path: root/Documentation
diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2014-12-11 14:27:06 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-11 14:27:06 -0800
commit70e71ca0af244f48a5dcf56dc435243792e3a495 (patch)
treef7d9c4c4d9a857a00043e9bf6aa2d6f533a34778 /Documentation
parentMerge tag 'sound-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound (diff)
parentFix race condition between vxlan_sock_add and vxlan_sock_release (diff)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
Pull networking updates from David Miller: 1) New offloading infrastructure and example 'rocker' driver for offloading of switching and routing to hardware. This work was done by a large group of dedicated individuals, not limited to: Scott Feldman, Jiri Pirko, Thomas Graf, John Fastabend, Jamal Hadi Salim, Andy Gospodarek, Florian Fainelli, Roopa Prabhu 2) Start making the networking operate on IOV iterators instead of modifying iov objects in-situ during transfers. Thanks to Al Viro and Herbert Xu. 3) A set of new netlink interfaces for the TIPC stack, from Richard Alpe. 4) Remove unnecessary looping during ipv6 routing lookups, from Martin KaFai Lau. 5) Add PAUSE frame generation support to gianfar driver, from Matei Pavaluca. 6) Allow for larger reordering levels in TCP, which are easily achievable in the real world right now, from Eric Dumazet. 7) Add a variable of napi_schedule that doesn't need to disable cpu interrupts, from Eric Dumazet. 8) Use a doubly linked list to optimize neigh_parms_release(), from Nicolas Dichtel. 9) Various enhancements to the kernel BPF verifier, and allow eBPF programs to actually be attached to sockets. From Alexei Starovoitov. 10) Support TSO/LSO in sunvnet driver, from David L Stevens. 11) Allow controlling ECN usage via routing metrics, from Florian Westphal. 12) Remote checksum offload, from Tom Herbert. 13) Add split-header receive, BQL, and xmit_more support to amd-xgbe driver, from Thomas Lendacky. 14) Add MPLS support to openvswitch, from Simon Horman. 15) Support wildcard tunnel endpoints in ipv6 tunnels, from Steffen Klassert. 16) Do gro flushes on a per-device basis using a timer, from Eric Dumazet. This tries to resolve the conflicting goals between the desired handling of bulk vs. RPC-like traffic. 17) Allow userspace to ask for the CPU upon what a packet was received/steered, via SO_INCOMING_CPU. From Eric Dumazet. 18) Limit GSO packets to half the current congestion window, from Eric Dumazet. 19) Add a generic helper so that all drivers set their RSS keys in a consistent way, from Eric Dumazet. 20) Add xmit_more support to enic driver, from Govindarajulu Varadarajan. 21) Add VLAN packet scheduler action, from Jiri Pirko. 22) Support configurable RSS hash functions via ethtool, from Eyal Perry. * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1820 commits) Fix race condition between vxlan_sock_add and vxlan_sock_release net/macb: fix compilation warning for print_hex_dump() called with skb->mac_header net/mlx4: Add support for A0 steering net/mlx4: Refactor QUERY_PORT net/mlx4_core: Add explicit error message when rule doesn't meet configuration net/mlx4: Add A0 hybrid steering net/mlx4: Add mlx4_bitmap zone allocator net/mlx4: Add a check if there are too many reserved QPs net/mlx4: Change QP allocation scheme net/mlx4_core: Use tasklet for user-space CQ completion events net/mlx4_core: Mask out host side virtualization features for guests net/mlx4_en: Set csum level for encapsulated packets be2net: Export tunnel offloads only when a VxLAN tunnel is created gianfar: Fix dma check map error when DMA_API_DEBUG is enabled cxgb4/csiostor: Don't use MASTER_MUST for fw_hello call net: fec: only enable mdio interrupt before phy device link up net: fec: clear all interrupt events to support i.MX6SX net: fec: reset fep link status in suspend function net: sock: fix access via invalid file descriptor net: introduce helper macro for_each_cmsghdr ...
Diffstat (limited to 'Documentation')
19 files changed, 498 insertions, 114 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
index e1b2e785bba8..beb8ec4dabbc 100644
--- a/Documentation/ABI/testing/sysfs-class-net
+++ b/Documentation/ABI/testing/sysfs-class-net
@@ -216,3 +216,11 @@ Contact: netdev@vger.kernel.org
Indicates the interface protocol type as a decimal value. See
include/uapi/linux/if_arp.h for all possible values.
+What: /sys/class/net/<iface>/phys_switch_id
+Date: November 2014
+KernelVersion: 3.19
+Contact: netdev@vger.kernel.org
+ Indicates the unique physical switch identifier of a switch this
+ port belongs to, as a string.
diff --git a/Documentation/Changes b/Documentation/Changes
index 1de131bb49fb..74bdda9272a4 100644
--- a/Documentation/Changes
+++ b/Documentation/Changes
@@ -383,7 +383,7 @@ o <http://www.iptables.org/downloads.html>
-o <ftp://ftp.tux.org/pub/net/ip-routing/iproute2-2.2.4-now-ss991023.tar.gz>
+o <https://www.kernel.org/pub/linux/utils/net/iproute2/>
diff --git a/Documentation/devicetree/bindings/btmrvl.txt b/Documentation/devicetree/bindings/btmrvl.txt
new file mode 100644
index 000000000000..58f964bb0a52
--- /dev/null
+++ b/Documentation/devicetree/bindings/btmrvl.txt
@@ -0,0 +1,29 @@
+Required properties:
+ - compatible : must be "btmrvl,cfgdata"
+Optional properties:
+ - btmrvl,cal-data : Calibration data downloaded to the device during
+ initialization. This is an array of 28 values(u8).
+ - btmrvl,gpio-gap : gpio and gap (in msecs) combination to be
+ configured.
+GPIO pin 13 is configured as a wakeup source and GAP is set to 100 msecs
+in below example.
