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.
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.
-vlad
> /* If we are already past ASSOCIATE, the lower
> * layers are responsible for association cleanup.
> */
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