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perfsonar / owamp

A tool for performing one-way or two-way active measurements
Apache License 2.0
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twamp: test packet size too small #31

Closed vvidic closed 6 years ago

vvidic commented 6 years ago

Packet size should be the same in both directions (41 bytes if no padding), but we are sending much less in request packets:

23:00:06.435012 IP 193.198.241.30.20862 > 193.62.143.100.20862: UDP, length 14
23:00:06.471514 IP 193.62.143.100.20862 > 193.198.241.30.20862: UDP, length 41
23:00:06.471593 IP 193.198.241.30.20862 > 193.62.143.100.20862: UDP, length 14
23:00:06.508119 IP 193.62.143.100.20862 > 193.198.241.30.20862: UDP, length 41
23:00:06.564528 IP 193.198.241.30.20862 > 193.62.143.100.20862: UDP, length 14
23:00:06.601050 IP 193.62.143.100.20862 > 193.198.241.30.20862: UDP, length 41
23:00:06.602768 IP 193.198.241.30.20862 > 193.62.143.100.20862: UDP, length 14
23:00:06.639293 IP 193.62.143.100.20862 > 193.198.241.30.20862: UDP, length 41

This is causing the wireshark dissector to report these as malformed packets.

vvidic commented 6 years ago

It seems the packets are not the same in the end. Client sents OWAMP-Test (size 14) and the server replies with TWAMP-Test (size 41). However the RFC5357 says the smaller packets may be padded in order to get the same size in both directions:

   Note that the Reflector test packet formats are larger than the
   Sender's formats.  The Session-Sender MAY append sufficient Packet
   Padding to allow the same IP packet payload lengths to be used in
   each direction of transmission (this is usually desirable).  To
   compensate for the Reflector's larger test packet format, the Sender
   appends at least 27 octets of padding in unauthenticated mode, and at
   least 56 octets in authenticated and encrypted modes.

The code for padding was already there but did not work correctly because auth mode was not set correctly.

laeti-tia commented 6 years ago

This needs to be properly tested with OWAMP deployments too.

vvidic commented 6 years ago

From my testing the packet size for owping does not change from 14 by this patch:

12:13:11.753677 IP 161.53.160.238.9747 > 193.198.241.30.9006: UDP, length 14
12:13:11.758480 IP 161.53.160.238.9747 > 193.198.241.30.9006: UDP, length 14
12:13:11.763926 IP 161.53.160.238.9747 > 193.198.241.30.9006: UDP, length 14
12:13:11.849438 IP 161.53.160.238.9747 > 193.198.241.30.9006: UDP, length 14
laeti-tia commented 6 years ago

Ok, thanks for the tests, that is already a good sign. What we also need to check is that the different authentication modes are still working fine. IIRC @erik-geant had added unit tests about that, but we also need to test it between 2 real (O|T)WAMP instances.

arlake228 commented 6 years ago

Can this be closed? It appears to have been merged and we have seen no issues with TWAMP.

erik-geant commented 6 years ago

yes, the unit test are still passing ... closing