Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /proc/sys/net/ipv4/* Variables: |
| 2 | |
| 3 | ip_forward - BOOLEAN |
| 4 | 0 - disabled (default) |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 5 | not 0 - enabled |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | |
| 7 | Forward Packets between interfaces. |
| 8 | |
| 9 | This variable is special, its change resets all configuration |
| 10 | parameters to their default state (RFC1122 for hosts, RFC1812 |
| 11 | for routers) |
| 12 | |
| 13 | ip_default_ttl - INTEGER |
| 14 | default 64 |
| 15 | |
| 16 | ip_no_pmtu_disc - BOOLEAN |
| 17 | Disable Path MTU Discovery. |
| 18 | default FALSE |
| 19 | |
| 20 | min_pmtu - INTEGER |
| 21 | default 562 - minimum discovered Path MTU |
| 22 | |
| 23 | mtu_expires - INTEGER |
| 24 | Time, in seconds, that cached PMTU information is kept. |
| 25 | |
| 26 | min_adv_mss - INTEGER |
| 27 | The advertised MSS depends on the first hop route MTU, but will |
| 28 | never be lower than this setting. |
| 29 | |
Neil Horman | 1080d70 | 2008-10-27 12:28:25 -0700 | [diff] [blame] | 30 | rt_cache_rebuild_count - INTEGER |
| 31 | The per net-namespace route cache emergency rebuild threshold. |
| 32 | Any net-namespace having its route cache rebuilt due to |
| 33 | a hash bucket chain being too long more than this many times |
| 34 | will have its route caching disabled |
| 35 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 36 | IP Fragmentation: |
| 37 | |
| 38 | ipfrag_high_thresh - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 39 | Maximum memory used to reassemble IP fragments. When |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 40 | ipfrag_high_thresh bytes of memory is allocated for this purpose, |
| 41 | the fragment handler will toss packets until ipfrag_low_thresh |
| 42 | is reached. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 43 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 44 | ipfrag_low_thresh - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 45 | See ipfrag_high_thresh |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 46 | |
| 47 | ipfrag_time - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 48 | Time in seconds to keep an IP fragment in memory. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 49 | |
| 50 | ipfrag_secret_interval - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 51 | Regeneration interval (in seconds) of the hash secret (or lifetime |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 52 | for the hash secret) for IP fragments. |
| 53 | Default: 600 |
| 54 | |
Herbert Xu | 89cee8b | 2005-12-13 23:14:27 -0800 | [diff] [blame] | 55 | ipfrag_max_dist - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 56 | ipfrag_max_dist is a non-negative integer value which defines the |
| 57 | maximum "disorder" which is allowed among fragments which share a |
| 58 | common IP source address. Note that reordering of packets is |
| 59 | not unusual, but if a large number of fragments arrive from a source |
| 60 | IP address while a particular fragment queue remains incomplete, it |
| 61 | probably indicates that one or more fragments belonging to that queue |
| 62 | have been lost. When ipfrag_max_dist is positive, an additional check |
| 63 | is done on fragments before they are added to a reassembly queue - if |
| 64 | ipfrag_max_dist (or more) fragments have arrived from a particular IP |
| 65 | address between additions to any IP fragment queue using that source |
| 66 | address, it's presumed that one or more fragments in the queue are |
| 67 | lost. The existing fragment queue will be dropped, and a new one |
Herbert Xu | 89cee8b | 2005-12-13 23:14:27 -0800 | [diff] [blame] | 68 | started. An ipfrag_max_dist value of zero disables this check. |
| 69 | |
| 70 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can |
| 71 | result in unnecessarily dropping fragment queues when normal |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 72 | reordering of packets occurs, which could lead to poor application |
| 73 | performance. Using a very large value, e.g. 50000, increases the |
| 74 | likelihood of incorrectly reassembling IP fragments that originate |
Herbert Xu | 89cee8b | 2005-12-13 23:14:27 -0800 | [diff] [blame] | 75 | from different IP datagrams, which could result in data corruption. |
| 76 | Default: 64 |
| 77 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 78 | INET peer storage: |
| 79 | |
| 80 | inet_peer_threshold - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 81 | The approximate size of the storage. Starting from this threshold |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 82 | entries will be thrown aggressively. This threshold also determines |
| 83 | entries' time-to-live and time intervals between garbage collection |
| 84 | passes. More entries, less time-to-live, less GC interval. |
| 85 | |
| 86 | inet_peer_minttl - INTEGER |
| 87 | Minimum time-to-live of entries. Should be enough to cover fragment |
| 88 | time-to-live on the reassembling side. This minimum time-to-live is |
| 89 | guaranteed if the pool size is less than inet_peer_threshold. |
Stephen Hemminger | 77a538d | 2008-07-01 17:22:48 -0700 | [diff] [blame] | 90 | Measured in seconds. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 91 | |
| 92 | inet_peer_maxttl - INTEGER |
| 93 | Maximum time-to-live of entries. Unused entries will expire after |
| 94 | this period of time if there is no memory pressure on the pool (i.e. |
| 95 | when the number of entries in the pool is very small). |
Stephen Hemminger | 77a538d | 2008-07-01 17:22:48 -0700 | [diff] [blame] | 96 | Measured in seconds. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 97 | |
| 98 | inet_peer_gc_mintime - INTEGER |
| 99 | Minimum interval between garbage collection passes. This interval is |
| 100 | in effect under high memory pressure on the pool. |
Stephen Hemminger | 77a538d | 2008-07-01 17:22:48 -0700 | [diff] [blame] | 101 | Measured in seconds. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 102 | |
| 103 | inet_peer_gc_maxtime - INTEGER |
| 104 | Minimum interval between garbage collection passes. This interval is |
| 105 | in effect under low (or absent) memory pressure on the pool. |
Stephen Hemminger | 77a538d | 2008-07-01 17:22:48 -0700 | [diff] [blame] | 106 | Measured in seconds. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 107 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 108 | TCP variables: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 109 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 110 | somaxconn - INTEGER |
| 111 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. |
| 112 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning |
| 113 | for TCP sockets. |
| 114 | |
Stephen Hemminger | 9772efb | 2005-11-10 17:09:53 -0800 | [diff] [blame] | 115 | tcp_abc - INTEGER |
Stephen Hemminger | b3a8a40 | 2006-09-13 19:51:02 -0700 | [diff] [blame] | 116 | Controls Appropriate Byte Count (ABC) defined in RFC3465. |
| 117 | ABC is a way of increasing congestion window (cwnd) more slowly |
| 118 | in response to partial acknowledgments. |
| 119 | Possible values are: |
| 120 | 0 increase cwnd once per acknowledgment (no ABC) |
| 121 | 1 increase cwnd once per acknowledgment of full sized segment |
| 122 | 2 allow increase cwnd by two if acknowledgment is |
| 123 | of two segments to compensate for delayed acknowledgments. |
| 124 | Default: 0 (off) |
Stephen Hemminger | 9772efb | 2005-11-10 17:09:53 -0800 | [diff] [blame] | 125 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 126 | tcp_abort_on_overflow - BOOLEAN |
| 127 | If listening service is too slow to accept new connections, |
| 128 | reset them. Default state is FALSE. It means that if overflow |
| 129 | occurred due to a burst, connection will recover. Enable this |
| 130 | option _only_ if you are really sure that listening daemon |
| 131 | cannot be tuned to accept connections faster. Enabling this |
| 132 | option can harm clients of your server. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 133 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 134 | tcp_adv_win_scale - INTEGER |
| 135 | Count buffering overhead as bytes/2^tcp_adv_win_scale |
| 136 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), |
| 137 | if it is <= 0. |
| 138 | Default: 2 |
| 139 | |
| 140 | tcp_allowed_congestion_control - STRING |
| 141 | Show/set the congestion control choices available to non-privileged |
| 142 | processes. The list is a subset of those listed in |
| 143 | tcp_available_congestion_control. |
| 144 | Default is "reno" and the default setting (tcp_congestion_control). |
| 145 | |
| 146 | tcp_app_win - INTEGER |
| 147 | Reserve max(window/2^tcp_app_win, mss) of window for application |
| 148 | buffer. Value 0 is special, it means that nothing is reserved. |
| 149 | Default: 31 |
| 150 | |
| 151 | tcp_available_congestion_control - STRING |
| 152 | Shows the available congestion control choices that are registered. |
| 153 | More congestion control algorithms may be available as modules, |
| 154 | but not loaded. |
| 155 | |
John Heffner | 71599cd | 2007-02-27 10:03:56 -0800 | [diff] [blame] | 156 | tcp_base_mss - INTEGER |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 157 | The initial value of search_low to be used by the packetization layer |
| 158 | Path MTU discovery (MTU probing). If MTU probing is enabled, |
| 159 | this is the initial MSS used by the connection. |
John Heffner | 71599cd | 2007-02-27 10:03:56 -0800 | [diff] [blame] | 160 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 161 | tcp_congestion_control - STRING |
| 162 | Set the congestion control algorithm to be used for new |
