Re: Re: [PATCH v2] net/ipv4: add tracepoint for icmp_send

[He Peilin]

> > From: Peilin He<he.peilin@xxxxxxxxxx>
> > 
> > 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/debug/tracing
> 
> FYI, that directory is obsolete. Please always reference /sys/kernel/tracing.
OK. 
> > 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
> > 
> > v1->v2:
> > Some fixes according to
> > https://lore.kernel.org/all/CANn89iL-y9e_VFpdw=sZtRnKRu_tnUwqHuFQTJvJsv-nz1xPDw@xxxxxxxxxxxxxx/
> > 	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@xxxxxxxxxx>
> > Reviewed-by: xu xin <xu.xin16@xxxxxxxxxx>
> > Reviewed-by: Yunkai Zhang <zhang.yunkai@xxxxxxxxxx>
> > Cc: Yang Yang <yang.yang29@xxxxxxxxxx>
> > Cc: Liu Chun <liu.chun2@xxxxxxxxxx>
> > Cc: Xuexin Jiang <jiang.xuexin@xxxxxxxxxx>
> > ---
> >  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..c3dc337be7bc
> > --- /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(__u16, sport)
> > +			__field(__u16, dport)
> > +			__field(int, type)
> > +			__field(int, code)
> > +			__array(__u8, saddr, 4)
> > +			__array(__u8, daddr, 4)
> > +                	__field(const void *, skbaddr)
> > +			__field(unsigned short, ulen)
> 
> Note, to prevent holes, I usually suggest pointers and longs go first,
> followed by ints, and then end with char.
> 
>                 	__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)
> 
> -- Steve
Thank you very much for your suggestion. We will rearrange the parameters in TP_STRUCT_entry, prioritizing pointers and longs, followed by ints, and ending with char. This will be reflected in Patch v3.
> 
> 
> > +		),
> > +
> > +		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;
> > +			}
> > +
> > +			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();
> >