+btmrvl {
+ compatible = "btmrvl,cfgdata";
+ btmrvl,cal-data = /bits/ 8 <
+ 0x37 0x01 0x1c 0x00 0xff 0xff 0xff 0xff 0x01 0x7f 0x04 0x02
+ 0x00 0x00 0xba 0xce 0xc0 0xc6 0x2d 0x00 0x00 0x00 0x00 0x00
+ 0x00 0x00 0xf0 0x00>;
+ btmrvl,gpio-gap = <0x0d64>;
diff --git a/Documentation/devicetree/bindings/bus/bcma.txt b/Documentation/devicetree/bindings/bus/bcma.txt
index 62a48348ac15..edd44d802139 100644
--- a/Documentation/devicetree/bindings/bus/bcma.txt
+++ b/Documentation/devicetree/bindings/bus/bcma.txt
@@ -8,6 +8,11 @@ Required properties:
The cores on the AXI bus are automatically detected by bcma with the
memory ranges they are using and they get registered afterwards.
+Automatic detection of the IRQ number is not working on
+BCM47xx/BCM53xx ARM SoCs. To assign IRQ numbers to the cores, provide
+them manually through device tree. Use an interrupt-map to specify the
+IRQ used by the devices on the bus. The first address is just an index,
+because we do not have any special register.
The top-level axi bus may contain children representing attached cores
(devices). This is needed since some hardware details can't be auto
@@ -22,6 +27,22 @@ Example:
ranges = <0x00000000 0x18000000 0x00100000>;
#address-cells = <1>;
#size-cells = <1>;
+ #interrupt-cells = <1>;
+ interrupt-map-mask = <0x000fffff 0xffff>;
+ interrupt-map =
+ /* Ethernet Controller 0 */
+ <0x00024000 0 &gic GIC_SPI 147 IRQ_TYPE_LEVEL_HIGH>,
+ /* Ethernet Controller 1 */
+ <0x00025000 0 &gic GIC_SPI 148 IRQ_TYPE_LEVEL_HIGH>;
+ /* PCIe Controller 0 */
+ <0x00012000 0 &gic GIC_SPI 126 IRQ_TYPE_LEVEL_HIGH>,
+ <0x00012000 1 &gic GIC_SPI 127 IRQ_TYPE_LEVEL_HIGH>,
+ <0x00012000 2 &gic GIC_SPI 128 IRQ_TYPE_LEVEL_HIGH>,
+ <0x00012000 3 &gic GIC_SPI 129 IRQ_TYPE_LEVEL_HIGH>,
+ <0x00012000 4 &gic GIC_SPI 130 IRQ_TYPE_LEVEL_HIGH>,
+ <0x00012000 5 &gic GIC_SPI 131 IRQ_TYPE_LEVEL_HIGH>;
chipcommon {
reg = <0x00000000 0x1000>;
diff --git a/Documentation/devicetree/bindings/net/amd-xgbe.txt b/Documentation/devicetree/bindings/net/amd-xgbe.txt
index 41354f730beb..26efd526d16c 100644
--- a/Documentation/devicetree/bindings/net/amd-xgbe.txt
+++ b/Documentation/devicetree/bindings/net/amd-xgbe.txt
@@ -7,7 +7,10 @@ Required properties:
- PCS registers
- interrupt-parent: Should be the phandle for the interrupt controller
that services interrupts for this device
-- interrupts: Should contain the amd-xgbe interrupt
+- interrupts: Should contain the amd-xgbe interrupt(s). The first interrupt
+ listed is required and is the general device interrupt. If the optional
+ amd,per-channel-interrupt property is specified, then one additional
+ interrupt for each DMA channel supported by the device should be specified
- clocks:
- DMA clock for the amd-xgbe device (used for calculating the
correct Rx interrupt watchdog timer value on a DMA channel
@@ -23,6 +26,9 @@ Optional properties:
- mac-address: mac address to be assigned to the device. Can be overridden
by UEFI.
- dma-coherent: Present if dma operations are coherent
+- amd,per-channel-interrupt: Indicates that Rx and Tx complete will generate
+ a unique interrupt for each DMA channel - this requires an additional
+ interrupt be configured for each DMA channel
xgbe@e0700000 {
@@ -30,7 +36,9 @@ Example:
reg = <0 0xe0700000 0 0x80000>,
<0 0xe0780000 0 0x80000>;
interrupt-parent = <&gic>;
- interrupts = <0 325 4>;
+ interrupts = <0 325 4>,
+ <0 326 1>, <0 327 1>, <0 328 1>, <0 329 1>;
+ amd,per-channel-interrupt;
clocks = <&xgbe_dma_clk>, <&xgbe_ptp_clk>;
clock-names = "dma_clk", "ptp_clk";
phy-handle = <&phy>;
diff --git a/Documentation/devicetree/bindings/net/can/c_can.txt b/Documentation/devicetree/bindings/net/can/c_can.txt
index 8f1ae81228e3..5a1d8b0c39e9 100644
--- a/Documentation/devicetree/bindings/net/can/c_can.txt
+++ b/Documentation/devicetree/bindings/net/can/c_can.txt
@@ -4,6 +4,8 @@ Bosch C_CAN/D_CAN controller Device Tree Bindings
Required properties:
- compatible : Should be "bosch,c_can" for C_CAN controllers and
"bosch,d_can" for D_CAN controllers.
+ Can be "ti,dra7-d_can", "ti,am3352-d_can" or
+ "ti,am4372-d_can".
- reg : physical base address and size of the C_CAN/D_CAN
registers map
- interrupts : property with a value describing the interrupt
@@ -12,6 +14,9 @@ Required properties:
Optional properties:
- ti,hwmods : Must be "d_can<n>" or "c_can<n>", n being the
instance number
+- syscon-raminit : Handle to system control region that contains the
+ RAMINIT register, register offset to the RAMINIT
+ register and the CAN instance number (0 offset).
Note: "ti,hwmods" field is used to fetch the base address and irq
resources from TI, omap hwmod data base during device registration.
diff --git a/Documentation/devicetree/bindings/net/dsa/dsa.txt b/Documentation/devicetree/bindings/net/dsa/dsa.txt
index a62c889aafca..e124847443f8 100644
--- a/Documentation/devicetree/bindings/net/dsa/dsa.txt
+++ b/Documentation/devicetree/bindings/net/dsa/dsa.txt
@@ -10,7 +10,7 @@ Required properties:
- dsa,ethernet : Should be a phandle to a valid Ethernet device node
- dsa,mii-bus : Should be a phandle to a valid MDIO bus device node
-Optionnal properties:
+Optional properties:
- interrupts : property with a value describing the switch
interrupt number (not supported by the driver)
@@ -23,6 +23,13 @@ Each of these switch child nodes should have the following required properties:
- #address-cells : Must be 1
- #size-cells : Must be 0
+A switch child node has the following optional property:
+- eeprom-length : Set to the length of an EEPROM connected to the
+ switch. Must be set if the switch can not detect
+ the presence and/or size of a connected EEPROM,
+ otherwise optional.
