We require the ability to disconnect from and reconnect to VMBus; if
we don't have this then there is no (viable) way for a loaded
operating system to continue to use any VMBus devices. (There is also
a small but non-zero risk that the host will continue to write to our
interrupt and monitor pages, since the VMBUS_UNLOAD message in earlier
versions is essentially a no-op.)
This requires us to ensure that the host supports protocol version 3.0
(VMBUS_VERSION_WIN8_1). However, we can't actually _use_ protocol
version 3.0, since doing so causes an iSCSI-booted Windows Server 2012
R2 VM to crash due to a NULL pointer dereference in vmbus.sys.
To work around this problem, we first ensure that we can connect using
protocol v3.0, then disconnect and reconnect using the oldest known
protocol.
This deliberately prevents the use of the iPXE native Hyper-V drivers
on older versions of Hyper-V, where we could use our drivers but in so
doing would break the loaded operating system.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Windows Server 2012 R2 generates an RNDIS_INDICATE_STATUS_MSG with a
status code of 0x4002006. This status code does not appear to be
documented anywhere within the sphere of human knowledge.
Explicitly ignore this status code in order to avoid unnecessarily
cluttering the display when RNDIS debugging is enabled.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The (undocumented) VMBus protocol seems to allow for transfer
page-based packets where the data payload is split into an arbitrary
set of ranges within the transfer page set.
The RNDIS protocol includes a length field within the header of each
message, and it is known from observation that multiple RNDIS messages
can be concatenated into a single VMBus message.
iPXE currently assumes that the transfer page range boundaries are
entirely arbitrary, and uses the RNDIS header length to determine the
RNDIS message boundaries.
Windows Server 2012 R2 generates an RNDIS_INDICATE_STATUS_MSG for an
undocumented and unknown status code (0x40020006) with a malformed
RNDIS header length: the length does not cover the StatusBuffer
portion of the message. This causes iPXE to report a malformed RNDIS
message and to discard any further RNDIS messages within the same
VMBus message.
The Linux Hyper-V driver assumes that the transfer page range
boundaries correspond to RNDIS message boundaries, and so does not
notice the malformed length field in the RNDIS header.
Match the behaviour of the Linux Hyper-V driver: assume that the
transfer page range boundaries correspond to the RNDIS message
boundaries and ignore the RNDIS header length. This avoids triggering
the "malformed packet" error and also avoids unnecessary data copying:
since we now have one I/O buffer per RNDIS message, there is no longer
any need to use iob_split().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Empirical observation suggests that 32 is a sensible size to minimise
the number of deferred packet transmissions without overflowing the
VMBus transmit ring buffer.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow for elision of transmitted TCP ACKs by handling all received
VMBus messages in each network device poll operation.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
On Windows Server 2012 R2, closing and reopening the device will
sometimes result in a non-functional RX datapath. The root cause is
unknown. Clearing the receive filter before closing the device seems
to fix the problem.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
On Windows Server 2012 R2, the receive buffer teardown completion
message seems to occasionally be deferred until after the VMBus
channel has been closed. This happens even if there are no packets
currently in the receive buffer.
Work around this problem by separating the revocation and teardown of
the receive buffer, and deferring the teardown until after the VMBus
channel has been closed.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The Hyper-V RNDIS implementation on Windows Server 2012 R2 requires
that we send an explicit RNDIS initialisation message in order to get
a working RX datapath.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
RNDIS devices may provide multiple packets encapsulated into a single
message. Provide an API to allow the RNDIS driver to split an I/O
buffer into smaller portions.
The current implementation will always copy the underlying data,
rather than splitting the buffer in situ.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Check the integrity of the free memory block list before and after any
modifications to the list. We check that certain invariants are
preserved:
- the list is a well-formed doubly linked list
- all blocks are at least MIN_MEMBLOCK_SIZE
- no block extends beyond the end of our address space
- blocks remain sorted in ascending order of address
- no blocks are adjacent (i.e. any adjacent blocks have been merged)
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We currently compare the entirety of the KeyHash object (including the
ASN.1 tag and length byte) against the raw SHA-1 hash of the
certificate's public key. This causes OCSP validation to fail for any
responses which identify the responder by key hash rather than by
name, and hence prevents the use of X.509 certificates where any
certificate in the chain has an OCSP responder which chooses to
identify itself via its key hash.
Fix by adding the missing asn1_enter() required to enter the ASN.1
octet string containing the key hash.
