[RFC PATCH v1 16/30] sysctl: net: use sysctl_field in MPTCP sysctls

[Alexey Gladkov]

The MPTCP sysctl table is cloned for every non-init network namespace
only to bind the entries to that namespace's pernet state. The cloned
table is then patched by index, which makes the registration path depend
on the table layout staying in sync with the data pointer assignments.

Use sysctl_field descriptors so the data pointers are derived from the
registration context. Keep the special min/max handling inside the
custom handlers that need it, and leave read-only informational entries
without data pointers.

This keeps the table const and removes the per-net allocation, pointer
patching, and free path.

Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx>
---
 net/mptcp/ctrl.c | 205 ++++++++++++++++++-----------------------------
 1 file changed, 76 insertions(+), 129 deletions(-)

diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
index d96130e49942..31bde3e2eb28 100644
--- a/net/mptcp/ctrl.c
+++ b/net/mptcp/ctrl.c
@@ -19,7 +19,7 @@
 static int mptcp_pernet_id;
 
 #ifdef CONFIG_SYSCTL
-static int mptcp_pm_type_max = __MPTCP_PM_TYPE_MAX;
+static unsigned int mptcp_pm_type_max = __MPTCP_PM_TYPE_MAX;
 #endif
 
 struct mptcp_pernet {
@@ -172,9 +172,12 @@ static int proc_blackhole_detect_timeout(const struct ctl_table *table,
 	struct mptcp_pernet *pernet = container_of(table->data,
 						   struct mptcp_pernet,
 						   blackhole_timeout);
+	struct ctl_table tmp = *table;
 	int ret;
 
-	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	tmp.extra1 = SYSCTL_ZERO;
+
+	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 	if (write && ret == 0)
 		atomic_set(&pernet->active_disable_times, 0);
 
@@ -236,9 +239,13 @@ static int proc_pm_type(const struct ctl_table *ctl, int write,
 	struct mptcp_pernet *pernet = container_of(ctl->data,
 						   struct mptcp_pernet,
 						   pm_type);
+	struct ctl_table tmp = *ctl;
 	int ret;
 
-	ret = proc_dou8vec_minmax(ctl, write, buffer, lenp, ppos);
+	tmp.extra1 = SYSCTL_UINT_ZERO;
+	tmp.extra2 = &mptcp_pm_type_max;
+
+	ret = proc_dou8vec_minmax(&tmp, write, buffer, lenp, ppos);
 	if (write && ret == 0) {
 		u8 pm_type = READ_ONCE(*(u8 *)ctl->data);
 		char *pm_name = "";
@@ -271,148 +278,88 @@ static int proc_available_path_managers(const struct ctl_table *ctl,
 	return ret;
 }
 
