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TIPC name table updates are distributed asynchronously in a cluster,
entailing a risk of certain race conditions. E.g., if two nodes
simultaneously issue conflicting (overlapping) publications, this may
not be detected until both publications have reached a third node, in
which case one of the publications will be silently dropped on that
node. Hence, we end up with an inconsistent name table.
In most cases this conflict is just a temporary race, e.g., one
node is issuing a publication under the assumption that a previous,
conflicting, publication has already been withdrawn by the other node.
However, because of the (rtt related) distributed update delay, this
may not yet hold true on all nodes. The symptom of this failure is a
syslog message: "tipc: Cannot publish {%u,%u,%u}, overlap error".
In this commit we add a resiliency queue at the receiving end of
the name table distributor. When insertion of an arriving publication
fails, we retain it in this queue for a short amount of time, assuming
that another update will arrive very soon and clear the conflict. If so
happens, we insert the publication, otherwise we drop it.
The (configurable) retention value defaults to 2000 ms. Knowing from
experience that the situation described above is extremely rare, there
is no risk that the queue will accumulate any large number of items.
Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
271 lines
9.7 KiB
Plaintext
271 lines
9.7 KiB
Plaintext
Documentation for /proc/sys/net/*
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(c) 1999 Terrehon Bowden <terrehon@pacbell.net>
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Bodo Bauer <bb@ricochet.net>
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(c) 2000 Jorge Nerin <comandante@zaralinux.com>
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(c) 2009 Shen Feng <shen@cn.fujitsu.com>
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For general info and legal blurb, please look in README.
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==============================================================
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This file contains the documentation for the sysctl files in
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/proc/sys/net
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The interface to the networking parts of the kernel is located in
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/proc/sys/net. The following table shows all possible subdirectories. You may
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see only some of them, depending on your kernel's configuration.
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Table : Subdirectories in /proc/sys/net
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..............................................................................
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Directory Content Directory Content
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core General parameter appletalk Appletalk protocol
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unix Unix domain sockets netrom NET/ROM
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802 E802 protocol ax25 AX25
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ethernet Ethernet protocol rose X.25 PLP layer
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ipv4 IP version 4 x25 X.25 protocol
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ipx IPX token-ring IBM token ring
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bridge Bridging decnet DEC net
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ipv6 IP version 6 tipc TIPC
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..............................................................................
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1. /proc/sys/net/core - Network core options
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-------------------------------------------------------
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bpf_jit_enable
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--------------
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This enables Berkeley Packet Filter Just in Time compiler.
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Currently supported on x86_64 architecture, bpf_jit provides a framework
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to speed packet filtering, the one used by tcpdump/libpcap for example.
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Values :
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0 - disable the JIT (default value)
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1 - enable the JIT
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2 - enable the JIT and ask the compiler to emit traces on kernel log.
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dev_weight
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--------------
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The maximum number of packets that kernel can handle on a NAPI interrupt,
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it's a Per-CPU variable.
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Default: 64
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default_qdisc
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--------------
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The default queuing discipline to use for network devices. This allows
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overriding the default queue discipline of pfifo_fast with an
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alternative. Since the default queuing discipline is created with the
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no additional parameters so is best suited to queuing disciplines that
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work well without configuration like stochastic fair queue (sfq),
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CoDel (codel) or fair queue CoDel (fq_codel). Don't use queuing disciplines
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like Hierarchical Token Bucket or Deficit Round Robin which require setting
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up classes and bandwidths.
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Default: pfifo_fast
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busy_read
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----------------
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Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
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Approximate time in us to busy loop waiting for packets on the device queue.
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This sets the default value of the SO_BUSY_POLL socket option.
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Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
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which is the preferred method of enabling. If you need to enable the feature
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globally via sysctl, a value of 50 is recommended.
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Will increase power usage.
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Default: 0 (off)
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busy_poll
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----------------
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Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
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Approximate time in us to busy loop waiting for events.
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Recommended value depends on the number of sockets you poll on.
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For several sockets 50, for several hundreds 100.
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For more than that you probably want to use epoll.
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Note that only sockets with SO_BUSY_POLL set will be busy polled,
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so you want to either selectively set SO_BUSY_POLL on those sockets or set
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sysctl.net.busy_read globally.
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Will increase power usage.
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Default: 0 (off)
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rmem_default
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------------
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The default setting of the socket receive buffer in bytes.
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rmem_max
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--------
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The maximum receive socket buffer size in bytes.
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wmem_default
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------------
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The default setting (in bytes) of the socket send buffer.
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wmem_max
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--------
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The maximum send socket buffer size in bytes.
