src/mux_pt.c

/*
 * Pass-through mux-demux for connections
 *
 * Copyright 2017 Willy Tarreau <w@1wt.eu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 */

#include <haproxy/api.h>
#include <haproxy/buf.h>
#include <haproxy/connection.h>
#include <haproxy/stream.h>
#include <haproxy/task.h>

struct mux_pt_ctx {
	struct conn_stream *cs;
	struct connection *conn;
	struct wait_event wait_event;
};

DECLARE_STATIC_POOL(pool_head_pt_ctx, "mux_pt", sizeof(struct mux_pt_ctx));

static void mux_pt_destroy(struct mux_pt_ctx *ctx)
{
	struct connection *conn = NULL;

	if (ctx) {
		/* The connection must be attached to this mux to be released */
		if (ctx->conn && ctx->conn->ctx == ctx)
			conn = ctx->conn;

		tasklet_free(ctx->wait_event.tasklet);

		if (conn && ctx->wait_event.events != 0)
			conn->xprt->unsubscribe(conn, conn->xprt_ctx, ctx->wait_event.events,
						&ctx->wait_event);
		pool_free(pool_head_pt_ctx, ctx);
	}

	if (conn) {
		conn->mux = NULL;
		conn->ctx = NULL;

		conn_stop_tracking(conn);
		conn_full_close(conn);
		if (conn->destroy_cb)
			conn->destroy_cb(conn);
		conn_free(conn);
	}
}

/* Callback, used when we get I/Os while in idle mode. This one is exported so
 * that "show fd" can resolve it.
 */
struct task *mux_pt_io_cb(struct task *t, void *tctx, unsigned int status)
{
	struct mux_pt_ctx *ctx = tctx;

	if (ctx->cs) {
		/* There's a small race condition.
		 * mux_pt_io_cb() is only supposed to be called if we have no
		 * stream attached. However, maybe the tasklet got woken up,
		 * and this connection was then attached to a new stream.
		 * If this happened, just wake the tasklet up if anybody
		 * subscribed to receive events, and otherwise call the wake
		 * method, to make sure the event is noticed.
		 */
		if (ctx->conn->subs) {
			ctx->conn->subs->events = 0;
			tasklet_wakeup(ctx->conn->subs->tasklet);
			ctx->conn->subs = NULL;
		} else if (ctx->cs->data_cb->wake)
			ctx->cs->data_cb->wake(ctx->cs);
		return t;
	}
	conn_ctrl_drain(ctx->conn);
	if (ctx->conn->flags & (CO_FL_ERROR | CO_FL_SOCK_RD_SH | CO_FL_SOCK_WR_SH)) {
		mux_pt_destroy(ctx);
		t = NULL;
	}
	else
		ctx->conn->xprt->subscribe(ctx->conn, ctx->conn->xprt_ctx, SUB_RETRY_RECV,
		    &ctx->wait_event);

	return t;
}

/* Initialize the mux once it's attached. It is expected that conn->ctx
 * points to the existing conn_stream (for outgoing connections) or NULL (for
 * incoming ones, in which case one will be allocated and a new stream will be
 * instantiated). Returns < 0 on error.
 */
static int mux_pt_init(struct connection *conn, struct proxy *prx, struct session *sess,
		       struct buffer *input)
{
	struct conn_stream *cs = conn->ctx;
	struct mux_pt_ctx *ctx = pool_alloc(pool_head_pt_ctx);

	if (!ctx)
		goto fail;

	ctx->wait_event.tasklet = tasklet_new();
	if (!ctx->wait_event.tasklet)
		goto fail_free_ctx;
	ctx->wait_event.tasklet->context = ctx;
	ctx->wait_event.tasklet->process = mux_pt_io_cb;
	ctx->wait_event.events = 0;
	ctx->conn = conn;

	if (!cs) {
		cs = cs_new(conn, conn->target);
		if (!cs)
			goto fail_free_ctx;

		if (stream_create_from_cs(cs, &BUF_NULL) < 0)
			goto fail_free;

	}
	conn->ctx = ctx;
	ctx->cs = cs;
	cs->flags |= CS_FL_RCV_MORE;
	if (global.tune.options & GTUNE_USE_SPLICE)
		cs->flags |= CS_FL_MAY_SPLICE;
	return 0;

 fail_free:
	cs_free(cs);
fail_free_ctx:
	if (ctx->wait_event.tasklet)
		tasklet_free(ctx->wait_event.tasklet);
	pool_free(pool_head_pt_ctx, ctx);
 fail:
	return -1;
}

