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Message-Id: <20220109063628.526990-2-imagedong@tencent.com>
Date: Sun, 9 Jan 2022 14:36:26 +0800
From: menglong8.dong@...il.com
To: rostedt@...dmis.org, dsahern@...nel.org
Cc: mingo@...hat.com, davem@...emloft.net, kuba@...nel.org,
nhorman@...driver.com, edumazet@...gle.com,
yoshfuji@...ux-ipv6.org, alobakin@...me, willemb@...gle.com,
cong.wang@...edance.com, keescook@...omium.org, pabeni@...hat.com,
talalahmad@...gle.com, haokexin@...il.com,
ilias.apalodimas@...aro.org, memxor@...il.com, atenart@...nel.org,
bigeasy@...utronix.de, weiwan@...gle.com, arnd@...db.de,
vvs@...tuozzo.com, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, jonathan.lemon@...il.com,
imagedong@...cent.com
Subject: [PATCH v4 net-next 1/3] net: skb: introduce kfree_skb_reason()
From: Menglong Dong <imagedong@...cent.com>
Introduce the interface kfree_skb_reason(), which is able to pass
the reason why the skb is dropped to 'kfree_skb' tracepoint.
Add the 'reason' field to 'trace_kfree_skb', therefor user can get
more detail information about abnormal skb with 'drop_monitor' or
eBPF.
All drop reasons are defined in the enum 'skb_drop_reason', and
they will be print as string in 'kfree_skb' tracepoint in format
of 'reason: XXX'.
( Maybe the reasons should be defined in a uapi header file, so that
user space can use them? )
Signed-off-by: Menglong Dong <imagedong@...cent.com>
---
v4:
- fix some code style in skb.h
v3:
- rename kfree_skb_with_reason() to kfree_skb_reason()
- turn kfree_skb() into a static inline calling kfree_skb_reason()
---
include/linux/skbuff.h | 23 ++++++++++++++++++++++-
include/trace/events/skb.h | 36 +++++++++++++++++++++++++++++-------
net/core/dev.c | 3 ++-
net/core/drop_monitor.c | 10 +++++++---
net/core/skbuff.c | 12 +++++++-----
5 files changed, 67 insertions(+), 17 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 642acb0d1646..ef0870abc791 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -305,6 +305,17 @@ struct sk_buff_head {
struct sk_buff;
+/* The reason of skb drop, which is used in kfree_skb_reason().
+ * en...maybe they should be splited by group?
+ *
+ * Each item here should also be in 'TRACE_SKB_DROP_REASON', which is
+ * used to translate the reason to string.
+ */
+enum skb_drop_reason {
+ SKB_DROP_REASON_NOT_SPECIFIED,
+ SKB_DROP_REASON_MAX,
+};
+
/* To allow 64K frame to be packed as single skb without frag_list we
* require 64K/PAGE_SIZE pages plus 1 additional page to allow for
* buffers which do not start on a page boundary.
@@ -1085,8 +1096,18 @@ static inline bool skb_unref(struct sk_buff *skb)
return true;
}
+void kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason);
+
+/**
+ * kfree_skb - free an sk_buff with 'NOT_SPECIFIED' reason
+ * @skb: buffer to free
+ */
+static inline void kfree_skb(struct sk_buff *skb)
+{
+ kfree_skb_reason(skb, SKB_DROP_REASON_NOT_SPECIFIED);
+}
+
void skb_release_head_state(struct sk_buff *skb);
-void kfree_skb(struct sk_buff *skb);
void kfree_skb_list(struct sk_buff *segs);
void skb_dump(const char *level, const struct sk_buff *skb, bool full_pkt);
void skb_tx_error(struct sk_buff *skb);
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 9e92f22eb086..294c61bbe44b 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -9,29 +9,51 @@
#include <linux/netdevice.h>
#include <linux/tracepoint.h>
+#define TRACE_SKB_DROP_REASON \
+ EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED) \
+ EMe(SKB_DROP_REASON_MAX, MAX)
+
+#undef EM
+#undef EMe
+
+#define EM(a, b) TRACE_DEFINE_ENUM(a);
+#define EMe(a, b) TRACE_DEFINE_ENUM(a);
+
+TRACE_SKB_DROP_REASON
+
