[PATCH net-next v4 0/3] net: extend drop reasons

[PATCH net-next v4 0/3] net: extend drop reasons

[Johannes Berg]

Hi,

Here's v4 of the extended drop reasons, with fixes to kernel-doc
and checkpatch.

johannes

[PATCH net-next v4 1/3] net: move dropreason.h to dropreason-core.h

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

This will, after the next patch, hold only the core
drop reasons and minimal infrastructure. Fix a small
kernel-doc issue while at it, to avoid the move
triggering a checker.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
v3: new patch
v4: fix a kernel-doc issue
---
 include/linux/netdevice.h                       | 2 +-
 include/linux/skbuff.h                          | 2 +-
 include/net/{dropreason.h => dropreason-core.h} | 7 ++++---
 include/net/inet_frag.h                         | 2 +-
 4 files changed, 7 insertions(+), 6 deletions(-)
 rename include/net/{dropreason.h => dropreason-core.h} (98%)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a740be3bb911..c7e05e6352a1 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -52,7 +52,7 @@
 #include <linux/rbtree.h>
 #include <net/net_trackers.h>
 #include <net/net_debug.h>
-#include <net/dropreason.h>
+#include <net/dropreason-core.h>
 
 struct netpoll_info;
 struct device;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 82511b2f61ea..795b091e6d7d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -37,7 +37,7 @@
 #include <linux/netfilter/nf_conntrack_common.h>
 #endif
 #include <net/net_debug.h>
-#include <net/dropreason.h>
+#include <net/dropreason-core.h>
 
 /**
  * DOC: skb checksums
diff --git a/include/net/dropreason.h b/include/net/dropreason-core.h
similarity index 98%
rename from include/net/dropreason.h
rename to include/net/dropreason-core.h
index c0a3ea806cd5..ade6d5b9186c 100644
--- a/include/net/dropreason.h
+++ b/include/net/dropreason-core.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
-#ifndef _LINUX_DROPREASON_H
-#define _LINUX_DROPREASON_H
+#ifndef _LINUX_DROPREASON_CORE_H
+#define _LINUX_DROPREASON_CORE_H
 
 #define DEFINE_DROP_REASON(FN, FNe)	\
 	FN(NOT_SPECIFIED)		\
@@ -334,7 +334,8 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_IPV6_NDISC_BAD_CODE,
 	/** @SKB_DROP_REASON_IPV6_NDISC_BAD_OPTIONS: invalid NDISC options. */
 	SKB_DROP_REASON_IPV6_NDISC_BAD_OPTIONS,
-	/** @SKB_DROP_REASON_IPV6_NDISC_NS_OTHERHOST: NEIGHBOUR SOLICITATION
+	/**
+	 * @SKB_DROP_REASON_IPV6_NDISC_NS_OTHERHOST: NEIGHBOUR SOLICITATION
 	 * for another host.
 	 */
 	SKB_DROP_REASON_IPV6_NDISC_NS_OTHERHOST,
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index b23ddec3cd5c..325ad893f624 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -7,7 +7,7 @@
 #include <linux/in6.h>
 #include <linux/rbtree_types.h>
 #include <linux/refcount.h>
-#include <net/dropreason.h>
+#include <net/dropreason-core.h>
 
 /* Per netns frag queues directory */
 struct fqdir {
-- 
2.40.0

[PATCH net-next v4 2/3] net: extend drop reasons for multiple subsystems

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

Extend drop reasons to make them usable by subsystems
other than core by reserving the high 16 bits for a
new subsystem ID, of which 0 of course is used for the
existing reasons immediately.

To still be able to have string reasons, restructure
that code a bit to make the loopup under RCU, the only
user of this (right now) is drop_monitor.

