netdev - [RFC PATCH net-next 3/3] net/l2tp: add netlink attribute to enable flow-based session creation

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Date:   Wed, 29 Sep 2021 10:45:14 +0100
From:   Tom Parkin <tparkin@...alix.com>
To:     netdev@...r.kernel.org
Cc:     jchapman@...alix.com, Tom Parkin <tparkin@...alix.com>
Subject: [RFC PATCH net-next 3/3] net/l2tp: add netlink attribute to enable flow-based session creation

Add an attribute to be used with L2TP_CMD_SESSION_CREATE in order to
enable the use of the flow-based datapath.

If the attribute is not included in the message, or is set false, the
traditional pseudowire lookup is used, which will lead to a virtual
session netdev being created.

If the attribute is included and is set, no virtual session netdev will
be created, and the administrator must use appropriate tc filter/action
rules in order to manage session data packets.

Signed-off-by: Tom Parkin <tparkin@...alix.com>
---
 include/uapi/linux/l2tp.h |  1 +
 net/l2tp/l2tp_netlink.c   | 36 +++++++++++++++++++++++-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/include/uapi/linux/l2tp.h b/include/uapi/linux/l2tp.h
index bab8c9708611..86e02c8e97a4 100644
--- a/include/uapi/linux/l2tp.h
+++ b/include/uapi/linux/l2tp.h
@@ -127,6 +127,7 @@ enum {
 	L2TP_ATTR_UDP_ZERO_CSUM6_TX,	/* flag */
 	L2TP_ATTR_UDP_ZERO_CSUM6_RX,	/* flag */
 	L2TP_ATTR_PAD,
+	L2TP_ATTR_FLOW_DATAPATH,	/* flag */
 	__L2TP_ATTR_MAX,
 };
 
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 96eb91be9238..5fb5fca74abd 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -528,6 +528,7 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
 	struct l2tp_session *session;
 	struct l2tp_session_cfg cfg = { 0, };
 	struct net *net = genl_info_net(info);
+	bool flow_path = false;
 
 	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
 		ret = -EINVAL;
@@ -617,22 +618,30 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
 	if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
 		cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
 
+	if (info->attrs[L2TP_ATTR_FLOW_DATAPATH])
+		flow_path = nla_get_flag(info->attrs[L2TP_ATTR_FLOW_DATAPATH]);
+
+	if (flow_path) {
+		ret = l2tp_flow_session_create(tunnel, session_id, peer_session_id, &cfg);
+	} else {
 #ifdef CONFIG_MODULES
-	if (!l2tp_nl_cmd_ops[cfg.pw_type]) {
-		genl_unlock();
-		request_module("net-l2tp-type-%u", cfg.pw_type);
-		genl_lock();
-	}
+		if (!l2tp_nl_cmd_ops[cfg.pw_type]) {
+			genl_unlock();
+			request_module("net-l2tp-type-%u", cfg.pw_type);
+			genl_lock();
+		}
 #endif
-	if (!l2tp_nl_cmd_ops[cfg.pw_type] || !l2tp_nl_cmd_ops[cfg.pw_type]->session_create) {
-		ret = -EPROTONOSUPPORT;
-		goto out_tunnel;
-	}
+		if (!l2tp_nl_cmd_ops[cfg.pw_type] ||
+		    !l2tp_nl_cmd_ops[cfg.pw_type]->session_create) {
+			ret = -EPROTONOSUPPORT;
+			goto out_tunnel;
+		}
 
-	ret = l2tp_nl_cmd_ops[cfg.pw_type]->session_create(net, tunnel,
-							   session_id,
-							   peer_session_id,
-							   &cfg);
+		ret = l2tp_nl_cmd_ops[cfg.pw_type]->session_create(net, tunnel,
+								   session_id,
+								   peer_session_id,
+								   &cfg);
+	}
 
 	if (ret >= 0) {
 		session = l2tp_tunnel_get_session(tunnel, session_id);
@@ -918,6 +927,7 @@ static const struct nla_policy l2tp_nl_policy[L2TP_ATTR_MAX + 1] = {
 		.type = NLA_BINARY,
 		.len = 8,
 	},
+	[L2TP_ATTR_FLOW_DATAPATH]	= { .type = NLA_U8 },
 };
 
 static const struct genl_small_ops l2tp_nl_ops[] = {
-- 
2.17.1