/* callback to be used by default for the pass-through mux. It calls the data
 * layer wake() callback if it is set otherwise returns 0.
 */
static int mux_pt_wake(struct connection *conn)
{
	struct mux_pt_ctx *ctx = conn->ctx;
	struct conn_stream *cs = ctx->cs;
	int ret = 0;

	if (cs) {
		ret = cs->data_cb->wake ? cs->data_cb->wake(cs) : 0;

		if (ret < 0)
			return ret;
	} else {
		conn_ctrl_drain(conn);
		if (conn->flags & (CO_FL_ERROR | CO_FL_SOCK_RD_SH)) {
			mux_pt_destroy(ctx);
			return -1;
		}
	}

	/* If we had early data, and we're done with the handshake
	 * then we know the data are safe, and we can remove the flag.
	 */
	if ((conn->flags & (CO_FL_EARLY_DATA | CO_FL_EARLY_SSL_HS | CO_FL_WAIT_XPRT)) ==
	    CO_FL_EARLY_DATA)
		conn->flags &= ~CO_FL_EARLY_DATA;
	return ret;
}

/*
 * Attach a new stream to a connection
 * (Used for outgoing connections)
 */
static struct conn_stream *mux_pt_attach(struct connection *conn, struct session *sess)
{
	struct conn_stream *cs;
	struct mux_pt_ctx *ctx = conn->ctx;

	if (ctx->wait_event.events)
		conn->xprt->unsubscribe(ctx->conn, conn->xprt_ctx, SUB_RETRY_RECV, &ctx->wait_event);
	cs = cs_new(conn, conn->target);
	if (!cs)
		goto fail;

	ctx->cs = cs;
	cs->flags |= CS_FL_RCV_MORE;
	return (cs);
fail:
	return NULL;
}

/* Retrieves a valid conn_stream from this connection, or returns NULL. For
 * this mux, it's easy as we can only store a single conn_stream.
 */
static const struct conn_stream *mux_pt_get_first_cs(const struct connection *conn)
{
	struct mux_pt_ctx *ctx = conn->ctx;
	struct conn_stream *cs = ctx->cs;

	return cs;
}

/* Destroy the mux and the associated connection if still attached to this mux
 * and no longer used */
static void mux_pt_destroy_meth(void *ctx)
{
	struct mux_pt_ctx *pt = ctx;

	if (!(pt->cs) || !(pt->conn) || pt->conn->ctx != pt)
		mux_pt_destroy(pt);
}

/*
 * Detach the stream from the connection and possibly release the connection.
 */
static void mux_pt_detach(struct conn_stream *cs)
{
	struct connection *conn = cs->conn;
	struct mux_pt_ctx *ctx = cs->conn->ctx;

	/* Subscribe, to know if we got disconnected */
	if (conn->owner != NULL &&
	    !(conn->flags & (CO_FL_ERROR | CO_FL_SOCK_RD_SH | CO_FL_SOCK_WR_SH))) {
		ctx->cs = NULL;
		conn->xprt->subscribe(conn, conn->xprt_ctx, SUB_RETRY_RECV, &ctx->wait_event);
	} else
		/* There's no session attached to that connection, destroy it */
		mux_pt_destroy(ctx);
}

/* returns the number of streams in use on a connection */
static int mux_pt_used_streams(struct connection *conn)
{
	struct mux_pt_ctx *ctx = conn->ctx;

	return ctx->cs ? 1 : 0;
}

/* returns the number of streams still available on a connection */
static int mux_pt_avail_streams(struct connection *conn)
{
	return 1 - mux_pt_used_streams(conn);
}

static void mux_pt_shutr(struct conn_stream *cs, enum cs_shr_mode mode)
{
	if (cs->flags & CS_FL_SHR)
		return;
	cs->flags &= ~(CS_FL_RCV_MORE | CS_FL_WANT_ROOM);
	if (conn_xprt_ready(cs->conn) && cs->conn->xprt->shutr)
		cs->conn->xprt->shutr(cs->conn, cs->conn->xprt_ctx,
		    (mode == CS_SHR_DRAIN));
	else if (mode == CS_SHR_DRAIN)
		conn_ctrl_drain(cs->conn);
	if (cs->flags & CS_FL_SHW)
		conn_full_close(cs->conn);
}

static void mux_pt_shutw(struct conn_stream *cs, enum cs_shw_mode mode)
{
	if (cs->flags & CS_FL_SHW)
		return;
	if (conn_xprt_ready(cs->conn) && cs->conn->xprt->shutw)
		cs->conn->xprt->shutw(cs->conn, cs->conn->xprt_ctx,
		    (mode == CS_SHW_NORMAL));
	if (!(cs->flags & CS_FL_SHR))
		conn_sock_shutw(cs->conn, (mode == CS_SHW_NORMAL));
	else
		conn_full_close(cs->conn);
}