Link: https://lore.kernel.org/netdev/00659771ed54353f92027702c5bbb84702da62ce.camel@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
v3:
 - new dropreason.h now that core codes are in dropreason-core.h
 - annotate RCU pointer init for sparse
v4:
 - fix kernel-doc, indentation
---
 include/net/dropreason-core.h | 14 ++++++---
 include/net/dropreason.h      | 31 ++++++++++++++++++
 net/core/drop_monitor.c       | 33 ++++++++++++++------
 net/core/skbuff.c             | 59 +++++++++++++++++++++++++++++++++--
 4 files changed, 121 insertions(+), 16 deletions(-)
 create mode 100644 include/net/dropreason.h

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index ade6d5b9186c..a2b953b57689 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -340,12 +340,20 @@ enum skb_drop_reason {
 	 */
 	SKB_DROP_REASON_IPV6_NDISC_NS_OTHERHOST,
 	/**
-	 * @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be
-	 * used as a real 'reason'
+	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
+	 * shouldn't be used as a real 'reason' - only for tracing code gen
 	 */
 	SKB_DROP_REASON_MAX,
+
+	/**
+	 * @SKB_DROP_REASON_SUBSYS_MASK: subsystem mask in drop reasons,
+	 * see &enum skb_drop_reason_subsys
+	 */
+	SKB_DROP_REASON_SUBSYS_MASK = 0xffff0000,
 };
 
+#define SKB_DROP_REASON_SUBSYS_SHIFT	16
+
 #define SKB_DR_INIT(name, reason)				\
 	enum skb_drop_reason name = SKB_DROP_REASON_##reason
 #define SKB_DR(name)						\
@@ -359,6 +367,4 @@ enum skb_drop_reason {
 			SKB_DR_SET(name, reason);		\
 	} while (0)
 
-extern const char * const drop_reasons[];
-
 #endif
diff --git a/include/net/dropreason.h b/include/net/dropreason.h
new file mode 100644
index 000000000000..f0f2378dbed0
--- /dev/null
+++ b/include/net/dropreason.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _LINUX_DROPREASON_H
+#define _LINUX_DROPREASON_H
+#include <net/dropreason-core.h>
+
+/**
+ * enum skb_drop_reason_subsys - subsystem tag for (extended) drop reasons
+ */
+enum skb_drop_reason_subsys {
+	/** @SKB_DROP_REASON_SUBSYS_CORE: core drop reasons defined above */
+	SKB_DROP_REASON_SUBSYS_CORE,
+
+	/** @SKB_DROP_REASON_SUBSYS_NUM: number of subsystems defined */
+	SKB_DROP_REASON_SUBSYS_NUM
+};
+
+struct drop_reason_list {
+	const char * const *reasons;
+	size_t n_reasons;
+};
+
+/* Note: due to dynamic registrations, access must be under RCU */
+extern const struct drop_reason_list __rcu *
+drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM];
+
+void drop_reasons_register_subsys(enum skb_drop_reason_subsys subsys,
+				  const struct drop_reason_list *list);
+void drop_reasons_unregister_subsys(enum skb_drop_reason_subsys subsys);
+
+#endif
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 5a782d1d8fd3..aff31cd944c2 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -21,6 +21,7 @@
 #include <linux/workqueue.h>
 #include <linux/netlink.h>
 #include <linux/net_dropmon.h>
+#include <linux/bitfield.h>
 #include <linux/percpu.h>
 #include <linux/timer.h>
 #include <linux/bitops.h>
@@ -29,6 +30,7 @@
 #include <net/genetlink.h>
 #include <net/netevent.h>
 #include <net/flow_offload.h>
+#include <net/dropreason.h>
 #include <net/devlink.h>
 
 #include <trace/events/skb.h>
@@ -504,8 +506,6 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
 	if (!nskb)
 		return;
 
-	if (unlikely(reason >= SKB_DROP_REASON_MAX || reason <= 0))
-		reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	cb = NET_DM_SKB_CB(nskb);
 	cb->reason = reason;
 	cb->pc = location;
@@ -552,9 +552,9 @@ static size_t net_dm_in_port_size(void)
 }
 
 #define NET_DM_MAX_SYMBOL_LEN 40
+#define NET_DM_MAX_REASON_LEN 50
 
-static size_t net_dm_packet_report_size(size_t payload_len,
-					enum skb_drop_reason reason)
+static size_t net_dm_packet_report_size(size_t payload_len)
 {
 	size_t size;
 