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message_burst and message_cost
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------------------------------
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These parameters are used to limit the warning messages written to the kernel
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log from the networking code. They enforce a rate limit to make a
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denial-of-service attack impossible. A higher message_cost factor, results in
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fewer messages that will be written. Message_burst controls when messages will
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be dropped. The default settings limit warning messages to one every five
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seconds.
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warnings
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--------
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This controls console messages from the networking stack that can occur because
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of problems on the network like duplicate address or bad checksums. Normally,
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this should be enabled, but if the problem persists the messages can be
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disabled.
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netdev_budget
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-------------
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Maximum number of packets taken from all interfaces in one polling cycle (NAPI
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poll). In one polling cycle interfaces which are registered to polling are
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probed in a round-robin manner.
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netdev_max_backlog
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------------------
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Maximum number of packets, queued on the INPUT side, when the interface
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receives packets faster than kernel can process them.
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netdev_tstamp_prequeue
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----------------------
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If set to 0, RX packet timestamps can be sampled after RPS processing, when
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the target CPU processes packets. It might give some delay on timestamps, but
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permit to distribute the load on several cpus.
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If set to 1 (default), timestamps are sampled as soon as possible, before
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queueing.
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optmem_max
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----------
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Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
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of struct cmsghdr structures with appended data.
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2. /proc/sys/net/unix - Parameters for Unix domain sockets
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-------------------------------------------------------
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There is only one file in this directory.
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unix_dgram_qlen limits the max number of datagrams queued in Unix domain
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socket's buffer. It will not take effect unless PF_UNIX flag is specified.
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3. /proc/sys/net/ipv4 - IPV4 settings
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-------------------------------------------------------
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Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
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descriptions of these entries.
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4. Appletalk
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-------------------------------------------------------
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The /proc/sys/net/appletalk directory holds the Appletalk configuration data
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when Appletalk is loaded. The configurable parameters are:
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aarp-expiry-time
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----------------
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The amount of time we keep an ARP entry before expiring it. Used to age out
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old hosts.
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aarp-resolve-time
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-----------------
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The amount of time we will spend trying to resolve an Appletalk address.
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aarp-retransmit-limit
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---------------------
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The number of times we will retransmit a query before giving up.
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aarp-tick-time
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--------------
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Controls the rate at which expires are checked.
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The directory /proc/net/appletalk holds the list of active Appletalk sockets
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on a machine.
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The fields indicate the DDP type, the local address (in network:node format)
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the remote address, the size of the transmit pending queue, the size of the
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received queue (bytes waiting for applications to read) the state and the uid
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owning the socket.
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/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
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shows the name of the interface, its Appletalk address, the network range on
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that address (or network number for phase 1 networks), and the status of the
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interface.
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/proc/net/atalk_route lists each known network route. It lists the target
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(network) that the route leads to, the router (may be directly connected), the
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route flags, and the device the route is using.
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5. IPX
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-------------------------------------------------------
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The IPX protocol has no tunable values in proc/sys/net.
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The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
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socket giving the local and remote addresses in Novell format (that is
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network:node:port). In accordance with the strange Novell tradition,
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everything but the port is in hex. Not_Connected is displayed for sockets that
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are not tied to a specific remote address. The Tx and Rx queue sizes indicate
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the number of bytes pending for transmission and reception. The state
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indicates the state the socket is in and the uid is the owning uid of the
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socket.
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The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
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it gives the network number, the node number, and indicates if the network is
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the primary network. It also indicates which device it is bound to (or
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Internal for internal networks) and the Frame Type if appropriate. Linux
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supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
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IPX.
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The /proc/net/ipx_route table holds a list of IPX routes. For each route it
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gives the destination network, the router node (or Directly) and the network
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address of the router (or Connected) for internal networks.
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6. TIPC
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-------------------------------------------------------
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tipc_rmem
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----------
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The TIPC protocol now has a tunable for the receive memory, similar to the
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tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
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# cat /proc/sys/net/tipc/tipc_rmem
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4252725 34021800 68043600
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#
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The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
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are scaled (shifted) versions of that same value. Note that the min value
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is not at this point in time used in any meaningful way, but the triplet is
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preserved in order to be consistent with things like tcp_rmem.
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named_timeout
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--------------
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TIPC name table updates are distributed asynchronously in a cluster, without
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any form of transaction handling. This means that different race scenarios are
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possible. One such is that a name withdrawal sent out by one node and received
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by another node may arrive after a second, overlapping name publication already
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has been accepted from a third node, although the conflicting updates
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originally may have been issued in the correct sequential order.
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If named_timeout is nonzero, failed topology updates will be placed on a defer
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queue until another event arrives that clears the error, or until the timeout
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expires. Value is in milliseconds.
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