This is a simple user-level networking environment which uses
the VFIO driver to map various network devices directly into 
the user address space.

*Nothing about the code should be considered anything but prototype and/or
demonstration quality.*

Each mapped device or virtual device has its own MAC address, and should
be assigned its own IP address using the ULD_IP environment variable.

The udpecho program can generate or respond to UDP echo datagrams on port 7.

The uldcap programs can capture packets ala tcpdump and can pipe directly
to tcpdump for decoding:
	./uldcap | tcpdump -r -

The threcho programs exercises the multi-threading support in the code by
having any number of simultaneous threads sending udp echo messages.

The uldmap program just attempts to map for DMA a buffer to verify that
the VFIO driver is working.

Common environment variables for all programs:

ULD_PCI=xx:xx.x
	The PCI device address of the device to be used. Must be previously
	bound to the VFIO driver.

ULD_IP=a.b.c.d
	The IPv4 address to use. Not needed for uldcap.

ULD_GW=e.f.g.h
	The IPv4 gateway address for non-local traffic.
	Defaults to host 1 on the subnet.

ULD_NETMASK=m.m.m.m
	The IPv4 net mask. Defaults to 255.255.255.0

If attempting to run these programs as non-root, you'll need to make sure
that /dev/uiommu and /dev/vfio* are accessible, and you'll need to crank up
the lockable page limit (ulimit -l) to whatever the underlying device
driver needs

The most accessible hardware to try this out on is the Intel 82576 PCIe card,
part number E1G42ET.  Beware - not all 82576 chips support SR-IOV, which is what
this driver depends on.

For those blessed with 10 Gigabit Ethernet, the Intel 82599 works (not 82598), also
in SR-IOV mode.

SR-IOV can be a pain to get working - many BIOSes don't do the right thing. And for
the Intel drivers, the corresponding physical driver/link must be brought "UP"
before the VF drivers will work.

Lastly, the code works with the Cisco "Palo" adapters - only available in Cisco
servers.