[PATCH net-next 08/12] bridge: mrp: Implement the MRP Interconnect API

[Horatiu Vultur]

Thie patch adds support for MRP Interconnect. Similar with the MRP ring,
if the HW can't generate MRP_InTest frames, then the SW will try to
generate them. And if also the SW fails to generate the frames then an
error is return to userspace.

The forwarding/termination of MRP_In frames is happening in the kernel
and is done by MRP instances.

Signed-off-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
---
 net/bridge/br_mrp.c         | 525 +++++++++++++++++++++++++++++++++---
 net/bridge/br_private_mrp.h |   4 +
 2 files changed, 498 insertions(+), 31 deletions(-)

diff --git a/net/bridge/br_mrp.c b/net/bridge/br_mrp.c
index d4176f8956d05..a82f311e968d7 100644
--- a/net/bridge/br_mrp.c
+++ b/net/bridge/br_mrp.c
@@ -4,6 +4,27 @@
 #include "br_private_mrp.h"
 
 static const u8 mrp_test_dmac[ETH_ALEN] = { 0x1, 0x15, 0x4e, 0x0, 0x0, 0x1 };
+static const u8 mrp_in_test_dmac[ETH_ALEN] = { 0x1, 0x15, 0x4e, 0x0, 0x0, 0x3 };
+
+static bool br_mrp_is_ring_port(struct net_bridge_port *p_port,
+				struct net_bridge_port *s_port,
+				struct net_bridge_port *port)
+{
+	if (port == p_port ||
+	    port == s_port)
+		return true;
+
+	return false;
+}
+
+static bool br_mrp_is_in_port(struct net_bridge_port *i_port,
+			      struct net_bridge_port *port)
+{
+	if (port == i_port)
+		return true;
+
+	return false;
+}
 
 static struct net_bridge_port *br_mrp_get_port(struct net_bridge *br,
 					       u32 ifindex)
@@ -37,6 +58,22 @@ static struct br_mrp *br_mrp_find_id(struct net_bridge *br, u32 ring_id)
 	return res;
 }
 
+static struct br_mrp *br_mrp_find_in_id(struct net_bridge *br, u32 in_id)
+{
+	struct br_mrp *res = NULL;
+	struct br_mrp *mrp;
+
+	list_for_each_entry_rcu(mrp, &br->mrp_list, list,
+				lockdep_rtnl_is_held()) {
+		if (mrp->in_id == in_id) {
+			res = mrp;
+			break;
+		}
+	}
+
+	return res;
+}
+
 static bool br_mrp_unique_ifindex(struct net_bridge *br, u32 ifindex)
 {
 	struct br_mrp *mrp;
@@ -52,6 +89,10 @@ static bool br_mrp_unique_ifindex(struct net_bridge *br, u32 ifindex)
 		p = rtnl_dereference(mrp->s_port);
 		if (p && p->dev->ifindex == ifindex)
 			return false;
+
+		p = rtnl_dereference(mrp->i_port);
+		if (p && p->dev->ifindex == ifindex)
+			return false;
 	}
 
 	return true;
@@ -66,7 +107,8 @@ static struct br_mrp *br_mrp_find_port(struct net_bridge *br,
 	list_for_each_entry_rcu(mrp, &br->mrp_list, list,
 				lockdep_rtnl_is_held()) {
 		if (rcu_access_pointer(mrp->p_port) == p ||
-		    rcu_access_pointer(mrp->s_port) == p) {
+		    rcu_access_pointer(mrp->s_port) == p ||
+		    rcu_access_pointer(mrp->i_port) == p) {
 			res = mrp;
 			break;
 		}
@@ -160,6 +202,36 @@ static struct sk_buff *br_mrp_alloc_test_skb(struct br_mrp *mrp,
 	return skb;
 }
 
