igb Linux* Base Driver for Intel(R) Ethernet Network Connection

================================================================================

September 11, 2023

================================================================================

Contents
========
- Overview
- Identifying Your Adapter
- Building and Installation
- Command Line Parameters
- Additional Configurations
- Known Issues
- Support
- License


Important Notes
===============

Configuring SR-IOV for improved network security
------------------------------------------------
In a virtualized environment, on Intel(R) Ethernet Network Adapters that
support SR-IOV or Intel(R) Scalable I/O Virtualization (Intel(R) Scalable IOV),
the virtual function (VF) may be subject to malicious behavior.
Software-generated layer two frames, like IEEE 802.3x (link flow control), IEEE
802.1Qbb (priority based flow-control), and others of this type, are not
expected and can throttle traffic between the host and the virtual switch,
reducing performance. To resolve this issue, and to ensure isolation from
unintended traffic streams, configure all SR-IOV or Intel Scalable IOV enabled
ports for VLAN tagging from the administrative interface on the PF. This
configuration allows unexpected, and potentially malicious, frames to be
dropped.


Overview
========
This driver supports kernel versions 2.6.30 or newer. However, some features
may require a newer kernel version. The associated Virtual Function (VF) driver
for this driver is igbvf.

Driver information can be obtained using ethtool, lspci, and ip. Instructions
on updating ethtool can be found in the section Additional Configurations later
in this document.

This driver is only supported as a loadable module at this time. Intel is not
supplying patches against the kernel source to allow for static linking of the
drivers.

For questions related to hardware requirements, refer to the documentation
supplied with your Intel adapter. All hardware requirements listed apply to use
with Linux.

The igb driver supports IEEE 1588 time stamping for kernels 2.6.30 and newer.


Related Documentation
=====================

See the "Intel(R) Ethernet Adapters and Devices User Guide" for additional
information on features. It is available on the Intel website at either of the
following:

- https://cdrdv2.intel.com/v1/dl/getContent/705831
-
https://www.intel.com/content/www/us/en/download/19373/adapter-user-guide-for-in
tel-ethernet-adapters.html


Identifying Your Adapter
========================
For information on how to identify your adapter, and for the latest Intel
network drivers, refer to the Intel Support website:
http://www.intel.com/support


Building and Installation
=========================

To manually build the driver
----------------------------
1. Move the base driver tar file to the directory of your choice.
   For example, use '/home/username/igb' or '/usr/local/src/igb'.

2. Untar/unzip the archive, where <x.x.x> is the version number for the
   driver tar file:

   # tar zxf igb-<x.x.x>.tar.gz

3. Change to the driver src directory, where <x.x.x> is the version number
   for the driver tar:

   # cd igb-<x.x.x>/src/

4. Compile the driver module:

   # make install

   The binary will be installed as:
   /lib/modules/<KERNEL VER>/updates/drivers/net/ethernet/intel/igb/igb.ko

   The install location listed above is the default location. This may differ
   for various Linux distributions.

5. Load the module using the modprobe command.

   To check the version of the driver and then load it:

   # modinfo igb
   # modprobe igb [parameter=port1_value,port2_value]

   Alternately, make sure that any older igb drivers are removed from the
   kernel before loading the new module:

   # rmmod igb; modprobe igb

6. Assign an IP address to the interface by entering the following,
   where <ethX> is the interface name that was shown in dmesg after modprobe:

   # ip address add <IP_address>/<netmask bits> dev <ethX>

7. Verify that the interface works. Enter the following, where IP_address
   is the IP address for another machine on the same subnet as the interface
   that is being tested:

   # ping <IP_address>

Note: For certain distributions like (but not limited to) Red Hat Enterprise
Linux 7 and Ubuntu, once the driver is installed, you may need to update the
initrd/initramfs file to prevent the OS loading old versions of the igb driver.
   For Red Hat distributions:
	# dracut --force

   For Ubuntu:
	# update-initramfs -u

 
To build a binary RPM package of this driver
--------------------------------------------
Note: RPM functionality has only been tested in Red Hat distributions.

1. Run the following command, where <x.x.x> is the version number for the
   driver tar file.

   # rpmbuild -tb igb-<x.x.x>.tar.gz

   NOTE: For the build to work properly, the currently running kernel MUST
   match the version and configuration of the installed kernel sources. If
   you have just recompiled the kernel, reboot the system before building.

