Re: [PATCH v3 resend] net/ipv4: add tracepoint for icmp_send

Jason Xing
2024-03-21T03:27:33Z

On Thu, Mar 21, 2024 at 11:09 AM <xu.xin16@zte.com.cn> wrote:
>
> From: he peilin <he.peilin@zte.com.cn>
>
> Introduce a tracepoint for icmp_send, which can help users to get more
> detail information conveniently when icmp abnormal events happen.
>
> 1. Giving an usecase example:
> =============================
> When an application experiences packet loss due to an unreachable UDP
> destination port, the kernel will send an exception message through the
> icmp_send function. By adding a trace point for icmp_send, developers or
> system administrators can obtain detailed information about the UDP
> packet loss, including the type, code, source address, destination address,
> source port, and destination port. This facilitates the trouble-shooting
> of UDP packet loss issues especially for those network-service
> applications.
>
> 2. Operation Instructions:
> ==========================
> Switch to the tracing directory.
> cd /sys/kernel/tracing
> Filter for destination port unreachable.
> echo "type==3 && code==3" > events/icmp/icmp_send/filter
> Enable trace event.
> echo 1 > events/icmp/icmp_send/enable
>
> 3. Result View:
> ================
> udp_client_erro-11370 [002] ...s.12 124.728002:
> icmp_send: icmp_send: type=3, code=3.
> From 127.0.0.1:41895 to 127.0.0.1:6666 ulen=23
> skbaddr=00000000589b167a
>
> Changelog
> ---------
> v2->v3:
> Some fixes according to
> https://lore.kernel.org/all/20240319102549.7f7f6f53@gandalf.local.home/
> 1. Change the tracking directory to/sys/kernel/tracking.
> 2. Adjust the layout of the TP-STRUCT_entry parameter structure.
>
> v1->v2:
> Some fixes according to
> https://lore.kernel.org/all/CANn89iL-y9e_VFpdw=sZtRnKRu_tnUwqHuFQTJvJsv-nz1xPDw@mail.gmail.com/
> 1. adjust the trace_icmp_send() to more protocols than UDP.
> 2. move the calling of trace_icmp_send after sanity checks
> in __icmp_send().
>
> Signed-off-by: Peilin He<he.peilin@zte.com.cn>
> Reviewed-by: xu xin <xu.xin16@zte.com.cn>
> Reviewed-by: Yunkai Zhang <zhang.yunkai@zte.com.cn>
> Cc: Yang Yang <yang.yang29@zte.com.cn>
> Cc: Liu Chun <liu.chun2@zte.com.cn>
> Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn>

I think it would be better to target net-next tree since it's not a
fix or something else important.

> ---
> include/trace/events/icmp.h | 64 +++++++++++++++++++++++++++++++++++++
> net/ipv4/icmp.c | 4 +++
> 2 files changed, 68 insertions(+)
> create mode 100644 include/trace/events/icmp.h
>
> diff --git a/include/trace/events/icmp.h b/include/trace/events/icmp.h
> new file mode 100644
> index 000000000000..2098d4b1b12e
> --- /dev/null
> +++ b/include/trace/events/icmp.h
> @@ -0,0 +1,64 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM icmp
> +
> +#if !defined(_TRACE_ICMP_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_ICMP_H
> +
> +#include <linux/icmp.h>
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT(icmp_send,
> +
> + TP_PROTO(const struct sk_buff *skb, int type, int code),
> +
> + TP_ARGS(skb, type, code),
> +
> + TP_STRUCT__entry(
> + __field(const void *, skbaddr)
> + __field(int, type)
> + __field(int, code)
> + __array(__u8, saddr, 4)
> + __array(__u8, daddr, 4)
> + __field(__u16, sport)
> + __field(__u16, dport)
> + __field(unsigned short, ulen)
> + ),
> +
> + TP_fast_assign(
> + struct iphdr *iph = ip_hdr(skb);
> + int proto_4 = iph->protocol;
> + __be32 *p32;
> +
> + __entry->skbaddr = skb;
> + __entry->type = type;
> + __entry->code = code;
> +
> + if (proto_4 == IPPROTO_UDP) {
> + struct udphdr *uh = udp_hdr(skb);
> + __entry->sport = ntohs(uh->source);
> + __entry->dport = ntohs(uh->dest);
> + __entry->ulen = ntohs(uh->len);
> + } else {
> + __entry->sport = 0;
> + __entry->dport = 0;
> + __entry->ulen = 0;
> + }

What about using the TP_STORE_ADDR_PORTS_SKB macro to record the sport
and dport like the patch[1] did through extending the use of header
for TCP and UDP?

And, I wonder what the use of tracing ulen of that skb?

[1]: https://lore.kernel.org/all/1c7156a3f164eb33ef3a25b8432e359f0bb60a8e.1710866188.git.balazs.scheidler@axoflow.com/

Thanks,
Jason

> +
> + p32 = (__be32 *) __entry->saddr;
> + *p32 = iph->saddr;
> +
> + p32 = (__be32 *) __entry->daddr;
> + *p32 = iph->daddr;
> + ),
> +
> + TP_printk("icmp_send: type=%d, code=%d. From %pI4:%u to %pI4:%u ulen=%d skbaddr=%p",
> + __entry->type, __entry->code,
> + __entry->saddr, __entry->sport, __entry->daddr,
> + __entry->dport, __entry->ulen, __entry->skbaddr)
> +);
> +
> +#endif /* _TRACE_ICMP_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> \ No newline at end of file
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index e63a3bf99617..21fb41257fe9 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -92,6 +92,8 @@
> #include <net/inet_common.h>
> #include <net/ip_fib.h>
> #include <net/l3mdev.h>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/icmp.h>
>
> /*
> * Build xmit assembly blocks
> @@ -672,6 +674,8 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
> }
> }
>
> + trace_icmp_send(skb_in, type, code);
> +
> /* Needed by both icmp_global_allow and icmp_xmit_lock */
> local_bh_disable();
>
> --
> 2.44.0
>