MEDIUM: h2: apply a timeout to h2 connections

Till now there was no way to deal with a dead H2 connection. Now each
connection creates a task that wakes up to kill the connection. Its
timeout is constantly refreshed when there's some activity. In case
the timeout triggers, the best effort attempts are made at sending a
clean GOAWAY message before closing and signaling the streams.

The timeout is automatically disabled when there's an active stream on
the connection, and restarted when the last stream finishes. This way
it should not affect long sessions.

src/mux_h2.c

@@ -21,6 +21,7 @@
 #include <proto/connection.h>
 #include <proto/h1.h>
 #include <proto/stream.h>
+#include <types/session.h>
 #include <eb32tree.h>
 
 
@@ -103,6 +104,8 @@ struct h2c {
 	int32_t mws; /* mux window size. Can be negative. */
 	int32_t mfs; /* mux's max frame size */
 
+	int timeout;        /* idle timeout duration in ticks */
+	struct task *task;  /* timeout management task */
 	struct eb_root streams_by_id; /* all active streams by their ID */
 	struct list send_list; /* list of blocked streams requesting to send */
 	struct list fctl_list; /* list of streams blocked by connection's fctl */
@@ -198,6 +201,7 @@ static const struct h2s *h2_idle_stream = &(const struct h2s){
 	.id        = 0,
 };
 
+static struct task *h2_timeout_task(struct task *t);
 
 /*****************************************************/
 /* functions below are for dynamic buffer management */
@@ -316,11 +320,17 @@ static inline void h2_release_mbuf(struct h2c *h2c)
 static int h2c_frt_init(struct connection *conn)
 {
 	struct h2c *h2c;
+	struct task *t = NULL;
+	struct session *sess = conn->owner;
 
 	h2c = pool_alloc2(pool2_h2c);
 	if (!h2c)
 		goto fail;
 
+	t = task_new(tid_bit);
+	if (!t)
+		goto fail;
+
 	h2c->ddht = hpack_dht_alloc(h2_settings_header_table_size);
 	if (!h2c->ddht)
 		goto fail;
@@ -350,10 +360,20 @@ static int h2c_frt_init(struct connection *conn)
 	LIST_INIT(&h2c->mbuf_wait.list);
 	conn->mux_ctx = h2c;
 
+	h2c->timeout = sess->fe->timeout.client;
+	h2c->task = t;
+	t->process = h2_timeout_task;
+	t->context = h2c;
+	t->expire = tick_add(now_ms, h2c->timeout);
+	task_queue(t);
+
 	conn_xprt_want_recv(conn);
+
 	/* mux->wake will be called soon to complete the operation */
 	return 0;
  fail:
+	if (t)
+		task_free(t);
 	pool_free2(pool2_h2c, h2c);
 	return -1;
 }
@@ -409,6 +429,12 @@ static void h2_release(struct connection *conn)
 		LIST_DEL(&h2c->mbuf_wait.list);
 		SPIN_UNLOCK(BUF_WQ_LOCK, &buffer_wq_lock);
 
+		if (h2c->task) {
+			task_delete(h2c->task);
+			task_free(h2c->task);
+			h2c->task = NULL;
+		}
+
 		pool_free2(pool2_h2c, h2c);
 	}
 
@@ -2003,11 +2029,9 @@ static int h2_wake(struct connection *conn)
 	/* stop being notified of incoming data if we can't process them */
 	if (h2c->st0 >= H2_CS_ERROR ||
 	    (h2c->flags & H2_CF_DEM_BLOCK_ANY) || conn_xprt_read0_pending(conn)) {
-		/* FIXME: we should clear a read timeout here */
 		__conn_xprt_stop_recv(conn);
 	}
 	else {
-		/* FIXME: we should (re-)arm a read timeout here */
 		__conn_xprt_want_recv(conn);
 	}
 
@@ -2017,18 +2041,67 @@ static int h2_wake(struct connection *conn)
 	     h2c->mbuf->o ||
 	     (h2c->mws > 0 && !LIST_ISEMPTY(&h2c->fctl_list)) ||
 	     (!(h2c->flags & H2_CF_MUX_BLOCK_ANY) && !LIST_ISEMPTY(&h2c->send_list)))) {
-		/* FIXME: we should (re-)arm a send timeout here */
 		__conn_xprt_want_send(conn);
 	}
 	else {
-		/* FIXME: we should clear a send timeout here */
 		h2_release_mbuf(h2c);
 		__conn_xprt_stop_send(conn);
 	}
 
+	if (eb_is_empty(&h2c->streams_by_id)) {
+		h2c->task->expire = tick_add(now_ms, h2c->timeout);
+		task_queue(h2c->task);
+	}
+	else
+		h2c->task->expire = TICK_ETERNITY;
+
 	return 0;
 }
 
+/* Connection timeout management. The principle is that if there's no receipt
+ * nor sending for a certain amount of time, the connection is closed. If the
+ * MUX buffer still has lying data or is not allocatable, the connection is
+ * immediately killed. If it's allocatable and empty, we attempt to send a
+ * GOAWAY frame.
+ */
+static struct task *h2_timeout_task(struct task *t)
+{
+	struct h2c *h2c = t->context;
+	int expired = tick_is_expired(t->expire, now_ms);
+
+	if (!expired)
+		return t;
+
+	h2c_error(h2c, H2_ERR_NO_ERROR);
+	h2_wake_some_streams(h2c, 0, 0);
+
+	if (h2c->mbuf->o) {
+		/* don't even try to send a GOAWAY, the buffer is stuck */
+		h2c->flags |= H2_CF_GOAWAY_FAILED;
+	}
+
+	/* try to send but no need to insist */
+	if (h2c_send_goaway_error(h2c, NULL) <= 0)
+		h2c->flags |= H2_CF_GOAWAY_FAILED;
+
+	if (h2c->mbuf->o && !(h2c->flags & H2_CF_GOAWAY_FAILED) && conn_xprt_ready(h2c->conn))
+		h2c->conn->xprt->snd_buf(h2c->conn, h2c->mbuf, 0);
+
+	if (!eb_is_empty(&h2c->streams_by_id))
+		goto wait;
+
+	h2_release(h2c->conn);
+	return NULL;
+
+ wait:
+	/* the streams have been notified, we must let them finish and close */
+	h2c->task = NULL;
+	task_delete(t);
+	task_free(t);
+	return NULL;
+}
+
+
 /*******************************************/
 /* functions below are used by the streams */
 /*******************************************/
@@ -2118,6 +2191,13 @@ static void h2_detach(struct conn_stream *cs)
 		/* h2s still attached to the h2c */
 		eb32_delete(&h2s->by_id);
 
+		if (eb_is_empty(&h2c->streams_by_id)) {
+			h2c->task->expire = tick_add(now_ms, h2c->timeout);
+			task_queue(h2c->task);
+		}
+		else
+			h2c->task->expire = TICK_ETERNITY;
+
 		/* We don't want to close right now unless we're removing the
 		 * last stream, and either the connection is in error, or it
 		 * reached the ID already specified in a GOAWAY frame received