Also add a corresponding test case including an OCSP response where
the responder is identified by key hash, to ensure that this
functionality cannot be broken in future.
Debugged-by: Brian Rak <brak@gameservers.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The i350 (and possibly other Intel NICs) have a non-trivial
correspondence between the PCI function number and the external
physical port number. For example, the i350 has a "LAN Function Sel"
bit within the EEPROM which can invert the mapping so that function 0
becomes port 3, function 1 becomes port 2, etc.
Unfortunately the MAC addresses within the EEPROM are indexed by
physical port number rather than PCI function number. The end result
is that when anything other than the default mapping is used, iPXE
will use the wrong address as the base MAC address.
Fix by using the autoloaded MAC address if it is valid, and falling
back to reading the MAC address directly from the EEPROM only if no
autoloaded address is available.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add the "-c <count>" option to the "ping" command, allowing for
automatic termination after a specified number of packets.
When a number of packets is specified:
- if a serious error (i.e. length mismatch or content mismatch)
occurs, then the ping will be immediately terminated with the relevant
status code;
- if at least one response is received successfully, and all errors
are non-serious (i.e. timeouts or out-of-sequence responses), then
the ping will be terminated after the final response (or timeout)
with a success status;
- if no responses are received successfully, then the ping will be
terminated after the final timeout with ETIMEDOUT.
If no number of packets is specified, then the ping will continue
until manually interrupted.
Originally-implemented-by: Cedric Levasseur <cyr-ius@ipocus.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
End users almost certainly don't care whether the underlying interface
is SNP or NII/UNDI. Try to minimise surprise and unnecessary
documentation by including the NII driver whenever the SNP driver is
requested.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
iPXE itself exposes a dummy NII protocol with no UNDI. Avoid
potentially dereferencing a NULL pointer by checking for a non-zero
UNDI address.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some UEFI network drivers provide a software UNDI interface which is
exposed via the Network Interface Identifier Protocol (NII), rather
than providing a Simple Network Protocol (SNP).
The UEFI platform firmware will usually include the SnpDxe driver,
which attaches to NII and provides an SNP interface. The SNP
interface is usually provided on the same handle as the underlying NII
device. This causes problems for our EFI driver model: when
efi_driver_connect() detaches existing drivers from the handle it will
cause the SNP interface to be uninstalled, and so our SNP driver will
not be able to attach to the handle. The platform firmware will
eventually reattach the SnpDxe driver and may attach us to the SNP
handle, but we have no way to prevent other drivers from attaching
first.
Fix by providing a driver which can attach directly to the NII
protocol, using the software UNDI interface to drive the network
device.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The snpnet driver uses netdev_tx_defer() and so must ensure that space
in the (single-entry) transmit descriptor ring is freed up before
calling netdev_tx_complete().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The EDK2 codebase uses -malign-double for 32-bit builds, which causes
64-bit integers to be naturally aligned. This affects the layout of
some structures (including EFI_BLOCK_IO_MEDIA).
This mirrors wimboot commit 7b8f39d ("[build] Fix building of 32-bit
UEFI version").
Signed-off-by: Michael Brown <mcb30@ipxe.org>
As of commit 03f0c23 ("[ipoib] Expose Ethernet-compatible eIPoIB
link-layer addresses and headers"), all link layers have used
addresses which fit within the DHCP chaddr field. The dhcp_chaddr()
function was therefore made obsolete by this commit, but was
accidentally left present (though unused) in the source code.
Remove the dhcp_chaddr() function and the only remaining use of it,
unnecessarily introduced in commit 08bcc0f ("[dhcp] Check for matching
chaddr in received DHCP packets").
Reported-by: Wissam Shoukair <wissams@mellanox.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
On large networks a DHCP XID collision is possible. Fix by explicitly
checking the chaddr in received DHCP packets.
Originally-fixed-by: Wissam Shoukair <wissams@mellanox.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some UEFI platforms will fail the call to LoadImage() with
EFI_INVALID_PARAMETER if we do not provide a device path (even though
we are providing a non-NULL SourceBuffer).
Fix by providing an empty device path for the call to LoadImage() in
efi_image_probe().
The call to LoadImage() in efi_image_exec() already constructs and
provides a device path (based on the most recently opened SNP device),
and so does not require this fix.
Reported-by: NICOLAS CATTIE <nicolas.cattie@mpsa.com>
Tested-by: NICOLAS CATTIE <nicolas.cattie@mpsa.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add the ID for the LM variant and differentiate it from the I217-V.
Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add utility for constructing EFI fat binaries (dual 32/64-bit
binaries, usable only on Apple EFI systems).
This utility is not part of the standard build process. To use it:
make util/efifatbin bin-i386-efi/ipxe.efi bin-x86_64-efi/ipxe.efi
and then
./util/efifatbin bin-*-efi/ipxe.efi fat-ipxe.efi
Requested-by: Brandon Penglase <bpenglase-ipxe@spaceservices.net>
Tested-by: Brandon Penglase <bpenglase-ipxe@spaceservices.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow a straightforward "make clean" or "make veryclean" to apply to
all binary directories (using the shell pattern "bin{,-*}").
Individual binary directories can be cleaned using e.g.
make bin clean
make bin-x86_64-efi clean
Reported-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We currently require information about the underlying PCI device to
populate the snpnet device's name and description. If the underlying
device is not a PCI device, this will fail and prevent the device from
being registered.
Fix by falling back to populating the device description with
information based on the EFI handle, if no PCI device information is
available.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some UEFI systems (observed with a Hyper-V virtual machine) do not
provide EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL. Make this an optional
protocol (and fail any attempts to access PCI configuration space via
the root bridge if the protocol is missing).
Reported-by: Colin Blacker <Colin.Blacker@computerplanet.co.uk>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Under UEFI, reads from PCI configuration space may fail. If this
happens, we should return all-ones (which will mimic the behaviour of
an absent PCI device).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some systems will install a child of the SNP device and use this as
our loaded image's device handle, duplicating the installation of the
underlying SNP protocol onto the child device handle. On such
systems, we want to end up driving the parent device (and
disconnecting any other drivers, such as MNP, which may be attached to
the parent device).
Fix by recording the SNP protocol instance at initialisation time, and
using this to match against device handles (rather than simply
comparing the handles themselves).
Reported-by: Jarrod Johnson <jarrod.b.johnson@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Propagate our modified EFI system table to any images loaded by the
image that we wrap, thereby allowing us to observe boot services calls
made by all subsequent EFI images.
Also show details of intercepted ExitBootServices() calls. When
wrapping is used, exiting boot services will almost certainly fail,
but this at least allows us to see when it happens.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The .mrom payload has a code type of 0xff and so the initialisation
length field (single byte at offset 0x02) does not need to be
present. Use only the PCI header's image length field, which allows
the .mrom payload to be up to 32MB in size.
Inspired-by: Swift Geek <swiftgeek@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
mromprefix.S currently uses the initialisation length field (single
byte at offset 0x02) to determine the length of a ROM image within a
multi-image ROM BAR. For PCI ROM images with a code type other than
0, the initialisation length field may not be present.
Fix by using the PCI header's image length field instead.
Inspired-by: Swift Geek <swiftgeek@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Option::ROM currently uses the initialisation length field (single
byte at offset 0x02) to determine the length of a ROM image within a
multi-image ROM file. For PCI ROM images with a code type other than
0, the initialisation length field may not be present.
Fix by using the PCI header's image length field instead. Note that
this does not prevent us from correctly handling ISA ROMs, since ISA
ROMs do not support multiple images within a single ROM BAR anyway.
Inspired-by: Swift Geek <swiftgeek@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
With extremely unlucky timing, it is possible to interrupt a build and
cause make to delete config/named.h (and possibly any local
configuration headers).
Mark config/named.h and all local configuration headers as .PRECIOUS
to prevent make from ever deleting them.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The build process has for a long time assumed that every ROM is a PCI
ROM, and will always include the PCI header and PCI-related
functionality (such as checking the PCI BIOS version, including the
PCI bus:dev.fn address within the ROM product name string, etc.).
While real ISA cards are no longer in use, some virtualisation
environments (notably VirtualBox) have support only for ISA ROMs.
This can cause problems: in particular, VirtualBox will call our
initialisation entry point with random garbage in %ax, which we then
treat as the PCI bus:dev.fn address of the autoboot device: this
generally prevents the default boot sequence from using any network
devices.
Create .isarom and .pcirom prefixes which can be used to explicitly
specify the type of ROM to be created. (Note that the .mrom prefix
always implies a PCI ROM, since the .mrom mechanism relies on
reconfiguring PCI BARs.)
