Re: [PATCH net-next v4 2/3] net: skb: use auto-generation to convert skb drop reason to string

From: Eric Dumazet
Date: Wed Aug 24 2022 - 20:45:39 EST

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On Sun, Jun 5, 2022 at 7:29 PM <menglong8.dong@xxxxxxxxx> wrote:
>
> From: Menglong Dong <imagedong@xxxxxxxxxxx>
>
> It is annoying to add new skb drop reasons to 'enum skb_drop_reason'
> and TRACE_SKB_DROP_REASON in trace/event/skb.h, and it's easy to forget
> to add the new reasons we added to TRACE_SKB_DROP_REASON.
>
> TRACE_SKB_DROP_REASON is used to convert drop reason of type number
> to string. For now, the string we passed to user space is exactly the
> same as the name in 'enum skb_drop_reason' with a 'SKB_DROP_REASON_'
> prefix. Therefore, we can use 'auto-generation' to generate these
> drop reasons to string at build time.
>
> The new source 'dropreason_str.c' will be auto generated during build
> time, which contains the string array
> 'const char * const drop_reasons[]'.

After this patch, I no longer have strings added after the reason: tag

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:
ip_defrag 14605 [021] 221.614304: skb:kfree_skb:
skbaddr=0xffff9d286e1ecb00 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614305: skb:kfree_skb:
skbaddr=0xffff9d2851242b00 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614306: skb:kfree_skb:
skbaddr=0xffff9d285fd23d00 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614308: skb:kfree_skb:
skbaddr=0xffff9d2851242e00 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614309: skb:kfree_skb:
skbaddr=0xffff9d285fd23200 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614310: skb:kfree_skb:
skbaddr=0xffff9d286dcb0600 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614311: skb:kfree_skb:
skbaddr=0xffff9d285fd23700 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614312: skb:kfree_skb:
skbaddr=0xffff9d286dcb0800 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614313: skb:kfree_skb:
skbaddr=0xffff9d284deb3b00 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614314: skb:kfree_skb:
skbaddr=0xffff9d286dcb0100 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614315: skb:kfree_skb:
skbaddr=0xffff9d284deb3c00 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614316: skb:kfree_skb:
skbaddr=0xffff9d286dcb0200 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614317: skb:kfree_skb:
skbaddr=0xffff9d284e378800 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614318: skb:kfree_skb:
skbaddr=0xffff9d286dcb0500 protocol=34525 location=0xffffffffa39346b1
reason:
ip_defrag 14605 [021] 221.614319: skb:kfree_skb:
skbaddr=0xffff9d284e378300 protocol=34525 location=0xffffffffa39346b1
reason:

