Commit 9cb252c4 authored by Menglong Dong's avatar Menglong Dong Committed by David S. Miller
Browse files

net: skb: export skb drop reaons to user by TRACE_DEFINE_ENUM 

As Eric reported, the 'reason' field is not presented when trace the
kfree_skb event by perf:

$ perf record -e skb:kfree_skb -a sleep 10
$ perf script
  ip_defrag 14605 [021]   221.614303:   skb:kfree_skb:
  skbaddr=0xffff9d2851242700 protocol=34525 location=0xffffffffa39346b1
  reason:

The cause seems to be passing kernel address directly to TP_printk(),
which is not right. As the enum 'skb_drop_reason' is not exported to
user space through TRACE_DEFINE_ENUM(), perf can't get the drop reason
string from the 'reason' field, which is a number.

Therefore, we introduce the macro DEFINE_DROP_REASON(), which is used
to define the trace enum by TRACE_DEFINE_ENUM(). With the help of
DEFINE_DROP_REASON(), now we can remove the auto-generate that we
introduced in the commit ec43908d
("net: skb: use auto-generation to convert skb drop reason to string"),
and define the string array 'drop_reasons'.

Hmmmm...now we come back to the situation that have to maintain drop
reasons in both enum skb_drop_reason and DEFINE_DROP_REASON. But they
are both in dropreason.h, which makes it easier.

After this commit, now the format of kfree_skb is like this:

$ cat /tracing/events/skb/kfree_skb/format
name: kfree_skb
ID: 1524
format:
        field:unsigned short common_type;       offset:0;       size:2; signed:0;
        field:unsigned char common_flags;       offset:2;       size:1; signed:0;
        field:unsigned char common_preempt_count;       offset:3;       size:1; signed:0;
        field:int common_pid;   offset:4;       size:4; signed:1;

        field:void * skbaddr;   offset:8;       size:8; signed:0;
        field:void * location;  offset:16;      size:8; signed:0;
        field:unsigned short protocol;  offset:24;      size:2; signed:0;
        field:enum skb_drop_reason reason;      offset:28;      size:4; signed:0;

print fmt: "skbaddr=%p protocol=%u location=%p reason: %s", REC->skbaddr, REC->protocol, REC->location, __print_symbolic(REC->reason, { 1, "NOT_SPECIFIED" }, { 2, "NO_SOCKET" } ......

Fixes: ec43908d ("net: skb: use auto-generation to convert skb drop reason to string")
Link: https://lore.kernel.org/netdev/CANn89i+bx0ybvE55iMYf5GJM48WwV1HNpdm9Q6t-HaEstqpCSA@mail.gmail.com/


Reported-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarMenglong Dong <imagedong@tencent.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0e80707d

include/net/dropreason.h

+67 −0
Original line number Diff line number Diff line
@@ -3,6 +3,73 @@ 
#ifndef _LINUX_DROPREASON_H

