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From: Peilin He <peilinhe2020@163.com>
To: kerneljasonxing@gmail.com
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	zhang.yunkai@zte.com.cn
Subject: Re: Re: Re: Subject: [PATCH net-next v4] net/ipv4: add tracepoint for icmp_send
Date: Thu, 11 Apr 2024 02:33:16 +0000
Message-Id: <20240411023316.137800-1-peilinhe2020@163.com>
In-Reply-To: <CAL+tcoC0wRbXfFziaXzvP9wuw4Qe6tZj5QRxbUhAcW5Np6kEgw@mail.gmail.com>
References: <CAL+tcoC0wRbXfFziaXzvP9wuw4Qe6tZj5QRxbUhAcW5Np6kEgw@mail.gmail.com>
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>[...]
>> >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.
>
>I'm not against what you did (tracing all the icmp_send() for UDP) in
>your original patch. I was suggesting that you could put
>trace_icmp_send() in the right place, then you don't have to check the
>possible error condition (like if the skb->head is valid or not, ...)
>in your trace function.
>
>One example that can avoid various checks existing in the
>__icmp_send() function:
>diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
>index e63a3bf99617..2c9f7364de45 100644
>--- a/net/ipv4/icmp.c
>+++ b/net/ipv4/icmp.c
>@@ -767,6 +767,7 @@ void __icmp_send(struct sk_buff *skb_in, int type,
>int code, __be32 info,
>        if (!fl4.saddr)
>                fl4.saddr = htonl(INADDR_DUMMY);
>
>+       trace_icmp_send(skb_in, type, code);
>        icmp_push_reply(sk, &icmp_param, &fl4, &ipc, &rt);
> ende:
>        ip_rt_put(rt);
>
>If we go here, it means we are ready to send the ICMP skb because
>we're done extracting the right information in the 'struct sk_buff
>skb_in'. Simpler and easier, right?
>
>Thanks,
>Jason

I may not fully agree with this viewpoint. When trace_icmp_send is placed
in this position, it cannot guarantee that all skbs in icmp are UDP protocols
(UDP needs to be distinguished based on the proto_4!=IPPROTO_UDP condition),
nor can it guarantee the legitimacy of udphdr (*uh legitimacy check is required).

With best wishes
Peilin He

>>
>> >> 2.Target this patch for net-next.
>> >>
>> >> 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=3DsZtRnKRu_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>
>> >> ---
>> >>  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