A switch may have multiple "port" children nodes
Each port children node must have the following mandatory properties:
diff --git a/Documentation/devicetree/bindings/net/micrel.txt b/Documentation/devicetree/bindings/net/micrel.txt
index e1d99b95c4ec..87496a8c64ab 100644
--- a/Documentation/devicetree/bindings/net/micrel.txt
+++ b/Documentation/devicetree/bindings/net/micrel.txt
@@ -6,19 +6,32 @@ Optional properties:
- micrel,led-mode : LED mode value to set for PHYs with configurable LEDs.
- Configure the LED mode with single value. The list of PHYs and
- the bits that are currently supported:
+ Configure the LED mode with single value. The list of PHYs and the
+ bits that are currently supported:
- KSZ8001: register 0x1e, bits 15..14
- KSZ8041: register 0x1e, bits 15..14
- KSZ8021: register 0x1f, bits 5..4
- KSZ8031: register 0x1f, bits 5..4
- KSZ8051: register 0x1f, bits 5..4
+ KSZ8001: register 0x1e, bits 15..14
+ KSZ8041: register 0x1e, bits 15..14
+ KSZ8021: register 0x1f, bits 5..4
+ KSZ8031: register 0x1f, bits 5..4
+ KSZ8051: register 0x1f, bits 5..4
+ KSZ8081: register 0x1f, bits 5..4
+ KSZ8091: register 0x1f, bits 5..4
- See the respective PHY datasheet for the mode values.
+ See the respective PHY datasheet for the mode values.
+ - micrel,rmii-reference-clock-select-25-mhz: RMII Reference Clock Select
+ bit selects 25 MHz mode
+ Setting the RMII Reference Clock Select bit enables 25 MHz rather
+ than 50 MHz clock mode.
+ Note that this option in only needed for certain PHY revisions with a
+ non-standard, inverted function of this configuration bit.
+ Specifically, a clock reference ("rmii-ref" below) is always needed to
+ actually select a mode.
- clocks, clock-names: contains clocks according to the common clock bindings.
- supported clocks:
- - KSZ8021, KSZ8031: "rmii-ref": The RMII refence input clock. Used
- to determine the XI input clock.
+ supported clocks:
+ - KSZ8021, KSZ8031, KSZ8081, KSZ8091: "rmii-ref": The RMII reference
+ input clock. Used to determine the XI input clock.
diff --git a/Documentation/devicetree/bindings/net/phy.txt b/Documentation/devicetree/bindings/net/phy.txt
index 5b8c58903077..40831fbaff72 100644
--- a/Documentation/devicetree/bindings/net/phy.txt
+++ b/Documentation/devicetree/bindings/net/phy.txt
@@ -19,7 +19,6 @@ Optional Properties:
specifications. If neither of these are specified, the default is to
assume clause 22. The compatible list may also contain other
-- max-speed: Maximum PHY supported speed (10, 100, 1000...)
If the phy's identifier is known then the list may contain an entry
of the form: "ethernet-phy-idAAAA.BBBB" where
@@ -29,6 +28,8 @@ Optional Properties:
4 hex digits. This is the chip vendor OUI bits 19:24,
followed by 10 bits of a vendor specific ID.
+- max-speed: Maximum PHY supported speed (10, 100, 1000...)
ethernet-phy@0 {
diff --git a/Documentation/devicetree/bindings/net/sh_eth.txt b/Documentation/devicetree/bindings/net/sh_eth.txt
index 34d4db1a4e25..2f6ec85fda8e 100644
--- a/Documentation/devicetree/bindings/net/sh_eth.txt
+++ b/Documentation/devicetree/bindings/net/sh_eth.txt
@@ -9,6 +9,7 @@ Required properties:
"renesas,ether-r8a7779" if the device is a part of R8A7779 SoC.
"renesas,ether-r8a7790" if the device is a part of R8A7790 SoC.
"renesas,ether-r8a7791" if the device is a part of R8A7791 SoC.
+ "renesas,ether-r8a7793" if the device is a part of R8A7793 SoC.
"renesas,ether-r8a7794" if the device is a part of R8A7794 SoC.
"renesas,ether-r7s72100" if the device is a part of R7S72100 SoC.
- reg: offset and length of (1) the E-DMAC/feLic register block (required),
diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
index eeb5b2e97bed..83bf4986baea 100644
--- a/Documentation/networking/bonding.txt
+++ b/Documentation/networking/bonding.txt
@@ -2230,11 +2230,8 @@ balance-rr: This mode is the only mode that will permit a single
It is possible to adjust TCP/IP's congestion limits by
altering the net.ipv4.tcp_reordering sysctl parameter. The
- usual default value is 3, and the maximum useful value is 127.
- For a four interface balance-rr bond, expect that a single
- TCP/IP stream will utilize no more than approximately 2.3
- interface's worth of throughput, even after adjusting
- tcp_reordering.
+ usual default value is 3. But keep in mind TCP stack is able
+ to automatically increase this when it detects reorders.
Note that the fraction of packets that will be delivered out of
order is highly variable, and is unlikely to be zero. The level
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index a476b08a43e0..9bffdfc648dc 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -383,9 +383,17 @@ tcp_orphan_retries - INTEGER
may consume significant resources. Cf. tcp_max_orphans.
tcp_reordering - INTEGER
- Maximal reordering of packets in a TCP stream.
+ Initial reordering level of packets in a TCP stream.
+ TCP stack can then dynamically adjust flow reordering level
+ between this initial value and tcp_max_reordering
Default: 3
+tcp_max_reordering - INTEGER
+ Maximal reordering level of packets in a TCP stream.
+ 300 is a fairly conservative value, but you might increase it
+ if paths are using per packet load balancing (like bonding rr mode)
+ Default: 300
tcp_retrans_collapse - BOOLEAN
Bug-to-bug compatibility with some broken printers.
