Date: Tue, 19 Sep 2023 17:33:37 -0700
From: Subash Abhinov Kasiviswanathan <quic_subashab@...cinc.com>
To: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org
Cc: Subash Abhinov Kasiviswanathan <quic_subashab@...cinc.com>,
        Sean Tranchetti <quic_stranche@...cinc.com>
Subject: [PATCH net-next] net: qualcomm: rmnet: Add side band flow control support

Individual rmnet devices map to specific network types such as internet,
multimedia messaging services, IP multimedia subsystem etc. Each of
these network types may support varying quality of service for different
bearers or traffic types.

The physical device interconnect to radio hardware may support a
higher data rate than what is actually supported by the radio network.
Any packets transmitted to the radio hardware which exceed the radio
network data rate limit maybe dropped. This patch tries to minimize the
loss of packets by adding support for bearer level flow control within a
rmnet device by ensuring that the packets transmitted do not exceed the
limit allowed by the radio network.

In order to support multiple bearers, rmnet must be created as a
multiqueue TX netdevice. Radio hardware communicates the supported
bearer information for a given network via side band signalling.
Consider the following mapping -

IPv4 UDP port 1234 - Mark 0x1001 - Queue 1
IPv6 TCP port 2345 - Mark 0x2001 - Queue 2

iptables can be used to install filters which mark packets matching these
specific traffic patterns and the RMNET_QUEUE_MAPPING_ADD operation can
then be to install the mapping of the mark to the specific txqueue.

If the traffic limit is exceeded for a particular bearer, radio hardware
would notify that the bearer cannot accept more packets and the
corresponding txqueue traffic can be stopped using RMNET_QUEUE_DISABLE.

Conversely, if radio hardware can send more traffic for a particular
bearer, RMNET_QUEUE_ENABLE can be used to allow traffic on that
particular txqueue. RMNET_QUEUE_MAPPING_REMOVE can be used to remove the
mark to queue mapping in case the radio network doesn't support that
particular bearer any longer.

Signed-off-by: Sean Tranchetti <quic_stranche@...cinc.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <quic_subashab@...cinc.com>
---
 .../ethernet/qualcomm/rmnet/rmnet_config.c    | 98 ++++++++++++++++++-
 .../ethernet/qualcomm/rmnet/rmnet_config.h    |  2 +
 .../net/ethernet/qualcomm/rmnet/rmnet_vnd.c   | 21 ++++
 include/uapi/linux/if_link.h                  | 16 +++
 4 files changed, 136 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
index 39d24e07f306..2ef5c66757e9 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2013-2018, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
  *
  * RMNET configuration engine
  */
@@ -19,6 +20,7 @@
 static const struct nla_policy rmnet_policy[IFLA_RMNET_MAX + 1] = {
 	[IFLA_RMNET_MUX_ID]	= { .type = NLA_U16 },
 	[IFLA_RMNET_FLAGS]	= { .len = sizeof(struct ifla_rmnet_flags) },
+	[IFLA_RMNET_QUEUE]	= { .len = sizeof(struct rmnet_queue_mapping) },
 };
 
 static int rmnet_is_real_dev_registered(const struct net_device *real_dev)
@@ -88,6 +90,68 @@ static int rmnet_register_real_device(struct net_device *real_dev,
 	return 0;
 }
 