@@ -576,7 +576,7 @@ static size_t net_dm_packet_report_size(size_t payload_len,
 	       /* NET_DM_ATTR_PROTO */
 	       nla_total_size(sizeof(u16)) +
 	       /* NET_DM_ATTR_REASON */
-	       nla_total_size(strlen(drop_reasons[reason]) + 1) +
+	       nla_total_size(NET_DM_MAX_REASON_LEN + 1) +
 	       /* NET_DM_ATTR_PAYLOAD */
 	       nla_total_size(payload_len);
 }
@@ -610,6 +610,8 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
 				     size_t payload_len)
 {
 	struct net_dm_skb_cb *cb = NET_DM_SKB_CB(skb);
+	const struct drop_reason_list *list = NULL;
+	unsigned int subsys, subsys_reason;
 	char buf[NET_DM_MAX_SYMBOL_LEN];
 	struct nlattr *attr;
 	void *hdr;
@@ -627,9 +629,24 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
 			      NET_DM_ATTR_PAD))
 		goto nla_put_failure;
 
+	rcu_read_lock();
+	subsys = u32_get_bits(cb->reason, SKB_DROP_REASON_SUBSYS_MASK);
+	if (subsys < SKB_DROP_REASON_SUBSYS_NUM)
+		list = rcu_dereference(drop_reasons_by_subsys[subsys]);
+	subsys_reason = cb->reason & ~SKB_DROP_REASON_SUBSYS_MASK;
+	if (!list ||
+	    subsys_reason >= list->n_reasons ||
+	    !list->reasons[subsys_reason] ||
+	    strlen(list->reasons[subsys_reason]) > NET_DM_MAX_REASON_LEN) {
+		list = rcu_dereference(drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_CORE]);
+		subsys_reason = SKB_DROP_REASON_NOT_SPECIFIED;
+	}
 	if (nla_put_string(msg, NET_DM_ATTR_REASON,
-			   drop_reasons[cb->reason]))
+			   list->reasons[subsys_reason])) {
+		rcu_read_unlock();
 		goto nla_put_failure;
+	}
+	rcu_read_unlock();
 
 	snprintf(buf, sizeof(buf), "%pS", cb->pc);
 	if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
@@ -687,9 +704,7 @@ static void net_dm_packet_report(struct sk_buff *skb)
 	if (net_dm_trunc_len)
 		payload_len = min_t(size_t, net_dm_trunc_len, payload_len);
 
-	msg = nlmsg_new(net_dm_packet_report_size(payload_len,
-						  NET_DM_SKB_CB(skb)->reason),
-			GFP_KERNEL);
+	msg = nlmsg_new(net_dm_packet_report_size(payload_len), GFP_KERNEL);
 	if (!msg)
 		goto out;
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 050a875d09c5..cf3b6b5d0b50 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -58,6 +58,7 @@
 #include <linux/scatterlist.h>
 #include <linux/errqueue.h>
 #include <linux/prefetch.h>
+#include <linux/bitfield.h>
 #include <linux/if_vlan.h>
 #include <linux/mpls.h>
 #include <linux/kcov.h>
@@ -72,6 +73,7 @@
 #include <net/mptcp.h>
 #include <net/mctp.h>
 #include <net/page_pool.h>
+#include <net/dropreason.h>
 
 #include <linux/uaccess.h>
 #include <trace/events/skb.h>
@@ -122,11 +124,59 @@ EXPORT_SYMBOL(sysctl_max_skb_frags);
 