2. After building the RPM, the last few lines of the tool output contain the
   location of the RPM file that was built. Install the RPM with one of the
   following commands, where <RPM> is the location of the RPM file:

   # rpm -Uvh <RPM>
       or
   # dnf/yum localinstall <RPM>

NOTES:
- To compile the driver on some kernel/arch combinations, you may need to
install a package with the development version of libelf (e.g. libelf-dev,
libelf-devel, elfutils-libelf-devel).
- When compiling an out-of-tree driver, details will vary by distribution.
However, you will usually need a kernel-devel RPM or some RPM that provides the
kernel headers at a minimum. The RPM kernel-devel will usually fill in the link
at /lib/modules/'uname -r'/build.


To build igb driver with DCA
----------------------------
If your kernel supports DCA, the driver will build by default with DCA enabled.


Command Line Parameters
=======================
If the driver is built as a module, enter optional parameters on the command
line with the following syntax:

# modprobe igb [<option>=<VAL1>,<VAL2>,...]

There needs to be a <VAL#> for each network port in the system supported by
this driver. The values will be applied to each instance, in function order.
For example:

# modprobe igb InterruptThrottleRate=16000,16000

In this case, there are two network ports supported by igb in the system.

- The default value for each parameter is generally the recommended setting,
unless otherwise noted.


InterruptThrottleRate
---------------------
Valid Range:
0=off
1=dynamic
3=dynamic conservative
<min_ITR>-<max_ITR>
Interrupt Throttle Rate controls the number of interrupts each interrupt
vector can generate per second. Increasing ITR lowers latency at the cost of
increased CPU utilization, though it may help throughput in some circumstances.
0 = Setting InterruptThrottleRate to 0 turns off any interrupt moderation
  and may improve small packet latency. However, this is generally not
  suitable for bulk throughput traffic due to the increased CPU utilization
  of the higher interrupt rate.
1 = Setting InterruptThrottleRate to Dynamic mode attempts to moderate
  interrupts per vector while maintaining very low latency. This can
  sometimes cause extra CPU utilization. If planning on deploying igb
  in a latency sensitive environment, this parameter should be considered.
<min_ITR>-<max_ITR> = 100-100000
  Setting InterruptThrottleRate to a value greater or equal to <min_ITR>
  will program the adapter to send at most that many interrupts
  per second, even if more packets have come in. This reduces interrupt load
  on the system and can lower CPU utilization under heavy load, but will
  increase latency as packets are not processed as quickly.

NOTE: InterruptThrottleRate is NOT supported by 82542, 82543, or 82544-based
adapters.


LLI (Low Latency Interrupts)
----------------------------

LLI allows for immediate generation of an interrupt upon processing receive
packets that match certain criteria as set by the parameters described below.
LLI parameters are not enabled when Legacy interrupts are used. You must be
using MSI or MSI-X (see cat /proc/interrupts) to successfully use LLI.


LLIPort
-------
Valid Range: 0-65535
LLI is configured with the LLIPort command-line parameter, which specifies
which TCP port should generate Low Latency Interrupts.
For example, using LLIPort=80 would cause the board to generate an immediate
interrupt upon receipt of any packet sent to TCP port 80 on the local machine.
WARNING: Enabling LLI can result in an excessive number of interrupts/second
that may cause problems with the system and in some cases may cause a kernel
panic.


LLIPush
-------
Valid Range: 0-1
LLIPush can be set to be enabled or disabled (default). It is most effective
in an environment with many small transactions.
NOTE: Enabling LLIPush may allow a denial of service attack.


LLISize
-------
Valid Range: 0-1500
LLISize causes an immediate interrupt if the board receives a packet smaller
than the specified size.


IntMode
-------
Valid Range: 0-2 (0 = Legacy Int, 1 = MSI and 2 = MSI-X)
IntMode controls the allowed load time control over the type of interrupt
registered for by the driver. MSI-X is required for multiple queue
support, and some kernels and combinations of kernel .config options
will force a lower level of interrupt support.
'cat /proc/interrupts' will show different values for each type of interrupt.


RSS
---
Valid Range: 0-8
0 = Assign up to the lesser value of the number of CPUs or the number of queues
X = Assign X queues, where X is less than or equal to the maximum number of
queues (8 queues).