+#undef EM
+#undef EMe
+#define EM(a, b) { a, #b },
+#define EMe(a, b) { a, #b }
+
/*
* Tracepoint for free an sk_buff:
*/
TRACE_EVENT(kfree_skb,
- TP_PROTO(struct sk_buff *skb, void *location),
+ TP_PROTO(struct sk_buff *skb, void *location,
+ enum skb_drop_reason reason),
- TP_ARGS(skb, location),
+ TP_ARGS(skb, location, reason),
TP_STRUCT__entry(
- __field( void *, skbaddr )
- __field( void *, location )
- __field( unsigned short, protocol )
+ __field(void *, skbaddr)
+ __field(void *, location)
+ __field(unsigned short, protocol)
+ __field(enum skb_drop_reason, reason)
),
TP_fast_assign(
__entry->skbaddr = skb;
__entry->location = location;
__entry->protocol = ntohs(skb->protocol);
+ __entry->reason = reason;
),
- TP_printk("skbaddr=%p protocol=%u location=%p",
- __entry->skbaddr, __entry->protocol, __entry->location)
+ TP_printk("skbaddr=%p protocol=%u location=%p reason: %s",
+ __entry->skbaddr, __entry->protocol, __entry->location,
+ __print_symbolic(__entry->reason,
+ TRACE_SKB_DROP_REASON))
);
TRACE_EVENT(consume_skb,
diff --git a/net/core/dev.c b/net/core/dev.c
index 83a4089990a0..84a0d9542fe9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4899,7 +4899,8 @@ static __latent_entropy void net_tx_action(struct softirq_action *h)
if (likely(get_kfree_skb_cb(skb)->reason == SKB_REASON_CONSUMED))
trace_consume_skb(skb);
else
- trace_kfree_skb(skb, net_tx_action);
+ trace_kfree_skb(skb, net_tx_action,
+ SKB_DROP_REASON_NOT_SPECIFIED);
if (skb->fclone != SKB_FCLONE_UNAVAILABLE)
__kfree_skb(skb);
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 3d0ab2eec916..7b288a121a41 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -110,7 +110,8 @@ static u32 net_dm_queue_len = 1000;
struct net_dm_alert_ops {
void (*kfree_skb_probe)(void *ignore, struct sk_buff *skb,
- void *location);
+ void *location,
+ enum skb_drop_reason reason);
void (*napi_poll_probe)(void *ignore, struct napi_struct *napi,
int work, int budget);
void (*work_item_func)(struct work_struct *work);
@@ -262,7 +263,9 @@ static void trace_drop_common(struct sk_buff *skb, void *location)
spin_unlock_irqrestore(&data->lock, flags);
}
-static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location)
+static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb,
+ void *location,
+ enum skb_drop_reason reason)
{
trace_drop_common(skb, location);
}
@@ -490,7 +493,8 @@ static const struct net_dm_alert_ops net_dm_alert_summary_ops = {
static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
struct sk_buff *skb,
- void *location)
+ void *location,
+ enum skb_drop_reason reason)
{
ktime_t tstamp = ktime_get_real();
struct per_cpu_dm_data *data;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e514a36bcffc..0118f0afaa4f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -759,21 +759,23 @@ void __kfree_skb(struct sk_buff *skb)
EXPORT_SYMBOL(__kfree_skb);
/**
- * kfree_skb - free an sk_buff
+ * kfree_skb_reason - free an sk_buff with special reason
* @skb: buffer to free
+ * @reason: reason why this skb is dropped
*
* Drop a reference to the buffer and free it if the usage count has
- * hit zero.
+ * hit zero. Meanwhile, pass the drop reason to 'kfree_skb'
+ * tracepoint.
*/
-void kfree_skb(struct sk_buff *skb)
+void kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
{
if (!skb_unref(skb))
return;
- trace_kfree_skb(skb, __builtin_return_address(0));
+ trace_kfree_skb(skb, __builtin_return_address(0), reason);
__kfree_skb(skb);
}
-EXPORT_SYMBOL(kfree_skb);
+EXPORT_SYMBOL(kfree_skb_reason);
void kfree_skb_list(struct sk_buff *segs)
{
--
2.34.1
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