 #undef FN
 #define FN(reason) [SKB_DROP_REASON_##reason] = #reason,
-const char * const drop_reasons[] = {
+static const char * const drop_reasons[] = {
 	[SKB_CONSUMED] = "CONSUMED",
 	DEFINE_DROP_REASON(FN, FN)
 };
-EXPORT_SYMBOL(drop_reasons);
+
+static const struct drop_reason_list drop_reasons_core = {
+	.reasons = drop_reasons,
+	.n_reasons = ARRAY_SIZE(drop_reasons),
+};
+
+const struct drop_reason_list __rcu *
+drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM] = {
+	[SKB_DROP_REASON_SUBSYS_CORE] = RCU_INITIALIZER(&drop_reasons_core),
+};
+EXPORT_SYMBOL(drop_reasons_by_subsys);
+
+/**
+ * drop_reasons_register_subsys - register another drop reason subsystem
+ * @subsys: the subsystem to register, must not be the core
+ * @list: the list of drop reasons within the subsystem, must point to
+ *	a statically initialized list
+ */
+void drop_reasons_register_subsys(enum skb_drop_reason_subsys subsys,
+				  const struct drop_reason_list *list)
+{
+	if (WARN(subsys <= SKB_DROP_REASON_SUBSYS_CORE ||
+		 subsys >= ARRAY_SIZE(drop_reasons_by_subsys),
+		 "invalid subsystem %d\n", subsys))
+		return;
+
+	/* must point to statically allocated memory, so INIT is OK */
+	RCU_INIT_POINTER(drop_reasons_by_subsys[subsys], list);
+}
+EXPORT_SYMBOL_GPL(drop_reasons_register_subsys);
+
+/**
+ * drop_reasons_unregister_subsys - unregister a drop reason subsystem
+ * @subsys: the subsystem to remove, must not be the core
+ *
+ * Note: This will synchronize_rcu() to ensure no users when it returns.
+ */
+void drop_reasons_unregister_subsys(enum skb_drop_reason_subsys subsys)
+{
+	if (WARN(subsys <= SKB_DROP_REASON_SUBSYS_CORE ||
+		 subsys >= ARRAY_SIZE(drop_reasons_by_subsys),
+		 "invalid subsystem %d\n", subsys))
+		return;
+
+	RCU_INIT_POINTER(drop_reasons_by_subsys[subsys], NULL);
+
+	synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(drop_reasons_unregister_subsys);
 
 /**
  *	skb_panic - private function for out-of-line support
@@ -984,7 +1034,10 @@ bool __kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
 	if (unlikely(!skb_unref(skb)))
 		return false;
 
-	DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
+	DEBUG_NET_WARN_ON_ONCE(reason == SKB_NOT_DROPPED_YET ||
+			       u32_get_bits(reason,
+					    SKB_DROP_REASON_SUBSYS_MASK) >=
+				SKB_DROP_REASON_SUBSYS_NUM);
 
 	if (reason == SKB_CONSUMED)
 		trace_consume_skb(skb, __builtin_return_address(0));
-- 
2.40.0

Re: [PATCH net-next v4 2/3] net: extend drop reasons for multiple subsystems

[Simon Horman]

On Wed, Apr 19, 2023 at 02:52:53PM +0200, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
> 
> Extend drop reasons to make them usable by subsystems
> other than core by reserving the high 16 bits for a
> new subsystem ID, of which 0 of course is used for the
> existing reasons immediately.
> 
> To still be able to have string reasons, restructure
> that code a bit to make the loopup under RCU, the only
> user of this (right now) is drop_monitor.

Hi Johannes,

a minor nit from my side that you may want to address if you need
to re-spin for some other reason:

s/loopup/lookup/

[PATCH net-next v4 3/3] mac80211: use the new drop reasons infrastructure

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

It can be really hard to analyse or debug why packets are
going missing in mac80211, so add the needed infrastructure
to use use the new per-subsystem drop reasons.

We actually use two drop reason subsystems here because of
the different handling of frames that are dropped but still
go to monitor for old versions of hostapd, and those that
are just completely unusable (e.g. crypto failed.)

Annotate a few reasons here just to illustrate this, we'll
need to go through and annotate more of them later.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
v4: fix kernel-doc
---
 include/net/dropreason.h   | 12 ++++++++
 net/mac80211/drop.h        | 56 ++++++++++++++++++++++++++++++++++
 net/mac80211/ieee80211_i.h |  8 +----
 net/mac80211/main.c        | 31 +++++++++++++++++++
 net/mac80211/rx.c          | 61 ++++++++++++++++++--------------------
 net/mac80211/wpa.c         | 24 +++++++--------
 6 files changed, 141 insertions(+), 51 deletions(-)
 create mode 100644 net/mac80211/drop.h

diff --git a/include/net/dropreason.h b/include/net/dropreason.h
index f0f2378dbed0..685fb37df8e8 100644
--- a/include/net/dropreason.h
+++ b/include/net/dropreason.h
@@ -11,6 +11,18 @@ enum skb_drop_reason_subsys {
 	/** @SKB_DROP_REASON_SUBSYS_CORE: core drop reasons defined above */
 	SKB_DROP_REASON_SUBSYS_CORE,
 
