Documentation/sysctl/net.txt

   1 Documentation for /proc/sys/net/*       kernel version 2.4.0-test11-pre4
   2         (c) 1999                Terrehon Bowden <terrehon@pacbell.net>
   3                                 Bodo Bauer <bb@ricochet.net>
   4         (c) 2000                Jorge Nerin <comandante@zaralinux.com>
   5         (c) 2009                Shen Feng <shen@cn.fujitsu.com>
   6
   7 For general info and legal blurb, please look in README.
   8
   9 ==============================================================
  10
  11 This file contains the documentation for the sysctl files in
  12 /proc/sys/net and is valid for Linux kernel version 2.4.0-test11-pre4.
  13
  14 The interface  to  the  networking  parts  of  the  kernel  is  located  in
  15 /proc/sys/net. The following table shows all possible subdirectories.You may
  16 see only some of them, depending on your kernel's configuration.
  17
  18
  19 Table : Subdirectories in /proc/sys/net
  20 ..............................................................................
  21  Directory Content             Directory  Content
  22  core      General parameter   appletalk  Appletalk protocol
  23  unix      Unix domain sockets netrom     NET/ROM
  24  802       E802 protocol       ax25       AX25
  25  ethernet  Ethernet protocol   rose       X.25 PLP layer
  26  ipv4      IP version 4        x25        X.25 protocol
  27  ipx       IPX                 token-ring IBM token ring
  28  bridge    Bridging            decnet     DEC net
  29  ipv6      IP version 6
  30 ..............................................................................
  31
  32 1. /proc/sys/net/core - Network core options
  33 -------------------------------------------------------
  34
  35 bpf_jit_enable
  36 --------------
  37
  38 This enables Berkeley Packet Filter Just in Time compiler.
  39 Currently supported on x86_64 architecture, bpf_jit provides a framework
  40 to speed packet filtering, the one used by tcpdump/libpcap for example.
  41 Values :
  42         0 - disable the JIT (default value)
  43         1 - enable the JIT
  44         2 - enable the JIT and ask the compiler to emit traces on kernel log.
  45
  46 dev_weight
  47 --------------
  48
  49 The maximum number of packets that kernel can handle on a NAPI interrupt,
  50 it's a Per-CPU variable.
  51 Default: 64
  52
  53 low_latency_poll
  54 ----------------
  55 Low latency busy poll timeout. (needs CONFIG_NET_LL_RX_POLL)
  56 Approximate time in us to spin waiting for packets on the device queue.
  57 Recommended value is 50. May increase power usage.
  58 Default: 0 (off)
  59
  60 rmem_default
  61 ------------
  62
  63 The default setting of the socket receive buffer in bytes.
  64
  65 rmem_max
  66 --------
  67
  68 The maximum receive socket buffer size in bytes.
  69
  70 wmem_default
  71 ------------
  72
  73 The default setting (in bytes) of the socket send buffer.
  74
  75 wmem_max
  76 --------
  77
  78 The maximum send socket buffer size in bytes.
  79
  80 message_burst and message_cost
  81 ------------------------------
  82
  83 These parameters  are used to limit the warning messages written to the kernel
  84 log from  the  networking  code.  They  enforce  a  rate  limit  to  make  a
  85 denial-of-service attack  impossible. A higher message_cost factor, results in
  86 fewer messages that will be written. Message_burst controls when messages will
  87 be dropped.  The  default  settings  limit  warning messages to one every five
  88 seconds.
  89
  90 warnings
  91 --------
  92
  93 This controls console messages from the networking stack that can occur because
  94 of problems on the network like duplicate address or bad checksums. Normally,
  95 this should be enabled, but if the problem persists the messages can be
  96 disabled.
  97
  98 netdev_budget
  99 -------------
 100
 101 Maximum number of packets taken from all interfaces in one polling cycle (NAPI
 102 poll). In one polling cycle interfaces which are registered to polling are
 103 probed in a round-robin manner.
 104
 105 netdev_max_backlog
 106 ------------------
 107
 108 Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
 109 receives packets faster than kernel can process them.