On retransmit try to send bigger packets to work around bugs in
@@ -1466,6 +1474,19 @@ suppress_frag_ndisc - INTEGER
1 - (default) discard fragmented neighbor discovery packets
0 - allow fragmented neighbor discovery packets
+optimistic_dad - BOOLEAN
+ Whether to perform Optimistic Duplicate Address Detection (RFC 4429).
+ 0: disabled (default)
+ 1: enabled
+use_optimistic - BOOLEAN
+ If enabled, do not classify optimistic addresses as deprecated during
+ source address selection. Preferred addresses will still be chosen
+ before optimistic addresses, subject to other ranking in the source
+ address selection algorithm.
+ 0: disabled (default)
+ 1: enabled
ratelimit - INTEGER
Limit the maximal rates for sending ICMPv6 packets.
diff --git a/Documentation/networking/ipvlan.txt b/Documentation/networking/ipvlan.txt
new file mode 100644
index 000000000000..cf996394e466
--- /dev/null
+++ b/Documentation/networking/ipvlan.txt
@@ -0,0 +1,107 @@
+Initial Release:
+ Mahesh Bandewar <maheshb AT google.com>
+1. Introduction:
+ This is conceptually very similar to the macvlan driver with one major
+exception of using L3 for mux-ing /demux-ing among slaves. This property makes
+the master device share the L2 with it's slave devices. I have developed this
+driver in conjuntion with network namespaces and not sure if there is use case
+outside of it.
+2. Building and Installation:
+ In order to build the driver, please select the config item CONFIG_IPVLAN.
+The driver can be built into the kernel (CONFIG_IPVLAN=y) or as a module
+3. Configuration:
+ There are no module parameters for this driver and it can be configured
+using IProute2/ip utility.
+ ip link add link <master-dev> <slave-dev> type ipvlan mode { l2 | L3 }
+ e.g. ip link add link ipvl0 eth0 type ipvlan mode l2
+4. Operating modes:
+ IPvlan has two modes of operation - L2 and L3. For a given master device,
+you can select one of these two modes and all slaves on that master will
+operate in the same (selected) mode. The RX mode is almost identical except
+that in L3 mode the slaves wont receive any multicast / broadcast traffic.
+L3 mode is more restrictive since routing is controlled from the other (mostly)
+default namespace.
+4.1 L2 mode:
+ In this mode TX processing happens on the stack instance attached to the
+slave device and packets are switched and queued to the master device to send
+out. In this mode the slaves will RX/TX multicast and broadcast (if applicable)
+as well.
+4.2 L3 mode:
+ In this mode TX processing upto L3 happens on the stack instance attached
+to the slave device and packets are switched to the stack instance of the
+master device for the L2 processing and routing from that instance will be
+used before packets are queued on the outbound device. In this mode the slaves
+will not receive nor can send multicast / broadcast traffic.
+5. What to choose (macvlan vs. ipvlan)?
+ These two devices are very similar in many regards and the specific use
+case could very well define which device to choose. if one of the following
+situations defines your use case then you can choose to use ipvlan -
+ (a) The Linux host that is connected to the external switch / router has
+policy configured that allows only one mac per port.
+ (b) No of virtual devices created on a master exceed the mac capacity and
+puts the NIC in promiscous mode and degraded performance is a concern.
+ (c) If the slave device is to be put into the hostile / untrusted network
+namespace where L2 on the slave could be changed / misused.
+6. Example configuration:
+ +=============================================================+
+ | Host: host1 |
+ | |
+ | +----------------------+ +----------------------+ |
+ | | NS:ns0 | | NS:ns1 | |
+ | | | | | |
+ | | | | | |
+ | | ipvl0 | | ipvl1 | |
+ | +----------#-----------+ +-----------#----------+ |
+ | # # |
+ | ################################ |
+ | # eth0 |
+ +==============================#==============================+
+ (a) Create two network namespaces - ns0, ns1
+ ip netns add ns0
+ ip netns add ns1
+ (b) Create two ipvlan slaves on eth0 (master device)
+ ip link add link eth0 ipvl0 type ipvlan mode l2
+ ip link add link eth0 ipvl1 type ipvlan mode l2
+ (c) Assign slaves to the respective network namespaces
+ ip link set dev ipvl0 netns ns0
+ ip link set dev ipvl1 netns ns1
+ (d) Now switch to the namespace (ns0 or ns1) to configure the slave devices
+ - For ns0
+ (1) ip netns exec ns0 bash
+ (2) ip link set dev ipvl0 up
+ (3) ip link set dev lo up
+ (4) ip -4 addr add dev lo
+ (5) ip -4 addr add $IPADDR dev ipvl0
+ (6) ip -4 route add default via $ROUTER dev ipvl0
+ - For ns1
+ (1) ip netns exec ns1 bash
+ (2) ip link set dev ipvl1 up
+ (3) ip link set dev lo up
+ (4) ip -4 addr add dev lo
+ (5) ip -4 addr add $IPADDR dev ipvl1
+ (6) ip -4 route add default via $ROUTER dev ipvl1
diff --git a/Documentation/networking/ixgbe.txt b/Documentation/networking/ixgbe.txt
index 96cccebb839b..0ace6e776ac8 100644
--- a/Documentation/networking/ixgbe.txt
+++ b/Documentation/networking/ixgbe.txt
@@ -138,7 +138,7 @@ Other ethtool Commands:
To enable Flow Director
ethtool -K ethX ntuple on
To add a filter
- Use -U switch. e.g., ethtool -U ethX flow-type tcp4 src-ip 0x178000a
+ Use -U switch. e.g., ethtool -U ethX flow-type tcp4 src-ip
action 1
To see the list of filters currently present:
ethtool -u ethX
diff --git a/Documentation/networking/stmmac.txt b/Documentation/networking/stmmac.txt
index 2090895b08d4..e655e2453c98 100644
--- a/Documentation/networking/stmmac.txt
+++ b/Documentation/networking/stmmac.txt
@@ -1,12 +1,12 @@
STMicroelectronics 10/100/1000 Synopsys Ethernet driver
-Copyright (C) 2007-2013 STMicroelectronics Ltd
+Copyright (C) 2007-2014 STMicroelectronics Ltd
Author: Giuseppe Cavallaro <peppe.cavallaro@st.com>
This is the driver for the MAC 10/100/1000 on-chip Ethernet controllers
(Synopsys IP blocks).
