On 03/03/2016 06:09 PM, Chris Leech wrote:
> When requests are being failed it's important to abort the TCP
> connection rather than let TCP wait and attempt a graceful shutdown.
>
> That can be accomplished by setting the SO_LINGER socket option with a
> linger time of 0 to drop queued data and close the connection with a RST
> instead of a FIN.
>
> Signed-off-by: Chris Leech <cle...@redhat.com>
> ---
> usr/io.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/usr/io.c b/usr/io.c
> index f552e1e..48b233c 100644
> --- a/usr/io.c
> +++ b/usr/io.c
> @@ -391,9 +391,24 @@ iscsi_io_tcp_poll(iscsi_conn_t *conn, int timeout_ms)
> void
> iscsi_io_tcp_disconnect(iscsi_conn_t *conn)
> {
> + struct linger so_linger = { .l_onoff = 1, .l_linger = 0 };
> +
> if (conn->socket_fd >= 0) {
> log_debug(1, "disconnecting conn %p, fd %d", conn,
> conn->socket_fd);
> +
> + /* If the state is not IN_LOGOUT, this isn't a clean shutdown
> + * and there's some sort of error handling going on. In that
> + * case, set a 0 SO_LINGER to force an abortive close (RST) and
> + * free whatever is sitting in the TCP transmit queue. This is
> + * done to prevent stale data from being sent should the
> + * network connection be restored before TCP times out.
> + */
> + if (conn->state != ISCSI_CONN_STATE_IN_LOGOUT) {
> + setsockopt(conn->socket_fd, SOL_SOCKET, SO_LINGER,
> + &so_linger, sizeof(so_linger));
> + }
> +
> close(conn->socket_fd);
> conn->socket_fd = -1;
> }
>
Nice.
For maybe a slightly different problem, but hoping I get lucky and your
patch fixes it too, I thought the network layer was still accessing
pages that we tried to send and was causing a oops. I get the part where
with your patch the network layer will not try to send data anymore, but
I guess I am asking if the network layer could still be doing some sort
of delayed cleanup process after close() has returned?
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