| 163 | connections. The algorithm "reno" is always available, but |
| 164 | additional choices may be available based on kernel configuration. |
| 165 | Default is set as part of kernel configuration. |
| 166 | |
William Allen Simpson | 519855c | 2009-12-02 18:14:19 +0000 | [diff] [blame] | 167 | tcp_cookie_size - INTEGER |
| 168 | Default size of TCP Cookie Transactions (TCPCT) option, that may be |
| 169 | overridden on a per socket basis by the TCPCT socket option. |
| 170 | Values greater than the maximum (16) are interpreted as the maximum. |
| 171 | Values greater than zero and less than the minimum (8) are interpreted |
| 172 | as the minimum. Odd values are interpreted as the next even value. |
| 173 | Default: 0 (off). |
| 174 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 175 | tcp_dsack - BOOLEAN |
| 176 | Allows TCP to send "duplicate" SACKs. |
| 177 | |
| 178 | tcp_ecn - BOOLEAN |
Ilpo Järvinen | 255cac9 | 2009-05-04 11:07:36 -0700 | [diff] [blame] | 179 | Enable Explicit Congestion Notification (ECN) in TCP. ECN is only |
| 180 | used when both ends of the TCP flow support it. It is useful to |
| 181 | avoid losses due to congestion (when the bottleneck router supports |
| 182 | ECN). |
| 183 | Possible values are: |
| 184 | 0 disable ECN |
| 185 | 1 ECN enabled |
| 186 | 2 Only server-side ECN enabled. If the other end does |
| 187 | not support ECN, behavior is like with ECN disabled. |
| 188 | Default: 2 |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 189 | |
| 190 | tcp_fack - BOOLEAN |
| 191 | Enable FACK congestion avoidance and fast retransmission. |
| 192 | The value is not used, if tcp_sack is not enabled. |
| 193 | |
| 194 | tcp_fin_timeout - INTEGER |
| 195 | Time to hold socket in state FIN-WAIT-2, if it was closed |
| 196 | by our side. Peer can be broken and never close its side, |
| 197 | or even died unexpectedly. Default value is 60sec. |
| 198 | Usual value used in 2.2 was 180 seconds, you may restore |
| 199 | it, but remember that if your machine is even underloaded WEB server, |
| 200 | you risk to overflow memory with kilotons of dead sockets, |
| 201 | FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1, |
| 202 | because they eat maximum 1.5K of memory, but they tend |
| 203 | to live longer. Cf. tcp_max_orphans. |
| 204 | |
Ilpo Järvinen | 8980806 | 2007-02-27 10:10:55 -0800 | [diff] [blame] | 205 | tcp_frto - INTEGER |
Ilpo Järvinen | cd99889 | 2007-09-20 11:35:26 -0700 | [diff] [blame] | 206 | Enables Forward RTO-Recovery (F-RTO) defined in RFC4138. |
| 207 | F-RTO is an enhanced recovery algorithm for TCP retransmission |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 208 | timeouts. It is particularly beneficial in wireless environments |
| 209 | where packet loss is typically due to random radio interference |
Ryousei Takano | 564262c1 | 2007-10-25 23:03:52 -0700 | [diff] [blame] | 210 | rather than intermediate router congestion. F-RTO is sender-side |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 211 | only modification. Therefore it does not require any support from |
| 212 | the peer. |
| 213 | |
Ilpo Järvinen | cd99889 | 2007-09-20 11:35:26 -0700 | [diff] [blame] | 214 | If set to 1, basic version is enabled. 2 enables SACK enhanced |
| 215 | F-RTO if flow uses SACK. The basic version can be used also when |
Ryousei Takano | 564262c1 | 2007-10-25 23:03:52 -0700 | [diff] [blame] | 216 | SACK is in use though scenario(s) with it exists where F-RTO |
Ilpo Järvinen | cd99889 | 2007-09-20 11:35:26 -0700 | [diff] [blame] | 217 | interacts badly with the packet counting of the SACK enabled TCP |
| 218 | flow. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 219 | |
Ilpo Järvinen | 8980806 | 2007-02-27 10:10:55 -0800 | [diff] [blame] | 220 | tcp_frto_response - INTEGER |
| 221 | When F-RTO has detected that a TCP retransmission timeout was |
| 222 | spurious (i.e, the timeout would have been avoided had TCP set a |
| 223 | longer retransmission timeout), TCP has several options what to do |
| 224 | next. Possible values are: |
| 225 | 0 Rate halving based; a smooth and conservative response, |
| 226 | results in halved cwnd and ssthresh after one RTT |
| 227 | 1 Very conservative response; not recommended because even |
| 228 | though being valid, it interacts poorly with the rest of |
| 229 | Linux TCP, halves cwnd and ssthresh immediately |
| 230 | 2 Aggressive response; undoes congestion control measures |
| 231 | that are now known to be unnecessary (ignoring the |
| 232 | possibility of a lost retransmission that would require |
| 233 | TCP to be more cautious), cwnd and ssthresh are restored |
| 234 | to the values prior timeout |
| 235 | Default: 0 (rate halving based) |
| 236 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 237 | tcp_keepalive_time - INTEGER |
| 238 | How often TCP sends out keepalive messages when keepalive is enabled. |
| 239 | Default: 2hours. |
| 240 | |
| 241 | tcp_keepalive_probes - INTEGER |
| 242 | How many keepalive probes TCP sends out, until it decides that the |
| 243 | connection is broken. Default value: 9. |
| 244 | |
| 245 | tcp_keepalive_intvl - INTEGER |
| 246 | How frequently the probes are send out. Multiplied by |
| 247 | tcp_keepalive_probes it is time to kill not responding connection, |
| 248 | after probes started. Default value: 75sec i.e. connection |
| 249 | will be aborted after ~11 minutes of retries. |
| 250 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 251 | tcp_low_latency - BOOLEAN |
| 252 | If set, the TCP stack makes decisions that prefer lower |
| 253 | latency as opposed to higher throughput. By default, this |
| 254 | option is not set meaning that higher throughput is preferred. |
| 255 | An example of an application where this default should be |
| 256 | changed would be a Beowulf compute cluster. |
| 257 | Default: 0 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 258 | |
| 259 | tcp_max_orphans - INTEGER |
| 260 | Maximal number of TCP sockets not attached to any user file handle, |
| 261 | held by system. If this number is exceeded orphaned connections are |
| 262 | reset immediately and warning is printed. This limit exists |
| 263 | only to prevent simple DoS attacks, you _must_ not rely on this |
| 264 | or lower the limit artificially, but rather increase it |
| 265 | (probably, after increasing installed memory), |
| 266 | if network conditions require more than default value, |
| 267 | and tune network services to linger and kill such states |
| 268 | more aggressively. Let me to remind again: each orphan eats |
| 269 | up to ~64K of unswappable memory. |
| 270 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 271 | tcp_max_syn_backlog - INTEGER |
| 272 | Maximal number of remembered connection requests, which are |
| 273 | still did not receive an acknowledgment from connecting client. |
| 274 | Default value is 1024 for systems with more than 128Mb of memory, |
| 275 | and 128 for low memory machines. If server suffers of overload, |
| 276 | try to increase this number. |
| 277 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 278 | tcp_max_tw_buckets - INTEGER |
| 279 | Maximal number of timewait sockets held by system simultaneously. |
| 280 | If this number is exceeded time-wait socket is immediately destroyed |
| 281 | and warning is printed. This limit exists only to prevent |
| 282 | simple DoS attacks, you _must_ not lower the limit artificially, |
| 283 | but rather increase it (probably, after increasing installed memory), |
| 284 | if network conditions require more than default value. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 285 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 286 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
| 287 | min: below this number of pages TCP is not bothered about its |
| 288 | memory appetite. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 289 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 290 | pressure: when amount of memory allocated by TCP exceeds this number |
| 291 | of pages, TCP moderates its memory consumption and enters memory |
| 292 | pressure mode, which is exited when memory consumption falls |
| 293 | under "min". |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 294 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 295 | max: number of pages allowed for queueing by all TCP sockets. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 296 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 297 | Defaults are calculated at boot time from amount of available |
| 298 | memory. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 299 | |
John Heffner | 71599cd | 2007-02-27 10:03:56 -0800 | [diff] [blame] | 300 | tcp_moderate_rcvbuf - BOOLEAN |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 301 | If set, TCP performs receive buffer auto-tuning, attempting to |
John Heffner | 71599cd | 2007-02-27 10:03:56 -0800 | [diff] [blame] | 302 | automatically size the buffer (no greater than tcp_rmem[2]) to |
| 303 | match the size required by the path for full throughput. Enabled by |
| 304 | default. |
| 305 | |
| 306 | tcp_mtu_probing - INTEGER |
| 307 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three |
| 308 | values: |
| 309 | 0 - Disabled |
| 310 | 1 - Disabled by default, enabled when an ICMP black hole detected |
| 311 | 2 - Always enabled, use initial MSS of tcp_base_mss. |
| 312 | |
| 313 | tcp_no_metrics_save - BOOLEAN |
| 314 | By default, TCP saves various connection metrics in the route cache |
| 315 | when the connection closes, so that connections established in the |
| 316 | near future can use these to set initial conditions. Usually, this |
| 317 | increases overall performance, but may sometimes cause performance |