+	/**
+	 * @SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE: mac80211 drop reasons
+	 * for unusable frames, see net/mac80211/drop.h
+	 */
+	SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE,
+
+	/**
+	 * @SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR: mac80211 drop reasons
+	 * for frames still going to monitor, see net/mac80211/drop.h
+	 */
+	SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR,
+
 	/** @SKB_DROP_REASON_SUBSYS_NUM: number of subsystems defined */
 	SKB_DROP_REASON_SUBSYS_NUM
 };
diff --git a/net/mac80211/drop.h b/net/mac80211/drop.h
new file mode 100644
index 000000000000..49dc809cab29
--- /dev/null
+++ b/net/mac80211/drop.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * mac80211 drop reason list
+ *
+ * Copyright (C) 2023 Intel Corporation
+ */
+
+#ifndef MAC80211_DROP_H
+#define MAC80211_DROP_H
+#include <net/dropreason.h>
+
+typedef unsigned int __bitwise ieee80211_rx_result;
+
+#define MAC80211_DROP_REASONS_MONITOR(R)	\
+	R(RX_DROP_M_UNEXPECTED_4ADDR_FRAME)	\
+	R(RX_DROP_M_BAD_BCN_KEYIDX)		\
+	R(RX_DROP_M_BAD_MGMT_KEYIDX)		\
+/* this line for the trailing \ - add before this */
+
+#define MAC80211_DROP_REASONS_UNUSABLE(R)	\
+	R(RX_DROP_U_MIC_FAIL)			\
+	R(RX_DROP_U_REPLAY)			\
+	R(RX_DROP_U_BAD_MMIE)			\
+/* this line for the trailing \ - add before this */
+
+/* having two enums allows for checking ieee80211_rx_result use with sparse */
+enum ___mac80211_drop_reason {
+/* if we get to the end of handlers with RX_CONTINUE this will be the reason */
+	___RX_CONTINUE	= SKB_CONSUMED,
+
+/* this never gets used as an argument to kfree_skb_reason() */
+	___RX_QUEUED	= SKB_NOT_DROPPED_YET,
+
+#define ENUM(x) ___ ## x,
+	___RX_DROP_MONITOR = SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR <<
+		SKB_DROP_REASON_SUBSYS_SHIFT,
+	MAC80211_DROP_REASONS_MONITOR(ENUM)
+
+	___RX_DROP_UNUSABLE = SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE <<
+		SKB_DROP_REASON_SUBSYS_SHIFT,
+	MAC80211_DROP_REASONS_UNUSABLE(ENUM)
+#undef ENUM
+};
+
+enum mac80211_drop_reason {
+	RX_CONTINUE	 = (__force ieee80211_rx_result)___RX_CONTINUE,
+	RX_QUEUED	 = (__force ieee80211_rx_result)___RX_QUEUED,
+	RX_DROP_MONITOR	 = (__force ieee80211_rx_result)___RX_DROP_MONITOR,
+	RX_DROP_UNUSABLE = (__force ieee80211_rx_result)___RX_DROP_UNUSABLE,
+#define DEF(x) x = (__force ieee80211_rx_result)___ ## x,
+	MAC80211_DROP_REASONS_MONITOR(DEF)
+	MAC80211_DROP_REASONS_UNUSABLE(DEF)
+#undef DEF
+};
+
+#endif /* MAC80211_DROP_H */
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 9b7e184430b8..a0a7839cb961 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -33,6 +33,7 @@
 #include "key.h"
 #include "sta_info.h"
 #include "debug.h"
+#include "drop.h"
 
 extern const struct cfg80211_ops mac80211_config_ops;
 
@@ -170,13 +171,6 @@ struct ieee80211_tx_data {
 	unsigned int flags;
 };
 
-
-typedef unsigned __bitwise ieee80211_rx_result;
-#define RX_CONTINUE		((__force ieee80211_rx_result) 0u)
-#define RX_DROP_UNUSABLE	((__force ieee80211_rx_result) 1u)
-#define RX_DROP_MONITOR		((__force ieee80211_rx_result) 2u)
-#define RX_QUEUED		((__force ieee80211_rx_result) 3u)
-
 /**
  * enum ieee80211_packet_rx_flags - packet RX flags
  * @IEEE80211_RX_AMSDU: a-MSDU packet
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index ddf2b7811c55..55cdfaef0f5d 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -22,6 +22,7 @@
 #include <linux/bitmap.h>
 #include <linux/inetdevice.h>
 #include <net/net_namespace.h>
+#include <net/dropreason.h>
 #include <net/cfg80211.h>
 #include <net/addrconf.h>
 