-Currently this network device driver is for all STM embedded MAC/GMAC
+Currently this network device driver is for all STi embedded MAC/GMAC
(i.e. 7xxx/5xxx SoCs), SPEAr (arm), Loongson1B (mips) and XLINX XC2V3000
FF1152AMT0221 D1215994A VIRTEX FPGA board.
@@ -22,6 +22,9 @@ The kernel configuration option is STMMAC_ETH:
Device Drivers ---> Network device support ---> Ethernet (1000 Mbit) --->
STMicroelectronics 10/100/1000 Ethernet driver (STMMAC_ETH)
+CONFIG_STMMAC_PLATFORM: is to enable the platform driver.
+CONFIG_STMMAC_PCI: is to enable the pci driver.
2) Driver parameters list:
debug: message level (0: no output, 16: all);
phyaddr: to manually provide the physical address to the PHY device;
@@ -45,10 +48,11 @@ Driver parameters can be also passed in command line by using:
The xmit method is invoked when the kernel needs to transmit a packet; it sets
the descriptors in the ring and informs the DMA engine that there is a packet
ready to be transmitted.
-Once the controller has finished transmitting the packet, an interrupt is
-triggered; So the driver will be able to release the socket buffers.
By default, the driver sets the NETIF_F_SG bit in the features field of the
-net_device structure enabling the scatter/gather feature.
+net_device structure enabling the scatter-gather feature. This is true on
+chips and configurations where the checksum can be done in hardware.
+Once the controller has finished transmitting the packet, napi will be
+scheduled to release the transmit resources.
4.2) Receive process
When one or more packets are received, an interrupt happens. The interrupts
@@ -58,20 +62,12 @@ This is based on NAPI so the interrupt handler signals only if there is work
to be done, and it exits.
Then the poll method will be scheduled at some future point.
The incoming packets are stored, by the DMA, in a list of pre-allocated socket
-buffers in order to avoid the memcpy (Zero-copy).
+buffers in order to avoid the memcpy (zero-copy).
4.3) Interrupt Mitigation
The driver is able to mitigate the number of its DMA interrupts
using NAPI for the reception on chips older than the 3.50.
New chips have an HW RX-Watchdog used for this mitigation.
-On Tx-side, the mitigation schema is based on a SW timer that calls the
-tx function (stmmac_tx) to reclaim the resource after transmitting the
-Also there is another parameter (like a threshold) used to program
-the descriptors avoiding to set the interrupt on completion bit in
-when the frame is sent (xmit).
Mitigation parameters can be tuned by ethtool.
4.4) WOL
@@ -79,7 +75,7 @@ Wake up on Lan feature through Magic and Unicast frames are supported for the
GMAC core.
4.5) DMA descriptors
-Driver handles both normal and enhanced descriptors. The latter has been only
+Driver handles both normal and alternate descriptors. The latter has been only
tested on DWC Ether MAC 10/100/1000 Universal version 3.41a and later.
STMMAC supports DMA descriptor to operate both in dual buffer (RING)
@@ -91,9 +87,20 @@ In CHAINED mode each descriptor will have pointer to next descriptor in
the list, hence creating the explicit chaining in the descriptor itself,
whereas such explicit chaining is not possible in RING mode.
+4.5.1) Extended descriptors
+ The extended descriptors give us information about the Ethernet payload
+ when it is carrying PTP packets or TCP/UDP/ICMP over IP.
+ These are not available on GMAC Synopsys chips older than the 3.50.
+ At probe time the driver will decide if these can be actually used.
+ This support also is mandatory for PTPv2 because the extra descriptors
+ are used for saving the hardware timestamps and Extended Status.
4.6) Ethtool support
-Ethtool is supported. Driver statistics and internal errors can be taken using:
-ethtool -S ethX command. It is possible to dump registers etc.
+Ethtool is supported.
+For example, driver statistics (including RMON), internal errors can be taken
+ # ethtool -S ethX command
4.7) Jumbo and Segmentation Offloading
Jumbo frames are supported and tested for the GMAC.
@@ -101,12 +108,11 @@ The GSO has been also added but it's performed in software.
LRO is not supported.
4.8) Physical
-The driver is compatible with PAL to work with PHY and GPHY devices.
+The driver is compatible with Physical Abstraction Layer to be connected with
+PHY and GPHY devices.
4.9) Platform information
-Several driver's information can be passed through the platform
-These are included in the include/linux/stmmac.h header file
-and detailed below as well:
+Several information can be passed through the platform and device-tree.
struct plat_stmmacenet_data {
char *phy_bus_name;
@@ -125,15 +131,18 @@ struct plat_stmmacenet_data {
int force_sf_dma_mode;
int force_thresh_dma_mode;
int riwt_off;
+ int max_speed;
+ int maxmtu;
void (*fix_mac_speed)(void *priv, unsigned int speed);
void (*bus_setup)(void __iomem *ioaddr);
void *(*setup)(struct platform_device *pdev);
+ void (*free)(struct platform_device *pdev, void *priv);
int (*init)(struct platform_device *pdev, void *priv);
void (*exit)(struct platform_device *pdev, void *priv);
void *custom_cfg;
void *custom_data;
void *bsp_priv;
- };
o phy_bus_name: phy bus name to attach to the stmmac.
@@ -258,32 +267,43 @@ and the second one, with a real PHY device attached to the bus,
by using the stmmac_mdio_bus_data structure (to provide the id, the
reset procedure etc).
-4.10) List of source files:
- o Kconfig
- o Makefile
- o stmmac_main.c: main network device driver;
- o stmmac_mdio.c: mdio functions;
- o stmmac_pci: PCI driver;
- o stmmac_platform.c: platform driver
- o stmmac_ethtool.c: ethtool support;
- o stmmac_timer.[ch]: timer code used for mitigating the driver dma interrupts
- (only tested on ST40 platforms based);
+Note that, starting from new chips, where it is available the HW capability
+register, many configurations are discovered at run-time for example to
+understand if EEE, HW csum, PTP, enhanced descriptor etc are actually
+available. As strategy adopted in this driver, the information from the HW
+capability register can replace what has been passed from the platform.