Simon Arlott | 0f035b8 | 2007-10-20 01:30:25 +0200 | [diff] [blame] | 318 | degradation. If set, TCP will not cache metrics on closing |
John Heffner | 71599cd | 2007-02-27 10:03:56 -0800 | [diff] [blame] | 319 | connections. |
| 320 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 321 | tcp_orphan_retries - INTEGER |
Damian Lukowski | 5d78922 | 2009-09-01 10:24:04 +0000 | [diff] [blame] | 322 | This value influences the timeout of a locally closed TCP connection, |
| 323 | when RTO retransmissions remain unacknowledged. |
| 324 | See tcp_retries2 for more details. |
| 325 | |
| 326 | The default value is 7. |
| 327 | If your machine is a loaded WEB server, |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 328 | you should think about lowering this value, such sockets |
| 329 | may consume significant resources. Cf. tcp_max_orphans. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 330 | |
| 331 | tcp_reordering - INTEGER |
| 332 | Maximal reordering of packets in a TCP stream. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 333 | Default: 3 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 334 | |
| 335 | tcp_retrans_collapse - BOOLEAN |
| 336 | Bug-to-bug compatibility with some broken printers. |
| 337 | On retransmit try to send bigger packets to work around bugs in |
| 338 | certain TCP stacks. |
| 339 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 340 | tcp_retries1 - INTEGER |
Damian Lukowski | 5d78922 | 2009-09-01 10:24:04 +0000 | [diff] [blame] | 341 | This value influences the time, after which TCP decides, that |
| 342 | something is wrong due to unacknowledged RTO retransmissions, |
| 343 | and reports this suspicion to the network layer. |
| 344 | See tcp_retries2 for more details. |
| 345 | |
| 346 | RFC 1122 recommends at least 3 retransmissions, which is the |
| 347 | default. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 348 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 349 | tcp_retries2 - INTEGER |
Damian Lukowski | 5d78922 | 2009-09-01 10:24:04 +0000 | [diff] [blame] | 350 | This value influences the timeout of an alive TCP connection, |
| 351 | when RTO retransmissions remain unacknowledged. |
| 352 | Given a value of N, a hypothetical TCP connection following |
| 353 | exponential backoff with an initial RTO of TCP_RTO_MIN would |
| 354 | retransmit N times before killing the connection at the (N+1)th RTO. |
| 355 | |
| 356 | The default value of 15 yields a hypothetical timeout of 924.6 |
| 357 | seconds and is a lower bound for the effective timeout. |
| 358 | TCP will effectively time out at the first RTO which exceeds the |
| 359 | hypothetical timeout. |
| 360 | |
| 361 | RFC 1122 recommends at least 100 seconds for the timeout, |
| 362 | which corresponds to a value of at least 8. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 363 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 364 | tcp_rfc1337 - BOOLEAN |
| 365 | If set, the TCP stack behaves conforming to RFC1337. If unset, |
| 366 | we are not conforming to RFC, but prevent TCP TIME_WAIT |
| 367 | assassination. |
| 368 | Default: 0 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 369 | |
| 370 | tcp_rmem - vector of 3 INTEGERs: min, default, max |
| 371 | min: Minimal size of receive buffer used by TCP sockets. |
| 372 | It is guaranteed to each TCP socket, even under moderate memory |
| 373 | pressure. |
| 374 | Default: 8K |
| 375 | |
J. Bruce Fields | 53025f5 | 2008-07-10 16:47:41 -0700 | [diff] [blame] | 376 | default: initial size of receive buffer used by TCP sockets. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 377 | This value overrides net.core.rmem_default used by other protocols. |
| 378 | Default: 87380 bytes. This value results in window of 65535 with |
| 379 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit |
| 380 | less for default tcp_app_win. See below about these variables. |
| 381 | |
| 382 | max: maximal size of receive buffer allowed for automatically |
| 383 | selected receiver buffers for TCP socket. This value does not override |
J. Bruce Fields | 53025f5 | 2008-07-10 16:47:41 -0700 | [diff] [blame] | 384 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
| 385 | automatic tuning of that socket's receive buffer size, in which |
| 386 | case this value is ignored. |
| 387 | Default: between 87380B and 4MB, depending on RAM size. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 388 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 389 | tcp_sack - BOOLEAN |
| 390 | Enable select acknowledgments (SACKS). |
Rick Jones | 15d99e0 | 2006-03-20 22:40:29 -0800 | [diff] [blame] | 391 | |
David S. Miller | 35089bb | 2006-06-13 22:33:04 -0700 | [diff] [blame] | 392 | tcp_slow_start_after_idle - BOOLEAN |
| 393 | If set, provide RFC2861 behavior and time out the congestion |
| 394 | window after an idle period. An idle period is defined at |
| 395 | the current RTO. If unset, the congestion window will not |
| 396 | be timed out after an idle period. |
| 397 | Default: 1 |
| 398 | |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 399 | tcp_stdurg - BOOLEAN |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 400 | Use the Host requirements interpretation of the TCP urgent pointer field. |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 401 | Most hosts use the older BSD interpretation, so if you turn this on |
| 402 | Linux might not communicate correctly with them. |
| 403 | Default: FALSE |
| 404 | |
| 405 | tcp_synack_retries - INTEGER |
| 406 | Number of times SYNACKs for a passive TCP connection attempt will |
| 407 | be retransmitted. Should not be higher than 255. Default value |
| 408 | is 5, which corresponds to ~180seconds. |
| 409 | |
| 410 | tcp_syncookies - BOOLEAN |
| 411 | Only valid when the kernel was compiled with CONFIG_SYNCOOKIES |
| 412 | Send out syncookies when the syn backlog queue of a socket |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 413 | overflows. This is to prevent against the common 'SYN flood attack' |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 414 | Default: FALSE |
| 415 | |
| 416 | Note, that syncookies is fallback facility. |
| 417 | It MUST NOT be used to help highly loaded servers to stand |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 418 | against legal connection rate. If you see SYN flood warnings |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 419 | in your logs, but investigation shows that they occur |
| 420 | because of overload with legal connections, you should tune |
| 421 | another parameters until this warning disappear. |
| 422 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. |
| 423 | |
| 424 | syncookies seriously violate TCP protocol, do not allow |
| 425 | to use TCP extensions, can result in serious degradation |
| 426 | of some services (f.e. SMTP relaying), visible not by you, |
| 427 | but your clients and relays, contacting you. While you see |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 428 | SYN flood warnings in logs not being really flooded, your server |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 429 | is seriously misconfigured. |
| 430 | |
| 431 | tcp_syn_retries - INTEGER |
| 432 | Number of times initial SYNs for an active TCP connection attempt |
| 433 | will be retransmitted. Should not be higher than 255. Default value |
| 434 | is 5, which corresponds to ~180seconds. |
| 435 | |
| 436 | tcp_timestamps - BOOLEAN |
| 437 | Enable timestamps as defined in RFC1323. |
| 438 | |
| 439 | tcp_tso_win_divisor - INTEGER |
| 440 | This allows control over what percentage of the congestion window |
| 441 | can be consumed by a single TSO frame. |
| 442 | The setting of this parameter is a choice between burstiness and |
| 443 | building larger TSO frames. |
| 444 | Default: 3 |
| 445 | |
| 446 | tcp_tw_recycle - BOOLEAN |
| 447 | Enable fast recycling TIME-WAIT sockets. Default value is 0. |
| 448 | It should not be changed without advice/request of technical |
| 449 | experts. |
| 450 | |
| 451 | tcp_tw_reuse - BOOLEAN |
| 452 | Allow to reuse TIME-WAIT sockets for new connections when it is |
| 453 | safe from protocol viewpoint. Default value is 0. |
| 454 | It should not be changed without advice/request of technical |
| 455 | experts. |
| 456 | |
| 457 | tcp_window_scaling - BOOLEAN |
| 458 | Enable window scaling as defined in RFC1323. |
| 459 | |
| 460 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
J. Bruce Fields | 53025f5 | 2008-07-10 16:47:41 -0700 | [diff] [blame] | 461 | min: Amount of memory reserved for send buffers for TCP sockets. |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 462 | Each TCP socket has rights to use it due to fact of its birth. |
| 463 | Default: 4K |
| 464 | |
J. Bruce Fields | 53025f5 | 2008-07-10 16:47:41 -0700 | [diff] [blame] | 465 | default: initial size of send buffer used by TCP sockets. This |
| 466 | value overrides net.core.wmem_default used by other protocols. |
| 467 | It is usually lower than net.core.wmem_default. |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 468 | Default: 16K |
| 469 | |
J. Bruce Fields | 53025f5 | 2008-07-10 16:47:41 -0700 | [diff] [blame] | 470 | max: Maximal amount of memory allowed for automatically tuned |
| 471 | send buffers for TCP sockets. This value does not override |
| 472 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables |
| 473 | automatic tuning of that socket's send buffer size, in which case |
| 474 | this value is ignored. |
| 475 | Default: between 64K and 4MB, depending on RAM size. |
Stephen Hemminger | ef56e62 | 2006-11-09 16:37:26 -0800 | [diff] [blame] | 476 | |
| 477 | tcp_workaround_signed_windows - BOOLEAN |
| 478 | If set, assume no receipt of a window scaling option means the |