>
> Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
> ---
> v3:
> - add new line in the end of .gitignore
> - fix awk warning by make '\;' to ';', as ';' is not need to be
> escaped
> - export 'drop_reasons' in skbuff.c
>
> v2:
> - generate source file instead of header file for drop reasons string
> array (Jakub Kicinski)
> ---
> include/net/dropreason.h | 2 +
> include/trace/events/skb.h | 89 +-------------------------------------
> net/core/.gitignore | 1 +
> net/core/Makefile | 23 +++++++++-
> net/core/drop_monitor.c | 13 ------
> net/core/skbuff.c | 3 ++
> 6 files changed, 29 insertions(+), 102 deletions(-)
> create mode 100644 net/core/.gitignore
>
> diff --git a/include/net/dropreason.h b/include/net/dropreason.h
> index ecd18b7b1364..013ff0f2543e 100644
> --- a/include/net/dropreason.h
> +++ b/include/net/dropreason.h
> @@ -181,4 +181,6 @@ enum skb_drop_reason {
> SKB_DR_SET(name, reason); \
> } while (0)
>
> +extern const char * const drop_reasons[];
> +
> #endif
> diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
> index a477bf907498..45264e4bb254 100644
> --- a/include/trace/events/skb.h
> +++ b/include/trace/events/skb.h
> @@ -9,92 +9,6 @@
> #include <linux/netdevice.h>
> #include <linux/tracepoint.h>
>
> -#define TRACE_SKB_DROP_REASON \
> - EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED) \
> - EM(SKB_DROP_REASON_NO_SOCKET, NO_SOCKET) \
> - EM(SKB_DROP_REASON_PKT_TOO_SMALL, PKT_TOO_SMALL) \
> - EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM) \
> - EM(SKB_DROP_REASON_SOCKET_FILTER, SOCKET_FILTER) \
> - EM(SKB_DROP_REASON_UDP_CSUM, UDP_CSUM) \
> - EM(SKB_DROP_REASON_NETFILTER_DROP, NETFILTER_DROP) \
> - EM(SKB_DROP_REASON_OTHERHOST, OTHERHOST) \
> - EM(SKB_DROP_REASON_IP_CSUM, IP_CSUM) \
> - EM(SKB_DROP_REASON_IP_INHDR, IP_INHDR) \
> - EM(SKB_DROP_REASON_IP_RPFILTER, IP_RPFILTER) \
> - EM(SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST, \
> - UNICAST_IN_L2_MULTICAST) \
> - EM(SKB_DROP_REASON_XFRM_POLICY, XFRM_POLICY) \
> - EM(SKB_DROP_REASON_IP_NOPROTO, IP_NOPROTO) \
> - EM(SKB_DROP_REASON_SOCKET_RCVBUFF, SOCKET_RCVBUFF) \
> - EM(SKB_DROP_REASON_PROTO_MEM, PROTO_MEM) \
> - EM(SKB_DROP_REASON_TCP_MD5NOTFOUND, TCP_MD5NOTFOUND) \
> - EM(SKB_DROP_REASON_TCP_MD5UNEXPECTED, \
> - TCP_MD5UNEXPECTED) \
> - EM(SKB_DROP_REASON_TCP_MD5FAILURE, TCP_MD5FAILURE) \
> - EM(SKB_DROP_REASON_SOCKET_BACKLOG, SOCKET_BACKLOG) \
> - EM(SKB_DROP_REASON_TCP_FLAGS, TCP_FLAGS) \
> - EM(SKB_DROP_REASON_TCP_ZEROWINDOW, TCP_ZEROWINDOW) \
> - EM(SKB_DROP_REASON_TCP_OLD_DATA, TCP_OLD_DATA) \
> - EM(SKB_DROP_REASON_TCP_OVERWINDOW, TCP_OVERWINDOW) \
> - EM(SKB_DROP_REASON_TCP_OFOMERGE, TCP_OFOMERGE) \
> - EM(SKB_DROP_REASON_TCP_OFO_DROP, TCP_OFO_DROP) \
> - EM(SKB_DROP_REASON_TCP_RFC7323_PAWS, TCP_RFC7323_PAWS) \
> - EM(SKB_DROP_REASON_TCP_INVALID_SEQUENCE, \
> - TCP_INVALID_SEQUENCE) \
> - EM(SKB_DROP_REASON_TCP_RESET, TCP_RESET) \
> - EM(SKB_DROP_REASON_TCP_INVALID_SYN, TCP_INVALID_SYN) \
> - EM(SKB_DROP_REASON_TCP_CLOSE, TCP_CLOSE) \
> - EM(SKB_DROP_REASON_TCP_FASTOPEN, TCP_FASTOPEN) \
> - EM(SKB_DROP_REASON_TCP_OLD_ACK, TCP_OLD_ACK) \
> - EM(SKB_DROP_REASON_TCP_TOO_OLD_ACK, TCP_TOO_OLD_ACK) \
> - EM(SKB_DROP_REASON_TCP_ACK_UNSENT_DATA, \
> - TCP_ACK_UNSENT_DATA) \
> - EM(SKB_DROP_REASON_TCP_OFO_QUEUE_PRUNE, \
> - TCP_OFO_QUEUE_PRUNE) \
> - EM(SKB_DROP_REASON_IP_OUTNOROUTES, IP_OUTNOROUTES) \
> - EM(SKB_DROP_REASON_BPF_CGROUP_EGRESS, \
> - BPF_CGROUP_EGRESS) \
> - EM(SKB_DROP_REASON_IPV6DISABLED, IPV6DISABLED) \
> - EM(SKB_DROP_REASON_NEIGH_CREATEFAIL, NEIGH_CREATEFAIL) \