#define _LINUX_DROPREASON_H



#define DEFINE_DROP_REASON(FN, FNe)	\

	FN(NOT_SPECIFIED)		\

	FN(NO_SOCKET)			\

	FN(PKT_TOO_SMALL)		\

	FN(TCP_CSUM)			\

	FN(SOCKET_FILTER)		\

	FN(UDP_CSUM)			\

	FN(NETFILTER_DROP)		\

	FN(OTHERHOST)			\

	FN(IP_CSUM)			\

	FN(IP_INHDR)			\

	FN(IP_RPFILTER)			\

	FN(UNICAST_IN_L2_MULTICAST)	\

	FN(XFRM_POLICY)			\

	FN(IP_NOPROTO)			\

	FN(SOCKET_RCVBUFF)		\

	FN(PROTO_MEM)			\

	FN(TCP_MD5NOTFOUND)		\

	FN(TCP_MD5UNEXPECTED)		\

	FN(TCP_MD5FAILURE)		\

	FN(SOCKET_BACKLOG)		\

	FN(TCP_FLAGS)			\

	FN(TCP_ZEROWINDOW)		\

	FN(TCP_OLD_DATA)		\

	FN(TCP_OVERWINDOW)		\

	FN(TCP_OFOMERGE)		\

	FN(TCP_RFC7323_PAWS)		\

	FN(TCP_INVALID_SEQUENCE)	\

	FN(TCP_RESET)			\

	FN(TCP_INVALID_SYN)		\

	FN(TCP_CLOSE)			\

	FN(TCP_FASTOPEN)		\

	FN(TCP_OLD_ACK)			\

	FN(TCP_TOO_OLD_ACK)		\

	FN(TCP_ACK_UNSENT_DATA)		\

	FN(TCP_OFO_QUEUE_PRUNE)		\

	FN(TCP_OFO_DROP)		\

	FN(IP_OUTNOROUTES)		\

	FN(BPF_CGROUP_EGRESS)		\

	FN(IPV6DISABLED)		\

	FN(NEIGH_CREATEFAIL)		\

	FN(NEIGH_FAILED)		\

	FN(NEIGH_QUEUEFULL)		\

	FN(NEIGH_DEAD)			\

	FN(TC_EGRESS)			\

	FN(QDISC_DROP)			\

	FN(CPU_BACKLOG)			\

	FN(XDP)				\

	FN(TC_INGRESS)			\

	FN(UNHANDLED_PROTO)		\

	FN(SKB_CSUM)			\

	FN(SKB_GSO_SEG)			\

	FN(SKB_UCOPY_FAULT)		\

	FN(DEV_HDR)			\

	FN(DEV_READY)			\

	FN(FULL_RING)			\

	FN(NOMEM)			\

	FN(HDR_TRUNC)			\

	FN(TAP_FILTER)			\

	FN(TAP_TXFILTER)		\

	FN(ICMP_CSUM)			\

	FN(INVALID_PROTO)		\

	FN(IP_INADDRERRORS)		\

	FN(IP_INNOROUTES)		\

	FN(PKT_TOO_BIG)			\

	FNe(MAX)



/**

 * enum skb_drop_reason - the reasons of skb drops

 *

include/trace/events/skb.h

+14 −1
Original line number Diff line number Diff line
@@ -9,6 +9,15 @@ 
#include <linux/netdevice.h>

#include <linux/tracepoint.h>



#undef FN

#define FN(reason)	TRACE_DEFINE_ENUM(SKB_DROP_REASON_##reason);

DEFINE_DROP_REASON(FN, FN)



#undef FN

#undef FNe

#define FN(reason)	{ SKB_DROP_REASON_##reason, #reason },

#define FNe(reason)	{ SKB_DROP_REASON_##reason, #reason }



/*

 * Tracepoint for free an sk_buff:

 */
@@ -35,9 +44,13 @@ TRACE_EVENT(kfree_skb, 


	TP_printk("skbaddr=%p protocol=%u location=%p reason: %s",

		  __entry->skbaddr, __entry->protocol, __entry->location,

		  drop_reasons[__entry->reason])

		  __print_symbolic(__entry->reason,

				   DEFINE_DROP_REASON(FN, FNe)))

);



#undef FN

#undef FNe



TRACE_EVENT(consume_skb,



	TP_PROTO(struct sk_buff *skb),

net/core/.gitignore

deleted100644 → 0
+0 −1
Original line number Diff line number Diff line 
dropreason_str.c

net/core/Makefile

+1 −21
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 


obj-y := sock.o request_sock.o skbuff.o datagram.o stream.o scm.o \

	 gen_stats.o gen_estimator.o net_namespace.o secure_seq.o \

	 flow_dissector.o dropreason_str.o

	 flow_dissector.o



obj-$(CONFIG_SYSCTL) += sysctl_net_core.o
@@ -40,23 +40,3 @@ obj-$(CONFIG_NET_SOCK_MSG) += skmsg.o 
obj-$(CONFIG_BPF_SYSCALL) += sock_map.o

obj-$(CONFIG_BPF_SYSCALL) += bpf_sk_storage.o

obj-$(CONFIG_OF)	+= of_net.o
 


clean-files := dropreason_str.c



quiet_cmd_dropreason_str = GEN     $@

cmd_dropreason_str = awk -F ',' 'BEGIN{ print "\#include <net/dropreason.h>\n"; \

	print "const char * const drop_reasons[] = {" }\

	/^enum skb_drop/ { dr=1; }\

	/^\};/ { dr=0; }\

	/^\tSKB_DROP_REASON_/ {\

		if (dr) {\

			sub(/\tSKB_DROP_REASON_/, "", $$1);\

			printf "\t[SKB_DROP_REASON_%s] = \"%s\",\n", $$1, $$1;\

		}\

	}\

	END{ print "};" }' $< > $@



$(obj)/dropreason_str.c: $(srctree)/include/net/dropreason.h

	$(call cmd,dropreason_str)



$(obj)/dropreason_str.o: $(obj)/dropreason_str.c

net/core/skbuff.c

+5 −1
Original line number Diff line number Diff line
@@ -91,7 +91,11 @@ static struct kmem_cache *skbuff_ext_cache __ro_after_init; 
int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;

EXPORT_SYMBOL(sysctl_max_skb_frags);



/* The array 'drop_reasons' is auto-generated in dropreason_str.c */

#undef FN

#define FN(reason) [SKB_DROP_REASON_##reason] = #reason,

const char * const drop_reasons[] = {

	DEFINE_DROP_REASON(FN, FN)

};

EXPORT_SYMBOL(drop_reasons);



/**