| 479 | remote TCP is broken and treats the window as a signed quantity. |
| 480 | If unset, assume the remote TCP is not broken even if we do |
| 481 | not receive a window scaling option from them. |
| 482 | Default: 0 |
| 483 | |
Chris Leech | 72d0b7a | 2007-03-08 09:57:35 -0800 | [diff] [blame] | 484 | tcp_dma_copybreak - INTEGER |
| 485 | Lower limit, in bytes, of the size of socket reads that will be |
| 486 | offloaded to a DMA copy engine, if one is present in the system |
| 487 | and CONFIG_NET_DMA is enabled. |
| 488 | Default: 4096 |
| 489 | |
Andreas Petlund | 36e31b0a | 2010-02-18 02:47:01 +0000 | [diff] [blame] | 490 | tcp_thin_linear_timeouts - BOOLEAN |
| 491 | Enable dynamic triggering of linear timeouts for thin streams. |
| 492 | If set, a check is performed upon retransmission by timeout to |
| 493 | determine if the stream is thin (less than 4 packets in flight). |
| 494 | As long as the stream is found to be thin, up to 6 linear |
| 495 | timeouts may be performed before exponential backoff mode is |
| 496 | initiated. This improves retransmission latency for |
| 497 | non-aggressive thin streams, often found to be time-dependent. |
| 498 | For more information on thin streams, see |
| 499 | Documentation/networking/tcp-thin.txt |
| 500 | Default: 0 |
| 501 | |
Andreas Petlund | 7e38017 | 2010-02-18 04:48:19 +0000 | [diff] [blame] | 502 | tcp_thin_dupack - BOOLEAN |
| 503 | Enable dynamic triggering of retransmissions after one dupACK |
| 504 | for thin streams. If set, a check is performed upon reception |
| 505 | of a dupACK to determine if the stream is thin (less than 4 |
| 506 | packets in flight). As long as the stream is found to be thin, |
| 507 | data is retransmitted on the first received dupACK. This |
| 508 | improves retransmission latency for non-aggressive thin |
| 509 | streams, often found to be time-dependent. |
| 510 | For more information on thin streams, see |
| 511 | Documentation/networking/tcp-thin.txt |
| 512 | Default: 0 |
| 513 | |
Hideo Aoki | 95766ff | 2007-12-31 00:29:24 -0800 | [diff] [blame] | 514 | UDP variables: |
| 515 | |
| 516 | udp_mem - vector of 3 INTEGERs: min, pressure, max |
| 517 | Number of pages allowed for queueing by all UDP sockets. |
| 518 | |
| 519 | min: Below this number of pages UDP is not bothered about its |
| 520 | memory appetite. When amount of memory allocated by UDP exceeds |
| 521 | this number, UDP starts to moderate memory usage. |
| 522 | |
| 523 | pressure: This value was introduced to follow format of tcp_mem. |
| 524 | |
| 525 | max: Number of pages allowed for queueing by all UDP sockets. |
| 526 | |
| 527 | Default is calculated at boot time from amount of available memory. |
| 528 | |
| 529 | udp_rmem_min - INTEGER |
| 530 | Minimal size of receive buffer used by UDP sockets in moderation. |
| 531 | Each UDP socket is able to use the size for receiving data, even if |
| 532 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. |
| 533 | Default: 4096 |
| 534 | |
| 535 | udp_wmem_min - INTEGER |
| 536 | Minimal size of send buffer used by UDP sockets in moderation. |
| 537 | Each UDP socket is able to use the size for sending data, even if |
| 538 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. |
| 539 | Default: 4096 |
| 540 | |
Paul Moore | 8802f61 | 2006-08-03 16:45:49 -0700 | [diff] [blame] | 541 | CIPSOv4 Variables: |
| 542 | |
| 543 | cipso_cache_enable - BOOLEAN |
| 544 | If set, enable additions to and lookups from the CIPSO label mapping |
| 545 | cache. If unset, additions are ignored and lookups always result in a |
| 546 | miss. However, regardless of the setting the cache is still |
| 547 | invalidated when required when means you can safely toggle this on and |
| 548 | off and the cache will always be "safe". |
| 549 | Default: 1 |
| 550 | |
| 551 | cipso_cache_bucket_size - INTEGER |
| 552 | The CIPSO label cache consists of a fixed size hash table with each |
| 553 | hash bucket containing a number of cache entries. This variable limits |
| 554 | the number of entries in each hash bucket; the larger the value the |
| 555 | more CIPSO label mappings that can be cached. When the number of |
| 556 | entries in a given hash bucket reaches this limit adding new entries |
| 557 | causes the oldest entry in the bucket to be removed to make room. |
| 558 | Default: 10 |
| 559 | |
| 560 | cipso_rbm_optfmt - BOOLEAN |
| 561 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of |
| 562 | the CIPSO draft specification (see Documentation/netlabel for details). |
| 563 | This means that when set the CIPSO tag will be padded with empty |
| 564 | categories in order to make the packet data 32-bit aligned. |
| 565 | Default: 0 |
| 566 | |
| 567 | cipso_rbm_structvalid - BOOLEAN |
| 568 | If set, do a very strict check of the CIPSO option when |
| 569 | ip_options_compile() is called. If unset, relax the checks done during |
| 570 | ip_options_compile(). Either way is "safe" as errors are caught else |
| 571 | where in the CIPSO processing code but setting this to 0 (False) should |
| 572 | result in less work (i.e. it should be faster) but could cause problems |
| 573 | with other implementations that require strict checking. |
| 574 | Default: 0 |
| 575 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 576 | IP Variables: |
| 577 | |
| 578 | ip_local_port_range - 2 INTEGERS |
| 579 | Defines the local port range that is used by TCP and UDP to |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 580 | choose the local port. The first number is the first, the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 581 | second the last local port number. Default value depends on |
| 582 | amount of memory available on the system: |
| 583 | > 128Mb 32768-61000 |
| 584 | < 128Mb 1024-4999 or even less. |
| 585 | This number defines number of active connections, which this |
| 586 | system can issue simultaneously to systems not supporting |
| 587 | TCP extensions (timestamps). With tcp_tw_recycle enabled |
| 588 | (i.e. by default) range 1024-4999 is enough to issue up to |
| 589 | 2000 connections per second to systems supporting timestamps. |
| 590 | |
Amerigo Wang | e3826f1 | 2010-05-05 00:27:06 +0000 | [diff] [blame] | 591 | ip_local_reserved_ports - list of comma separated ranges |
| 592 | Specify the ports which are reserved for known third-party |
| 593 | applications. These ports will not be used by automatic port |
| 594 | assignments (e.g. when calling connect() or bind() with port |
| 595 | number 0). Explicit port allocation behavior is unchanged. |
| 596 | |
| 597 | The format used for both input and output is a comma separated |
| 598 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and |
| 599 | 10). Writing to the file will clear all previously reserved |
| 600 | ports and update the current list with the one given in the |
| 601 | input. |
| 602 | |
| 603 | Note that ip_local_port_range and ip_local_reserved_ports |
| 604 | settings are independent and both are considered by the kernel |
| 605 | when determining which ports are available for automatic port |
| 606 | assignments. |
| 607 | |
| 608 | You can reserve ports which are not in the current |
| 609 | ip_local_port_range, e.g.: |
| 610 | |
| 611 | $ cat /proc/sys/net/ipv4/ip_local_port_range |
| 612 | 32000 61000 |
| 613 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports |
| 614 | 8080,9148 |
| 615 | |
| 616 | although this is redundant. However such a setting is useful |
| 617 | if later the port range is changed to a value that will |
| 618 | include the reserved ports. |
| 619 | |
| 620 | Default: Empty |
| 621 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 622 | ip_nonlocal_bind - BOOLEAN |
| 623 | If set, allows processes to bind() to non-local IP addresses, |
| 624 | which can be quite useful - but may break some applications. |
| 625 | Default: 0 |
| 626 | |
| 627 | ip_dynaddr - BOOLEAN |
| 628 | If set non-zero, enables support for dynamic addresses. |
| 629 | If set to a non-zero value larger than 1, a kernel log |
| 630 | message will be printed when dynamic address rewriting |
| 631 | occurs. |
| 632 | Default: 0 |
| 633 | |
| 634 | icmp_echo_ignore_all - BOOLEAN |
David S. Miller | 7ce31246 | 2005-10-03 16:07:30 -0700 | [diff] [blame] | 635 | If set non-zero, then the kernel will ignore all ICMP ECHO |
| 636 | requests sent to it. |
| 637 | Default: 0 |
| 638 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 639 | icmp_echo_ignore_broadcasts - BOOLEAN |
David S. Miller | 7ce31246 | 2005-10-03 16:07:30 -0700 | [diff] [blame] | 640 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
| 641 | TIMESTAMP requests sent to it via broadcast/multicast. |
| 642 | Default: 1 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 643 | |
| 644 | icmp_ratelimit - INTEGER |
| 645 | Limit the maximal rates for sending ICMP packets whose type matches |
| 646 | icmp_ratemask (see below) to specific targets. |
Stephen Hemminger | 6dbf4bc | 2008-07-01 19:29:07 -0700 | [diff] [blame] | 647 | 0 to disable any limiting, |
| 648 | otherwise the minimal space between responses in milliseconds. |
| 649 | Default: 1000 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 650 | |
| 651 | icmp_ratemask - INTEGER |
| 652 | Mask made of ICMP types for which rates are being limited. |
| 653 | Significant bits: IHGFEDCBA9876543210 |
| 654 | Default mask: 0000001100000011000 (6168) |
| 655 | |
| 656 | Bit definitions (see include/linux/icmp.h): |
| 657 | 0 Echo Reply |
| 658 | 3 Destination Unreachable * |
| 659 | 4 Source Quench * |
| 660 | 5 Redirect |
| 661 | 8 Echo Request |
| 662 | B Time Exceeded * |
| 663 | C Parameter Problem * |
| 664 | D Timestamp Request |
| 665 | E Timestamp Reply |
| 666 | F Info Request |
| 667 | G Info Reply |
