Wei Yongjun wrote:
>> Wei Yongjun wrote:
>>
>>> It should be possible to send a message and set the SCTP_EOF flag
>>> at the same time, but we don't support it yet. This patch fix the
>>> sendmsg() flag SCTP_EOF to comply to spec.
>>>
>>> Signed-off-by: Wei Yongjun <yjwei@xxxxxxxxxxxxxx>
>>> ---
>>> V2 -> V3:
>>> - return -EWOULDBLOCK in non-blocking limitation case
>>> - allow SCTP_EOF in CLOSED state
>>> ---
>>> net/sctp/socket.c | 39 +++++++++++++++++++++++++++++++--------
>>> 1 files changed, 31 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
>>> index 0af3a8c..fcd8128 100644
>>> --- a/net/sctp/socket.c
>>> +++ b/net/sctp/socket.c
>>> @@ -1555,13 +1555,11 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
>>> goto out_nounlock;
>>> }
>>>
>>> - /* If SCTP_EOF is set, no data can be sent. Disallow sending zero
>>> - * length messages when SCTP_EOF|SCTP_ABORT is not set.
>>> - * If SCTP_ABORT is set, the message length could be non zero with
>>> - * the msg_iov set to the user abort reason.
>>> + /* Disallow sending zero length messages when SCTP_EOF|SCTP_ABORT
>>> + * is not set. If SCTP_ABORT is set, the message length could be
>>> + * non zero with the msg_iov set to the user abort reason.
>>> */
>>> - if (((sinfo_flags & SCTP_EOF) && (msg_len > 0)) ||
>>> - (!(sinfo_flags & (SCTP_EOF|SCTP_ABORT)) && (msg_len == 0))) {
>>> + if (!(sinfo_flags & (SCTP_EOF|SCTP_ABORT)) && (msg_len == 0)) {
>>> err = -EINVAL;
>>> goto out_nounlock;
>>> }
>>> @@ -1618,13 +1616,24 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
>>> goto out_unlock;
>>> }
>>>
>>> - if (sinfo_flags & SCTP_EOF) {
>>> + /* Forbid SCTP_EOF and send a message combination
>>> + * on non-blocking sockets.
>>> + */
>>> + if ((sinfo_flags & SCTP_EOF) && msg_len != 0 &&
>>> + sk->sk_socket->file &&
>>> + (sk->sk_socket->file->f_flags & O_NONBLOCK)) {
>>> + err = -EWOULDBLOCK;
>>> + goto out_nounlock;
>>> + }
>>> +
>>> + if (sinfo_flags & SCTP_EOF && msg_len == 0) {
>>> SCTP_DEBUG_PRINTK("Shutting down association: %p\n",
>>> asoc);
>>> sctp_primitive_SHUTDOWN(asoc, NULL);
>>> err = 0;
>>> goto out_unlock;
>>> }
>>> +
>>> if (sinfo_flags & SCTP_ABORT) {
>>>
>>> chunk = sctp_make_abort_user(asoc, msg, msg_len);
>>> @@ -1644,7 +1653,7 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
>>> if (!asoc) {
>>> SCTP_DEBUG_PRINTK("There is no association yet.\n");
>>>
>>> - if (sinfo_flags & (SCTP_EOF | SCTP_ABORT)) {
>>> + if (sinfo_flags & SCTP_ABORT) {
>>> err = -EINVAL;
>>> goto out_unlock;
>>> }
>>> @@ -1850,6 +1859,20 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
>>> else
>>> err = msg_len;
>>>
>>> + if (sinfo_flags & SCTP_EOF) {
>>> + if (sctp_state(asoc, ESTABLISHED)) {
>>> + SCTP_DEBUG_PRINTK("Shutting down association: %p\n",
>>> + asoc);
>>> + sctp_primitive_SHUTDOWN(asoc, NULL);
>>> + } else {
>>> + /* Delay to shutdown association until assoc enter
>>> + * ESTABLISHED state
>>> + */
>>> + asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] = HZ/20;
>>> + asoc->autoclose = 1;
>>> + }
>>> + }
>>> +
>>>
>> Interesting approach and I applaud for creativity, but it doesn't work if there is
>> data loss.
>>
>> I see only one way out of this mess and that's to remove the SHUTDOWN_PENDING
>> state and make that a modifier/flag that can be set on other states <= ESTABLISHED.
>>
>
> Do you mean we should support multi send() with EOF flag?
>
> send(msg, SCTP_EOF);
> send(msg, SCTP_EOF);
> ...
As long as they are for different associations. SCTP_EOF is a way to do
shutdown() for 1-to-many sockets. If the second send() is for the same
association, it should fail.
I just realized that this might actually work.... Autoclose timer isn't started
until association is up, so that takes care of any INIT retransmissions.
And the autoclose will do the right thing by entering SHUTDOWN_PENDING and
retransmitting DATA as needed.
The only thing still missing is something that prevents the above multiple send
scenario.
That's why I though that removing the SHUTDOWN_PENDING state and changing it into
a bit/flag would work. This way, sends would return failure because even though
we may be in COOKIE_WAIT, if the SHUTDOWN_PENDING flag is set, further writes are
disallowed.
With this code, multiple writes with EOF for the same association will work,
if the init process takes a long time (due to retransmissions or long rto).
-vlad
>
>> In other words, if the user has queued up data to the association, even if it is
>> not established, we should exhaust all retransmits before failing.
>>
>
> shutdown after all the outdata is acked?
>
>> -vlad
>>
>>
>>> /* If we are already past ASSOCIATE, the lower
>>> * layers are responsible for association cleanup.
>>> */
>>>
>>
>
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