+static struct sk_buff *br_mrp_alloc_in_test_skb(struct br_mrp *mrp,
+						struct net_bridge_port *p,
+						enum br_mrp_port_role_type port_role)
+{
+	struct br_mrp_in_test_hdr *hdr = NULL;
+	struct sk_buff *skb = NULL;
+
+	if (!p)
+		return NULL;
+
+	skb = br_mrp_skb_alloc(p, p->dev->dev_addr, mrp_in_test_dmac);
+	if (!skb)
+		return NULL;
+
+	br_mrp_skb_tlv(skb, BR_MRP_TLV_HEADER_IN_TEST, sizeof(*hdr));
+	hdr = skb_put(skb, sizeof(*hdr));
+
+	hdr->id = cpu_to_be16(mrp->in_id);
+	ether_addr_copy(hdr->sa, p->br->dev->dev_addr);
+	hdr->port_role = cpu_to_be16(port_role);
+	hdr->state = cpu_to_be16(mrp->in_state);
+	hdr->transitions = cpu_to_be16(mrp->in_transitions);
+	hdr->timestamp = cpu_to_be32(jiffies_to_msecs(jiffies));
+
+	br_mrp_skb_common(skb, mrp);
+	br_mrp_skb_tlv(skb, BR_MRP_TLV_HEADER_END, 0x0);
+
+	return skb;
+}
+
 /* This function is continuously called in the following cases:
  * - when node role is MRM, in this case test_monitor is always set to false
  *   because it needs to notify the userspace that the ring is open and needs to
@@ -239,6 +311,83 @@ static void br_mrp_test_work_expired(struct work_struct *work)
 			   usecs_to_jiffies(mrp->test_interval));
 }
 
+/* This function is continuously called when the node has the interconnect rol
+ * MIM. It would generate interconnect test frames and will send them on all 3
+ * ports. But will also check if it stop receiving interconnect test frames.
+ */
+static void br_mrp_in_test_work_expired(struct work_struct *work)
+{
+	struct delayed_work *del_work = to_delayed_work(work);
+	struct br_mrp *mrp = container_of(del_work, struct br_mrp, in_test_work);
+	struct net_bridge_port *p;
+	bool notify_open = false;
+	struct sk_buff *skb;
+
+	if (time_before_eq(mrp->in_test_end, jiffies))
+		return;
+
+	if (mrp->in_test_count_miss < mrp->in_test_max_miss) {
+		mrp->in_test_count_miss++;
+	} else {
+		/* Notify that the interconnect ring is open only if the
+		 * interconnect ring state is closed, otherwise it would
+		 * continue to notify at every interval.
+		 */
+		if (mrp->in_state == BR_MRP_IN_STATE_CLOSED)
+			notify_open = true;
+	}
+
+	rcu_read_lock();
+
+	p = rcu_dereference(mrp->p_port);
+	if (p) {
+		skb = br_mrp_alloc_in_test_skb(mrp, p,
+					       BR_MRP_PORT_ROLE_PRIMARY);
+		if (!skb)
+			goto out;
+
+		skb_reset_network_header(skb);
+		dev_queue_xmit(skb);
+
+		if (notify_open && !mrp->in_role_offloaded)
+			br_mrp_in_port_open(p->dev, true);
+	}
+
+	p = rcu_dereference(mrp->s_port);
+	if (p) {
+		skb = br_mrp_alloc_in_test_skb(mrp, p,
+					       BR_MRP_PORT_ROLE_SECONDARY);
+		if (!skb)
+			goto out;
+
+		skb_reset_network_header(skb);
+		dev_queue_xmit(skb);
+
+		if (notify_open && !mrp->in_role_offloaded)
+			br_mrp_in_port_open(p->dev, true);
+	}
+
+	p = rcu_dereference(mrp->i_port);
+	if (p) {
+		skb = br_mrp_alloc_in_test_skb(mrp, p,
+					       BR_MRP_PORT_ROLE_INTER);
+		if (!skb)
+			goto out;
+
+		skb_reset_network_header(skb);
+		dev_queue_xmit(skb);
+
+		if (notify_open && !mrp->in_role_offloaded)
+			br_mrp_in_port_open(p->dev, true);
+	}
+
+out:
+	rcu_read_unlock();
+
+	queue_delayed_work(system_wq, &mrp->in_test_work,
+			   usecs_to_jiffies(mrp->in_test_interval));
+}
+
 /* Deletes the MRP instance.
  * note: called under rtnl_lock
  */
@@ -278,6 +427,18 @@ static void br_mrp_del_impl(struct net_bridge *br, struct br_mrp *mrp)
 		rcu_assign_pointer(mrp->s_port, NULL);
 	}
 