| 668 | H Address Mask Request |
| 669 | I Address Mask Reply |
| 670 | |
| 671 | * These are rate limited by default (see default mask above) |
| 672 | |
| 673 | icmp_ignore_bogus_error_responses - BOOLEAN |
| 674 | Some routers violate RFC1122 by sending bogus responses to broadcast |
| 675 | frames. Such violations are normally logged via a kernel warning. |
| 676 | If this is set to TRUE, the kernel will not give such warnings, which |
| 677 | will avoid log file clutter. |
| 678 | Default: FALSE |
| 679 | |
Horms | 95f7daf | 2006-02-02 17:02:25 -0800 | [diff] [blame] | 680 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
| 681 | |
| 682 | If zero, icmp error messages are sent with the primary address of |
| 683 | the exiting interface. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 684 | |
Horms | 95f7daf | 2006-02-02 17:02:25 -0800 | [diff] [blame] | 685 | If non-zero, the message will be sent with the primary address of |
| 686 | the interface that received the packet that caused the icmp error. |
| 687 | This is the behaviour network many administrators will expect from |
| 688 | a router. And it can make debugging complicated network layouts |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 689 | much easier. |
Horms | 95f7daf | 2006-02-02 17:02:25 -0800 | [diff] [blame] | 690 | |
| 691 | Note that if no primary address exists for the interface selected, |
| 692 | then the primary address of the first non-loopback interface that |
Matt LaPlante | d6bc8ac | 2006-10-03 22:54:15 +0200 | [diff] [blame] | 693 | has one will be used regardless of this setting. |
Horms | 95f7daf | 2006-02-02 17:02:25 -0800 | [diff] [blame] | 694 | |
| 695 | Default: 0 |
| 696 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 697 | igmp_max_memberships - INTEGER |
| 698 | Change the maximum number of multicast groups we can subscribe to. |
| 699 | Default: 20 |
| 700 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 701 | conf/interface/* changes special settings per interface (where "interface" is |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 702 | the name of your network interface) |
| 703 | conf/all/* is special, changes the settings for all interfaces |
| 704 | |
| 705 | |
| 706 | log_martians - BOOLEAN |
| 707 | Log packets with impossible addresses to kernel log. |
| 708 | log_martians for the interface will be enabled if at least one of |
| 709 | conf/{all,interface}/log_martians is set to TRUE, |
| 710 | it will be disabled otherwise |
| 711 | |
| 712 | accept_redirects - BOOLEAN |
| 713 | Accept ICMP redirect messages. |
| 714 | accept_redirects for the interface will be enabled if: |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 715 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
| 716 | forwarding for the interface is enabled |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 717 | or |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 718 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
| 719 | case forwarding for the interface is disabled |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 720 | accept_redirects for the interface will be disabled otherwise |
| 721 | default TRUE (host) |
| 722 | FALSE (router) |
| 723 | |
| 724 | forwarding - BOOLEAN |
| 725 | Enable IP forwarding on this interface. |
| 726 | |
| 727 | mc_forwarding - BOOLEAN |
| 728 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE |
| 729 | and a multicast routing daemon is required. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 730 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
| 731 | routing for the interface |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 732 | |
| 733 | medium_id - INTEGER |
| 734 | Integer value used to differentiate the devices by the medium they |
| 735 | are attached to. Two devices can have different id values when |
| 736 | the broadcast packets are received only on one of them. |
| 737 | The default value 0 means that the device is the only interface |
| 738 | to its medium, value of -1 means that medium is not known. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 739 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 740 | Currently, it is used to change the proxy_arp behavior: |
| 741 | the proxy_arp feature is enabled for packets forwarded between |
| 742 | two devices attached to different media. |
| 743 | |
| 744 | proxy_arp - BOOLEAN |
| 745 | Do proxy arp. |
| 746 | proxy_arp for the interface will be enabled if at least one of |
| 747 | conf/{all,interface}/proxy_arp is set to TRUE, |
| 748 | it will be disabled otherwise |
| 749 | |
Jesper Dangaard Brouer | 6532414 | 2010-01-05 05:50:47 +0000 | [diff] [blame] | 750 | proxy_arp_pvlan - BOOLEAN |
| 751 | Private VLAN proxy arp. |
| 752 | Basically allow proxy arp replies back to the same interface |
| 753 | (from which the ARP request/solicitation was received). |
| 754 | |
| 755 | This is done to support (ethernet) switch features, like RFC |
| 756 | 3069, where the individual ports are NOT allowed to |
| 757 | communicate with each other, but they are allowed to talk to |
| 758 | the upstream router. As described in RFC 3069, it is possible |
| 759 | to allow these hosts to communicate through the upstream |
| 760 | router by proxy_arp'ing. Don't need to be used together with |
| 761 | proxy_arp. |
| 762 | |
| 763 | This technology is known by different names: |
| 764 | In RFC 3069 it is called VLAN Aggregation. |
| 765 | Cisco and Allied Telesyn call it Private VLAN. |
| 766 | Hewlett-Packard call it Source-Port filtering or port-isolation. |
| 767 | Ericsson call it MAC-Forced Forwarding (RFC Draft). |
| 768 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 769 | shared_media - BOOLEAN |
| 770 | Send(router) or accept(host) RFC1620 shared media redirects. |
| 771 | Overrides ip_secure_redirects. |
| 772 | shared_media for the interface will be enabled if at least one of |
| 773 | conf/{all,interface}/shared_media is set to TRUE, |
| 774 | it will be disabled otherwise |
| 775 | default TRUE |
| 776 | |
| 777 | secure_redirects - BOOLEAN |
| 778 | Accept ICMP redirect messages only for gateways, |
| 779 | listed in default gateway list. |
| 780 | secure_redirects for the interface will be enabled if at least one of |
| 781 | conf/{all,interface}/secure_redirects is set to TRUE, |
| 782 | it will be disabled otherwise |
| 783 | default TRUE |
| 784 | |
| 785 | send_redirects - BOOLEAN |
| 786 | Send redirects, if router. |
| 787 | send_redirects for the interface will be enabled if at least one of |
| 788 | conf/{all,interface}/send_redirects is set to TRUE, |
| 789 | it will be disabled otherwise |
| 790 | Default: TRUE |
| 791 | |
| 792 | bootp_relay - BOOLEAN |
| 793 | Accept packets with source address 0.b.c.d destined |
| 794 | not to this host as local ones. It is supposed, that |
| 795 | BOOTP relay daemon will catch and forward such packets. |
| 796 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay |
| 797 | for the interface |
| 798 | default FALSE |
| 799 | Not Implemented Yet. |
| 800 | |
| 801 | accept_source_route - BOOLEAN |
| 802 | Accept packets with SRR option. |
| 803 | conf/all/accept_source_route must also be set to TRUE to accept packets |
| 804 | with SRR option on the interface |
| 805 | default TRUE (router) |
| 806 | FALSE (host) |
| 807 | |
Patrick McHardy | 8153a10 | 2009-12-03 01:25:58 +0000 | [diff] [blame] | 808 | accept_local - BOOLEAN |
| 809 | Accept packets with local source addresses. In combination with |
| 810 | suitable routing, this can be used to direct packets between two |
| 811 | local interfaces over the wire and have them accepted properly. |
| 812 | default FALSE |
| 813 | |
Stephen Hemminger | c1cf842 | 2009-02-20 08:25:36 +0000 | [diff] [blame] | 814 | rp_filter - INTEGER |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 815 | 0 - No source validation. |
Stephen Hemminger | c1cf842 | 2009-02-20 08:25:36 +0000 | [diff] [blame] | 816 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
| 817 | Each incoming packet is tested against the FIB and if the interface |
| 818 | is not the best reverse path the packet check will fail. |
| 819 | By default failed packets are discarded. |
| 820 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path |
| 821 | Each incoming packet's source address is also tested against the FIB |
| 822 | and if the source address is not reachable via any interface |
| 823 | the packet check will fail. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 824 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 825 | Current recommended practice in RFC3704 is to enable strict mode |
Jesper Dangaard Brouer | bf869c3 | 2009-02-23 04:37:55 +0000 | [diff] [blame] | 826 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 827 | or other complicated routing, then loose mode is recommended. |
Stephen Hemminger | c1cf842 | 2009-02-20 08:25:36 +0000 | [diff] [blame] | 828 | |
Shan Wei | 1f5865e | 2009-12-02 15:39:04 -0800 | [diff] [blame] | 829 | The max value from conf/{all,interface}/rp_filter is used |
| 830 | when doing source validation on the {interface}. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 831 | |
| 832 | Default value is 0. Note that some distributions enable it |
| 833 | in startup scripts. |
| 834 | |
| 835 | arp_filter - BOOLEAN |
| 836 | 1 - Allows you to have multiple network interfaces on the same |
| 837 | subnet, and have the ARPs for each interface be answered |
| 838 | based on whether or not the kernel would route a packet from |
| 839 | the ARP'd IP out that interface (therefore you must use source |
| 840 | based routing for this to work). In other words it allows control |
| 841 | of which cards (usually 1) will respond to an arp request. |
| 842 | |
