Possible -HEAD problem with the Pi3 onboard ethernet

[Karl Denninger]

Update: This MAY be caused by net.inet.tcp.rfc6675_pipe=1, which I had
recently enabled since I am now moving data over WAN-style distances on
a regular basis and since both ends are FreeBSD with this capability I
figured it might help performance.

If so it almost-certainly isn't ARM-specific...... I shut that off (it
was recently turned on) and thus far I'm not able to recreate the
network hangs....

Hmmmm... CCing into freebsd-net, as this is looking increasingly like a
non-ARM-specific thing.  Feel free to remove freebsd-arm from responses
(in fact, probably ought to unless someone can confirm it's working
properly on other architectures but not on ARM.)


On 5/12/2017 12:45, Karl Denninger wrote:
> Under fairly heavy stress (~50% of the 100Mbps possible FDX performance)
> I've now run into a problem that is turning into something I can repeat
> without too much trouble by transmitting a large file through the device.
>
> The system appears to "crash" from the outside.  It's not dead, however
> -- it's got some sort of network buffer hang going on.  This is a Pi3
> with current (-HEAD, FreeBSD 12.0-CURRENT #0 r318193M: Thu May 11
> 16:18:20 CDT 2017) software on it -- reverting to a mid-March kernel did
> NOT change the behavior.
>
> The symptomology is that the unit will start printing this on the console:
>
> May 12 12:25:46 IPGw dhcpd: send_packet: No buffer space available
> May 12 12:25:46 IPGw dhcpd: dhcp.c:3974: Failed to send 300 byte long
> packet over ue0.3 interface.
>
> ue0.3 is a VLAN for a private subnet and is not specific to the issue;
> it also complains about no space on the primary too:
>
> May 12 12:27:06 IPGw dhcpd: dhcp.c:3974: Failed to send 300 byte long
> packet over ue0 interface.
> May 12 12:27:13 IPGw dhcpd: send_packet: No buffer space available
>
> netstat -m does /not /show any denied or delayed requests for network
> buffers or mbuf exhaustion.  Systat -vm shows plenty of RAM available
> (roughly half.)
>
> An ifconfig ue0 down / ifconfig ue0 up sequence from the console clears
> the hang.
>
> Has anyone else seen anything similar to this?
>

-- 
Karl Denninger
karl at denninger.net <mailto:karl at denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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