+	p = rtnl_dereference(mrp->i_port);
+	if (p) {
+		spin_lock_bh(&br->lock);
+		state = netif_running(br->dev) ?
+				BR_STATE_FORWARDING : BR_STATE_DISABLED;
+		p->state = state;
+		p->flags &= ~BR_MRP_AWARE;
+		spin_unlock_bh(&br->lock);
+		br_mrp_port_switchdev_set_state(p, state);
+		rcu_assign_pointer(mrp->i_port, NULL);
+	}
+
 	list_del_rcu(&mrp->list);
 	kfree_rcu(mrp, rcu);
 }
@@ -511,6 +672,140 @@ int br_mrp_start_test(struct net_bridge *br,
 	return 0;
 }
 
+/* Set in state, int state can be only Open or Closed
+ * note: already called with rtnl_lock
+ */
+int br_mrp_set_in_state(struct net_bridge *br, struct br_mrp_in_state *state)
+{
+	struct br_mrp *mrp = br_mrp_find_in_id(br, state->in_id);
+
+	if (!mrp)
+		return -EINVAL;
+
+	if (mrp->in_state == BR_MRP_IN_STATE_CLOSED &&
+	    state->in_state != BR_MRP_IN_STATE_CLOSED)
+		mrp->in_transitions++;
+
+	mrp->in_state = state->in_state;
+
+	br_mrp_switchdev_set_in_state(br, mrp, state->in_state);
+
+	return 0;
+}
+
+/* Set in role, in role can be only MIM(Media Interconnection Manager) or
+ * MIC(Media Interconnection Client).
+ * note: already called with rtnl_lock
+ */
+int br_mrp_set_in_role(struct net_bridge *br, struct br_mrp_in_role *role)
+{
+	struct br_mrp *mrp = br_mrp_find_id(br, role->ring_id);
+	struct net_bridge_port *p;
+	int err;
+
+	if (!mrp)
+		return -EINVAL;
+
+	if (!br_mrp_get_port(br, role->i_ifindex))
+		return -EINVAL;
+
+	/* It is not possible to have the same port part of multiple rings */
+	if (!br_mrp_unique_ifindex(br, role->i_ifindex))
+		return -EINVAL;
+
+	p = br_mrp_get_port(br, role->i_ifindex);
+	spin_lock_bh(&br->lock);
+	p->state = BR_STATE_FORWARDING;
+	p->flags |= BR_MRP_AWARE;
+	spin_unlock_bh(&br->lock);
+	rcu_assign_pointer(mrp->i_port, p);
+
+	mrp->in_role = role->in_role;
+	mrp->in_id = role->in_id;
+
+	INIT_DELAYED_WORK(&mrp->in_test_work, br_mrp_in_test_work_expired);
+
+	/* If there is an error just bailed out */
+	err = br_mrp_switchdev_set_in_role(br, mrp, role->in_id,
+					   role->ring_id, role->in_role);
+	if (err && err != -EOPNOTSUPP)
+		return err;
+
+	/* Now detect if the HW actually applied the role or not. If the HW
+	 * applied the role it means that the SW will not to do those operations
+	 * anymore. For example if the role is MIM then the HW will notify the
+	 * SW when interconnect ring is open, but if the is not pushed to the HW
+	 * the SW will need to detect when the interconnect ring is open.
+	 */
+	mrp->in_role_offloaded = err == -EOPNOTSUPP ? 0 : 1;
+
+	return 0;
+}
+
+int br_mrp_start_in_test(struct net_bridge *br,
+			 struct br_mrp_start_in_test *in_test)
+{
+	struct br_mrp *mrp = br_mrp_find_in_id(br, in_test->in_id);
+
+	if (!mrp)
+		return -EINVAL;
+
+	/* Try to push it to the HW and if it fails then continue with SW
+	 * implementation and if that also fails then return error.
+	 */
+	if (!br_mrp_switchdev_send_in_test(br, mrp, in_test->interval,
+					   in_test->max_miss, in_test->period))
+		return 0;
+
+	mrp->in_test_interval = in_test->interval;
+	mrp->in_test_end = jiffies + usecs_to_jiffies(in_test->period);
+	mrp->in_test_max_miss = in_test->max_miss;
+	mrp->in_test_count_miss = 0;
+	queue_delayed_work(system_wq, &mrp->in_test_work,
+			   usecs_to_jiffies(in_test->interval));
+
+	return 0;
+}
+
+/* Determin if the frame type is a ring frame */
+static bool br_mrp_ring_frame(struct sk_buff *skb)
+{
+	const struct br_mrp_tlv_hdr *hdr;
+	struct br_mrp_tlv_hdr _hdr;
+
+	hdr = skb_header_pointer(skb, sizeof(uint16_t), sizeof(_hdr), &_hdr);
+	if (!hdr)
+		return false;
+
+	if (hdr->type == BR_MRP_TLV_HEADER_RING_TEST ||
+	    hdr->type == BR_MRP_TLV_HEADER_RING_TOPO ||
+	    hdr->type == BR_MRP_TLV_HEADER_RING_LINK_DOWN ||
+	    hdr->type == BR_MRP_TLV_HEADER_RING_LINK_UP ||
+	    hdr->type == BR_MRP_TLV_HEADER_OPTION)
+		return true;
+
+	return false;
+}
+
+/* Determin if the frame type is an interconnect frame */
+static bool br_mrp_in_frame(struct sk_buff *skb)
+{
+	const struct br_mrp_tlv_hdr *hdr;
+	struct br_mrp_tlv_hdr _hdr;
+
+	hdr = skb_header_pointer(skb, sizeof(uint16_t), sizeof(_hdr), &_hdr);
+	if (!hdr)
+		return false;
+
+	if (hdr->type == BR_MRP_TLV_HEADER_IN_TEST ||
+	    hdr->type == BR_MRP_TLV_HEADER_IN_TOPO ||
+	    hdr->type == BR_MRP_TLV_HEADER_IN_LINK_DOWN ||
+	    hdr->type == BR_MRP_TLV_HEADER_IN_LINK_UP)
+		return true;
+
+	return false;
+}
+
 /* Process only MRP Test frame. All the other MRP frames are processed by
  * userspace application
  * note: already called with rcu_read_lock
@@ -591,17 +886,92 @@ static void br_mrp_mra_process(struct br_mrp *mrp, struct net_bridge *br,
 		mrp->test_count_miss = 0;
 }
 
