Documentation for /proc/sys/net/* kernel version 2.4.0-test11-pre4
(c) 1999 Terrehon Bowden terrehon@pacbell.net
Bodo Bauer bb@ricochet.net
(c) 2000 Jorge Nerin comandante@zaralinux.com
(c) 2009 Shen Feng shen@cn.fujitsu.com
For general info and legal blurb, please look in README.
==============================================================
This file contains the documentation for the sysctl files in
/proc/sys/net and is valid for Linux kernel version 2.4.0-test11-pre4.
The interface to the networking parts of the kernel is located in
/proc/sys/net. The following table shows all possible subdirectories.You may
see only some of them, depending on your kernel’s configuration.
Table : Subdirectories in /proc/sys/net
……………………………………………………………………
Directory Content Directory Content
core General parameter appletalk Appletalk protocol
unix Unix domain sockets netrom NET/ROM
802 E802 protocol ax25 AX25
ethernet Ethernet protocol rose X.25 PLP layer
ipv4 IP version 4 x25 X.25 protocol
ipx IPX token-ring IBM token ring
bridge Bridging decnet DEC net
ipv6 IP version 6
……………………………………………………………………
- /proc/sys/net/core - Network core options
bpf_jit_enable
This enables Berkeley Packet Filter Just in Time compiler.
Currently supported on x86_64 architecture, bpf_jit provides a framework
to speed packet filtering, the one used by tcpdump/libpcap for example.
Values :
0 - disable the JIT (default value)
1 - enable the JIT
2 - enable the JIT and ask the compiler to emit traces on kernel log.
bpf_jit_harden
This enables hardening for the Berkeley Packet Filter Just in Time compiler.
Supported are eBPF JIT backends. Enabling hardening trades off performance,
but can mitigate JIT spraying.
Values :
0 - disable JIT hardening (default value)
1 - enable JIT hardening for unprivileged users only
2 - enable JIT hardening for all users
dev_weight
The maximum number of packets that kernel can handle on a NAPI interrupt,
it’s a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware
aggregated packet is counted as one packet in this context.
Default: 64
dev_weight_rx_bias
RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function
of the driver for the per softirq cycle netdev_budget. This parameter influences
the proportion of the configured netdev_budget that is spent on RPS based packet
processing during RX softirq cycles. It is further meant for making current
dev_weight adaptable for asymmetric CPU needs on RX/TX side of the network stack.
(see dev_weight_tx_bias) It is effective on a per CPU basis. Determination is based
on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias).
Default: 1
dev_weight_tx_bias
Scales the maximum number of packets that can be processed during a TX softirq cycle.
Effective on a per CPU basis. Allows scaling of current dev_weight for asymmetric
net stack processing needs. Be careful to avoid making TX softirq processing a CPU hog.
Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias).
Default: 1
default_qdisc
The default queuing discipline to use for network devices. This allows
overriding the default of pfifo_fast with an alternative. Since the default
queuing discipline is created without additional parameters so is best suited
to queuing disciplines that work well without configuration like stochastic
fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don’t use
queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
which require setting up classes and bandwidths. Note that physical multiqueue
interfaces still use mq as root qdisc, which in turn uses this default for its
leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
default to noqueue.
Default: pfifo_fast
busy_read
Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
Approximate time in us to busy loop waiting for packets on the device queue.
This sets the default value of the SO_BUSY_POLL socket option.
Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
which is the preferred method of enabling. If you need to enable the feature
globally via sysctl, a value of 50 is recommended.
Will increase power usage.
Default: 0 (off)
busy_poll
Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
Approximate time in us to busy loop waiting for events.
Recommended value depends on the number of sockets you poll on.
For several sockets 50, for several hundreds 100.
For more than that you probably want to use epoll.
Note that only sockets with SO_BUSY_POLL set will be busy polled,
so you want to either selectively set SO_BUSY_POLL on those sockets or set
sysctl.net.busy_read globally.
Will increase power usage.
Default: 0 (off)
rmem_default
The default setting of the socket receive buffer in bytes.
rmem_max
The maximum receive socket buffer size in bytes.
wmem_default
The default setting (in bytes) of the socket send buffer.
wmem_max
The maximum send socket buffer size in bytes.
message_burst and message_cost
These parameters are used to limit the warning messages written to the kernel
log from the networking code. They enforce a rate limit to make a
denial-of-service attack impossible. A higher message_cost factor, results in
fewer messages that will be written. Message_burst controls when messages will
be dropped. The default settings limit warning messages to one every five
seconds.
warnings
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
disabled.
netdev_budget
Maximum number of packets taken from all interfaces in one polling cycle (NAPI
poll). In one polling cycle interfaces which are registered to polling are
probed in a round-robin manner. The limit of packets in one such probe can be
set per-device via sysfs class/net/
netdev_max_backlog
Maximum number of packets, queued on the INPUT side, when the interface
receives packets faster than kernel can process them.
netdev_rss_key
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.
Note:
/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:
84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89
netdev_tstamp_prequeue
If set to 0, RX packet timestamps can be sampled after RPS processing, when
the target CPU processes packets. It might give some delay on timestamps, but
permit to distribute the load on several cpus.
If set to 1 (default), timestamps are sampled as soon as possible, before
queueing.
optmem_max
Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
of struct cmsghdr structures with appended data.
- /proc/sys/net/unix - Parameters for Unix domain sockets
There is only one file in this directory.
unix_dgram_qlen limits the max number of datagrams queued in Unix domain
socket’s buffer. It will not take effect unless PF_UNIX flag is specified.
- /proc/sys/net/ipv4 - IPV4 settings
Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
descriptions of these entries.
- Appletalk
The /proc/sys/net/appletalk directory holds the Appletalk configuration data
when Appletalk is loaded. The configurable parameters are:
aarp-expiry-time
The amount of time we keep an ARP entry before expiring it. Used to age out
old hosts.
aarp-resolve-time
The amount of time we will spend trying to resolve an Appletalk address.
aarp-retransmit-limit
The number of times we will retransmit a query before giving up.
aarp-tick-time
Controls the rate at which expires are checked.
The directory /proc/net/appletalk holds the list of active Appletalk sockets
on a machine.
The fields indicate the DDP type, the local address (in network:node format)
the remote address, the size of the transmit pending queue, the size of the
received queue (bytes waiting for applications to read) the state and the uid
owning the socket.
/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
shows the name of the interface, its Appletalk address, the network range on
that address (or network number for phase 1 networks), and the status of the
interface.
/proc/net/atalk_route lists each known network route. It lists the target
(network) that the route leads to, the router (may be directly connected), the
route flags, and the device the route is using.
- IPX
The IPX protocol has no tunable values in proc/sys/net.
The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
socket giving the local and remote addresses in Novell format (that is
network:node:port). In accordance with the strange Novell tradition,
everything but the port is in hex. Not_Connected is displayed for sockets that
are not tied to a specific remote address. The Tx and Rx queue sizes indicate
the number of bytes pending for transmission and reception. The state
indicates the state the socket is in and the uid is the owning uid of the
socket.
The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
it gives the network number, the node number, and indicates if the network is
the primary network. It also indicates which device it is bound to (or
Internal for internal networks) and the Frame Type if appropriate. Linux
supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
IPX.
The /proc/net/ipx_route table holds a list of IPX routes. For each route it
gives the destination network, the router node (or Directly) and the network
address of the router (or Connected) for internal networks.
