-current network buffer exhaustion on RPi2 armv7

From time to time a Raspberry Pi 2 v1.1 (armv7) running -current reports

Feb 16 08:23:34 generic syslogd: last message repeated 1 times, op=20, val=0, arg_len=7]: Can't assign requested address send_packet: No buffer space available
(I think the numerical values repeat, but I'm not certain of it)

In this case, the ethernet network (via a usb-wifi adapter) remained up:

root@generic:/usr/src # ping 192.168.1.254
PING 192.168.1.254 (192.168.1.254): 56 data bytes
64 bytes from 192.168.1.254: icmp_seq=0 ttl=64 time=4.406 ms
64 bytes from 192.168.1.254: icmp_seq=1 ttl=64 time=4.101 ms
64 bytes from 192.168.1.254: icmp_seq=2 ttl=64 time=3.989 ms
64 bytes from 192.168.1.254: icmp_seq=3 ttl=64 time=4.186 ms
64 bytes from 192.168.1.254: icmp_seq=4 ttl=64 time=4.119 ms
64 bytes from 192.168.1.254: icmp_seq=5 ttl=64 time=3.948 ms
64 bytes from 192.168.1.254: icmp_seq=6 ttl=64 time=4.478 ms
64 bytes from 192.168.1.254: icmp_seq=7 ttl=64 time=5.119 ms
64 bytes from 192.168.1.254: icmp_seq=8 ttl=64 time=4.417 ms
^C
--- 192.168.1.254 ping statistics ---
9 packets transmitted, 9 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 3.948/4.307/5.119/0.339 ms

Anybody have an idea what the machine is complaining about? 
At the time of these observations the machine was running a
-j4 buildworld with about 500M of swap in use. Within a few
minutes swap use declined to ~70M and no further complaints
were reported.

The ethernet adapter is a
ugen0.5: <RT5370 Wireless Adapter Ralink Technology, Corp.> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (450mA)
running on a powered hub, together with the root device, a usb-sata 
mechanical hard disk drive. 

Could this be indicative of a conflict or traffic jam between the
root device and the network by way of USB?

Thanks for reading,

bob prohaska