The maximum number of queues allowed are:
  - I350-based adapters: 8 queues
  - 82575-based adapters: 4 queues
  - 82576-based and newer adapters: 8 queues
  - I210-based adapters: 4 queues
  - I211-based adapters: 2 queues
This parameter is also affected by the VMDq parameter in that it will limit
the queues more. For example, if you set an 82575 device to VMDQ Mode 2, you
will only be able to set 3 RSS queues. See the following table.
Model	VMDQ Mode
Number	0 1 2 3+
82575	4 4 3 1
82576	8 2 2 2
82580	8 1 1 1


VMDQ
----
Valid Range: 0-4 on 82575-based adapters; 0-8 for 82576/82580-based adapters
Supports enabling VMDq pools as this is needed to support SR-IOV.
0 = Disabled
1 = Sets the netdev as pool 0
2+ = Add additional queues but they currently are not used
This parameter is forced to 1 or more if the max_vfs module parameter is used.
In addition, the number of queues available for RSS is limited if this is set
to 1 or greater.

NOTE: When either SR-IOV mode or VMDq mode is enabled, hardware VLAN filtering
and VLAN tag stripping/insertion will remain enabled.


max_vfs
-------
This parameter adds support for SR-IOV. It causes the driver to spawn up to
max_vfs worth of virtual functions.
Valid Range:  0-7
If the value is greater than 0 it will also force the VMDq parameter to be 1 or
more.

The parameters for the driver are referenced by position. Thus, if you have a
dual port adapter, or more than one adapter in your system, and want N virtual
functions per port, you must specify a number for each port with each parameter
separated by a comma. For example:

# modprobe igb max_vfs=4

This will spawn 4 VFs on the first port.

# modprobe igb max_vfs=2,4

This will spawn 2 VFs on the first port and 4 VFs on the second port.

NOTE: Caution must be used in loading the driver with these parameters.
Depending on your system configuration, number of slots, etc., it is impossible
to predict in all cases where the positions would be on the command line.

NOTE: Neither the device nor the driver control how VFs are mapped into config
space. Bus layout will vary by operating system. On operating systems that
support it, you can check sysfs to find the mapping.

NOTE: When either SR-IOV mode or VMDq mode is enabled, hardware VLAN filtering
and VLAN tag stripping/insertion will remain enabled. Please remove the old
VLAN filter before the new VLAN filter is added. For example:

# ip link set eth0 vf 0 vlan 100	// set vlan 100 for VF 0
# ip link set eth0 vf 0 vlan 0	// Delete vlan 100
# ip link set eth0 vf 0 vlan 200	// set a new vlan 200 for VF 0


QueuePairs
----------
Valid Range: 0-1
If set to 0, when MSI-X is enabled, the Tx and Rx will attempt to occupy
separate vectors.
This option can be overridden to 1 if there are not sufficient interrupts
available. This can occur if any combination of RSS, VMDQ, and max_vfs results
in more than 4 queues being used.


Node
----
Valid Range: 0-n
0 - n: where n is the number of the NUMA node that should be used to allocate
memory for this adapter port.
-1: uses the driver default of allocating memory on whichever processor is
running modprobe.
The Node parameter allows you to choose which NUMA node you want to have the
adapter allocate memory from. All driver structures, in-memory queues, and
receive buffers will be allocated on the node specified. This parameter is
only useful when interrupt affinity is specified; otherwise, part of the
interrupt time could run on a different core than where the memory is
allocated causing slower memory access and impacting throughput, CPU, or both.


EEE (Energy Efficient Ethernet)
-------------------------------
Valid Range: 0-1
0 = Disables EEE
1 = Enables EEE

A link between two EEE-compliant devices will result in periodic bursts of data
followed by periods where the link is in an idle state. This Low Power Idle
(LPI) state is supported at 1 Gbps and 100 Mbps link speeds.

NOTES:
- EEE support requires auto-negotiation.
- Both link partners must support EEE.
- EEE is not supported on all Intel(R) Ethernet Network devices or at all link
speeds.