+4.10) Device-tree support.
+Please see the following document:
+ Documentation/devicetree/bindings/net/stmmac.txt
+and the stmmac_of_data structure inside the include/linux/stmmac.h header file.
+4.11) This is a summary of the content of some relevant files:
+ o stmmac_main.c: to implement the main network device driver;
+ o stmmac_mdio.c: to provide mdio functions;
+ o stmmac_pci: this the PCI driver;
+ o stmmac_platform.c: this the platform driver (OF supported)
+ o stmmac_ethtool.c: to implement the ethtool support;
o stmmac.h: private driver structure;
o common.h: common definitions and VFTs;
o descs.h: descriptor structure definitions;
- o dwmac1000_core.c: GMAC core functions;
- o dwmac1000_dma.c: dma functions for the GMAC chip;
- o dwmac1000.h: specific header file for the GMAC;
- o dwmac100_core: MAC 100 core and dma code;
- o dwmac100_dma.c: dma functions for the MAC chip;
+ o dwmac1000_core.c: dwmac GiGa core functions;
+ o dwmac1000_dma.c: dma functions for the GMAC chip;
+ o dwmac1000.h: specific header file for the dwmac GiGa;
+ o dwmac100_core: dwmac 100 core code;
+ o dwmac100_dma.c: dma functions for the dwmac 100 chip;
o dwmac1000.h: specific header file for the MAC;
- o dwmac_lib.c: generic DMA functions shared among chips;
+ o dwmac_lib.c: generic DMA functions;
o enh_desc.c: functions for handling enhanced descriptors;
o norm_desc.c: functions for handling normal descriptors;
o chain_mode.c/ring_mode.c:: functions to manage RING/CHAINED modes;
o mmc_core.c/mmc.h: Management MAC Counters;
- o stmmac_hwtstamp.c: HW timestamp support for PTP
- o stmmac_ptp.c: PTP 1588 clock
+ o stmmac_hwtstamp.c: HW timestamp support for PTP;
+ o stmmac_ptp.c: PTP 1588 clock;
+ o dwmac-<XXX>.c: these are for the platform glue-logic file; e.g. dwmac-sti.c
+ for STMicroelectronics SoCs.
5) Debug Information
@@ -298,23 +318,14 @@ to get statistics: e.g. using: ethtool -S ethX
(that shows the Management counters (MMC) if supported)
or sees the MAC/DMA registers: e.g. using: ethtool -d ethX
-Compiling the Kernel with CONFIG_DEBUG_FS and enabling the
-STMMAC_DEBUG_FS option the driver will export the following
+Compiling the Kernel with CONFIG_DEBUG_FS the driver will export the following
debugfs entries:
To show the DMA TX/RX descriptor rings
-Developer can also use the "debug" module parameter to get
-further debug information.
-In the end, there are other macros (that cannot be enabled
-via menuconfig) to turn-on the RX/TX DMA debugging,
-specific MAC core debug printk etc. Others to enable the
-debug in the TX and RX processes.
-All these are only useful during the developing stage
-and should never enabled inside the code for general usage.
-In fact, these can generate an huge amount of debug messages.
+Developer can also use the "debug" module parameter to get further debug
+information (please see: NETIF Msg Level).
6) Energy Efficient Ethernet
@@ -337,15 +348,7 @@ To enter in Tx LPI mode the driver needs to have a software timer
that enable and disable the LPI mode when there is nothing to be
-7) Extended descriptors
-The extended descriptors give us information about the receive Ethernet payload
-when it is carrying PTP packets or TCP/UDP/ICMP over IP.
-These are not available on GMAC Synopsys chips older than the 3.50.
-At probe time the driver will decide if these can be actually used.
-This support also is mandatory for PTPv2 because the extra descriptors 6 and 7
-are used for saving the hardware timestamps.
-8) Precision Time Protocol (PTP)
+7) Precision Time Protocol (PTP)
The driver supports the IEEE 1588-2002, Precision Time Protocol (PTP),
which enables precise synchronization of clocks in measurement and
control systems implemented with technologies such as network
@@ -355,7 +358,7 @@ In addition to the basic timestamp features mentioned in IEEE 1588-2002
Timestamps, new GMAC cores support the advanced timestamp features.
IEEE 1588-2008 that can be enabled when configure the Kernel.
-9) SGMII/RGMII supports
+8) SGMII/RGMII supports
New GMAC devices provide own way to manage RGMII/SGMII.
This information is available at run-time by looking at the
HW capability register. This means that the stmmac can manage
@@ -364,8 +367,3 @@ In fact, the HW provides a subset of extended registers to
restart the ANE, verify Full/Half duplex mode and Speed.
Also thanks to these registers it is possible to look at the
Auto-negotiated Link Parter Ability.
-10) TODO:
- o XGMAC is not supported.
- o Complete the TBI & RTBI support.
- o extend VLAN support for 3.70a SYNP GMAC.
diff --git a/Documentation/networking/switchdev.txt b/Documentation/networking/switchdev.txt
new file mode 100644
index 000000000000..f981a9295a39
--- /dev/null
+++ b/Documentation/networking/switchdev.txt
@@ -0,0 +1,59 @@
+Switch (and switch-ish) device drivers HOWTO
+Please note that the word "switch" is here used in very generic meaning.
+This include devices supporting L2/L3 but also various flow offloading chips,
+including switches embedded into SR-IOV NICs.
+Lets describe a topology a bit. Imagine the following example:
+ +----------------------------+ +---------------+
+ | SOME switch chip | | CPU |
+ +----------------------------+ +---------------+
+ port1 port2 port3 port4 MNGMNT | PCI-E |
+ | | | | | +---------------+
+ PHY PHY | | | | NIC0 NIC1
+ | | | | | |
+ | | +- PCI-E -+ | |
+ | +------- MII -------+ |
+ +------------- MII ------------+
+In this example, there are two independent lines between the switch silicon
+and CPU. NIC0 and NIC1 drivers are not aware of a switch presence. They are
+separate from the switch driver. SOME switch chip is by managed by a driver
+via PCI-E device MNGMNT. Note that MNGMNT device, NIC0 and NIC1 may be
+connected to some other type of bus.