-/* This will just forward the frame to the other mrp ring port(MRC role) or will
- * not do anything.
+/* Process only MRP InTest frame. All the other MRP frames are processed by
+ * userspace application
+ * note: already called with rcu_read_lock
+ */
+static bool br_mrp_mim_process(struct br_mrp *mrp, struct net_bridge_port *port,
+			       struct sk_buff *skb)
+{
+	const struct br_mrp_in_test_hdr *in_hdr;
+	struct br_mrp_in_test_hdr _in_hdr;
+	const struct br_mrp_tlv_hdr *hdr;
+	struct br_mrp_tlv_hdr _hdr;
+
+	/* Each MRP header starts with a version field which is 16 bits.
+	 * Therefore skip the version and get directly the TLV header.
+	 */
+	hdr = skb_header_pointer(skb, sizeof(uint16_t), sizeof(_hdr), &_hdr);
+	if (!hdr)
+		return false;
+
+	/* The check for InTest frame type was already done */
+	in_hdr = skb_header_pointer(skb, sizeof(uint16_t) + sizeof(_hdr),
+				    sizeof(_in_hdr), &_in_hdr);
+	if (!in_hdr)
+		return false;
+
+	/* It needs to process only it's own InTest frames. */
+	if (mrp->in_id != ntohs(in_hdr->id))
+		return false;
+
+	mrp->in_test_count_miss = 0;
+
+	/* Notify the userspace that the ring is closed only when the ring is
+	 * not closed
+	 */
+	if (mrp->in_state != BR_MRP_IN_STATE_CLOSED)
+		br_mrp_in_port_open(port->dev, false);
+
+	return true;
+}
+
+/* Get the MRP frame type
+ * note: already called with rcu_read_lock
+ */
+static u8 br_mrp_get_frame_type(struct sk_buff *skb)
+{
+	const struct br_mrp_tlv_hdr *hdr;
+	struct br_mrp_tlv_hdr _hdr;
+
+	/* Each MRP header starts with a version field which is 16 bits.
+	 * Therefore skip the version and get directly the TLV header.
+	 */
+	hdr = skb_header_pointer(skb, sizeof(uint16_t), sizeof(_hdr), &_hdr);
+	if (!hdr)
+		return 0xff;
+
+	return hdr->type;
+}
+
+static bool br_mrp_mrm_behaviour(struct br_mrp *mrp)
+{
+	if (mrp->ring_role == BR_MRP_RING_ROLE_MRM ||
+	    (mrp->ring_role == BR_MRP_RING_ROLE_MRA && !mrp->test_monitor))
+		return true;
+
+	return false;
+}
+
+static bool br_mrp_mrc_behaviour(struct br_mrp *mrp)
+{
+	if (mrp->ring_role == BR_MRP_RING_ROLE_MRC ||
+	    (mrp->ring_role == BR_MRP_RING_ROLE_MRA && mrp->test_monitor))
+		return true;
+
+	return false;
+}
+
+/* This will just forward the frame to the other mrp ring ports, depending on
+ * the frame type, ring role and interconnect role
  * note: already called with rcu_read_lock
  */
 static int br_mrp_rcv(struct net_bridge_port *p,
 		      struct sk_buff *skb, struct net_device *dev)
 {
-	struct net_device *s_dev, *p_dev, *d_dev;
-	struct net_bridge_port *p_port, *s_port;
+	struct net_bridge_port *p_port, *s_port, *i_port = NULL;
+	struct net_bridge_port *p_dst, *s_dst, *i_dst = NULL;
 	struct net_bridge *br;
-	struct sk_buff *nskb;
 	struct br_mrp *mrp;
 