 110
 111 netdev_tstamp_prequeue
 112 ----------------------
 113
 114 If set to 0, RX packet timestamps can be sampled after RPS processing, when
 115 the target CPU processes packets. It might give some delay on timestamps, but
 116 permit to distribute the load on several cpus.
 117
 118 If set to 1 (default), timestamps are sampled as soon as possible, before
 119 queueing.
 120
 121 optmem_max
 122 ----------
 123
 124 Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
 125 of struct cmsghdr structures with appended data.
 126
 127 2. /proc/sys/net/unix - Parameters for Unix domain sockets
 128 -------------------------------------------------------
 129
 130 There is only one file in this directory.
 131 unix_dgram_qlen limits the max number of datagrams queued in Unix domain
 132 socket's buffer. It will not take effect unless PF_UNIX flag is specified.
 133
 134
 135 3. /proc/sys/net/ipv4 - IPV4 settings
 136 -------------------------------------------------------
 137 Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
 138 descriptions of these entries.
 139
 140
 141 4. Appletalk
 142 -------------------------------------------------------
 143
 144 The /proc/sys/net/appletalk  directory  holds the Appletalk configuration data
 145 when Appletalk is loaded. The configurable parameters are:
 146
 147 aarp-expiry-time
 148 ----------------
 149
 150 The amount  of  time  we keep an ARP entry before expiring it. Used to age out
 151 old hosts.
 152
 153 aarp-resolve-time
 154 -----------------
 155
 156 The amount of time we will spend trying to resolve an Appletalk address.
 157
 158 aarp-retransmit-limit
 159 ---------------------
 160
 161 The number of times we will retransmit a query before giving up.
 162
 163 aarp-tick-time
 164 --------------
 165
 166 Controls the rate at which expires are checked.
 167
 168 The directory  /proc/net/appletalk  holds the list of active Appletalk sockets
 169 on a machine.
 170
 171 The fields  indicate  the DDP type, the local address (in network:node format)
 172 the remote  address,  the  size of the transmit pending queue, the size of the
 173 received queue  (bytes waiting for applications to read) the state and the uid
 174 owning the socket.
 175
 176 /proc/net/atalk_iface lists  all  the  interfaces  configured for appletalk.It
 177 shows the  name  of the interface, its Appletalk address, the network range on
 178 that address  (or  network number for phase 1 networks), and the status of the
 179 interface.
 180
 181 /proc/net/atalk_route lists  each  known  network  route.  It lists the target
 182 (network) that the route leads to, the router (may be directly connected), the
 183 route flags, and the device the route is using.
 184
 185
 186 5. IPX
 187 -------------------------------------------------------
 188
 189 The IPX protocol has no tunable values in proc/sys/net.
 190
 191 The IPX  protocol  does,  however,  provide  proc/net/ipx. This lists each IPX
 192 socket giving  the  local  and  remote  addresses  in  Novell  format (that is
 193 network:node:port). In  accordance  with  the  strange  Novell  tradition,
 194 everything but the port is in hex. Not_Connected is displayed for sockets that
 195 are not  tied to a specific remote address. The Tx and Rx queue sizes indicate
 196 the number  of  bytes  pending  for  transmission  and  reception.  The  state
 197 indicates the  state  the  socket  is  in and the uid is the owning uid of the
 198 socket.
 199
 200 The /proc/net/ipx_interface  file lists all IPX interfaces. For each interface
 201 it gives  the network number, the node number, and indicates if the network is
 202 the primary  network.  It  also  indicates  which  device  it  is bound to (or
 203 Internal for  internal  networks)  and  the  Frame  Type if appropriate. Linux
 204 supports 802.3,  802.2,  802.2  SNAP  and DIX (Blue Book) ethernet framing for
 205 IPX.
 206
 207 The /proc/net/ipx_route  table  holds  a list of IPX routes. For each route it
 208 gives the  destination  network, the router node (or Directly) and the network
 209 address of the router (or Connected) for internal networks.