+static int rmnet_update_queue_map(struct net_device *dev, u8 operation,
+				  u8 txqueue, u32 mark,
+				  struct netlink_ext_ack *extack)
+{
+	struct rmnet_priv *priv = netdev_priv(dev);
+	struct netdev_queue *q;
+	void *p;
+	u8 txq;
+
+	if (unlikely(txqueue >= dev->num_tx_queues)) {
+		NL_SET_ERR_MSG_MOD(extack, "invalid txqueue");
+		return -EINVAL;
+	}
+
+	switch (operation) {
+	case RMNET_QUEUE_MAPPING_ADD:
+		p = xa_store(&priv->queue_map, mark, xa_mk_value(txqueue), GFP_ATOMIC);
+		if (xa_is_err(p)) {
+			NL_SET_ERR_MSG_MOD(extack, "unable to add mapping");
+			return -EINVAL;
+		}
+		break;
+	case RMNET_QUEUE_MAPPING_REMOVE:
+		p = xa_erase(&priv->queue_map, mark);
+		if (xa_is_err(p)) {
+			NL_SET_ERR_MSG_MOD(extack, "unable to remove mapping");
+			return -EINVAL;
+		}
+		break;
+	case RMNET_QUEUE_ENABLE:
+	case RMNET_QUEUE_DISABLE:
+		p = xa_load(&priv->queue_map, mark);
+		if (p && xa_is_value(p)) {
+			txq = xa_is_value(p);
+			if (txq >= dev->num_tx_queues) {
+				NL_SET_ERR_MSG_MOD(extack,
+						   "queue mapping limit exceeded");
+				return -EINVAL;
+			}
+
+			q = netdev_get_tx_queue(dev, txq);
+			if (unlikely(!q)) {
+				NL_SET_ERR_MSG_MOD(extack,
+						   "unsupported queue mapping");
+				return -EINVAL;
+			}
+
+			operation == RMNET_QUEUE_ENABLE ? netif_tx_wake_queue(q) :
+							  netif_tx_stop_queue(q);
+		} else {
+			NL_SET_ERR_MSG_MOD(extack, "invalid queue mapping");
+			return -EINVAL;
+		}
+		break;
+	default:
+		NL_SET_ERR_MSG_MOD(extack, "unsupported operation");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static void rmnet_unregister_bridge(struct rmnet_port *port)
 {
 	struct net_device *bridge_dev, *real_dev, *rmnet_dev;
@@ -175,8 +239,24 @@ static int rmnet_newlink(struct net *src_net, struct net_device *dev,
 	netdev_dbg(dev, "data format [0x%08X]\n", data_format);
 	port->data_format = data_format;
 
+	if (data[IFLA_RMNET_QUEUE]) {
+		struct rmnet_queue_mapping *queue_map;
+
+		queue_map = nla_data(data[IFLA_RMNET_QUEUE]);
+		if (rmnet_update_queue_map(dev, queue_map->operation,
+					   queue_map->txqueue, queue_map->mark,
+					   extack))
+			goto err3;
+
+		netdev_dbg(dev, "op %02x txq %02x mark %08x\n",
+			   queue_map->operation, queue_map->txqueue,
+			   queue_map->mark);
+	}
+
 	return 0;
 
+err3:
+	hlist_del_init_rcu(&ep->hlnode);
 err2:
 	unregister_netdevice(dev);
 	rmnet_vnd_dellink(mux_id, port, ep);
@@ -352,6 +432,20 @@ static int rmnet_changelink(struct net_device *dev, struct nlattr *tb[],
 		}
 	}
 
+	if (data[IFLA_RMNET_QUEUE]) {
+		struct rmnet_queue_mapping *queue_map;
+
+		queue_map = nla_data(data[IFLA_RMNET_QUEUE]);
+		if (rmnet_update_queue_map(dev, queue_map->operation,
+					   queue_map->txqueue, queue_map->mark,
+					   extack))
+			return -EINVAL;
+
+		netdev_dbg(dev, "op %02x txq %02x mark %08x\n",
+			   queue_map->operation, queue_map->txqueue,
+			   queue_map->mark);
+	}
+
 	return 0;
 }
 