Example:

# ethtool --show-eee <ethX>
# ethtool --set-eee <ethX> [eee on|off]


DMAC
----
Valid Range: 0, 1, 250, 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000,
9000, 10000
This parameter enables or disables DMA Coalescing feature. Values are in
microseconds and set the internal DMA Coalescing internal timer.
DMA (Direct Memory Access) allows the network device to move packet data
directly to the system's memory, reducing CPU utilization. However, the
frequency and random intervals at which packets arrive do not allow the system
to enter a lower power state. DMA Coalescing allows the adapter to collect
packets before it initiates a DMA event. This may increase network latency but
also increases the chances that the system will enter a lower power state.
Turning on DMA Coalescing may save energy with kernel 2.6.32 and newer. DMA
Coalescing must be enabled across all active ports in order to save platform
power.


MDD (Malicious Driver Detection)
--------------------------------
Valid Range: 0-1
0 = Disabled
1 = Enabled
This parameter is only relevant for I350 devices operating in SR-IOV mode.
When this parameter is set, the driver detects malicious VF driver and
disables its Tx/Rx queues until a VF driver reset occurs.


Additional Features and Configurations
======================================

ethtool
-------
The driver utilizes the ethtool interface for driver configuration and
diagnostics, as well as displaying statistical information. The latest ethtool
version is required for this functionality. Download it at:
https://kernel.org/pub/software/network/ethtool/


Viewing Link Messages
---------------------
Link messages will not be displayed to the console if the distribution is
restricting system messages. In order to see network driver link messages on
your console, set dmesg to eight by entering the following:

# dmesg -n 8

NOTE: This setting is not saved across reboots.


Configuring the Driver on Different Distributions
-------------------------------------------------
Configuring a network driver to load properly when the system is started is
distribution dependent. Typically, the configuration process involves adding an
alias line to /etc/modules.conf or /etc/modprobe.conf as well as editing other
system startup scripts and/or configuration files. Many popular Linux
distributions ship with tools to make these changes for you. To learn the
proper way to configure a network device for your system, refer to your
distribution documentation. If during this process you are asked for the driver
or module name, the name for the Base Driver is igb.

For example, if you install the igb driver for two adapters (eth0 and eth1) and
want to set the interrupt mode to MSI-X and MSI, respectively, add the
following to modules.conf or /etc/modprobe.conf:
  alias eth0 igb
  alias eth1 igb
  options igb IntMode=2,1


Jumbo Frames
------------
Jumbo Frames support is enabled by changing the Maximum Transmission Unit (MTU)
to a value larger than the default value of 1500.

Use the ip command to increase the MTU size. For example, enter the following
where <ethX> is the interface number:

# ip link set mtu 9000 dev <ethX>
# ip link set up dev <ethX>

This setting is not saved across reboots.

Add 'MTU=9000' to the following file to make the setting change permanent:
  /etc/sysconfig/network-scripts/ifcfg-<ethX> for RHEL
      or
  /etc/sysconfig/network/<config_file> for SLES

NOTE: The maximum MTU setting for jumbo frames is 9216. This corresponds to the
maximum jumbo frame size of 9234 bytes.

NOTE: Using jumbo frames at 10 or 100 Mbps is not supported and may result in
poor performance or loss of link.

NOTE: Packet loss may have a greater impact on throughput when you use jumbo
frames. If you observe a drop in performance after enabling jumbo frames,
enabling flow control may mitigate the issue.


Speed and Duplex Configuration
------------------------------
In addressing speed and duplex configuration issues, you need to distinguish
between copper-based adapters and fiber-based adapters.

In the default mode, an Intel(R) Ethernet Network Adapter using copper
connections will attempt to auto-negotiate with its link partner to determine
the best setting. If the adapter cannot establish link with the link partner
using auto-negotiation, you may need to manually configure the adapter and link
partner to identical settings to establish link and pass packets. This should
only be needed when attempting to link with an older switch that does not
support auto-negotiation or one that has been forced to a specific speed or
duplex mode. Your link partner must match the setting you choose. 1 Gbps speeds
and higher cannot be forced. Use the autonegotiation advertising setting to
manually set devices for 1 Gbps and higher.

Speed, duplex, and autonegotiation advertising are configured through the
ethtool utility.

To see the speed configurations your device supports, run the following:

# ethtool <ethX>

Caution: Only experienced network administrators should force speed and duplex
or change autonegotiation advertising manually. The settings at the switch must
always match the adapter settings. Adapter performance may suffer or your
adapter may not operate if you configure the adapter differently from your
switch.