| 843 | 0 - (default) The kernel can respond to arp requests with addresses |
| 844 | from other interfaces. This may seem wrong but it usually makes |
| 845 | sense, because it increases the chance of successful communication. |
| 846 | IP addresses are owned by the complete host on Linux, not by |
| 847 | particular interfaces. Only for more complex setups like load- |
| 848 | balancing, does this behaviour cause problems. |
| 849 | |
| 850 | arp_filter for the interface will be enabled if at least one of |
| 851 | conf/{all,interface}/arp_filter is set to TRUE, |
| 852 | it will be disabled otherwise |
| 853 | |
| 854 | arp_announce - INTEGER |
| 855 | Define different restriction levels for announcing the local |
| 856 | source IP address from IP packets in ARP requests sent on |
| 857 | interface: |
| 858 | 0 - (default) Use any local address, configured on any interface |
| 859 | 1 - Try to avoid local addresses that are not in the target's |
| 860 | subnet for this interface. This mode is useful when target |
| 861 | hosts reachable via this interface require the source IP |
| 862 | address in ARP requests to be part of their logical network |
| 863 | configured on the receiving interface. When we generate the |
| 864 | request we will check all our subnets that include the |
| 865 | target IP and will preserve the source address if it is from |
| 866 | such subnet. If there is no such subnet we select source |
| 867 | address according to the rules for level 2. |
| 868 | 2 - Always use the best local address for this target. |
| 869 | In this mode we ignore the source address in the IP packet |
| 870 | and try to select local address that we prefer for talks with |
| 871 | the target host. Such local address is selected by looking |
| 872 | for primary IP addresses on all our subnets on the outgoing |
| 873 | interface that include the target IP address. If no suitable |
| 874 | local address is found we select the first local address |
| 875 | we have on the outgoing interface or on all other interfaces, |
| 876 | with the hope we will receive reply for our request and |
| 877 | even sometimes no matter the source IP address we announce. |
| 878 | |
| 879 | The max value from conf/{all,interface}/arp_announce is used. |
| 880 | |
| 881 | Increasing the restriction level gives more chance for |
| 882 | receiving answer from the resolved target while decreasing |
| 883 | the level announces more valid sender's information. |
| 884 | |
| 885 | arp_ignore - INTEGER |
| 886 | Define different modes for sending replies in response to |
| 887 | received ARP requests that resolve local target IP addresses: |
| 888 | 0 - (default): reply for any local target IP address, configured |
| 889 | on any interface |
| 890 | 1 - reply only if the target IP address is local address |
| 891 | configured on the incoming interface |
| 892 | 2 - reply only if the target IP address is local address |
| 893 | configured on the incoming interface and both with the |
| 894 | sender's IP address are part from same subnet on this interface |
| 895 | 3 - do not reply for local addresses configured with scope host, |
| 896 | only resolutions for global and link addresses are replied |
| 897 | 4-7 - reserved |
| 898 | 8 - do not reply for all local addresses |
| 899 | |
| 900 | The max value from conf/{all,interface}/arp_ignore is used |
| 901 | when ARP request is received on the {interface} |
| 902 | |
Stephen Hemminger | eefef1c | 2009-02-01 01:04:33 -0800 | [diff] [blame] | 903 | arp_notify - BOOLEAN |
| 904 | Define mode for notification of address and device changes. |
| 905 | 0 - (default): do nothing |
| 906 | 1 - Generate gratuitous arp replies when device is brought up |
| 907 | or hardware address changes. |
| 908 | |
Neil Horman | c1b1bce | 2006-03-20 22:40:03 -0800 | [diff] [blame] | 909 | arp_accept - BOOLEAN |
Octavian Purdila | 6d95518 | 2010-01-18 12:58:44 +0000 | [diff] [blame] | 910 | Define behavior for gratuitous ARP frames who's IP is not |
| 911 | already present in the ARP table: |
| 912 | 0 - don't create new entries in the ARP table |
| 913 | 1 - create new entries in the ARP table |
| 914 | |
| 915 | Both replies and requests type gratuitous arp will trigger the |
| 916 | ARP table to be updated, if this setting is on. |
| 917 | |
| 918 | If the ARP table already contains the IP address of the |
| 919 | gratuitous arp frame, the arp table will be updated regardless |
| 920 | if this setting is on or off. |
| 921 | |
Neil Horman | c1b1bce | 2006-03-20 22:40:03 -0800 | [diff] [blame] | 922 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 923 | app_solicit - INTEGER |
| 924 | The maximum number of probes to send to the user space ARP daemon |
| 925 | via netlink before dropping back to multicast probes (see |
| 926 | mcast_solicit). Defaults to 0. |
| 927 | |
| 928 | disable_policy - BOOLEAN |
| 929 | Disable IPSEC policy (SPD) for this interface |
| 930 | |
| 931 | disable_xfrm - BOOLEAN |
| 932 | Disable IPSEC encryption on this interface, whatever the policy |
| 933 | |
| 934 | |
| 935 | |
| 936 | tag - INTEGER |
| 937 | Allows you to write a number, which can be used as required. |
| 938 | Default value is 0. |
| 939 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 940 | Alexey Kuznetsov. |
| 941 | kuznet@ms2.inr.ac.ru |
| 942 | |
| 943 | Updated by: |
| 944 | Andi Kleen |
| 945 | ak@muc.de |
| 946 | Nicolas Delon |
| 947 | delon.nicolas@wanadoo.fr |
| 948 | |
| 949 | |
| 950 | |
| 951 | |
| 952 | /proc/sys/net/ipv6/* Variables: |
| 953 | |
| 954 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also |
| 955 | apply to IPv6 [XXX?]. |
| 956 | |
| 957 | bindv6only - BOOLEAN |
| 958 | Default value for IPV6_V6ONLY socket option, |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 959 | which restricts use of the IPv6 socket to IPv6 communication |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 960 | only. |
| 961 | TRUE: disable IPv4-mapped address feature |
| 962 | FALSE: enable IPv4-mapped address feature |
| 963 | |
| 964 | Default: FALSE (as specified in RFC2553bis) |
| 965 | |
| 966 | IPv6 Fragmentation: |
| 967 | |
| 968 | ip6frag_high_thresh - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 969 | Maximum memory used to reassemble IPv6 fragments. When |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 970 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
| 971 | the fragment handler will toss packets until ip6frag_low_thresh |
| 972 | is reached. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 973 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 974 | ip6frag_low_thresh - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 975 | See ip6frag_high_thresh |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 976 | |
| 977 | ip6frag_time - INTEGER |
| 978 | Time in seconds to keep an IPv6 fragment in memory. |
| 979 | |
| 980 | ip6frag_secret_interval - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 981 | Regeneration interval (in seconds) of the hash secret (or lifetime |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 982 | for the hash secret) for IPv6 fragments. |
| 983 | Default: 600 |
| 984 | |
| 985 | conf/default/*: |
| 986 | Change the interface-specific default settings. |
| 987 | |
| 988 | |
| 989 | conf/all/*: |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 990 | Change all the interface-specific settings. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 991 | |
| 992 | [XXX: Other special features than forwarding?] |
| 993 | |
| 994 | conf/all/forwarding - BOOLEAN |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 995 | Enable global IPv6 forwarding between all interfaces. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 996 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 997 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 998 | to control which interfaces may forward packets and which not. |
| 999 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1000 | This also sets all interfaces' Host/Router setting |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1001 | 'forwarding' to the specified value. See below for details. |
| 1002 | |
| 1003 | This referred to as global forwarding. |
| 1004 | |
YOSHIFUJI Hideaki | fbea49e | 2006-09-22 14:43:49 -0700 | [diff] [blame] | 1005 | proxy_ndp - BOOLEAN |
| 1006 | Do proxy ndp. |
| 1007 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1008 | conf/interface/*: |
| 1009 | Change special settings per interface. |
| 1010 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1011 | The functional behaviour for certain settings is different |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1012 | depending on whether local forwarding is enabled or not. |
| 1013 | |
| 1014 | accept_ra - BOOLEAN |
| 1015 | Accept Router Advertisements; autoconfigure using them. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1016 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1017 | Functional default: enabled if local forwarding is disabled. |
| 1018 | disabled if local forwarding is enabled. |
| 1019 | |
YOSHIFUJI Hideaki | 65f5c7c | 2006-03-20 16:55:08 -0800 | [diff] [blame] | 1020 | accept_ra_defrtr - BOOLEAN |
| 1021 | Learn default router in Router Advertisement. |
| 1022 | |
| 1023 | Functional default: enabled if accept_ra is enabled. |
| 1024 | disabled if accept_ra is disabled. |
| 1025 | |
YOSHIFUJI Hideaki | c4fd30e | 2006-03-20 16:55:26 -0800 | [diff] [blame] | 1026 | accept_ra_pinfo - BOOLEAN |
Matt LaPlante | 2fe0ae7 | 2006-10-03 22:50:39 +0200 | [diff] [blame] | 1027 | Learn Prefix Information in Router Advertisement. |
YOSHIFUJI Hideaki | c4fd30e | 2006-03-20 16:55:26 -0800 | [diff] [blame] | 1028 | |
| 1029 | Functional default: enabled if accept_ra is enabled. |
