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DSCP values are dropped on egress #300
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If you google for 'DSCP trust' you will find various discussions around this. Apparently there is a general configuration that a switch removes DSCP bits while a router should pass them unchanged. |
I guess the points here would then be 1) document that BISDN Linux comes with this DSCP trust feature disabled by default, and 2) have DSCP trust configurable in the switch as a feature. Still, I do find odd that a plain L2 bridge configuration ends up with this behavior by default. |
Expected Behavior
Whenever packets marked with a DSCP value arrive to the switch its value should be preserved on egress, if there are no specific forwarding rules that explicitly change this behavior.
Actual Behavior
Packets marked with a DSCP value have their DSCP value set to 0 on egress.
Steps to Reproduce the Problem
Switch configuration
On the switch, configure a bridge with two ports:
Server
In this example,
enp8s0f0np0
is connected toport7
andenp8s0f1np1
toport8
on the switch, respectively.Terminal 1
Install iperf3, setup 2 namespaces, assign IP addresses. and start iperf3 server on
ns0
:Terminal 2
Start traffic capture on
ns0
:Terminal 3
Start traffic capture on
ns1
:Terminal 4
Start iperf3 client on
ns1
setting the DSCP value with the--dscp
option:Observable results
The terminal capturing traffic on
ns0
will show the DSCP value set to 0 on all packets. Onns1
, it is possible to observe the configured value on thetos
field:Terminal 2
Terminal 3
Specifications
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