An Intel(R) Ethernet Network Adapter using fiber-based connections, however,
will not attempt to auto-negotiate with its link partner since those adapters
operate only in full duplex and only at their native speed.


Wake on LAN (WoL) Support
-------------------------
Some adapters do not support Wake on LAN (WoL). To determine if your adapter
supports WoL, run the following command:

# ethtool <ethX>

WoL is configured through the ethtool utility. If your Linux distribution does
not include ethtool, download and install it from the following website:
https://kernel.org/pub/software/network/ethtool/.

For instructions on enabling WoL with ethtool, refer to the website listed
above.

WoL will be enabled on the system during the next shutdown or reboot. For this
driver version, in order to enable WoL, the igb driver must be loaded prior to
shutting down or suspending the system.

NOTES:
- Wake on LAN is only supported on port A of multi-port devices.
- Wake On LAN is not supported for the Intel(R) Gigabit VT Quad Port Server
  Adapter.


Multiqueue
----------
In this mode, a separate MSI-X vector is allocated for each queue and one for
"other" interrupts such as link status change and errors. All interrupts are
throttled via interrupt moderation. Interrupt moderation must be used to avoid
interrupt storms while the driver is processing one interrupt. The moderation
value should be at least as large as the expected time for the driver to
process an interrupt. Multiqueue is off by default.

REQUIREMENTS: MSI-X support is required for Multiqueue. If MSI-X is not found,
the system will fallback to MSI or to Legacy interrupts. This driver supports
multiqueue in kernel versions 2.6.24 and newer. This driver supports receive
multiqueue on all kernels that support MSI-X.

NOTES:
- Do not use MSI-X with the 2.6.19 or 2.6.20 kernels.
- On some kernels a reboot is required to switch between single queue mode
and multiqueue mode or vice-versa.


LRO
---
Valid Range: 0(off), 1(on)
Large Receive Offload (LRO) is a technique for increasing inbound throughput
of high-bandwidth network connections by reducing CPU overhead. It works by
aggregating multiple incoming packets from a single stream into a larger
buffer before they are passed higher up the networking stack, thus reducing
the number of packets that have to be processed. LRO combines multiple
Ethernet frames into a single receive in the stack, thereby potentially
decreasing CPU utilization for receives.
NOTE: LRO requires 2.4.22 or later kernel version.
IGB_NO_LRO is a compile time flag. The user can enable it at compile time to
add support for LRO from the driver. The flag is used by adding
CFLAGS_EXTRA="-DIGB_NO_LRO" to the make file when it's being compiled.

# make CFLAGS_EXTRA="-DIGB_NO_LRO" install
You can verify that the driver is using LRO by looking at these counters in
ethtool:
- lro_aggregated - counts total packets that were combined
- lro_flushed - counts the number of packets flushed out of LRO
- lro_recycled - counts the number of buffers returned to the ring from
  recycling
NOTE: IPv6 and UDP are not supported by LRO.


IEEE 1588 Precision Time Protocol (PTP) Hardware Clock (PHC)
------------------------------------------------------------
Precision Time Protocol (PTP) is used to synchronize clocks in a computer
network. PTP support varies among Intel devices that support this driver. Use
'ethtool -T <ethX>' to get a definitive list of PTP capabilities supported by
the device.

NOTE: PTP requires 3.0.0 or later kernel version that has PTP support enabled
in the kernel and a user-space software daemon.

IGB_PTP is a compile time flag. The user can enable it at compile time to add
support for PTP from the driver. The flag is used by editing the make file as
follows when it is being compiled:

# make CFLAGS_EXTRA="-DIGB_PTP" install

NOTE: The driver will fail to compile if your kernel does not support PTP.

You can verify that the driver is using PTP by looking at the system log to see
whether a PHC was attempted to be registered or not. If you have a kernel and
version of ethtool with PTP support, you can check the PTP support in the
driver by executing:

# ethtool -T <ethX>


Configuring VLAN Tagging on SR-IOV Enabled Adapter Ports
--------------------------------------------------------
To configure VLAN tagging for the ports on an SR-IOV enabled adapter, use the
following command. The VLAN configuration should be done before the VF driver
is loaded or the VM is booted. The VF is not aware of the VLAN tag being
inserted on transmit and removed on received frames (sometimes called "port
VLAN" mode).

# ip link set dev <ethX> vf <id> vlan <vlan id>

For example, the following will configure PF eth0 and the first VF on VLAN 10:

# ip link set dev eth0 vf 0 vlan 10


MAC and VLAN Anti-Spoofing Feature for VFs
------------------------------------------
When a malicious driver on a Virtual Function (VF) interface attempts to send a
spoofed packet, it is dropped by the hardware and not transmitted.

An interrupt is sent to the PF driver notifying it of the spoof attempt. When a
spoofed packet is detected, the PF driver will send the following message to
the system log (displayed by the "dmesg" command):
  Spoof event(s) detected on VF(n), where n = the VF that attempted to do
  the spoofing


Setting MAC Address, VLAN, and Rate Limit Using IProute2 Tool
------------------------------------------------------------
You can set a MAC address of a Virtual Function (VF), a default VLAN, and the
rate limit using the IProute2 tool. Download the latest version of the
IProute2 tool from Sourceforge if your version does not have all the features
you require.

Double VLAN support
-------------------

** Configuration

By default support for double vlans (i.e. Double VLAN mode in hardware) isn't
active. One might use following command to activate it:

  # ethtool --set-priv-flags eth2 vlan-stag-rx on

To change Ethernet frame Type field id from default ETH_P_8021Q (0x8100) to
ETH_P_8021AD (0x88a8) as per IEEE 802.1ad specification one might use
following command:

  # ethtool --set-priv-flags eth2 vlan-stag-ethertype-802.1ad on

and checked with following:

  # ethtool --show-priv-flags eth2
  Private flags for eth2:
  vlan-stag-rx               : on
  vlan-stag-filter           : on
  vlan-stag-ethertype-802.1ad: on

** Implementation details

According to "Intel(R) 82575EB Gigabit Ethernet Controller Software
Developer’s Manual and EEPROM Guide" and future documentation hardware
supports Double VLAN (DV) mode for stacked vlan scenarious. However it has few
limitations:

  o It is assumed that in this mode frame contains at least one VLAN header:
    no hardware offloading will be provided for frames without it.

  o If only one header present in the frame it is assumed to be outer.

  o Hardware does not provide any additional offload except skipping outer
    header to parse inner and next protocols (e.g. IP, IPv6).

  o No support for outer header strip/insert and filtering based on vid in
    hardware.

  o Support for inner header strip/insert and filtering based on vid in
    hardware is available as in single vlan mode.

Note that Linux pushes VLAN headers for stacked vlans in native order: from
upper to lower. Later is put into skb->vlan_tci when output network device
declares support for hardware offload for header insertion on transmit.

Same applies to filtering: only vids from lowest vlan propagated to the
driver/hardware.

Also Linux has strict assumption about Ethernet frame Type (EtherType) field
and VLAN encapsulated protocol (EncapProto):

  o Outer header should have ETH_P_8021AD in EtherType.

  o Inner header should have ETH_P_8021Q in outer header EncapProto.

All above places following restrictions on implementation of double vlans
support in the driver:

  o Filtering based on inner vid must be turned off: VFTA (VLAN Filter Table
    Array) contains vids from lowest vlans (outer) but hardware applies
    filtering to vids from upper vlans (outer).

  o No support for inner header insertion by hardware: skb->vlan_tci contains
    information for outer header, inner header already added to packet buffer
    by software. Hardware expects to find inner header vlan_tci in transmit
    descriptor to offload header insertion.

  o Filtering based on outer vid implemented in software and turned on by
    default: user might turn it off if required. Promiscuous mode is supported
    and can be turned on either implicitly or explicitly (e.g. via
    ip-link(8)).

  o Inner header stripping supported in hardware and turned on by default:
    user might turn it off with adding neligible overhead.

Note about EtherType field for outer VLAN header:

  o On receive hardware skips outer header when EtherType value matches one
    configured in NIC specific register (VET.VET_EXT or VET.EXT_VET in newer
    Inte(R) documents).

    If it does not match, inner header stripping, filtering by vid and any
    hardware offload for next protocol isn't provided. Frame is delivered as
    is to upper layers.

    This behavior is identical to one in single vlan mode: no offload for
    frames with unknown EtherType.

  o Turning off "rx-vlan-filter" (e.g. by ethtool) isn't supported when
    "vlan-stag-rx" private flag is "on": though not active in hardware since
    applies to inner header this flag is checked by Linux before calling
    driver specific routines to add/kill vids to VFTA.