Make .rom a magic prefix which will automatically select the
appropriate PCI or ISA ROM prefix for ROMs defined via a PCI_ROM() or
ISA_ROM() macro. To maintain backwards compatibility, we default to
building a PCI ROM for anything which is not directly derived from a
PCI_ROM() or ISA_ROM() macro (e.g. bin/intel.rom).
Add a selection of targets to "make everything" to ensure that the
(relatively obscure) ISA ROM build process is included within the
per-commit QA checks.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Since some PnP BIOSes fail to set %es:di to point to the PnP signature
on entry, we identify a PnP BIOS by scanning through the top 64kB of
base memory looking for the PnP structure. We therefore don't
actually use the values of %es:di provided to the initialisation entry
point, and so there is no need to preserve them.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
ICH8 devices have an errata which requires us to reconfigure the
packet buffer size (PBS) register, and correspondingly adjust the
packet buffer allocation (PBA) register. The "Intel I/O Controller
Hub ICH8/9/10 and 82566/82567/82562V Software Developer's Manual"
notes for the PBS register that:
10.4.20 Packet Buffer Size - PBS (01008h; R/W)
Note: The default setting of this register is 20 KB and is
incorrect. This register must be programmed to 16 KB.
Initial value: 0014h
0018h (ICH9/ICH10)
It is unclear from this comment precisely which devices require the
workaround to be applied. We currently attempt to err on the side of
caution: if we detect an initial value of either 0x14 or 0x18 then the
workaround will be applied. If the workaround is applied
unnecessarily, then the effect should be just that we use less than
the full amount of the available packet buffer memory.
Unfortunately this approach does not play nicely with other device
drivers. For example, the Linux e1000e driver will rewrite PBA while
assuming that PBS still contains the default value, which can result
in inconsistent values between the two registers, and a corresponding
inability to transmit or receive packets. Even more unfortunately,
the contents of PBS and PBA are not reset by anything less than a
power cycle, meaning that this error condition will survive a hardware
reset.
The Linux driver (written and maintained by Intel) applies the PBS/PBA
errata workaround only for devices in the ICH8 family, identified via
the PCI device ID. Adopt a similar approach, using the PCI_ROM()
driver data field to indicate when the workaround is required.
Reported-by: Donald Bindner <dbindner@truman.edu>
Debugged-by: Donald Bindner <dbindner@truman.edu>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow named configurations to be specified via the CONFIG=... build
parameter. For headers in config/*.h which support named
configurations, the following files will be included when building
with CONFIG=<name>:
- config/defaults/<platform>.h (e.g. config/defaults/pcbios.h)
- config/<header>.h
- config/<name>/<header>.h (only if the directory config/<name> exists)
- config/local/<header>.h (autocreated if necessary)
- config/local/<name>/<header>.h (autocreated if necessary)
This mechanism allows for predefined named configurations to be
checked in to the source tree, as a directory config/<name> containing
all of the required header files.
The mechanism also allows for users to define multiple local
configurations, by creating header files in the directory
config/local/<name>.
Note that the config/*.h files which are used only to configure
internal iPXE APIs (e.g. config/ioapi.h) cannot be modified via a
named configuration. This avoids rebuilding the entire iPXE codebase
whenever switching to a different named configuration.
Inspired-by: Robin Smidsrød <robin@smidsrod.no>
Tested-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Under some circumstances (e.g. if iPXE itself is booted via iSCSI, or
after an unclean reboot), the backend may not be in the expected
InitWait state when iPXE starts up.
There is no generic reset mechanism for Xenbus devices. Recent
versions of xen-netback will gracefully perform all of the required
steps if the frontend sets its state to Initialising. Older versions
(such as that found in XenServer 6.2.0) require the frontend to
transition through Closed before reaching Initialising.
Add a reset mechanism for netfront devices which does the following:
- read current backend state
- if backend state is anything other than InitWait, then set the
frontend state to Closed and wait for the backend to also reach
Closed
- set the frontend state to Initialising and wait for the backend to
reach InitWait.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Using version 1 grant tables limits guests to using 16TB of grantable
RAM, and prevents the use of subpage grants. Some versions of the Xen
hypervisor refuse to allow the grant table version to be set after the
first grant references have been created, so the loaded operating
system may be stuck with whatever choice we make here. We therefore
currently use version 2 grant tables, since they give the most
flexibility to the loaded OS.
Current versions (7.2.0) of the Windows PV drivers have no support for
version 2 grant tables, and will merrily create version 1 entries in
what the hypervisor believes to be a version 2 table. This causes
some confusion.