 	/* If port is disabled don't accept any frames */
@@ -616,46 +986,139 @@ static int br_mrp_rcv(struct net_bridge_port *p,
 	p_port = rcu_dereference(mrp->p_port);
 	if (!p_port)
 		return 0;
+	p_dst = p_port;
 
 	s_port = rcu_dereference(mrp->s_port);
 	if (!s_port)
 		return 0;
+	s_dst = s_port;
 
-	/* If the role is MRM then don't forward the frames */
-	if (mrp->ring_role == BR_MRP_RING_ROLE_MRM) {
-		br_mrp_mrm_process(mrp, p, skb);
-		return 1;
-	}
-
-	/* If the role is MRA then don't forward the frames if it behaves as
-	 * MRM node
+	/* If the frame is a ring frame then it is not required to check the
+	 * interconnect role and ports to process or forward the frame
 	 */
-	if (mrp->ring_role == BR_MRP_RING_ROLE_MRA) {
-		if (!mrp->test_monitor) {
+	if (br_mrp_ring_frame(skb)) {
+		/* If the role is MRM then don't forward the frames */
+		if (mrp->ring_role == BR_MRP_RING_ROLE_MRM) {
 			br_mrp_mrm_process(mrp, p, skb);
-			return 1;
+			goto no_forward;
 		}
 
-		br_mrp_mra_process(mrp, br, p, skb);
+		/* If the role is MRA then don't forward the frames if it
+		 * behaves as MRM node
+		 */
+		if (mrp->ring_role == BR_MRP_RING_ROLE_MRA) {
+			if (!mrp->test_monitor) {
+				br_mrp_mrm_process(mrp, p, skb);
+				goto no_forward;
+			}
+
+			br_mrp_mra_process(mrp, br, p, skb);
+		}
+
+		goto forward;
 	}
 
-	/* Clone the frame and forward it on the other MRP port */
-	nskb = skb_clone(skb, GFP_ATOMIC);
-	if (!nskb)
-		return 0;
+	if (br_mrp_in_frame(skb)) {
+		u8 in_type = br_mrp_get_frame_type(skb);
 
-	p_dev = p_port->dev;
-	s_dev = s_port->dev;
+		i_port = rcu_dereference(mrp->i_port);
+		i_dst = i_port;
 