@@ -1542,6 +1543,28 @@ void ieee80211_free_hw(struct ieee80211_hw *hw)
 }
 EXPORT_SYMBOL(ieee80211_free_hw);
 
+static const char * const drop_reasons_monitor[] = {
+#define V(x)	#x,
+	[0] = "RX_DROP_MONITOR",
+	MAC80211_DROP_REASONS_MONITOR(V)
+};
+
+static struct drop_reason_list drop_reason_list_monitor = {
+	.reasons = drop_reasons_monitor,
+	.n_reasons = ARRAY_SIZE(drop_reasons_monitor),
+};
+
+static const char * const drop_reasons_unusable[] = {
+	[0] = "RX_DROP_UNUSABLE",
+	MAC80211_DROP_REASONS_UNUSABLE(V)
+#undef V
+};
+
+static struct drop_reason_list drop_reason_list_unusable = {
+	.reasons = drop_reasons_unusable,
+	.n_reasons = ARRAY_SIZE(drop_reasons_unusable),
+};
+
 static int __init ieee80211_init(void)
 {
 	struct sk_buff *skb;
@@ -1559,6 +1582,11 @@ static int __init ieee80211_init(void)
 	if (ret)
 		goto err_netdev;
 
+	drop_reasons_register_subsys(SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR,
+				     &drop_reason_list_monitor);
+	drop_reasons_register_subsys(SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE,
+				     &drop_reason_list_unusable);
+
 	return 0;
  err_netdev:
 	rc80211_minstrel_exit();
@@ -1574,6 +1602,9 @@ static void __exit ieee80211_exit(void)
 
 	ieee80211_iface_exit();
 
+	drop_reasons_unregister_subsys(SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR);
+	drop_reasons_unregister_subsys(SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE);
+
 	rcu_barrier();
 }
 
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index db3451f5f2fb..58222c077898 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1826,7 +1826,7 @@ ieee80211_rx_h_sta_process(struct ieee80211_rx_data *rx)
 				cfg80211_rx_unexpected_4addr_frame(
 					rx->sdata->dev, sta->sta.addr,
 					GFP_ATOMIC);
-			return RX_DROP_MONITOR;
+			return RX_DROP_M_UNEXPECTED_4ADDR_FRAME;
 		}
 		/*
 		 * Update counter and free packet here to avoid
@@ -1961,7 +1961,7 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 				cfg80211_rx_unprot_mlme_mgmt(rx->sdata->dev,
 							     skb->data,
 							     skb->len);
-			return RX_DROP_MONITOR; /* unexpected BIP keyidx */
+			return RX_DROP_M_BAD_BCN_KEYIDX;
 		}
 
 		rx->key = ieee80211_rx_get_bigtk(rx, mmie_keyidx);
@@ -1975,7 +1975,7 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 
 		if (mmie_keyidx < NUM_DEFAULT_KEYS ||
 		    mmie_keyidx >= NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS)
-			return RX_DROP_MONITOR; /* unexpected BIP keyidx */
+			return RX_DROP_M_BAD_MGMT_KEYIDX; /* unexpected BIP keyidx */
 		if (rx->link_sta) {
 			if (ieee80211_is_group_privacy_action(skb) &&
 			    test_sta_flag(rx->sta, WLAN_STA_MFP))
@@ -3960,7 +3960,8 @@ ieee80211_rx_h_mgmt(struct ieee80211_rx_data *rx)
 }
 
 static void ieee80211_rx_cooked_monitor(struct ieee80211_rx_data *rx,
-					struct ieee80211_rate *rate)
+					struct ieee80211_rate *rate,
+					ieee80211_rx_result reason)
 {
 	struct ieee80211_sub_if_data *sdata;
 	struct ieee80211_local *local = rx->local;
@@ -4024,42 +4025,38 @@ static void ieee80211_rx_cooked_monitor(struct ieee80211_rx_data *rx,
 	}
 
  out_free_skb:
-	dev_kfree_skb(skb);
+	kfree_skb_reason(skb, (__force u32)reason);
 }
 
