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net: skb: introduce kfree_skb_reason()

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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@tencent.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Menglong Dong 2022-01-09 14:36:26 +08:00 committed by Jakub Kicinski
parent 342402c426
commit c504e5c2f9
5 changed files with 67 additions and 17 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

23
include/linux/skbuff.h
View file

@ -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);

36
include/trace/events/skb.h
View file

@ -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,

3
net/core/dev.c
View file

@ -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);

10
net/core/drop_monitor.c
View file

@ -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;

12
net/core/skbuff.c
View file

@ -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)
{