Re: Re: Subject: [PATCH net-next v4] net/ipv4: add tracepoint for icmp_send

[Peilin He]

>> From: hepeilin <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:
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
>=3D=3D=3D=3D=3D
>> 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 addres=
>s,
>> source port, and destination port. This facilitates the trouble-shooting
>> of UDP packet loss issues especially for those network-service
>> applications.
>>
>> 2. Operation Instructions:
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
>=3D=3D
>> Switch to the tracing directory.
>>         cd /sys/kernel/tracing
>> Filter for destination port unreachable.
>>         echo "type=3D=3D3 && code=3D=3D3" > events/icmp/icmp_send/filter
>> Enable trace event.
>>         echo 1 > events/icmp/icmp_send/enable
>>
>> 3. Result View:
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>>  udp_client_erro-11370   [002] ...s.12   124.728002:
>>  icmp_send: icmp_send: type=3D3, code=3D3.
>>  From 127.0.0.1:41895 to 127.0.0.1:6666 ulen=3D23
>>  skbaddr=3D00000000589b167a
>>
>> v3->v4:
>> Some fixes according to
>> https://lore.kernel.org/all/CANn89i+EFEr7VHXNdOi59Ba_R1nFKSBJzBzkJFVgCTdX=
>Bx=3DYBg@xxxxxxxxxxxxxx/
>> 1.Add legality check for UDP header in SKB.
>
>I think my understanding based on what Eric depicted differs from you:
>we're supposed to filter out those many invalid cases and only trace
>the valid action of sending a icmp, so where to add a new tracepoint
>is important instead of adding more checks in the tracepoint itself.
>Please refer to what trace_tcp_retransmit_skb() does :)
>
>Thanks,
>Jason
Okay, thank you for your suggestion. In order to avoid filtering out
those many invalid cases and only tracing the valid action of sending
a icmp, the next patch will add udd_fail_no_port trancepoint to the
include/trace/events/udp.h. This will solve the problem you mentioned
very well. At this point, only UDP protocol exceptions will be tracked,
without the need to track them in icmp_send.

>> 2.Target this patch for net-next.
>>
>> v2->v3:
>> Some fixes according to
>> https://lore.kernel.org/all/20240319102549.7f7f6f53@xxxxxxxxxxxxxxxxxx/
>> 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=3DsZtRnKRu_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 | 65 +++++++++++++++++++++++++++++++++++++
>>  net/ipv4/icmp.c             |  4 +++
>>  2 files changed, 69 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..7d5190f48a28
>> --- /dev/null
>> +++ b/include/trace/events/icmp.h
>> @@ -0,0 +1,65 @@
>> +/* 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 =3D ip_hdr(skb);
>> +                       int proto_4 =3D iph->protocol;
>> +                       __be32 *p32;
>> +
>> +                       __entry->skbaddr =3D skb;
>> +                       __entry->type =3D type;
>> +                       __entry->code =3D code;
>> +
>> +                       struct udphdr *uh =3D udp_hdr(skb);
>> +                       if (proto_4 !=3D IPPROTO_UDP || (u8 *)uh < skb->h=
>ead ||
>> +                               (u8 *)uh + sizeof(struct udphdr) > skb_ta=
>il_pointer(skb)) {
>> +                               __entry->sport =3D 0;
>> +                               __entry->dport =3D 0;
>> +                               __entry->ulen =3D 0;
>> +                       } else {
>> +                               __entry->sport =3D ntohs(uh->source);
>> +                               __entry->dport =3D ntohs(uh->dest);
>> +                               __entry->ulen =3D ntohs(uh->len);
>> +                       }
>> +
>> +                       p32 =3D (__be32 *) __entry->saddr;
>> +                       *p32 =3D iph->saddr;
>> +
>> +                       p32 =3D (__be32 *) __entry->daddr;
>> +                       *p32 =3D iph->daddr;
>> +               ),
>> +
>> +               TP_printk("icmp_send: type=3D%d, code=3D%d. From %pI4:%u =
>to %pI4:%u ulen=3D%d skbaddr=3D%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 8cebb476b3ab..224551d75c02 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, in=
>t code, __be32 info,
>>                 }
>>         }
>>
>> +       trace_icmp_send(skb_in, type, code);
>> +
>>         /* Needed by both icmp_global_allow and icmp_xmit_lock */
>>         local_bh_disable();
>>
>> --
>> 2.25.1