Commit ba8de796 authored by Yan Zhai's avatar Yan Zhai Committed by David S. Miller
Browse files

net: introduce sk_skb_reason_drop function 



Long used destructors kfree_skb and kfree_skb_reason do not pass
receiving socket to packet drop tracepoints trace_kfree_skb.
This makes it hard to track packet drops of a certain netns (container)
or a socket (user application).

The naming of these destructors are also not consistent with most sk/skb
operating functions, i.e. functions named "sk_xxx" or "skb_xxx".
Introduce a new functions sk_skb_reason_drop as drop-in replacement for
kfree_skb_reason on local receiving path. Callers can now pass receiving
sockets to the tracepoints.

kfree_skb and kfree_skb_reason are still usable but they are now just
inline helpers that call sk_skb_reason_drop.

Note it is not feasible to do the same to consume_skb. Packets not
dropped can flow through multiple receive handlers, and have multiple
receiving sockets. Leave it untouched for now.

Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarYan Zhai <yan@cloudflare.com>
Acked-by: default avatarJesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c53795d4

include/linux/skbuff.h

+8 −2
Original line number Diff line number Diff line
@@ -1251,8 +1251,14 @@ static inline bool skb_data_unref(const struct sk_buff *skb, 
	return true;

}



void __fix_address

kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason);

void __fix_address sk_skb_reason_drop(struct sock *sk, struct sk_buff *skb,

				      enum skb_drop_reason reason);



static inline void

kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)

{

	sk_skb_reason_drop(NULL, skb, reason);

}



/**

 *	kfree_skb - free an sk_buff with 'NOT_SPECIFIED' reason

net/core/skbuff.c

+12 −10
Original line number Diff line number Diff line
@@ -1190,7 +1190,8 @@ void __kfree_skb(struct sk_buff *skb) 
EXPORT_SYMBOL(__kfree_skb);



static __always_inline

bool __kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)

bool __sk_skb_reason_drop(struct sock *sk, struct sk_buff *skb,

			  enum skb_drop_reason reason)

{

	if (unlikely(!skb_unref(skb)))

		return false;
@@ -1203,26 +1204,27 @@ bool __kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason) 
	if (reason == SKB_CONSUMED)

		trace_consume_skb(skb, __builtin_return_address(0));

	else

		trace_kfree_skb(skb, __builtin_return_address(0), reason, NULL);

		trace_kfree_skb(skb, __builtin_return_address(0), reason, sk);

	return true;

}



/**

 *	kfree_skb_reason - free an sk_buff with special reason

 *	sk_skb_reason_drop - free an sk_buff with special reason

 *	@sk: the socket to receive @skb, or NULL if not applicable

 *	@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. Meanwhile, pass the drop reason to 'kfree_skb'

 *	tracepoint.

 *	Drop a reference to the buffer and free it if the usage count has hit

 *	zero. Meanwhile, pass the receiving socket and drop reason to

 *	'kfree_skb' tracepoint.

 */

void __fix_address

kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)

sk_skb_reason_drop(struct sock *sk, struct sk_buff *skb, enum skb_drop_reason reason)

{

	if (__kfree_skb_reason(skb, reason))

	if (__sk_skb_reason_drop(sk, skb, reason))

		__kfree_skb(skb);

}

EXPORT_SYMBOL(kfree_skb_reason);

EXPORT_SYMBOL(sk_skb_reason_drop);



#define KFREE_SKB_BULK_SIZE	16
@@ -1261,7 +1263,7 @@ kfree_skb_list_reason(struct sk_buff *segs, enum skb_drop_reason reason) 
	while (segs) {

		struct sk_buff *next = segs->next;



		if (__kfree_skb_reason(segs, reason)) {

		if (__sk_skb_reason_drop(NULL, segs, reason)) {

			skb_poison_list(segs);

			kfree_skb_add_bulk(segs, &sa, reason);

		}