 static void ieee80211_rx_handlers_result(struct ieee80211_rx_data *rx,
 					 ieee80211_rx_result res)
 {
-	switch (res) {
-	case RX_DROP_MONITOR:
-		I802_DEBUG_INC(rx->sdata->local->rx_handlers_drop);
-		if (rx->sta)
-			rx->link_sta->rx_stats.dropped++;
-		fallthrough;
-	case RX_CONTINUE: {
-		struct ieee80211_rate *rate = NULL;
-		struct ieee80211_supported_band *sband;
-		struct ieee80211_rx_status *status;
+	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(rx->skb);
+	struct ieee80211_supported_band *sband;
+	struct ieee80211_rate *rate = NULL;
 
-		status = IEEE80211_SKB_RXCB((rx->skb));
-
-		sband = rx->local->hw.wiphy->bands[status->band];
-		if (status->encoding == RX_ENC_LEGACY)
-			rate = &sband->bitrates[status->rate_idx];
-
-		ieee80211_rx_cooked_monitor(rx, rate);
-		break;
-		}
-	case RX_DROP_UNUSABLE:
-		I802_DEBUG_INC(rx->sdata->local->rx_handlers_drop);
-		if (rx->sta)
-			rx->link_sta->rx_stats.dropped++;
-		dev_kfree_skb(rx->skb);
-		break;
-	case RX_QUEUED:
+	if (res == RX_QUEUED) {
 		I802_DEBUG_INC(rx->sdata->local->rx_handlers_queued);
-		break;
+		return;
 	}
+
+	if (res != RX_CONTINUE) {
+		I802_DEBUG_INC(rx->sdata->local->rx_handlers_drop);
+		if (rx->sta)
+			rx->link_sta->rx_stats.dropped++;
+	}
+
+	if (u32_get_bits((__force u32)res, SKB_DROP_REASON_SUBSYS_MASK) ==
+			SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE) {
+		kfree_skb_reason(rx->skb, (__force u32)res);
+		return;
+	}
+
+	sband = rx->local->hw.wiphy->bands[status->band];
+	if (status->encoding == RX_ENC_LEGACY)
+		rate = &sband->bitrates[status->rate_idx];
+
+	ieee80211_rx_cooked_monitor(rx, rate, res);
 }
 
 static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index 20f742b5503b..4133496da378 100644
--- a/net/mac80211/wpa.c
+++ b/net/mac80211/wpa.c
@@ -550,7 +550,7 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx,
 		if (res < 0 ||
 		    (!res && !(status->flag & RX_FLAG_ALLOW_SAME_PN))) {
 			key->u.ccmp.replays++;
-			return RX_DROP_UNUSABLE;
+			return RX_DROP_U_REPLAY;
 		}
 
 		if (!(status->flag & RX_FLAG_DECRYPTED)) {
@@ -564,7 +564,7 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx,
 				    skb->data + hdrlen + IEEE80211_CCMP_HDR_LEN,
 				    data_len,
 				    skb->data + skb->len - mic_len))
-				return RX_DROP_UNUSABLE;
+				return RX_DROP_U_MIC_FAIL;
 		}
 
 		memcpy(key->u.ccmp.rx_pn[queue], pn, IEEE80211_CCMP_PN_LEN);
@@ -746,7 +746,7 @@ ieee80211_crypto_gcmp_decrypt(struct ieee80211_rx_data *rx)
 		if (res < 0 ||
 		    (!res && !(status->flag & RX_FLAG_ALLOW_SAME_PN))) {
 			key->u.gcmp.replays++;
-			return RX_DROP_UNUSABLE;
+			return RX_DROP_U_REPLAY;
 		}
 
 		if (!(status->flag & RX_FLAG_DECRYPTED)) {
@@ -761,7 +761,7 @@ ieee80211_crypto_gcmp_decrypt(struct ieee80211_rx_data *rx)
 				    data_len,
 				    skb->data + skb->len -
 				    IEEE80211_GCMP_MIC_LEN))
-				return RX_DROP_UNUSABLE;
+				return RX_DROP_U_MIC_FAIL;
 		}
 
 		memcpy(key->u.gcmp.rx_pn[queue], pn, IEEE80211_GCMP_PN_LEN);
@@ -930,13 +930,13 @@ ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 		(skb->data + skb->len - sizeof(*mmie));
 	if (mmie->element_id != WLAN_EID_MMIE ||
 	    mmie->length != sizeof(*mmie) - 2)
-		return RX_DROP_UNUSABLE; /* Invalid MMIE */
+		return RX_DROP_U_BAD_MMIE; /* Invalid MMIE */
 
 	bip_ipn_swap(ipn, mmie->sequence_number);
 
 	if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 		key->u.aes_cmac.replays++;
-		return RX_DROP_UNUSABLE;
+		return RX_DROP_U_REPLAY;
 	}
 