    As said before Linux has strict assumption about EtherType and EncapProto
    for inner and outer headers. This affects filtering in following manner:

      if "rx-vlan-filter" is "on" then vids for vlans with ETH_P_8021Q
      protocol will trigger call to driver specific routine to add/kill
      vids in VFTA

      if "vlan-stag-rx" private flag is "on" then vids for vlans with
      ETH_P_8021AD protocol will trigger call to driver specific routine to
      add/kill vids in VFTA

    Turning off "vlan-stag-rx" later would not stop traffic for
    configured vlans by hardware filters for inner header.

    This preserves interoperability with "vlan-stag-rx" "off" mode in
    which double vlan feature is off.

** Troubleshooting and debugging

There are two NIC registers participating in Double VLAN mode configuration and
functioning: CTRL_EXT and VET. Additionally RCTL register might be interesting
to ensure filtering based on inner header vid is turned off/on:

  0x00100: RCTL (Receive control register)              0x00000000
         Receiver:                                      disabled
         Store bad packets:                             disabled
         Unicast promiscuous:                           disabled
         Multicast promiscuous:                         disabled
         Long packet:                                   disabled
         Descriptor minimum threshold size:             1/2
         Broadcast accept mode:                         ignore
         VLAN filter:                                   disabled
                                                        ^^^^^^^^
                                                        filters off for DV

  0x00018: CTRL_EXT    (Extended device control)        0x14180C00
                                                           ^
                                                           0x4000000[26]

  0x00038: VET         (VLAN Ether type)                0x81008100
                                                          ^^^^
                                                          EtherType for DV

Their contents can be dumped by ethtool(8) using following command:

  # ethtool --register-dump eth2

In CTRL_EXT register bit 26 is set when Double VLAN mode is in effect and
VET[16:31] contains Little Endian (LE) representation of EtherType.

Known Issues/Troubleshooting
============================

MAC address of Virtual Function changes unexpectedly
----------------------------------------------------
If a Virtual Function's MAC address is not assigned in the host, then the VF
(virtual function) driver will use a random MAC address. This random MAC
address may change each time the VF driver is reloaded. You can assign a static
MAC address in the host machine. This static MAC address will survive a VF
driver reload.


Hardware Issues
---------------
For known hardware and troubleshooting issues, either refer to the "Release
Notes" in your User Guide, or for more detailed information, go to
http://www.intel.com.

In the search box enter your devices controller ID followed by "spec update"
(i.e., 82599 spec update). The specification update file has complete
information on known hardware issues.


Software Issues
---------------
NOTE: After installing the driver, if your Intel Ethernet Network Connection
is not working, verify that you have installed the correct driver.

Intel(R) Active Management Technology 2.0, 2.1, 2.5 are not supported in
conjunction with the linux driver.


Using the igb driver on 2.4 or older 2.6 based kernels
------------------------------------------------------
Due to limited support for PCI-Express in 2.4 kernels and older 2.6 kernels,
the igb driver may run into interrupt related problems on some systems, such
as no link or hang when bringing up the device.

We recommend the newer 2.6 based kernels, as these kernels correctly configure
the PCI-Express configuration space of the adapter and all intervening
bridges. If you are required to use a 2.4 kernel, use a 2.4 kernel newer than
2.4.30. For 2.6 kernels we recommend using the 2.6.21 kernel or newer.

Alternatively, on 2.6 kernels you may disable MSI support in the kernel by
booting with the "pci=nomsi" option or permanently disable MSI support in your
kernel by configuring your kernel with CONFIG_PCI_MSI unset.


Detected Tx Unit Hang in Quad Port Adapters
-------------------------------------------
In some cases, ports 3 and 4 don't pass traffic and report "Detected Tx Unit
Hang" followed by "NETDEV WATCHDOG: <ethX>: transmit timed out" errors. Ports 1
and 2 do not show any errors and will pass traffic.

This issue may be resolved by updating to the latest kernel and BIOS. You
should use an OS that fully supports Message Signaled Interrupts (MSI) and make
sure that MSI is enabled in your system's BIOS.


