Comment 20 for bug 1252900
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| Darragh O'Reilly (darragh-oreilly) wrote | #20 |
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bbfa235
(Get the code!)
Hi GMi, what issue are you referring to? The bug reporter has confirmed that disabling GRO resolves the issue that this bug report is for.
The attached tcpdump shows packets of size greater than 1514 bytes. These hardly came from the Internet site. The internal Neutron network has a smaller MTU on its interfaces, so the Neutron router is not able to forward these large packets properly. TCP on the endpoints struggles to get the job done in spite of this.
TCP is an end-to-end protocol. GRO is okay if the interface is for TCP endpoints - that is why the Squid experiment worked. But the interface in br-ex is for a Neutron router which is not a TCP endpoint. So GRO on this interface interfers and hinders end-to-end TCP comms. Even though I have not tried to recreate this myself, I am confident that this is the root cause.
I don't know why you don't see this problem. Maybe it is your kernel level or nic/driver.