (sctp_state(asoc, CLOSED)) {
                                sctp_association_free(asoc);
                                continue;
                        }

and your suggestion to improve for his case [1] is to not schedule
SCTP_CMD_DELETE_TCB
(only for tcp style). right ?

Yes

I don't agree with before/after thing, but I agree with the solution. :)

  Marcelo

On Tue, Jun 7, 2016 at 8:08 PM, Marcelo Ricardo Leitner
[off-list ref] wrote:

On Tue, Jun 07, 2016 at 07:03:55PM +0800, Xin Long wrote:

quoted

On Sat, Jun 4, 2016 at 8:22 PM, Marcelo Ricardo Leitner
[off-list ref] wrote:

quoted

Return error? Please don't. Adam Endrodi asked in May (linux-sctp@) a way to
return the addresses used on such attempts and currently this address
returned by accept() is the only one we can get.

[1] I've checked Adam's email, what he asked  was different case,  in
his case, the assoc
closed *after* sctp_accept, that's why he can catch the SCTP_COMM_UP event on
accept_sk but asoc is freed already.

It doesn't have to be after sctp_accept because we will queue
SCTP_COMM_UP as reactions to COOKIE_ECHO and COOKIE_ACK, and then such
event will be moved to the new socket upon sctp_accept() call (which
calls sctp_sock_migrate()).

I meant in his case, assoc close must be *after* sctp_accept.
and he said he couldn't get it as asoc was gone.

cause if assoc close is *before* sctp_accept return, assoc won't
be freed [2], he can still  get the addrs from asoc in SCTP_COMM_UP event

quoted

[2] if assoc close *before* sctp_accept return, I mean asoc close
during sctp_accept schedule out.
listen sk will be the assoc's parent sk, in sctp_cmd_delete_tcb
(SCTP_CMD_DELETE_TCB):

        if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING) &&
            (!asoc->temp) && (sk->sk_shutdown != SHUTDOWN_MASK))
                return;

assoc can't be freed. and the event skb will be appended to
listen_sk->sk_receive_queue
when sctp_accept schedule back, it will transfer to
accept_sk->sk_receive_queue. we can
still get the closed assoc information. until we call sctp_close:
                        if (sctp_state(asoc, CLOSED)) {
                                sctp_association_free(asoc);
                                continue;
                        }

and your suggestion to improve for his case [1] is to not schedule
SCTP_CMD_DELETE_TCB
(only for tcp style). right ?

Yes

quoted

if so, in the case [2] that assoc close *before* sctp_accept return,
we should also update
the newsk->sk_state, like:

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -7565,10 +7565,12 @@ static void sctp_sock_migrate(struct sock

*oldsk, struct sock *newsk,
        /* If the association on the newsk is already closed before accept()
         * is called, set RCV_SHUTDOWN flag.
         */
-       if (sctp_state(assoc, CLOSED) && sctp_style(newsk, TCP))
+       if (sctp_state(assoc, CLOSED) && sctp_style(newsk, TCP)) {
+               newsk->sk_state = SCTP_SS_CLOSING;
                newsk->sk_shutdown |= RCV_SHUTDOWN;
+       } else
+               newsk->sk_state = SCTP_SS_ESTABLISHED;

-       newsk->sk_state = SCTP_SS_ESTABLISHED;

so that this two cases have the similar process, and wait for
sctp_close to clean assoc.
what do you think ?

I don't agree with before/after thing, but I agree with the solution. :)

ok, I will post v3. :D

  Marcelo

On Tue, Jun 7, 2016 at 7:03 PM, Xin Long [off-list ref] wrote:

I'm still thinking about this, if we want to get addrs info from
closed assoc, like Adam's requirement. this will make it more
impossible.

case in
sctp_getsockopt_peer_addrs()->sctp_id2assoc():

                if (!sctp_sstate(sk, ESTABLISHED))
                        return NULL;

we can't  get assoc as sstate is SS_CLOSING already.

Em 08-06-2016 07:42, Xin Long escreveu:

On Tue, Jun 7, 2016 at 7:03 PM, Xin Long [off-list ref] wrote:

quoted

On Sat, Jun 4, 2016 at 8:22 PM, Marcelo Ricardo Leitner

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -7565,10 +7565,12 @@ static void sctp_sock_migrate(struct sock

*oldsk, struct sock *newsk,
        /* If the association on the newsk is already closed before accept()
         * is called, set RCV_SHUTDOWN flag.
         */
-       if (sctp_state(assoc, CLOSED) && sctp_style(newsk, TCP))
+       if (sctp_state(assoc, CLOSED) && sctp_style(newsk, TCP)) {
+               newsk->sk_state = SCTP_SS_CLOSING;
                newsk->sk_shutdown |= RCV_SHUTDOWN;
+       } else
+               newsk->sk_state = SCTP_SS_ESTABLISHED;

-       newsk->sk_state = SCTP_SS_ESTABLISHED;

I'm still thinking about this, if we want to get addrs info from
closed assoc, like Adam's requirement. this will make it more
impossible.

case in
sctp_getsockopt_peer_addrs()->sctp_id2assoc():

                if (!sctp_sstate(sk, ESTABLISHED))
                        return NULL;

we can't  get assoc as sstate is SS_CLOSING already.

We probably can add another state to that if(). So far ESTABLISHED was 
the only reasonable state in there, but SS_CLOSING will make sense too 
then, I guess. A throughout check is necessary for this.

   Marcelo