| 1030 | disabled if accept_ra is disabled. |
| 1031 | |
YOSHIFUJI Hideaki | 09c884d | 2006-03-20 17:07:03 -0800 | [diff] [blame] | 1032 | accept_ra_rt_info_max_plen - INTEGER |
| 1033 | Maximum prefix length of Route Information in RA. |
| 1034 | |
| 1035 | Route Information w/ prefix larger than or equal to this |
| 1036 | variable shall be ignored. |
| 1037 | |
| 1038 | Functional default: 0 if accept_ra_rtr_pref is enabled. |
| 1039 | -1 if accept_ra_rtr_pref is disabled. |
| 1040 | |
YOSHIFUJI Hideaki | 930d6ff | 2006-03-20 17:05:30 -0800 | [diff] [blame] | 1041 | accept_ra_rtr_pref - BOOLEAN |
| 1042 | Accept Router Preference in RA. |
| 1043 | |
| 1044 | Functional default: enabled if accept_ra is enabled. |
| 1045 | disabled if accept_ra is disabled. |
| 1046 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1047 | accept_redirects - BOOLEAN |
| 1048 | Accept Redirects. |
| 1049 | |
| 1050 | Functional default: enabled if local forwarding is disabled. |
| 1051 | disabled if local forwarding is enabled. |
| 1052 | |
YOSHIFUJI Hideaki | 0bcbc92 | 2007-04-24 14:58:30 -0700 | [diff] [blame] | 1053 | accept_source_route - INTEGER |
| 1054 | Accept source routing (routing extension header). |
| 1055 | |
YOSHIFUJI Hideaki | bb4dbf9 | 2007-07-10 22:55:49 -0700 | [diff] [blame] | 1056 | >= 0: Accept only routing header type 2. |
YOSHIFUJI Hideaki | 0bcbc92 | 2007-04-24 14:58:30 -0700 | [diff] [blame] | 1057 | < 0: Do not accept routing header. |
| 1058 | |
| 1059 | Default: 0 |
| 1060 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1061 | autoconf - BOOLEAN |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1062 | Autoconfigure addresses using Prefix Information in Router |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1063 | Advertisements. |
| 1064 | |
YOSHIFUJI Hideaki | c4fd30e | 2006-03-20 16:55:26 -0800 | [diff] [blame] | 1065 | Functional default: enabled if accept_ra_pinfo is enabled. |
| 1066 | disabled if accept_ra_pinfo is disabled. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1067 | |
| 1068 | dad_transmits - INTEGER |
| 1069 | The amount of Duplicate Address Detection probes to send. |
| 1070 | Default: 1 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1071 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1072 | forwarding - BOOLEAN |
| 1073 | Configure interface-specific Host/Router behaviour. |
| 1074 | |
| 1075 | Note: It is recommended to have the same setting on all |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1076 | interfaces; mixed router/host scenarios are rather uncommon. |
| 1077 | |
| 1078 | FALSE: |
| 1079 | |
| 1080 | By default, Host behaviour is assumed. This means: |
| 1081 | |
| 1082 | 1. IsRouter flag is not set in Neighbour Advertisements. |
| 1083 | 2. Router Solicitations are being sent when necessary. |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1084 | 3. If accept_ra is TRUE (default), accept Router |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1085 | Advertisements (and do autoconfiguration). |
| 1086 | 4. If accept_redirects is TRUE (default), accept Redirects. |
| 1087 | |
| 1088 | TRUE: |
| 1089 | |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1090 | If local forwarding is enabled, Router behaviour is assumed. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1091 | This means exactly the reverse from the above: |
| 1092 | |
| 1093 | 1. IsRouter flag is set in Neighbour Advertisements. |
| 1094 | 2. Router Solicitations are not sent. |
| 1095 | 3. Router Advertisements are ignored. |
| 1096 | 4. Redirects are ignored. |
| 1097 | |
| 1098 | Default: FALSE if global forwarding is disabled (default), |
| 1099 | otherwise TRUE. |
| 1100 | |
| 1101 | hop_limit - INTEGER |
| 1102 | Default Hop Limit to set. |
| 1103 | Default: 64 |
| 1104 | |
| 1105 | mtu - INTEGER |
| 1106 | Default Maximum Transfer Unit |
| 1107 | Default: 1280 (IPv6 required minimum) |
| 1108 | |
YOSHIFUJI Hideaki | 52e1635 | 2006-03-20 17:05:47 -0800 | [diff] [blame] | 1109 | router_probe_interval - INTEGER |
| 1110 | Minimum interval (in seconds) between Router Probing described |
| 1111 | in RFC4191. |
| 1112 | |
| 1113 | Default: 60 |
| 1114 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1115 | router_solicitation_delay - INTEGER |
| 1116 | Number of seconds to wait after interface is brought up |
| 1117 | before sending Router Solicitations. |
| 1118 | Default: 1 |
| 1119 | |
| 1120 | router_solicitation_interval - INTEGER |
| 1121 | Number of seconds to wait between Router Solicitations. |
| 1122 | Default: 4 |
| 1123 | |
| 1124 | router_solicitations - INTEGER |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1125 | Number of Router Solicitations to send until assuming no |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1126 | routers are present. |
| 1127 | Default: 3 |
| 1128 | |
| 1129 | use_tempaddr - INTEGER |
| 1130 | Preference for Privacy Extensions (RFC3041). |
| 1131 | <= 0 : disable Privacy Extensions |
| 1132 | == 1 : enable Privacy Extensions, but prefer public |
| 1133 | addresses over temporary addresses. |
| 1134 | > 1 : enable Privacy Extensions and prefer temporary |
| 1135 | addresses over public addresses. |
| 1136 | Default: 0 (for most devices) |
| 1137 | -1 (for point-to-point devices and loopback devices) |
| 1138 | |
| 1139 | temp_valid_lft - INTEGER |
| 1140 | valid lifetime (in seconds) for temporary addresses. |
| 1141 | Default: 604800 (7 days) |
| 1142 | |
| 1143 | temp_prefered_lft - INTEGER |
| 1144 | Preferred lifetime (in seconds) for temporary addresses. |
| 1145 | Default: 86400 (1 day) |
| 1146 | |
| 1147 | max_desync_factor - INTEGER |
| 1148 | Maximum value for DESYNC_FACTOR, which is a random value |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1149 | that ensures that clients don't synchronize with each |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1150 | other and generate new addresses at exactly the same time. |
| 1151 | value is in seconds. |
| 1152 | Default: 600 |
Jesper Dangaard Brouer | e18f5fe | 2009-02-23 04:39:04 +0000 | [diff] [blame] | 1153 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1154 | regen_max_retry - INTEGER |
| 1155 | Number of attempts before give up attempting to generate |
| 1156 | valid temporary addresses. |
| 1157 | Default: 5 |
| 1158 | |
| 1159 | max_addresses - INTEGER |
Brian Haley | e79dc48 | 2010-02-22 12:27:21 +0000 | [diff] [blame] | 1160 | Maximum number of autoconfigured addresses per interface. Setting |
| 1161 | to zero disables the limitation. It is not recommended to set this |
| 1162 | value too large (or to zero) because it would be an easy way to |
| 1163 | crash the kernel by allowing too many addresses to be created. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1164 | Default: 16 |
| 1165 | |
YOSHIFUJI Hideaki | 778d80b | 2008-06-28 14:17:11 +0900 | [diff] [blame] | 1166 | disable_ipv6 - BOOLEAN |
Brian Haley | 9bdd8d4 | 2009-03-18 18:22:48 -0700 | [diff] [blame] | 1167 | Disable IPv6 operation. If accept_dad is set to 2, this value |
| 1168 | will be dynamically set to TRUE if DAD fails for the link-local |
| 1169 | address. |
YOSHIFUJI Hideaki | 778d80b | 2008-06-28 14:17:11 +0900 | [diff] [blame] | 1170 | Default: FALSE (enable IPv6 operation) |
| 1171 | |
Brian Haley | 56d417b | 2009-06-01 03:07:33 -0700 | [diff] [blame] | 1172 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
| 1173 | it will dynamically create a link-local address on the given |
| 1174 | interface and start Duplicate Address Detection, if necessary. |
| 1175 | |
| 1176 | When this value is changed from 0 to 1 (IPv6 is being disabled), |
| 1177 | it will dynamically delete all address on the given interface. |
| 1178 | |
YOSHIFUJI Hideaki | 1b34be7 | 2008-06-28 14:18:38 +0900 | [diff] [blame] | 1179 | accept_dad - INTEGER |
| 1180 | Whether to accept DAD (Duplicate Address Detection). |
| 1181 | 0: Disable DAD |
| 1182 | 1: Enable DAD (default) |
| 1183 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate |
| 1184 | link-local address has been found. |
| 1185 | |
Octavian Purdila | f7734fd | 2009-10-02 11:39:15 +0000 | [diff] [blame] | 1186 | force_tllao - BOOLEAN |
| 1187 | Enable sending the target link-layer address option even when |
| 1188 | responding to a unicast neighbor solicitation. |
| 1189 | Default: FALSE |
| 1190 | |
| 1191 | Quoting from RFC 2461, section 4.4, Target link-layer address: |
| 1192 | |
| 1193 | "The option MUST be included for multicast solicitations in order to |
| 1194 | avoid infinite Neighbor Solicitation "recursion" when the peer node |
| 1195 | does not have a cache entry to return a Neighbor Advertisements |
| 1196 | message. When responding to unicast solicitations, the option can be |
| 1197 | omitted since the sender of the solicitation has the correct link- |
| 1198 | layer address; otherwise it would not have be able to send the unicast |
| 1199 | solicitation in the first place. However, including the link-layer |
| 1200 | address in this case adds little overhead and eliminates a potential |
| 1201 | race condition where the sender deletes the cached link-layer address |
| 1202 | prior to receiving a response to a previous solicitation." |
| 1203 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1204 | icmp/*: |
| 1205 | ratelimit - INTEGER |
| 1206 | Limit the maximal rates for sending ICMPv6 packets. |
Stephen Hemminger | 6dbf4bc | 2008-07-01 19:29:07 -0700 | [diff] [blame] | 1207 | 0 to disable any limiting, |
| 1208 | otherwise the minimal space between responses in milliseconds. |
| 1209 | Default: 1000 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1210 | |
| 1211 | |
| 1212 | IPv6 Update by: |
| 1213 | Pekka Savola <pekkas@netcore.fi> |