+Now, for the previous example show the representation in kernel:
+ +----------------------------+ +---------------+
+ | SOME switch chip | | CPU |
+ +----------------------------+ +---------------+
+ sw0p0 sw0p1 sw0p2 sw0p3 MNGMNT | PCI-E |
+ | | | | | +---------------+
+ PHY PHY | | | | eth0 eth1
+ | | | | | |
+ | | +- PCI-E -+ | |
+ | +------- MII -------+ |
+ +------------- MII ------------+
+Lets call the example switch driver for SOME switch chip "SOMEswitch". This
+driver takes care of PCI-E device MNGMNT. There is a netdevice instance sw0pX
+created for each port of a switch. These netdevices are instances
+of "SOMEswitch" driver. sw0pX netdevices serve as a "representation"
+of the switch chip. eth0 and eth1 are instances of some other existing driver.
+The only difference of the switch-port netdevice from the ordinary netdevice
+is that is implements couple more NDOs:
+ ndo_switch_parent_id_get - This returns the same ID for two port netdevices
+ of the same physical switch chip. This is
+ mandatory to be implemented by all switch drivers
+ and serves the caller for recognition of a port
+ netdevice.
+ ndo_switch_parent_* - Functions that serve for a manipulation of the switch
+ chip itself (it can be though of as a "parent" of the
+ port, therefore the name). They are not port-specific.
+ Caller might use arbitrary port netdevice of the same
+ switch and it will make no difference.
+ ndo_switch_port_* - Functions that serve for a port-specific manipulation.
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 1d6d02d6ba52..a5c784c89312 100644
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt
1.3.3 Timestamp Options
-The interface supports one option
+The interface supports the options
@@ -130,19 +130,36 @@ SOF_TIMESTAMPING_OPT_ID:
have multiple concurrent timestamping requests outstanding. Packets
can be reordered in the transmit path, for instance in the packet
scheduler. In that case timestamps will be queued onto the error
- queue out of order from the original send() calls. This option
- embeds a counter that is incremented at send() time, to order
- timestamps within a flow.
+ queue out of order from the original send() calls. It is not always
+ possible to uniquely match timestamps to the original send() calls
+ based on timestamp order or payload inspection alone, then.
+ This option associates each packet at send() with a unique
+ identifier and returns that along with the timestamp. The identifier
+ is derived from a per-socket u32 counter (that wraps). For datagram
+ sockets, the counter increments with each sent packet. For stream
+ sockets, it increments with every byte.
+ The counter starts at zero. It is initialized the first time that
+ the socket option is enabled. It is reset each time the option is
+ enabled after having been disabled. Resetting the counter does not
+ change the identifiers of existing packets in the system.
This option is implemented only for transmit timestamps. There, the
timestamp is always looped along with a struct sock_extended_err.
The option modifies field ee_data to pass an id that is unique
among all possibly concurrently outstanding timestamp requests for
- that socket. In practice, it is a monotonically increasing u32
- (that wraps).
+ that socket.
- In datagram sockets, the counter increments on each send call. In
- stream sockets, it increments with every byte.
+ Support recv() cmsg for all timestamped packets. Control messages
+ are already supported unconditionally on all packets with receive
+ timestamps and on IPv6 packets with transmit timestamp. This option
+ extends them to IPv4 packets with transmit timestamp. One use case
+ is to correlate packets with their egress device, by enabling socket
+ option IP_PKTINFO simultaneously.
1.4 Bytestream Timestamps
diff --git a/Documentation/networking/timestamping/txtimestamp.c b/Documentation/networking/timestamping/txtimestamp.c
index b32fc2a07734..876f71c5625a 100644
--- a/Documentation/networking/timestamping/txtimestamp.c
+++ b/Documentation/networking/timestamping/txtimestamp.c
@@ -46,6 +46,7 @@
#include <netpacket/packet.h>
#include <poll.h>
#include <stdarg.h>
+#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
@@ -58,6 +59,14 @@
#include <time.h>
#include <unistd.h>
+/* ugly hack to work around netinet/in.h and linux/ipv6.h conflicts */
+#ifndef in6_pktinfo
+struct in6_pktinfo {
+ struct in6_addr ipi6_addr;
+ int ipi6_ifindex;
/* command line parameters */
static int cfg_proto = SOCK_STREAM;
static int cfg_ipproto = IPPROTO_TCP;
@@ -65,6 +74,8 @@ static int cfg_num_pkts = 4;
static int do_ipv4 = 1;
static int do_ipv6 = 1;
static int cfg_payload_len = 10;
+static bool cfg_show_payload;
+static bool cfg_do_pktinfo;
static uint16_t dest_port = 9000;
static struct sockaddr_in daddr;
@@ -131,6 +142,30 @@ static void print_timestamp(struct scm_timestamping *tss, int tstype,
__print_timestamp(tsname, &tss->ts[0], tskey, payload_len);
+/* TODO: convert to check_and_print payload once API is stable */
+static void print_payload(char *data, int len)
+ int i;
+ if (len > 70)
+ len = 70;
+ fprintf(stderr, "payload: ");
+ for (i = 0; i < len; i++)
+ fprintf(stderr, "%02hhx ", data[i]);
+ fprintf(stderr, "\n");
+static void print_pktinfo(int family, int ifindex, void *saddr, void *daddr)
+ fprintf(stderr, " pktinfo: ifindex=%u src=%s dst=%s\n",
+ ifindex,
