Commit c504e5c2 authored by Menglong Dong's avatar Menglong Dong Committed by Jakub Kicinski
Browse files

net: skb: introduce kfree_skb_reason() 



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: default avatarMenglong Dong <imagedong@tencent.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 342402c4

include/linux/skbuff.h

+22 −1
Original line number Diff line number Diff line
@@ -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);

include/trace/events/skb.h

+29 −7
Original line number Diff line number Diff line
@@ -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(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,

net/core/dev.c

+2 −1
Original line number Diff line number Diff line
@@ -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);

net/core/drop_monitor.c

+7 −3
Original line number Diff line number Diff line
@@ -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;

net/core/skbuff.c

+7 −5
Original line number Diff line number Diff line
@@ -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)

{