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 <20240411023316.137800-1-peilinhe2020@163.com>
In-Reply-To: <20240411023316.137800-1-peilinhe2020@163.com>
From: Jason Xing <kerneljasonxing@gmail.com>
Date: Thu, 11 Apr 2024 11:02:05 +0800
Message-ID: <CAL+tcoDS6yGAP0UqN9YCSzB2zSUz5b7Vmh+M7Gk-k3SZdmfj1Q@mail.gmail.com>
Subject: Re: 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
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On Thu, Apr 11, 2024 at 10:34=E2=80=AFAM Peilin He <peilinhe2020@163.com> w=
rote:
>
> >[...]
> >> >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 =3D 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 proto=
cols
> (UDP needs to be distinguished based on the proto_4!=3DIPPROTO_UDP condit=
ion),
> nor can it guarantee the legitimacy of udphdr (*uh legitimacy check is re=
quired).

Of course, the UDP test statement is absolutely needed! Eric
previously pointed this out in the V1 patch thread. I'm not referring
to this one but like skb->head check something like this which exists
in __icmp_send() function. You can see there are so many checks in it
before sending.

So only keeping the UDP check is enough, I think.

Thanks,
Jason

>
> 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.h=
ome/
> >> >> 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=3D3DsZtRnKRu_tnUwqHu=
FQTJvJsv=3D
> >> >-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/icm=
p.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 c=
ode),
> >> >> +
> >> >> +               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 =3D3D ip_hdr(skb);
> >> >> +                       int proto_4 =3D3D iph->protocol;
> >> >> +                       __be32 *p32;
> >> >> +
> >> >> +                       __entry->skbaddr =3D3D skb;
> >> >> +                       __entry->type =3D3D type;
> >> >> +                       __entry->code =3D3D code;
> >> >> +
> >> >> +                       struct udphdr *uh =3D3D udp_hdr(skb);
> >> >> +                       if (proto_4 !=3D3D IPPROTO_UDP || (u8 *)uh =
< skb->h=3D
> >> >ead ||
> >> >> +                               (u8 *)uh + sizeof(struct udphdr) > =
skb_ta=3D
> >> >il_pointer(skb)) {
> >> >> +                               __entry->sport =3D3D 0;
> >> >> +                               __entry->dport =3D3D 0;
> >> >> +                               __entry->ulen =3D3D 0;
> >> >> +                       } else {
> >> >> +                               __entry->sport =3D3D ntohs(uh->sour=
ce);
> >> >> +                               __entry->dport =3D3D ntohs(uh->dest=
);
> >> >> +                               __entry->ulen =3D3D ntohs(uh->len);
> >> >> +                       }
> >> >> +
> >> >> +                       p32 =3D3D (__be32 *) __entry->saddr;
> >> >> +                       *p32 =3D3D iph->saddr;
> >> >> +
> >> >> +                       p32 =3D3D (__be32 *) __entry->daddr;
> >> >> +                       *p32 =3D3D iph->daddr;
> >> >> +               ),
> >> >> +
> >> >> +               TP_printk("icmp_send: type=3D3D%d, code=3D3D%d. Fro=
m %pI4:%u =3D
> >> >to %pI4:%u ulen=3D3D%d skbaddr=3D3D%p",
> >> >> +                       __entry->type, __entry->code,
> >> >> +                       __entry->saddr, __entry->sport, __entry->da=
ddr,
> >> >> +                       __entry->dport, __entry->ulen, __entry->skb=
addr)
> >> >> +);
> >> >> +
> >> >> +#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 ty=
pe, in=3D
> >> >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
>
>