> - EM(SKB_DROP_REASON_NEIGH_FAILED, NEIGH_FAILED) \
> - EM(SKB_DROP_REASON_NEIGH_QUEUEFULL, NEIGH_QUEUEFULL) \
> - EM(SKB_DROP_REASON_NEIGH_DEAD, NEIGH_DEAD) \
> - EM(SKB_DROP_REASON_TC_EGRESS, TC_EGRESS) \
> - EM(SKB_DROP_REASON_QDISC_DROP, QDISC_DROP) \
> - EM(SKB_DROP_REASON_CPU_BACKLOG, CPU_BACKLOG) \
> - EM(SKB_DROP_REASON_XDP, XDP) \
> - EM(SKB_DROP_REASON_TC_INGRESS, TC_INGRESS) \
> - EM(SKB_DROP_REASON_UNHANDLED_PROTO, UNHANDLED_PROTO) \
> - EM(SKB_DROP_REASON_SKB_CSUM, SKB_CSUM) \
> - EM(SKB_DROP_REASON_SKB_GSO_SEG, SKB_GSO_SEG) \
> - EM(SKB_DROP_REASON_SKB_UCOPY_FAULT, SKB_UCOPY_FAULT) \
> - EM(SKB_DROP_REASON_DEV_HDR, DEV_HDR) \
> - EM(SKB_DROP_REASON_DEV_READY, DEV_READY) \
> - EM(SKB_DROP_REASON_FULL_RING, FULL_RING) \
> - EM(SKB_DROP_REASON_NOMEM, NOMEM) \
> - EM(SKB_DROP_REASON_HDR_TRUNC, HDR_TRUNC) \
> - EM(SKB_DROP_REASON_TAP_FILTER, TAP_FILTER) \
> - EM(SKB_DROP_REASON_TAP_TXFILTER, TAP_TXFILTER) \
> - EM(SKB_DROP_REASON_ICMP_CSUM, ICMP_CSUM) \
> - EM(SKB_DROP_REASON_INVALID_PROTO, INVALID_PROTO) \
> - EM(SKB_DROP_REASON_IP_INADDRERRORS, IP_INADDRERRORS) \
> - EM(SKB_DROP_REASON_IP_INNOROUTES, IP_INNOROUTES) \
> - EM(SKB_DROP_REASON_PKT_TOO_BIG, PKT_TOO_BIG) \
> - 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:
> */
> @@ -121,8 +35,7 @@ TRACE_EVENT(kfree_skb,
>
> TP_printk("skbaddr=%p protocol=%u location=%p reason: %s",
> __entry->skbaddr, __entry->protocol, __entry->location,
> - __print_symbolic(__entry->reason,
> - TRACE_SKB_DROP_REASON))
> + drop_reasons[__entry->reason])
> );
>
> TRACE_EVENT(consume_skb,
> diff --git a/net/core/.gitignore b/net/core/.gitignore
> new file mode 100644
> index 000000000000..df1e74372cce
> --- /dev/null
> +++ b/net/core/.gitignore
> @@ -0,0 +1 @@
> +dropreason_str.c
> diff --git a/net/core/Makefile b/net/core/Makefile
> index a8e4f737692b..e8ce3bd283a6 100644
> --- a/net/core/Makefile
> +++ b/net/core/Makefile
> @@ -4,7 +4,8 @@
> #
>
> 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
> + gen_stats.o gen_estimator.o net_namespace.o secure_seq.o \
> + flow_dissector.o dropreason_str.o
>
> obj-$(CONFIG_SYSCTL) += sysctl_net_core.o
>
> @@ -39,3 +40,23 @@ obj-$(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
> diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
> index 41cac0e4834e..4ad1decce724 100644
> --- a/net/core/drop_monitor.c
> +++ b/net/core/drop_monitor.c
> @@ -48,19 +48,6 @@
> static int trace_state = TRACE_OFF;
> static bool monitor_hw;
>
> -#undef EM
> -#undef EMe
> -
> -#define EM(a, b) [a] = #b,
> -#define EMe(a, b) [a] = #b
> -
> -/* drop_reasons is used to translate 'enum skb_drop_reason' to string,
> - * which is reported to user space.
> - */
> -static const char * const drop_reasons[] = {
> - TRACE_SKB_DROP_REASON
> -};
> -
> /* net_dm_mutex
> *
> * An overall lock guarding every operation coming from userspace.
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 1d10bb4adec1..74864e6c1835 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -91,6 +91,9 @@ 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 */
> +EXPORT_SYMBOL(drop_reasons);
> +
> /**
> * skb_panic - private function for out-of-line support
> * @skb: buffer
> --
> 2.36.1
>

Next message: Alexei Starovoitov: "Re: [RESEND PATCH bpf-next v9 0/5] bpf: rstat: cgroup hierarchical"
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Next in thread: Jakub Kicinski: "Re: [PATCH net-next v4 2/3] net: skb: use auto-generation to convert skb drop reason to string"
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