-static struct ctl_table mptcp_sysctl_table[] = {
-	{
-		.procname = "enabled",
-		.maxlen = sizeof(u8),
-		.mode = 0644,
-		/* users with CAP_NET_ADMIN or root (not and) can change this
-		 * value, same as other sysctl or the 'net' tree.
-		 */
-		.proc_handler = proc_dou8vec_minmax,
-		.extra1       = SYSCTL_ZERO,
-		.extra2       = SYSCTL_ONE
-	},
-	{
-		.procname = "add_addr_timeout",
-		.maxlen = sizeof(unsigned int),
-		.mode = 0644,
-		.proc_handler = proc_dointvec_jiffies,
-	},
-	{
-		.procname = "checksum_enabled",
-		.maxlen = sizeof(u8),
-		.mode = 0644,
-		.proc_handler = proc_dou8vec_minmax,
-		.extra1       = SYSCTL_ZERO,
-		.extra2       = SYSCTL_ONE
-	},
-	{
-		.procname = "allow_join_initial_addr_port",
-		.maxlen = sizeof(u8),
-		.mode = 0644,
-		.proc_handler = proc_dou8vec_minmax,
-		.extra1       = SYSCTL_ZERO,
-		.extra2       = SYSCTL_ONE
-	},
-	{
-		.procname = "stale_loss_cnt",
-		.maxlen = sizeof(unsigned int),
-		.mode = 0644,
-		.proc_handler = proc_douintvec_minmax,
-	},
-	{
-		.procname = "pm_type",
-		.maxlen = sizeof(u8),
-		.mode = 0644,
-		.proc_handler = proc_pm_type,
-		.extra1       = SYSCTL_ZERO,
-		.extra2       = &mptcp_pm_type_max
-	},
-	{
-		.procname = "scheduler",
-		.maxlen	= MPTCP_SCHED_NAME_MAX,
-		.mode = 0644,
-		.proc_handler = proc_scheduler,
-	},
-	{
-		.procname = "available_schedulers",
-		.maxlen	= MPTCP_SCHED_BUF_MAX,
-		.mode = 0444,
-		.proc_handler = proc_available_schedulers,
-	},
-	{
-		.procname = "close_timeout",
-		.maxlen = sizeof(unsigned int),
-		.mode = 0644,
-		.proc_handler = proc_dointvec_jiffies,
-	},
-	{
-		.procname = "blackhole_timeout",
-		.maxlen = sizeof(unsigned int),
-		.mode = 0644,
-		.proc_handler = proc_blackhole_detect_timeout,
-		.extra1 = SYSCTL_ZERO,
-	},
-	{
-		.procname = "syn_retrans_before_tcp_fallback",
-		.maxlen = sizeof(u8),
-		.mode = 0644,
-		.proc_handler = proc_dou8vec_minmax,
-	},
-	{
-		.procname = "path_manager",
-		.maxlen	= MPTCP_PM_NAME_MAX,
-		.mode = 0644,
-		.proc_handler = proc_path_manager,
-	},
-	{
-		.procname = "available_path_managers",
-		.maxlen	= MPTCP_PM_BUF_MAX,
-		.mode = 0444,
-		.proc_handler = proc_available_path_managers,
-	},
+#define MPTCP_DATA(type, field)						\
+static type *mptcp_ ## field ## _data(const struct sysctl_context *ctx)	\
+{									\
+	return &mptcp_get_pernet(ctx->ns.net_ns)->field;		\
+}
+
+#define MPTCP_CUSTOM_DATA(field)					\
+static void *mptcp_ ## field ## _data(const struct sysctl_context *ctx)	\
+{									\
+	return &mptcp_get_pernet(ctx->ns.net_ns)->field;		\
+}
+
+static u8 *mptcp_enabled_data(const struct sysctl_context *ctx)
+{
+	return &mptcp_get_pernet(ctx->ns.net_ns)->mptcp_enabled;
+}
+
+MPTCP_CUSTOM_DATA(add_addr_timeout)
+MPTCP_DATA(u8, checksum_enabled)
+MPTCP_DATA(u8, allow_join_initial_addr_port)
+MPTCP_DATA(unsigned int, stale_loss_cnt)
+MPTCP_CUSTOM_DATA(pm_type)
+MPTCP_CUSTOM_DATA(scheduler)
+MPTCP_CUSTOM_DATA(close_timeout)
+MPTCP_CUSTOM_DATA(blackhole_timeout)
+MPTCP_DATA(u8, syn_retrans_before_tcp_fallback)
+MPTCP_CUSTOM_DATA(path_manager)
+
+static const struct sysctl_field mptcp_sysctl_table[] = {
+	/* users with CAP_NET_ADMIN or root (not and) can change this
+	 * value, same as other sysctl or the 'net' tree.
+	 */
+	SYSCTL_FIELD_STATIC_U8_MINMAX("enabled", 0644, mptcp_enabled_data,
+				   SYSCTL_UINT_ZERO, SYSCTL_UINT_ONE),
+	SYSCTL_FIELD_CUSTOM("add_addr_timeout", 0644, sizeof(unsigned int),
+			 mptcp_add_addr_timeout_data, proc_dointvec_jiffies),
+	SYSCTL_FIELD_STATIC_U8_MINMAX("checksum_enabled", 0644,
+				   mptcp_checksum_enabled_data,
+				   SYSCTL_UINT_ZERO, SYSCTL_UINT_ONE),
+	SYSCTL_FIELD_STATIC_U8_MINMAX("allow_join_initial_addr_port", 0644,
+				   mptcp_allow_join_initial_addr_port_data,
+				   SYSCTL_UINT_ZERO, SYSCTL_UINT_ONE),
+	SYSCTL_FIELD_UINT("stale_loss_cnt", 0644, mptcp_stale_loss_cnt_data),
+	SYSCTL_FIELD_CUSTOM("pm_type", 0644, sizeof(u8),
+			 mptcp_pm_type_data, proc_pm_type),
+	SYSCTL_FIELD_CUSTOM("scheduler", 0644, MPTCP_SCHED_NAME_MAX,
+			 mptcp_scheduler_data, proc_scheduler),
+	SYSCTL_FIELD_CUSTOM("available_schedulers", 0444, MPTCP_SCHED_BUF_MAX,
+			 NULL, proc_available_schedulers),
+	SYSCTL_FIELD_CUSTOM("close_timeout", 0644, sizeof(unsigned int),
+			 mptcp_close_timeout_data, proc_dointvec_jiffies),
+	SYSCTL_FIELD_CUSTOM("blackhole_timeout", 0644, sizeof(unsigned int),
+			 mptcp_blackhole_timeout_data,
+			 proc_blackhole_detect_timeout),
+	SYSCTL_FIELD_U8("syn_retrans_before_tcp_fallback", 0644,
+		     mptcp_syn_retrans_before_tcp_fallback_data),
+	SYSCTL_FIELD_CUSTOM("path_manager", 0644, MPTCP_PM_NAME_MAX,
+			 mptcp_path_manager_data, proc_path_manager),
+	SYSCTL_FIELD_CUSTOM("available_path_managers", 0444, MPTCP_PM_BUF_MAX,
+			 NULL, proc_available_path_managers),
 };
 
