Received-SPF: pass (google.com: domain of linux-kernel+bounces-138585-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Precedence: bulk
MIME-Version: 1.0
References: <CAL+tcoAcagGKkzJLrgCmFRv52uBbdAN_ufspvmkbG2MaFw2_tQ@mail.gmail.com>
 <20240410121605.132052-1-peilinhe2020@163.com>
In-Reply-To: <20240410121605.132052-1-peilinhe2020@163.com>
From: Jason Xing <kerneljasonxing@gmail.com>
Date: Wed, 10 Apr 2024 21:19:05 +0800
Message-ID: <CAL+tcoC0wRbXfFziaXzvP9wuw4Qe6tZj5QRxbUhAcW5Np6kEgw@mail.gmail.com>
Subject: Re: Re: Subject: [PATCH net-next v4] net/ipv4: add tracepoint for icmp_send
To: Peilin He <peilinhe2020@163.com>
Cc: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, 
	fan.yu9@zte.com.cn, he.peilin@zte.com.cn, jiang.xuexin@zte.com.cn, 
	kuba@kernel.org, linux-kernel@vger.kernel.org, 
	linux-trace-kernel@vger.kernel.org, liu.chun2@zte.com.cn, mhiramat@kernel.org, 
	netdev@vger.kernel.org, qiu.yutan@zte.com.cn, rostedt@goodmis.org, 
	xu.xin16@zte.com.cn, yang.yang29@zte.com.cn, zhang.yunkai@zte.com.cn
Content-Type: text/plain; charset="UTF-8"

[...]
> >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

>
> >> 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
>
>