From: Stephen Hemminger <stephen@networkplumber.org>
To: netdev@vger.kernel.org
Subject: Fw: [Bug 220766] New: Packets dessapear
Date: Fri, 7 Nov 2025 08:13:24 -0800 [thread overview]
Message-ID: <20251107081324.3ab69917@phoenix> (raw)
Begin forwarded message:
Date: Fri, 07 Nov 2025 15:47:37 +0000
From: bugzilla-daemon@kernel.org
To: stephen@networkplumber.org
Subject: [Bug 220766] New: Packets dessapear
https://bugzilla.kernel.org/show_bug.cgi?id=220766
Bug ID: 220766
Summary: Packets dessapear
Product: Networking
Version: 2.5
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P3
Component: Other
Assignee: stephen@networkplumber.org
Reporter: wads31566@gmail.com
Regression: No
Created attachment 308921
--> https://bugzilla.kernel.org/attachment.cgi?id=308921&action=edit
Network topology
A network hierarchy (network_topo.png) implementation with namespace and TC get
packets lost unexpectedly.
Linux namespaces(created via "ip netns") and connected via veths to a single
bridge inside of the root-namespace. For setting up a veth settings TC is used
like that:
"$CLI tc qdisc add dev veth-${TARGET} root handle 1: netem delay ${DELAY_MS}ms
${DELAY_DISTRIBUTION_MS}ms distribution normal
$CLI tc qdisc add dev veth-${TARGET} parent 1: handle 2: netem loss 0 rate
100Mbit corrupt 1% duplicate 1%"
At this case, where we have a non-zero delay and banwidth limit. And when both
of those attributes are set it produces some packet-loss, i.e. packets are
counted as sent on the client namespace link statistics, but the received
amount of packets on the client side is always various and real loss percentage
is different from defined one. Usually the loss is about 3-7%.
Loss is counted as a servers-bridge sum of received packets and sum of packets
sent from the namespace link statistics.
But when only delay and no other netem params used - it works fine.
Mine assumption is that is becomes a bug, when several params are used.
Uname: Linux 6.14.0-35-generic #35-Ubuntu SMP PREEMPT_DYNAMIC Sat Oct 11
10:06:31 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
tc -V: tc utility, iproute2-6.14.0, libbpf 1.5.0
Distros: kubuntu, openSUSE Tumbleweed
As a traffic generator iPerf3 was used.
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