 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
@@ -946,7 +946,7 @@ ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 				   skb->data + 24, skb->len - 24, mic);
 		if (crypto_memneq(mic, mmie->mic, sizeof(mmie->mic))) {
 			key->u.aes_cmac.icverrors++;
-			return RX_DROP_UNUSABLE;
+			return RX_DROP_U_MIC_FAIL;
 		}
 	}
 
@@ -986,7 +986,7 @@ ieee80211_crypto_aes_cmac_256_decrypt(struct ieee80211_rx_data *rx)
 
 	if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 		key->u.aes_cmac.replays++;
-		return RX_DROP_UNUSABLE;
+		return RX_DROP_U_REPLAY;
 	}
 
 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
@@ -996,7 +996,7 @@ ieee80211_crypto_aes_cmac_256_decrypt(struct ieee80211_rx_data *rx)
 				       skb->data + 24, skb->len - 24, mic);
 		if (crypto_memneq(mic, mmie->mic, sizeof(mmie->mic))) {
 			key->u.aes_cmac.icverrors++;
-			return RX_DROP_UNUSABLE;
+			return RX_DROP_U_MIC_FAIL;
 		}
 	}
 
@@ -1079,13 +1079,13 @@ ieee80211_crypto_aes_gmac_decrypt(struct ieee80211_rx_data *rx)
 		(skb->data + skb->len - sizeof(*mmie));
 	if (mmie->element_id != WLAN_EID_MMIE ||
 	    mmie->length != sizeof(*mmie) - 2)
-		return RX_DROP_UNUSABLE; /* Invalid MMIE */
+		return RX_DROP_U_BAD_MMIE; /* Invalid MMIE */
 
 	bip_ipn_swap(ipn, mmie->sequence_number);
 
 	if (memcmp(ipn, key->u.aes_gmac.rx_pn, 6) <= 0) {
 		key->u.aes_gmac.replays++;
-		return RX_DROP_UNUSABLE;
+		return RX_DROP_U_REPLAY;
 	}
 
 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
@@ -1104,7 +1104,7 @@ ieee80211_crypto_aes_gmac_decrypt(struct ieee80211_rx_data *rx)
 		    crypto_memneq(mic, mmie->mic, sizeof(mmie->mic))) {
 			key->u.aes_gmac.icverrors++;
 			kfree(mic);
-			return RX_DROP_UNUSABLE;
+			return RX_DROP_U_MIC_FAIL;
 		}
 		kfree(mic);
 	}
-- 
2.40.0

Re: [PATCH net-next v4 3/3] mac80211: use the new drop reasons infrastructure

[Simon Horman]

On Wed, Apr 19, 2023 at 02:52:54PM +0200, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
> 
> It can be really hard to analyse or debug why packets are
> going missing in mac80211, so add the needed infrastructure
> to use use the new per-subsystem drop reasons.

Hi Johannes,

a minor nit from my side that you may want to address if you need
to re-spin for some other reason:

s/use use/use/

...

Re: [PATCH net-next v4 0/3] net: extend drop reasons

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 19 Apr 2023 14:52:51 +0200 you wrote:
> Hi,
> 
> Here's v4 of the extended drop reasons, with fixes to kernel-doc
> and checkpatch.
> 
> johannes

Here is the summary with links:
  - [net-next,v4,1/3] net: move dropreason.h to dropreason-core.h
    https://git.kernel.org/netdev/net-next/c/5b8285cca6fe
  - [net-next,v4,2/3] net: extend drop reasons for multiple subsystems
    https://git.kernel.org/netdev/net-next/c/071c0fc6fb91
  - [net-next,v4,3/3] mac80211: use the new drop reasons infrastructure
    (no matching commit)

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html