Introduce a hooks layer for the MPSAFE TTY layer.

One of the features that prevented us from fixing some of the TTY
consumers to work once again, was an interface that allowed consumers to
do the following:

- `Sniff' incoming data, which is used by the snp(4) driver.

- Take direct control of the input and output paths of a TTY, which is
  used by ng_tty(4), ppp(4), sl(4), etc.

There's no practical advantage in committing a hooks layer without
having any consumers. In P4 there is a preliminary port of snp(4) and
thompsa@ is busy porting ng_tty(4) to this interface. I already want to
have it in the tree, because this may stimulate others to work on the
remaining modules.

Discussed with:	thompsa
Obtained from:	//depot/projects/mpsafetty/...

1 files changed, 147 insertions, 0 deletions

diff --git a/sys/sys/ttyhook.h b/sys/sys/ttyhook.h
new file mode 100644
index 0000000..7a0a0bc
--- /dev/null
+++ b/sys/sys/ttyhook.h
@@ -0,0 +1,147 @@
+/*-
+ * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS_TTYHOOK_H_
+#define	_SYS_TTYHOOK_H_
+
+#ifndef _SYS_TTY_H_
+#error "can only be included through <sys/tty.h>"
+#endif /* !_SYS_TTY_H_ */
+
+struct tty;
+
+/*
+ * Hooks interface, which allows to capture and inject traffic into the
+ * input and output paths of a TTY.
+ */
+
+typedef int th_rint_t(struct tty *tp, char c, int flags);
+typedef size_t th_rint_bypass_t(struct tty *tp, const void *buf, size_t len);
+typedef void th_rint_done_t(struct tty *tp);
+typedef size_t th_rint_poll_t(struct tty *tp);
+
+typedef size_t th_getc_inject_t(struct tty *tp, void *buf, size_t len);
+typedef void th_getc_capture_t(struct tty *tp, const void *buf, size_t len);
+typedef size_t th_getc_poll_t(struct tty *tp);
+
+typedef void th_close_t(struct tty *tp);
+
+struct ttyhook {
+	/* Character input. */
+	th_rint_t		*th_rint;
+	th_rint_bypass_t	*th_rint_bypass;
+	th_rint_done_t		*th_rint_done;
+	th_rint_poll_t		*th_rint_poll;
+
+	/* Character output. */
+	th_getc_inject_t	*th_getc_inject;
+	th_getc_capture_t	*th_getc_capture;
+	th_getc_poll_t		*th_getc_poll;
+
+	th_close_t		*th_close;
+};
+
+int	ttyhook_register(struct tty **, struct thread *, int,
+    struct ttyhook *, void *);
+void	ttyhook_unregister(struct tty *);
+#define	ttyhook_softc(tp)		((tp)->t_hooksoftc)
+#define	ttyhook_hashook(tp,hook)	((tp)->t_hook != NULL && \
+					(tp)->t_hook->th_ ## hook != NULL)
+
+static __inline int
+ttyhook_rint(struct tty *tp, char c, int flags)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_hook->th_rint(tp, c, flags);
+}
+
+static __inline size_t
+ttyhook_rint_bypass(struct tty *tp, const void *buf, size_t len)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_hook->th_rint_bypass(tp, buf, len);
+}
+
+static __inline void
+ttyhook_rint_done(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	tp->t_hook->th_rint_done(tp);
+}
+
+static __inline size_t
+ttyhook_rint_poll(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_hook->th_rint_poll(tp);
+}
+
+static __inline size_t
+ttyhook_getc_inject(struct tty *tp, void *buf, size_t len)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_hook->th_getc_inject(tp, buf, len);
+}
+
+static __inline void
+ttyhook_getc_capture(struct tty *tp, const void *buf, size_t len)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	tp->t_hook->th_getc_capture(tp, buf, len);
+}
+
+static __inline size_t
+ttyhook_getc_poll(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_hook->th_getc_poll(tp);
+}
+
+static __inline void
+ttyhook_close(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+
+	tp->t_hook->th_close(tp);
+}
+
+#endif /* !_SYS_TTYHOOK_H_ */