Traffic "corruption" in 12-stable

[Mark Johnston]

On Sun, Jul 26, 2020 at 06:16:07PM -0400, Joe Clarke wrote:
> About two weeks ago, I upgraded from the latest 11-stable to the latest 12-stable.  After that, I periodically see the network throughput come to a near standstill.  This FreeBSD machine is an ESXi VM with two interfaces.  It acts as a router.  It uses vmxnet3 interfaces for both LAN and WAN.  It runs ipfw with in-kernel NAT.  The LAN side uses a bridge with vmx0 and a tap0 L2 VPN interface.  My LAN side uses an MTU of 9000, and my vmx1 (WAN side) uses the default 1500.
> 
> Besides seeing massive packet loss and huge latency (~ 200 ms for on-LAN ping times), I know the problem has occurred because my lldpd reports:
> 
> Jul 26 15:47:03 namale lldpd[1126]: frame too short for tlv received on bridge0
> 
> And if I turn on ipfw verbose messages, I see tons of:
> 
> Jul 26 16:02:23 namale kernel: ipfw: pullup failed
> 
> This leads to me to believe packets are being corrupted on ingress.  I’ve applied all the recent iflib changes, but the problem persists. What causes it, I don’t know.
> 
> The only thing that changed (and yes, it’s a big one) is I upgraded to 12-stable.  Meaning, the rest of the network infra and topology has remained the same.  This did not happen at all in 11-stable.
> 
> I’m open to suggestions.

There are some fixes for vmx not present in stable/12 (yet).  I did a
merge of a number of outstanding revisions.  Would you be able to test
the patch?  I haven't observed any problems with it on a host using igb,
but I have no ability to test vmx at the moment.

https://people.freebsd.org/~markj/patches/iflib-stable12.diff