| 1214 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> |
| 1215 | |
| 1216 | |
| 1217 | /proc/sys/net/bridge/* Variables: |
| 1218 | |
| 1219 | bridge-nf-call-arptables - BOOLEAN |
| 1220 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. |
| 1221 | 0 : disable this. |
| 1222 | Default: 1 |
| 1223 | |
| 1224 | bridge-nf-call-iptables - BOOLEAN |
| 1225 | 1 : pass bridged IPv4 traffic to iptables' chains. |
| 1226 | 0 : disable this. |
| 1227 | Default: 1 |
| 1228 | |
| 1229 | bridge-nf-call-ip6tables - BOOLEAN |
| 1230 | 1 : pass bridged IPv6 traffic to ip6tables' chains. |
| 1231 | 0 : disable this. |
| 1232 | Default: 1 |
| 1233 | |
| 1234 | bridge-nf-filter-vlan-tagged - BOOLEAN |
Michael Milner | 516299d | 2007-04-12 22:14:23 -0700 | [diff] [blame] | 1235 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
| 1236 | 0 : disable this. |
| 1237 | Default: 1 |
| 1238 | |
| 1239 | bridge-nf-filter-pppoe-tagged - BOOLEAN |
| 1240 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1241 | 0 : disable this. |
| 1242 | Default: 1 |
| 1243 | |
| 1244 | |
Vlad Yasevich | 32e8d49 | 2008-07-08 16:43:29 -0700 | [diff] [blame] | 1245 | proc/sys/net/sctp/* Variables: |
| 1246 | |
| 1247 | addip_enable - BOOLEAN |
| 1248 | Enable or disable extension of Dynamic Address Reconfiguration |
| 1249 | (ADD-IP) functionality specified in RFC5061. This extension provides |
| 1250 | the ability to dynamically add and remove new addresses for the SCTP |
| 1251 | associations. |
| 1252 | |
| 1253 | 1: Enable extension. |
| 1254 | |
| 1255 | 0: Disable extension. |
| 1256 | |
| 1257 | Default: 0 |
| 1258 | |
| 1259 | addip_noauth_enable - BOOLEAN |
| 1260 | Dynamic Address Reconfiguration (ADD-IP) requires the use of |
| 1261 | authentication to protect the operations of adding or removing new |
| 1262 | addresses. This requirement is mandated so that unauthorized hosts |
| 1263 | would not be able to hijack associations. However, older |
| 1264 | implementations may not have implemented this requirement while |
| 1265 | allowing the ADD-IP extension. For reasons of interoperability, |
| 1266 | we provide this variable to control the enforcement of the |
| 1267 | authentication requirement. |
| 1268 | |
| 1269 | 1: Allow ADD-IP extension to be used without authentication. This |
| 1270 | should only be set in a closed environment for interoperability |
| 1271 | with older implementations. |
| 1272 | |
| 1273 | 0: Enforce the authentication requirement |
| 1274 | |
| 1275 | Default: 0 |
| 1276 | |
| 1277 | auth_enable - BOOLEAN |
| 1278 | Enable or disable Authenticated Chunks extension. This extension |
| 1279 | provides the ability to send and receive authenticated chunks and is |
| 1280 | required for secure operation of Dynamic Address Reconfiguration |
| 1281 | (ADD-IP) extension. |
| 1282 | |
| 1283 | 1: Enable this extension. |
| 1284 | 0: Disable this extension. |
| 1285 | |
| 1286 | Default: 0 |
| 1287 | |
| 1288 | prsctp_enable - BOOLEAN |
| 1289 | Enable or disable the Partial Reliability extension (RFC3758) which |
| 1290 | is used to notify peers that a given DATA should no longer be expected. |
| 1291 | |
| 1292 | 1: Enable extension |
| 1293 | 0: Disable |
| 1294 | |
| 1295 | Default: 1 |
| 1296 | |
| 1297 | max_burst - INTEGER |
| 1298 | The limit of the number of new packets that can be initially sent. It |
| 1299 | controls how bursty the generated traffic can be. |
| 1300 | |
| 1301 | Default: 4 |
| 1302 | |
| 1303 | association_max_retrans - INTEGER |
| 1304 | Set the maximum number for retransmissions that an association can |
| 1305 | attempt deciding that the remote end is unreachable. If this value |
| 1306 | is exceeded, the association is terminated. |
| 1307 | |
| 1308 | Default: 10 |
| 1309 | |
| 1310 | max_init_retransmits - INTEGER |
| 1311 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks |
| 1312 | that an association will attempt before declaring the destination |
| 1313 | unreachable and terminating. |
| 1314 | |
| 1315 | Default: 8 |
| 1316 | |
| 1317 | path_max_retrans - INTEGER |
| 1318 | The maximum number of retransmissions that will be attempted on a given |
| 1319 | path. Once this threshold is exceeded, the path is considered |
| 1320 | unreachable, and new traffic will use a different path when the |
| 1321 | association is multihomed. |
| 1322 | |
| 1323 | Default: 5 |
| 1324 | |
| 1325 | rto_initial - INTEGER |
| 1326 | The initial round trip timeout value in milliseconds that will be used |
| 1327 | in calculating round trip times. This is the initial time interval |
| 1328 | for retransmissions. |
| 1329 | |
| 1330 | Default: 3000 |
| 1331 | |
| 1332 | rto_max - INTEGER |
| 1333 | The maximum value (in milliseconds) of the round trip timeout. This |
| 1334 | is the largest time interval that can elapse between retransmissions. |
| 1335 | |
| 1336 | Default: 60000 |
| 1337 | |
| 1338 | rto_min - INTEGER |
| 1339 | The minimum value (in milliseconds) of the round trip timeout. This |
| 1340 | is the smallest time interval the can elapse between retransmissions. |
| 1341 | |
| 1342 | Default: 1000 |
| 1343 | |
| 1344 | hb_interval - INTEGER |
| 1345 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks |
| 1346 | are sent at the specified interval on idle paths to probe the state of |
| 1347 | a given path between 2 associations. |
| 1348 | |
| 1349 | Default: 30000 |
| 1350 | |
| 1351 | sack_timeout - INTEGER |
| 1352 | The amount of time (in milliseconds) that the implementation will wait |
| 1353 | to send a SACK. |
| 1354 | |
| 1355 | Default: 200 |
| 1356 | |
| 1357 | valid_cookie_life - INTEGER |
| 1358 | The default lifetime of the SCTP cookie (in milliseconds). The cookie |
| 1359 | is used during association establishment. |
| 1360 | |
| 1361 | Default: 60000 |
| 1362 | |
| 1363 | cookie_preserve_enable - BOOLEAN |
| 1364 | Enable or disable the ability to extend the lifetime of the SCTP cookie |
| 1365 | that is used during the establishment phase of SCTP association |
| 1366 | |
| 1367 | 1: Enable cookie lifetime extension. |
| 1368 | 0: Disable |
| 1369 | |
| 1370 | Default: 1 |
| 1371 | |
| 1372 | rcvbuf_policy - INTEGER |
| 1373 | Determines if the receive buffer is attributed to the socket or to |
| 1374 | association. SCTP supports the capability to create multiple |
| 1375 | associations on a single socket. When using this capability, it is |
| 1376 | possible that a single stalled association that's buffering a lot |
| 1377 | of data may block other associations from delivering their data by |
| 1378 | consuming all of the receive buffer space. To work around this, |
| 1379 | the rcvbuf_policy could be set to attribute the receiver buffer space |
| 1380 | to each association instead of the socket. This prevents the described |
| 1381 | blocking. |
| 1382 | |
| 1383 | 1: rcvbuf space is per association |
| 1384 | 0: recbuf space is per socket |
| 1385 | |
| 1386 | Default: 0 |
| 1387 | |
| 1388 | sndbuf_policy - INTEGER |
| 1389 | Similar to rcvbuf_policy above, this applies to send buffer space. |
| 1390 | |
| 1391 | 1: Send buffer is tracked per association |
| 1392 | 0: Send buffer is tracked per socket. |
| 1393 | |
| 1394 | Default: 0 |
| 1395 | |
| 1396 | sctp_mem - vector of 3 INTEGERs: min, pressure, max |
| 1397 | Number of pages allowed for queueing by all SCTP sockets. |
| 1398 | |
| 1399 | min: Below this number of pages SCTP is not bothered about its |
| 1400 | memory appetite. When amount of memory allocated by SCTP exceeds |
| 1401 | this number, SCTP starts to moderate memory usage. |
| 1402 | |
| 1403 | pressure: This value was introduced to follow format of tcp_mem. |
| 1404 | |
| 1405 | max: Number of pages allowed for queueing by all SCTP sockets. |
| 1406 | |
| 1407 | Default is calculated at boot time from amount of available memory. |
| 1408 | |
| 1409 | sctp_rmem - vector of 3 INTEGERs: min, default, max |
| 1410 | See tcp_rmem for a description. |
| 1411 | |
| 1412 | sctp_wmem - vector of 3 INTEGERs: min, default, max |
| 1413 | See tcp_wmem for a description. |
| 1414 | |
Bhaskar Dutta | 7238843 | 2009-09-03 17:25:47 +0530 | [diff] [blame] | 1415 | addr_scope_policy - INTEGER |
| 1416 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 |
| 1417 | |
| 1418 | 0 - Disable IPv4 address scoping |
| 1419 | 1 - Enable IPv4 address scoping |
| 1420 | 2 - Follow draft but allow IPv4 private addresses |
| 1421 | 3 - Follow draft but allow IPv4 link local addresses |
| 1422 | |
| 1423 | Default: 1 |
| 1424 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1425 | |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 1426 | /proc/sys/net/core/* |
Wang Tinggong | 705efc3 | 2009-05-14 22:49:36 +0000 | [diff] [blame] | 1427 | dev_weight - INTEGER |
| 1428 | The maximum number of packets that kernel can handle on a NAPI |
| 1429 | interrupt, it's a Per-CPU variable. |
| 1430 | |
| 1431 | Default: 64 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1432 | |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 1433 | /proc/sys/net/unix/* |
Wang Tinggong | 705efc3 | 2009-05-14 22:49:36 +0000 | [diff] [blame] | 1434 | max_dgram_qlen - INTEGER |
| 1435 | The maximum length of dgram socket receive queue |
| 1436 | |
| 1437 | Default: 10 |
| 1438 | |
| 1439 | |
| 1440 | UNDOCUMENTED: |
Stephen Hemminger | 4edc2f3 | 2008-07-10 16:50:26 -0700 | [diff] [blame] | 1441 | |
| 1442 | /proc/sys/net/irda/* |
| 1443 | fast_poll_increase FIXME |
| 1444 | warn_noreply_time FIXME |
| 1445 | discovery_slots FIXME |
| 1446 | slot_timeout FIXME |
| 1447 | max_baud_rate FIXME |
| 1448 | discovery_timeout FIXME |
| 1449 | lap_keepalive_time FIXME |
| 1450 | max_noreply_time FIXME |
| 1451 | max_tx_data_size FIXME |
| 1452 | max_tx_window FIXME |
| 1453 | min_tx_turn_time FIXME |