/*
 * Called from the upper layer, to get more data
 */
static size_t mux_pt_rcv_buf(struct conn_stream *cs, struct buffer *buf, size_t count, int flags)
{
	size_t ret;

	if (!count) {
		cs->flags |= (CS_FL_RCV_MORE | CS_FL_WANT_ROOM);
		return 0;
	}
	b_realign_if_empty(buf);
	ret = cs->conn->xprt->rcv_buf(cs->conn, cs->conn->xprt_ctx, buf, count, flags);
	if (conn_xprt_read0_pending(cs->conn)) {
		cs->flags &= ~(CS_FL_RCV_MORE | CS_FL_WANT_ROOM);
		cs->flags |= CS_FL_EOS;
	}
	if (cs->conn->flags & CO_FL_ERROR) {
		cs->flags &= ~(CS_FL_RCV_MORE | CS_FL_WANT_ROOM);
		cs->flags |= CS_FL_ERROR;
	}
	return ret;
}

/* Called from the upper layer, to send data */
static size_t mux_pt_snd_buf(struct conn_stream *cs, struct buffer *buf, size_t count, int flags)
{
	size_t ret;

	ret = cs->conn->xprt->snd_buf(cs->conn, cs->conn->xprt_ctx, buf, count, flags);

	if (ret > 0)
		b_del(buf, ret);
	return ret;
}

/* Called from the upper layer, to subscribe <es> to events <event_type>. The
 * event subscriber <es> is not allowed to change from a previous call as long
 * as at least one event is still subscribed. The <event_type> must only be a
 * combination of SUB_RETRY_RECV and SUB_RETRY_SEND. It always returns 0.
 */
static int mux_pt_subscribe(struct conn_stream *cs, int event_type, struct wait_event *es)
{
	return cs->conn->xprt->subscribe(cs->conn, cs->conn->xprt_ctx, event_type, es);
}

/* Called from the upper layer, to unsubscribe <es> from events <event_type>.
 * The <es> pointer is not allowed to differ from the one passed to the
 * subscribe() call. It always returns zero.
 */
static int mux_pt_unsubscribe(struct conn_stream *cs, int event_type, struct wait_event *es)
{
	return cs->conn->xprt->unsubscribe(cs->conn, cs->conn->xprt_ctx, event_type, es);
}

#if defined(USE_LINUX_SPLICE)
/* Send and get, using splicing */
static int mux_pt_rcv_pipe(struct conn_stream *cs, struct pipe *pipe, unsigned int count)
{
	int ret;

	ret = cs->conn->xprt->rcv_pipe(cs->conn, cs->conn->xprt_ctx, pipe, count);
	if (conn_xprt_read0_pending(cs->conn))
		cs->flags |= CS_FL_EOS;
	if (cs->conn->flags & CO_FL_ERROR)
		cs->flags |= CS_FL_ERROR;
	return (ret);
}

static int mux_pt_snd_pipe(struct conn_stream *cs, struct pipe *pipe)
{
	return (cs->conn->xprt->snd_pipe(cs->conn, cs->conn->xprt_ctx, pipe));
}
#endif

static int mux_pt_ctl(struct connection *conn, enum mux_ctl_type mux_ctl, void *output)
{
	int ret = 0;
	switch (mux_ctl) {
	case MUX_STATUS:
		if (!(conn->flags & CO_FL_WAIT_XPRT))
			ret |= MUX_STATUS_READY;
		return ret;
	case MUX_EXIT_STATUS:
		return MUX_ES_UNKNOWN;
	default:
		return -1;
	}
}

/* The mux operations */
const struct mux_ops mux_pt_ops = {
	.init = mux_pt_init,
	.wake = mux_pt_wake,
	.rcv_buf = mux_pt_rcv_buf,
	.snd_buf = mux_pt_snd_buf,
	.subscribe = mux_pt_subscribe,
	.unsubscribe = mux_pt_unsubscribe,
#if defined(USE_LINUX_SPLICE)
	.rcv_pipe = mux_pt_rcv_pipe,
	.snd_pipe = mux_pt_snd_pipe,
#endif
	.attach = mux_pt_attach,
	.get_first_cs = mux_pt_get_first_cs,
	.detach = mux_pt_detach,
	.avail_streams = mux_pt_avail_streams,
	.used_streams = mux_pt_used_streams,
	.destroy = mux_pt_destroy_meth,
	.ctl = mux_pt_ctl,
	.shutr = mux_pt_shutr,
	.shutw = mux_pt_shutw,
	.flags = MX_FL_NONE,
	.name = "PASS",
};

/* PROT selection : default mux has empty name */
static struct mux_proto_list mux_proto_pt =
	{ .token = IST(""), .mode = PROTO_MODE_TCP, .side = PROTO_SIDE_BOTH, .mux = &mux_pt_ops };

INITCALL1(STG_REGISTER, register_mux_proto, &mux_proto_pt);