@@ -361,7 +455,9 @@ static size_t rmnet_get_size(const struct net_device *dev)
 		/* IFLA_RMNET_MUX_ID */
 		nla_total_size(2) +
 		/* IFLA_RMNET_FLAGS */
-		nla_total_size(sizeof(struct ifla_rmnet_flags));
+		nla_total_size(sizeof(struct ifla_rmnet_flags)) +
+		/* IFLA_RMNET_QUEUE */
+		nla_total_size(sizeof(struct rmnet_queue_mapping));
 }
 
 static int rmnet_fill_info(struct sk_buff *skb, const struct net_device *dev)
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.h b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.h
index ed112d51ac5a..ae8300fc5ed7 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.h
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.h
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /* Copyright (c) 2013-2014, 2016-2018, 2021 The Linux Foundation.
  * All rights reserved.
+ * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
  *
  * RMNET Data configuration engine
  */
@@ -87,6 +88,7 @@ struct rmnet_priv {
 	struct rmnet_pcpu_stats __percpu *pcpu_stats;
 	struct gro_cells gro_cells;
 	struct rmnet_priv_stats stats;
+	struct xarray queue_map;
 };
 
 struct rmnet_port *rmnet_get_port_rcu(struct net_device *real_dev);
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
index 046b5f7d8e7c..6dfee4a4d634 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2013-2018, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
  *
  * RMNET Data virtual network driver
  */
@@ -158,6 +159,23 @@ static void rmnet_get_stats64(struct net_device *dev,
 	s->tx_dropped = total_stats.tx_drops;
 }
 
+static u16 rmnet_vnd_select_queue(struct net_device *dev,
+				  struct sk_buff *skb,
+				  struct net_device *sb_dev)
+{
+	struct rmnet_priv *priv = netdev_priv(dev);
+	void *p = xa_load(&priv->queue_map, skb->mark);
+	u8 txq;
+
+	if (!p && !xa_is_value(p))
+		return 0;
+
+	txq = xa_to_value(p);
+
+	netdev_dbg(dev, "mark %u -> txq %u\n", skb->mark, txq);
+	return (txq < dev->num_tx_queues) ? txq : 0;
+}
+
 static const struct net_device_ops rmnet_vnd_ops = {
 	.ndo_start_xmit = rmnet_vnd_start_xmit,
 	.ndo_change_mtu = rmnet_vnd_change_mtu,
@@ -167,6 +185,7 @@ static const struct net_device_ops rmnet_vnd_ops = {
 	.ndo_init       = rmnet_vnd_init,
 	.ndo_uninit     = rmnet_vnd_uninit,
 	.ndo_get_stats64 = rmnet_get_stats64,
+	.ndo_select_queue = rmnet_vnd_select_queue,
 };
 
 static const char rmnet_gstrings_stats[][ETH_GSTRING_LEN] = {
@@ -334,6 +353,8 @@ int rmnet_vnd_newlink(u8 id, struct net_device *rmnet_dev,
 
 		priv->mux_id = id;
 
+		xa_init(&priv->queue_map);
+
 		netdev_dbg(rmnet_dev, "rmnet dev created\n");
 	}
 
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index ce3117df9cec..01485177f7ee 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -1368,6 +1368,7 @@ enum {
 	IFLA_RMNET_UNSPEC,
 	IFLA_RMNET_MUX_ID,
 	IFLA_RMNET_FLAGS,
+	IFLA_RMNET_QUEUE,
 	__IFLA_RMNET_MAX,
 };
 
@@ -1378,6 +1379,21 @@ struct ifla_rmnet_flags {
 	__u32	mask;
 };
 
+enum {
+	RMNET_QUEUE_OPERATION_UNSPEC,
+	RMNET_QUEUE_MAPPING_ADD,	/* Add new queue <-> mark mapping */
+	RMNET_QUEUE_MAPPING_REMOVE,	/* Remove existing queue <-> mark mapping */
+	RMNET_QUEUE_ENABLE,		/* Allow traffic on an existing queue */
+	RMNET_QUEUE_DISABLE,		/* Stop traffic on an existing queue */
+};
+
+struct rmnet_queue_mapping {
+	u8 operation;
+	u8 txqueue;
+	u16 padding;
+	u32 mark;
+};
+
 /* MCTP section */
 
 enum {
-- 
2.34.1

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