Avoid this problem by attempting to use version 1 tables, since
otherwise we may render Windows unable to boot.
Play nicely with other potential bootloaders by accepting either
version 1 or version 2 grant tables (if we are unable to set our
requested version).
Note that the use of version 1 tables on a 64-bit system introduces a
possible failure path in which a frame number cannot fit into the
32-bit field within the v1 structure. This in turn introduces
additional failure paths into netfront_transmit() and
netfront_refill_rx().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
At some point during XenServer development history, the Windows PV
drivers changed to using a PCI device ID of 5853:0002 rather than
5853:0001. Current (7.2.0) drivers will bind to either 5853:0001 or
5853:0002, and the general approach taken by the world at large
(including Amazon EC2) seems to be to use only 5853:0001.
However, the current version of XenServer (6.2.0) will create the
platform device as 5853:0002 (via the platform:device_id VM parameter)
for any VMs created using the built-in templates for Windows Vista or
later.
Accept either PCI ID, since the underlying device is identical.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The behavior observed in the Apple EFI (1.10) RecieveFilters() call
is:
- failure if any of the PROMISCUOUS or MULTICAST filters are
included
- success if only UNICAST is included, however the result is
UNICAST|BROADCAST
- success if only UNICAST and BROADCAST are included
- if UNICAST, or UNICAST|BROADCAST are used, but the previous call
tried (and failed) to set UNICAST|BROADCAST|MULTICAST, then the
result is UNICAST|BROADCAST|MULTICAST
Work around this apparently broken SNP implementation by trying
RecieveFilterMask, then falling back to UNICAST|BROADCAST|MULTICAST,
then UNICAST|BROADCAST, and finally UNICAST.
Modified-by: Michael Brown <mcb30@ipxe.org>
Tested-by: Curtis Larsen <larsen@dixie.edu>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some EFI 1.10 systems (observed on an Apple iMac) do not allow us to
open the device path protocol with an attribute of
EFI_OPEN_PROTOCOL_BY_DRIVER and so we cannot maintain a safe,
long-lived pointer to the device path. Work around this by instead
opening the device path protocol with an attribute of
EFI_OPEN_PROTOCOL_GET_PROTOCOL whenever we need to use it.
Debugged-by: Curtis Larsen <larsen@dixie.edu>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
According to the UEFI specification, the MCastFilter parameter (which
we currently pass as NULL, along with a zero MCastFilterCnt) is
optional only if ResetMCastFilter is true.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The ComponentName and ComponentName2 protocols differ only in the
standard which is used for language name codes.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Try very hard to avoid ever doing something invalid while attempting
to generate a debug message.
Debugged-by: Curtis Larsen <larsen@dixie.edu>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Dump the existing openers of a protocol whenever we are unable to open
a protocol using attributes of BY_DEVICE, EXCLUSIVE, or
BY_CHILD_CONTROLLER.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
efi_file_install() and efi_download_install() are both used to install
onto existing handles. There is therefore no need to allow for each
of their calls to InstallMultipleProtocolInterfaces() to create a new
handle.
By passing the handle directly (rather than a pointer to the handle),
we avoid potential confusion (and erroneous debug message colours).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The EFI headers define EFI_HANDLE as a void pointer, which renders
type checking on anything dealing with EFI handles somewhat useless.
Work around this bizarre sabotage attempt by redefining EFI_HANDLE as
a pointer to an anonymous structure.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Using efi_devpath_text() is marginally more efficient if we already
have the device path protocol available, but the mild increase in
efficiency is not worth compromising the clarity of the pattern:
DBGC ( device, "THING %p %s ...", device, efi_handle_name ( device ) );
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Provide a function efi_handle_name() (as a generalisation of
efi_handle_devpath_text()) which tries various methods to produce a
human-readable name for an EFI handle.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
HII seems to fail on several systems. Since it is non-essential,
treat HII problems as non-fatal.
Debugged-by: Curtis Larsen <larsen@dixie.edu>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Reject network devices which appear to be duplicates of those already
available via a different underlying hardware device. On a Xen PV-HVM
system, this allows us to filter out the emulated PCI NICs (which
would otherwise appear alongside the netfront NICs).
Note that we cannot use the Xen facility to "unplug" the emulated PCI
NICs, since there is no guarantee that the OS we subsequently load
will have a native netfront driver.
We permit devices with the same MAC address if they are attached to
the same underlying hardware device (e.g. VLAN devices).
Inspired-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown