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[NOAAPORT #HTM-284378]: NOAAPort UDP Bad Length

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  • Subject: [NOAAPORT #HTM-284378]: NOAAPort UDP Bad Length
  • Date: Fri, 20 Apr 2018 09:36:57 -0600
Hi Justin,

re:
> I am trying to diagnose an issue where tcpdump is showing a ton of bad
> length messages for anything over the MTU or 1472 with the NOAAPort UDP
> broadcast. A similar reference is NOAAPORT #YJE-806765.
> 
> I have added the recommended changes of these settings (below) to the sysctl.
> 
> sysctl -w net.ipv4.ipfrag_max_dist=4096
> sysctl -w net.ipv4.conf.default.rp_filter=2

We are using something close, but slightly different:

#
# Enable DVBS reception
#
net.ipv4.conf.default.rp_filter = 2

#
# DVBS multicast fragment reassembly 
#
net.ipv4.ipfrag_max_dist = 0

re:
> SELINUX is also disabled.

OK.

re:
> Any ideas on what I may be doing incorrectly for the config?

Nothing that I can see.

re:
> Sample tcpdump reports (below).
> 
> 10:44:38.506979 IP 10.0.9.51.52171 > 224.0.1.10.eoss: UDP, bad length 4032 > 
> 1472
> 10:44:38.507112 IP 10.0.9.51 > 224.0.1.10: ip-proto-17
> 10:44:38.507196 IP 10.0.9.51 > 224.0.1.10: ip-proto-17
> 10:44:38.507348 IP 10.0.9.51.52171 > 224.0.1.10.eoss: UDP, bad length 4032 > 
> 1472
> 10:44:38.507544 IP 10.0.9.51 > 224.0.1.10: ip-proto-17
> 10:44:38.507628 IP 10.0.9.51 > 224.0.1.10: ip-proto-17
> 10:44:38.507809 IP 10.0.9.51.52171 > 224.0.1.10.eoss: UDP, bad length 4032 > 
> 1472
> 10:44:38.507970 IP 10.0.9.51 > 224.0.1.10: ip-proto-17

Questions:

- are you using the Novra S300N receiver?

- if yes, what version of the firmware are you running?

- again if yes, what does your Novra report for:

  Uncorrectable Rate:
  Packet Error Rate:

  and

  Carrier to Noise C/N:


Cheers,

Tom
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Ticket Details
===================
Ticket ID: HTM-284378
Department: Support NOAAPORT
Priority: Normal
Status: Closed
===================
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