Compiling the Driver
--------------------
When trying to compile the driver by running make install, the following error
may occur: "Linux kernel source not configured - missing version.h"

To solve this issue, create the version.h file by going to the Linux source
tree and entering:

# make include/linux/version.h


Performance Degradation with Jumbo Frames
-----------------------------------------
Degradation in throughput performance may be observed in some Jumbo frames
environments. If this is observed, increasing the application's socket buffer
size and/or increasing the /proc/sys/net/ipv4/tcp_*mem entry values may help.
See the specific application manual and
/usr/src/linux*/Documentation/networking/ip-sysctl.txt for more details.


Jumbo Frames on Foundry BigIron 8000 switch
-------------------------------------------
There is a known issue using Jumbo frames when connected to a Foundry BigIron
8000 switch. This is a 3rd party limitation. If you experience loss of
packets, lower the MTU size.


Multiple Interfaces on Same Ethernet Broadcast Network
------------------------------------------------------
Due to the default ARP behavior on Linux, it is not possible to have one system
on two IP networks in the same Ethernet broadcast domain (non-partitioned
switch) behave as expected. All Ethernet interfaces will respond to IP traffic
for any IP address assigned to the system. This results in unbalanced receive
traffic.

If you have multiple interfaces in a server, either turn on ARP filtering by
entering the following:

# echo 1 > /proc/sys/net/ipv4/conf/all/arp_filter

This only works if your kernel's version is higher than 2.4.5.

NOTE: This setting is not saved across reboots. The configuration change can be
made permanent by adding the following line to the file /etc/sysctl.conf:

  net.ipv4.conf.all.arp_filter = 1

Another alternative is to install the interfaces in separate broadcast domains
(either in different switches or in a switch partitioned to VLANs).


Disable Rx Flow Control with ethtool
------------------------------------
In order to disable receive flow control using ethtool, you must turn off
auto-negotiation on the same command line:

# ethtool -A <ethX> autoneg off rx off


Unplugging Network Cable While ethtool -p is Running
----------------------------------------------------
In kernel versions 2.5.50 and newer, unplugging the network cable while ethtool
-p is running will cause the system to become unresponsive to keyboard
commands, except for control-alt-delete. Restarting the system should resolve
the issue.


Do Not Use LRO When Routing Packets
-----------------------------------
Due to a known general compatibility issue with LRO and routing, do not use LRO
when routing packets.


Build Error with Asianux 3.0 - Redefinition of typedef 'irq_handler_t'
----------------------------------------------------------------------
Some systems may experience build issues due to the redefinition of
irq_handler_t. To resolve this issue, build the driver (step 4 above) using the
command:

# make CFLAGS_EXTRA=-DAX_RELEASE_CODE=1 install


Rx Page Allocation Errors
-------------------------
'Page allocation failure. order:0' errors may occur under stress with kernels
2.6.25 and newer. This is caused by the way the Linux kernel reports this
stressed condition.

Unloading Physical Function (PF) Driver Causes System Reboots When VM is
Running and VF is Loaded on the VM.

Do not unload the PF driver (igb) while VFs are assigned to guests.


Host May Reboot after Removing PF when VF is Active in Guest
------------------------------------------------------------
Using kernel versions earlier than 3.2, do not unload the PF driver with
active VFs. Doing this will cause your VFs to stop working until you reload
the PF driver and may cause a spontaneous reboot of your system.

Prior to unloading the PF driver, you must first ensure that all VFs are
no longer active. Do this by shutting down all VMs and unloading the VF driver.


Support
=======
For general information, go to the Intel support website at:
http://www.intel.com/support/

or the Intel Wired Networking project hosted by Sourceforge at:
http://sourceforge.net/projects/e1000

If an issue is identified with the released source code on a supported kernel
with a supported adapter, email the specific information related to the issue
to e1000-devel@lists.sf.net.


License
=======
This program is free software; you can redistribute it and/or modify it under
the terms and conditions of the GNU General Public License, version 2, as
published by the Free Software Foundation.

This program is distributed in the hope it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
St - Fifth Floor, Boston, MA 02110-1301 USA.

The full GNU General Public License is included in this distribution in the
file called "COPYING".

Copyright(c) 1999 - 2023 Intel Corporation.


Trademarks
==========
Intel is a trademark or registered trademark of Intel Corporation or its
subsidiaries in the United States and/or other countries.

* Other names and brands may be claimed as the property of others.