 static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
 {
+	struct sysctl_context ctx = {
+		.ns.net_ns = net,
+	};
 	struct ctl_table_header *hdr;
-	struct ctl_table *table;
-
-	table = mptcp_sysctl_table;
-	if (!net_eq(net, &init_net)) {
-		table = kmemdup(table, sizeof(mptcp_sysctl_table), GFP_KERNEL);
-		if (!table)
-			goto err_alloc;
-	}
 
-	table[0].data = &pernet->mptcp_enabled;
-	table[1].data = &pernet->add_addr_timeout;
-	table[2].data = &pernet->checksum_enabled;
-	table[3].data = &pernet->allow_join_initial_addr_port;
-	table[4].data = &pernet->stale_loss_cnt;
-	table[5].data = &pernet->pm_type;
-	table[6].data = &pernet->scheduler;
-	/* table[7] is for available_schedulers which is read-only info */
-	table[8].data = &pernet->close_timeout;
-	table[9].data = &pernet->blackhole_timeout;
-	table[10].data = &pernet->syn_retrans_before_tcp_fallback;
-	table[11].data = &pernet->path_manager;
-	/* table[12] is for available_path_managers which is read-only info */
-
-	hdr = register_net_sysctl_sz(net, MPTCP_SYSCTL_PATH, table,
-				     ARRAY_SIZE(mptcp_sysctl_table));
+	hdr = register_sysctl_fields(&net->sysctls, MPTCP_SYSCTL_PATH,
+				     mptcp_sysctl_table, &ctx);
 	if (!hdr)
-		goto err_reg;
+		return -ENOMEM;
 
 	pernet->ctl_table_hdr = hdr;
 
 	return 0;
-
-err_reg:
-	if (!net_eq(net, &init_net))
-		kfree(table);
-err_alloc:
-	return -ENOMEM;
 }
 
 static void mptcp_pernet_del_table(struct mptcp_pernet *pernet)
 {
-	const struct ctl_table *table = pernet->ctl_table_hdr->ctl_table_arg;
-
 	unregister_net_sysctl_table(pernet->ctl_table_hdr);
-
-	kfree(table);
 }
 
 #else
-- 
2.55.0