-	if (p_dev == dev)
-		d_dev = s_dev;
-	else
-		d_dev = p_dev;
+		/* If the ring port is in block state it should not forward
+		 * In_Test frames
+		 */
+		if (br_mrp_is_ring_port(p_port, s_port, p) &&
+		    p->state == BR_STATE_BLOCKING &&
+		    in_type == BR_MRP_TLV_HEADER_IN_TEST)
+			goto no_forward;
+
+		/* Nodes that behaves as MRM needs to stop forwarding the
+		 * frames in case the ring is closed, otherwise will be a loop.
+		 * In this case the frame is no forward between the ring ports.
+		 */
+		if (br_mrp_mrm_behaviour(mrp) &&
+		    br_mrp_is_ring_port(p_port, s_port, p) &&
+		    (s_port->state != BR_STATE_FORWARDING ||
+		     p_port->state != BR_STATE_FORWARDING)) {
+			p_dst = NULL;
+			s_dst = NULL;
+		}
+
+		/* A node that behaves as MRC and doesn't have a interconnect
+		 * role then it should forward all frames between the ring ports
+		 * because it doesn't have an interconnect port
+		 */
+		if (br_mrp_mrc_behaviour(mrp) &&
+		    mrp->in_role == BR_MRP_IN_ROLE_DISABLED)
+			goto forward;
+
+		if (mrp->in_role == BR_MRP_IN_ROLE_MIM) {
+			if (in_type == BR_MRP_TLV_HEADER_IN_TEST) {
+				/* MIM should not forward it's own InTest
+				 * frames
+				 */
+				if (br_mrp_mim_process(mrp, p, skb)) {
+					goto no_forward;
+				} else {
+					if (br_mrp_is_ring_port(p_port, s_port,
+								p))
+						i_dst = NULL;
+
+					if (br_mrp_is_in_port(i_port, p))
+						goto no_forward;
+				}
+			} else {
+				/* MIM should forward IntLinkChange and
+				 * IntTopoChange between ring ports but MIM
+				 * should not forward IntLinkChange and
+				 * IntTopoChange if the frame was received at
+				 * the interconnect port
+				 */
+				if (br_mrp_is_ring_port(p_port, s_port, p))
+					i_dst = NULL;
+
+				if (br_mrp_is_in_port(i_port, p))
+					goto no_forward;
+			}
+		}
+
+		if (mrp->in_role == BR_MRP_IN_ROLE_MIC) {
+			/* MIC should forward InTest frames on all ports
+			 * regardless of the received port
+			 */
+			if (in_type == BR_MRP_TLV_HEADER_IN_TEST)
+				goto forward;
+
+			/* MIC should forward IntLinkChange frames only if they
+			 * are received on ring ports to all the ports
+			 */
+			if (br_mrp_is_ring_port(p_port, s_port, p) &&
+			    (in_type == BR_MRP_TLV_HEADER_IN_LINK_UP ||
+			     in_type == BR_MRP_TLV_HEADER_IN_LINK_DOWN))
+				goto forward;
+
+			/* Should forward the InTopo frames only between the
+			 * ring ports
+			 */
+			if (in_type == BR_MRP_TLV_HEADER_IN_TOPO) {
+				i_dst = NULL;
+				goto forward;
+			}
+
+			/* In all the other cases don't forward the frames */
+			goto no_forward;
+		}
+	}
 
-	nskb->dev = d_dev;
-	skb_push(nskb, ETH_HLEN);
-	dev_queue_xmit(nskb);
+forward:
+	if (p_dst)
+		br_forward(p_dst, skb, true, false);
+	if (s_dst)
+		br_forward(s_dst, skb, true, false);
+	if (i_dst)
+		br_forward(i_dst, skb, true, false);
 
+no_forward:
 	return 1;
 }
 
diff --git a/net/bridge/br_private_mrp.h b/net/bridge/br_private_mrp.h
index 50dbf046a9be3..81e7955190456 100644
--- a/net/bridge/br_private_mrp.h
+++ b/net/bridge/br_private_mrp.h
@@ -57,6 +57,10 @@ int br_mrp_set_ring_state(struct net_bridge *br,
 			  struct br_mrp_ring_state *state);
 int br_mrp_set_ring_role(struct net_bridge *br, struct br_mrp_ring_role *role);
 int br_mrp_start_test(struct net_bridge *br, struct br_mrp_start_test *test);
+int br_mrp_set_in_state(struct net_bridge *br, struct br_mrp_in_state *state);
+int br_mrp_set_in_role(struct net_bridge *br, struct br_mrp_in_role *role);
+int br_mrp_start_in_test(struct net_bridge *br,
+			 struct br_mrp_start_in_test *test);
 
 /* br_mrp_switchdev.c */
 int br_mrp_switchdev_add(struct net_bridge *br, struct br_mrp *mrp);
-- 
2.27.0