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From: Lee Eric <openlinuxsource@gmail.com>
To: systemtap@sourceware.org
Subject: Question about udp.sendmsg / udp.recvmsg
Date: Wed, 15 Jul 2020 21:01:32 -0700	[thread overview]
Message-ID: <CAOJJ1Zry9LKLTZ-qwr4JkBnsc_xNLfRux6iwQ3_MvRZaKkcO3g@mail.gmail.com> (raw)

Hi,

I have a quick question about what udp.sendmsg captures. I wrote a
small script to capture all processes are sending / receiving UDP
packets:

#!/usr/bin/env stap

probe udp.sendmsg {
printf("Req - time: [%s] pid: [%d] cmd: [%s] %s:%d => %s:%d\n",
ctime(gettimeofday_s()), pid(), execname(), saddr, sport, daddr,
dport)
}

probe udp.recvmsg {
printf("Resp - time: [%s] pid: [%d] cmd: [%s] %s:%d => %s:%d\n",
ctime(gettimeofday_s()), pid(), execname(), daddr, dport, saddr,
sport)
}

So I also triggered tcpdump to capture UDP traffic. I noticed the
systemtap shows some udp.sendmsg / udp.recvmsg probes are triggered
but there's no request on tcpdump side. So what possible reason can
cause this behavior? Is that normal?

Thanks.

Eric

                 reply	other threads:[~2020-07-16  4:01 UTC|newest]

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