+ saddr ? inet_ntop(family, saddr, sa, sizeof(sa)) : "unknown",
+ daddr ? inet_ntop(family, daddr, da, sizeof(da)) : "unknown");
static void __poll(int fd)
struct pollfd pollfd;
@@ -156,10 +191,9 @@ static void __recv_errmsg_cmsg(struct msghdr *msg, int payload_len)
cm->cmsg_type == SCM_TIMESTAMPING) {
tss = (void *) CMSG_DATA(cm);
} else if ((cm->cmsg_level == SOL_IP &&
- cm->cmsg_type == IP_RECVERR) ||
- (cm->cmsg_level == SOL_IPV6 &&
- cm->cmsg_type == IPV6_RECVERR)) {
+ cm->cmsg_type == IP_RECVERR) ||
+ (cm->cmsg_level == SOL_IPV6 &&
+ cm->cmsg_type == IPV6_RECVERR)) {
serr = (void *) CMSG_DATA(cm);
if (serr->ee_errno != ENOMSG ||
serr->ee_origin != SO_EE_ORIGIN_TIMESTAMPING) {
@@ -168,6 +202,16 @@ static void __recv_errmsg_cmsg(struct msghdr *msg, int payload_len)
serr = NULL;
+ } else if (cm->cmsg_level == SOL_IP &&
+ cm->cmsg_type == IP_PKTINFO) {
+ struct in_pktinfo *info = (void *) CMSG_DATA(cm);
+ print_pktinfo(AF_INET, info->ipi_ifindex,
+ &info->ipi_spec_dst, &info->ipi_addr);
+ } else if (cm->cmsg_level == SOL_IPV6 &&
+ cm->cmsg_type == IPV6_PKTINFO) {
+ struct in6_pktinfo *info6 = (void *) CMSG_DATA(cm);
+ print_pktinfo(AF_INET6, info6->ipi6_ifindex,
+ NULL, &info6->ipi6_addr);
} else
fprintf(stderr, "unknown cmsg %d,%d\n",
cm->cmsg_level, cm->cmsg_type);
@@ -206,7 +250,11 @@ static int recv_errmsg(int fd)
if (ret == -1 && errno != EAGAIN)
error(1, errno, "recvmsg");
- __recv_errmsg_cmsg(&msg, ret);
+ if (ret > 0) {
+ __recv_errmsg_cmsg(&msg, ret);
+ if (cfg_show_payload)
+ print_payload(data, cfg_payload_len);
+ }
return ret == -1;
@@ -215,9 +263,9 @@ static int recv_errmsg(int fd)
static void do_test(int family, unsigned int opt)
char *buf;
- int fd, i, val, total_len;
+ int fd, i, val = 1, total_len;
- if (family == IPPROTO_IPV6 && cfg_proto != SOCK_STREAM) {
+ if (family == AF_INET6 && cfg_proto != SOCK_STREAM) {
/* due to lack of checksum generation code */
fprintf(stderr, "test: skipping datagram over IPv6\n");
@@ -239,7 +287,6 @@ static void do_test(int family, unsigned int opt)
error(1, errno, "socket");
if (cfg_proto == SOCK_STREAM) {
- val = 1;
if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
(char*) &val, sizeof(val)))
error(1, 0, "setsockopt no nagle");
@@ -253,7 +300,20 @@ static void do_test(int family, unsigned int opt)
+ if (cfg_do_pktinfo) {
+ if (family == AF_INET6) {
+ if (setsockopt(fd, SOL_IPV6, IPV6_RECVPKTINFO,
+ &val, sizeof(val)))
+ error(1, errno, "setsockopt pktinfo ipv6");
+ } else {
+ if (setsockopt(fd, SOL_IP, IP_PKTINFO,
+ &val, sizeof(val)))
+ error(1, errno, "setsockopt pktinfo ipv4");
+ }
+ }
if (setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING,
(char *) &opt, sizeof(opt)))
@@ -262,8 +322,6 @@ static void do_test(int family, unsigned int opt)
for (i = 0; i < cfg_num_pkts; i++) {
memset(&ts_prev, 0, sizeof(ts_prev));
memset(buf, 'a' + i, total_len);
- buf[total_len - 2] = '\n';
- buf[total_len - 1] = '\0';
if (cfg_proto == SOCK_RAW) {
struct udphdr *udph;
@@ -324,11 +382,13 @@ static void __attribute__((noreturn)) usage(const char *filepath)
" -4: only IPv4\n"
" -6: only IPv6\n"
" -h: show this message\n"
+ " -I: request PKTINFO\n"
" -l N: send N bytes at a time\n"
" -r: use raw\n"
" -R: use raw (IP_HDRINCL)\n"
" -p N: connect to port N\n"
- " -u: use udp\n",
+ " -u: use udp\n"
+ " -x: show payload (up to 70 bytes)\n",
@@ -338,7 +398,7 @@ static void parse_opt(int argc, char **argv)
int proto_count = 0;
char c;
- while ((c = getopt(argc, argv, "46hl:p:rRu")) != -1) {
+ while ((c = getopt(argc, argv, "46hIl:p:rRux")) != -1) {
switch (c) {
case '4':
do_ipv6 = 0;
@@ -346,6 +406,9 @@ static void parse_opt(int argc, char **argv)
case '6':
do_ipv4 = 0;
+ case 'I':
+ cfg_do_pktinfo = true;
+ break;
case 'r':
cfg_proto = SOCK_RAW;
@@ -367,6 +430,9 @@ static void parse_opt(int argc, char **argv)
case 'p':
dest_port = strtoul(optarg, NULL, 10);
+ case 'x':
+ cfg_show_payload = true;
+ break;
case 'h':
diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt
index 04892b821157..666594b43cff 100644
--- a/Documentation/sysctl/net.txt
+++ b/Documentation/sysctl/net.txt
@@ -120,10 +120,14 @@ seconds.
-This controls console messages from the networking stack that can occur because
-of problems on the network like duplicate address or bad checksums. Normally,
-this should be enabled, but if the problem persists the messages can be
+This sysctl is now unused.
+This was used to control console messages from the networking stack that
+occur because of problems on the network like duplicate address or bad
+These messages are now emitted at KERN_DEBUG and can generally be enabled
+and controlled by the dynamic_debug facility.
@@ -138,6 +142,28 @@ netdev_max_backlog
Maximum number of packets, queued on the INPUT side, when the interface
receives packets faster than kernel can process them.
+RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
+randomly generated.
+Some user space might need to gather its content even if drivers do not
+provide ethtool -x support yet.
+myhost:~# cat /proc/sys/net/core/netdev_rss_key
+84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8: ... (52 bytes total)
+File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
+/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
+but most drivers only use 40 bytes of it.
+myhost:~# ethtool -x eth0
+RX flow hash indirection table for eth0 with 8 RX ring(s):
+ 0: 0 1 2 3 4 5 6 7
+RSS hash key: