net/ipv4/Kconfig

   1 #
   2 # IP configuration
   3 #
   4 config IP_MULTICAST
   5         bool "IP: multicasting"
   6         help
   7           This is code for addressing several networked computers at once,
   8           enlarging your kernel by about 2 KB. You need multicasting if you
   9           intend to participate in the MBONE, a high bandwidth network on top
  10           of the Internet which carries audio and video broadcasts. More
  11           information about the MBONE is on the WWW at
  12           <http://www.savetz.com/mbone/>. Information about the multicast
  13           capabilities of the various network cards is contained in
  14           <file:Documentation/networking/multicast.txt>. For most people, it's
  15           safe to say N.
  16
  17 config IP_ADVANCED_ROUTER
  18         bool "IP: advanced router"
  19         ---help---
  20           If you intend to run your Linux box mostly as a router, i.e. as a
  21           computer that forwards and redistributes network packets, say Y; you
  22           will then be presented with several options that allow more precise
  23           control about the routing process.
  24
  25           The answer to this question won't directly affect the kernel:
  26           answering N will just cause the configurator to skip all the
  27           questions about advanced routing.
  28
  29           Note that your box can only act as a router if you enable IP
  30           forwarding in your kernel; you can do that by saying Y to "/proc
  31           file system support" and "Sysctl support" below and executing the
  32           line
  33
  34           echo "1" > /proc/sys/net/ipv4/ip_forward
  35
  36           at boot time after the /proc file system has been mounted.
  37
  38           If you turn on IP forwarding, you will also get the rp_filter, which
  39           automatically rejects incoming packets if the routing table entry
  40           for their source address doesn't match the network interface they're
  41           arriving on. This has security advantages because it prevents the
  42           so-called IP spoofing, however it can pose problems if you use
  43           asymmetric routing (packets from you to a host take a different path
  44           than packets from that host to you) or if you operate a non-routing
  45           host which has several IP addresses on different interfaces. To turn
  46           rp_filter on use:
  47
  48           echo 1 > /proc/sys/net/ipv4/conf/<device>/rp_filter
  49           or
  50           echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter
  51
  52           If unsure, say N here.
  53
  54 choice
  55         prompt "Choose IP: FIB lookup algorithm (choose FIB_HASH if unsure)"
  56         depends on IP_ADVANCED_ROUTER
  57         default ASK_IP_FIB_HASH
  58
  59 config ASK_IP_FIB_HASH
  60         bool "FIB_HASH"
  61         ---help---
  62         Current FIB is very proven and good enough for most users.
  63
  64 config IP_FIB_TRIE
  65         bool "FIB_TRIE"
  66         ---help---
  67         Use new experimental LC-trie as FIB lookup algorithm.
  68         This improves lookup performance if you have a large
  69         number of routes.
  70
  71         LC-trie is a longest matching prefix lookup algorithm which
  72         performs better than FIB_HASH for large routing tables.
  73         But, it consumes more memory and is more complex.
  74
  75         LC-trie is described in:
  76
  77         IP-address lookup using LC-tries. Stefan Nilsson and Gunnar Karlsson
  78         IEEE Journal on Selected Areas in Communications, 17(6):1083-1092, June 1999
  79         An experimental study of compression methods for dynamic tries
  80         Stefan Nilsson and Matti Tikkanen. Algorithmica, 33(1):19-33, 2002.
  81         http://www.nada.kth.se/~snilsson/public/papers/dyntrie2/
  82
  83 endchoice
  84
  85 config IP_FIB_HASH
  86         def_bool ASK_IP_FIB_HASH || !IP_ADVANCED_ROUTER
  87
  88 config IP_FIB_TRIE_STATS
  89         bool "FIB TRIE statistics"
  90         depends on IP_FIB_TRIE
  91         ---help---
  92           Keep track of statistics on structure of FIB TRIE table.
  93           Useful for testing and measuring TRIE performance.
  94
  95 config IP_MULTIPLE_TABLES
  96         bool "IP: policy routing"
  97         depends on IP_ADVANCED_ROUTER
  98         select FIB_RULES
  99         ---help---
 100           Normally, a router decides what to do with a received packet based
 101           solely on the packet's final destination address. If you say Y here,
 102           the Linux router will also be able to take the packet's source
 103           address into account. Furthermore, the TOS (Type-Of-Service) field
 104           of the packet can be used for routing decisions as well.
 105
 106           If you are interested in this, please see the preliminary
 107           documentation at <http://www.compendium.com.ar/policy-routing.txt>
 108           and <ftp://post.tepkom.ru/pub/vol2/Linux/docs/advanced-routing.tex>.
 109           You will need supporting software from
 110           <ftp://ftp.tux.org/pub/net/ip-routing/>.
 111
 112           If unsure, say N.
 113
 114 config IP_ROUTE_MULTIPATH
 115         bool "IP: equal cost multipath"
 116         depends on IP_ADVANCED_ROUTER
 117         help
 118           Normally, the routing tables specify a single action to be taken in
 119           a deterministic manner for a given packet. If you say Y here
 120           however, it becomes possible to attach several actions to a packet
 121           pattern, in effect specifying several alternative paths to travel
 122           for those packets. The router considers all these paths to be of
 123           equal "cost" and chooses one of them in a non-deterministic fashion
 124           if a matching packet arrives.
 125
 126 config IP_ROUTE_VERBOSE
 127         bool "IP: verbose route monitoring"
 128         depends on IP_ADVANCED_ROUTER
 129         help
 130           If you say Y here, which is recommended, then the kernel will print
 131           verbose messages regarding the routing, for example warnings about
 132           received packets which look strange and could be evidence of an
 133           attack or a misconfigured system somewhere. The information is
 134           handled by the klogd daemon which is responsible for kernel messages
 135           ("man klogd").
 136
 137 config IP_PNP
 138         bool "IP: kernel level autoconfiguration"
 139         help
 140           This enables automatic configuration of IP addresses of devices and
 141           of the routing table during kernel boot, based on either information
 142           supplied on the kernel command line or by BOOTP or RARP protocols.
 143           You need to say Y only for diskless machines requiring network
 144           access to boot (in which case you want to say Y to "Root file system
 145           on NFS" as well), because all other machines configure the network
 146           in their startup scripts.
 147
 148 config IP_PNP_DHCP
 149         bool "IP: DHCP support"
 150         depends on IP_PNP
 151         ---help---
 152           If you want your Linux box to mount its whole root file system (the
 153           one containing the directory /) from some other computer over the
 154           net via NFS and you want the IP address of your computer to be
 155           discovered automatically at boot time using the DHCP protocol (a
 156           special protocol designed for doing this job), say Y here. In case
 157           the boot ROM of your network card was designed for booting Linux and
 158           does DHCP itself, providing all necessary information on the kernel
 159           command line, you can say N here.
 160
 161           If unsure, say Y. Note that if you want to use DHCP, a DHCP server
 162           must be operating on your network.  Read
 163           <file:Documentation/filesystems/nfsroot.txt> for details.
 164
 165 config IP_PNP_BOOTP
 166         bool "IP: BOOTP support"
 167         depends on IP_PNP
 168         ---help---
 169           If you want your Linux box to mount its whole root file system (the
 170           one containing the directory /) from some other computer over the
 171           net via NFS and you want the IP address of your computer to be
 172           discovered automatically at boot time using the BOOTP protocol (a
 173           special protocol designed for doing this job), say Y here. In case
 174           the boot ROM of your network card was designed for booting Linux and
 175           does BOOTP itself, providing all necessary information on the kernel
 176           command line, you can say N here. If unsure, say Y. Note that if you
 177           want to use BOOTP, a BOOTP server must be operating on your network.
 178           Read <file:Documentation/filesystems/nfsroot.txt> for details.
 179
 180 config IP_PNP_RARP
 181         bool "IP: RARP support"
 182         depends on IP_PNP
 183         help
 184           If you want your Linux box to mount its whole root file system (the
 185           one containing the directory /) from some other computer over the
 186           net via NFS and you want the IP address of your computer to be
 187           discovered automatically at boot time using the RARP protocol (an
 188           older protocol which is being obsoleted by BOOTP and DHCP), say Y
 189           here. Note that if you want to use RARP, a RARP server must be
 190           operating on your network. Read
 191           <file:Documentation/filesystems/nfsroot.txt> for details.
 192
 193 # not yet ready..
 194 #   bool '    IP: ARP support' CONFIG_IP_PNP_ARP
 195 config NET_IPIP
 196         tristate "IP: tunneling"
 197         select INET_TUNNEL
 198         ---help---
 199           Tunneling means encapsulating data of one protocol type within
 200           another protocol and sending it over a channel that understands the
 201           encapsulating protocol. This particular tunneling driver implements
 202           encapsulation of IP within IP, which sounds kind of pointless, but
 203           can be useful if you want to make your (or some other) machine
 204           appear on a different network than it physically is, or to use
 205           mobile-IP facilities (allowing laptops to seamlessly move between
 206           networks without changing their IP addresses).
 207
 208           Saying Y to this option will produce two modules ( = code which can
 209           be inserted in and removed from the running kernel whenever you
 210           want). Most people won't need this and can say N.
 211
 212 config NET_IPGRE
 213         tristate "IP: GRE tunnels over IP"
 214         help
 215           Tunneling means encapsulating data of one protocol type within
 216           another protocol and sending it over a channel that understands the
 217           encapsulating protocol. This particular tunneling driver implements
 218           GRE (Generic Routing Encapsulation) and at this time allows
 219           encapsulating of IPv4 or IPv6 over existing IPv4 infrastructure.
 220           This driver is useful if the other endpoint is a Cisco router: Cisco
 221           likes GRE much better than the other Linux tunneling driver ("IP
 222           tunneling" above). In addition, GRE allows multicast redistribution
 223           through the tunnel.
 224
 225 config NET_IPGRE_BROADCAST
 226         bool "IP: broadcast GRE over IP"
 227         depends on IP_MULTICAST && NET_IPGRE
 228         help
 229           One application of GRE/IP is to construct a broadcast WAN (Wide Area
 230           Network), which looks like a normal Ethernet LAN (Local Area
 231           Network), but can be distributed all over the Internet. If you want
 232           to do that, say Y here and to "IP multicast routing" below.
 233
 234 config IP_MROUTE
 235         bool "IP: multicast routing"
 236         depends on IP_MULTICAST
 237         help
 238           This is used if you want your machine to act as a router for IP
 239           packets that have several destination addresses. It is needed on the
 240           MBONE, a high bandwidth network on top of the Internet which carries
 241           audio and video broadcasts. In order to do that, you would most
 242           likely run the program mrouted. Information about the multicast
 243           capabilities of the various network cards is contained in
 244           <file:Documentation/networking/multicast.txt>. If you haven't heard
 245           about it, you don't need it.
 246
 247 config IP_PIMSM_V1
 248         bool "IP: PIM-SM version 1 support"
 249         depends on IP_MROUTE
 250         help
 251           Kernel side support for Sparse Mode PIM (Protocol Independent
 252           Multicast) version 1. This multicast routing protocol is used widely
 253           because Cisco supports it. You need special software to use it
 254           (pimd-v1). Please see <http://netweb.usc.edu/pim/> for more
 255           information about PIM.
 256
 257           Say Y if you want to use PIM-SM v1. Note that you can say N here if
 258           you just want to use Dense Mode PIM.
 259
 260 config IP_PIMSM_V2
 261         bool "IP: PIM-SM version 2 support"
 262         depends on IP_MROUTE
 263         help
 264           Kernel side support for Sparse Mode PIM version 2. In order to use
 265           this, you need an experimental routing daemon supporting it (pimd or
 266           gated-5). This routing protocol is not used widely, so say N unless
 267           you want to play with it.
 268
 269 config ARPD
 270         bool "IP: ARP daemon support (EXPERIMENTAL)"
 271         depends on EXPERIMENTAL
 272         ---help---
 273           Normally, the kernel maintains an internal cache which maps IP
 274           addresses to hardware addresses on the local network, so that
 275           Ethernet/Token Ring/ etc. frames are sent to the proper address on
 276           the physical networking layer. For small networks having a few
 277           hundred directly connected hosts or less, keeping this address
 278           resolution (ARP) cache inside the kernel works well. However,
 279           maintaining an internal ARP cache does not work well for very large
 280           switched networks, and will use a lot of kernel memory if TCP/IP
 281           connections are made to many machines on the network.
 282
 283           If you say Y here, the kernel's internal ARP cache will never grow
 284           to more than 256 entries (the oldest entries are expired in a LIFO
 285           manner) and communication will be attempted with the user space ARP
 286           daemon arpd. Arpd then answers the address resolution request either
 287           from its own cache or by asking the net.
 288
 289           This code is experimental and also obsolete. If you want to use it,
 290           you need to find a version of the daemon arpd on the net somewhere,
 291           and you should also say Y to "Kernel/User network link driver",
 292           below. If unsure, say N.
 293
 294 config SYN_COOKIES
 295         bool "IP: TCP syncookie support (disabled per default)"
 296         ---help---
 297           Normal TCP/IP networking is open to an attack known as "SYN
 298           flooding". This denial-of-service attack prevents legitimate remote
 299           users from being able to connect to your computer during an ongoing
 300           attack and requires very little work from the attacker, who can
 301           operate from anywhere on the Internet.
 302
 303           SYN cookies provide protection against this type of attack. If you
 304           say Y here, the TCP/IP stack will use a cryptographic challenge
 305           protocol known as "SYN cookies" to enable legitimate users to
 306           continue to connect, even when your machine is under attack. There
 307           is no need for the legitimate users to change their TCP/IP software;
 308           SYN cookies work transparently to them. For technical information
 309           about SYN cookies, check out <http://cr.yp.to/syncookies.html>.
 310
 311           If you are SYN flooded, the source address reported by the kernel is
 312           likely to have been forged by the attacker; it is only reported as
 313           an aid in tracing the packets to their actual source and should not
 314           be taken as absolute truth.
 315
 316           SYN cookies may prevent correct error reporting on clients when the
 317           server is really overloaded. If this happens frequently better turn
 318           them off.
 319
 320           If you say Y here, note that SYN cookies aren't enabled by default;
 321           you can enable them by saying Y to "/proc file system support" and
 322           "Sysctl support" below and executing the command
 323
 324           echo 1 >/proc/sys/net/ipv4/tcp_syncookies
 325
 326           at boot time after the /proc file system has been mounted.
 327
 328           If unsure, say N.
 329
 330 config INET_AH
 331         tristate "IP: AH transformation"
 332         select XFRM
 333         select CRYPTO
 334         select CRYPTO_HMAC
 335         select CRYPTO_MD5
 336         select CRYPTO_SHA1
 337         ---help---
 338           Support for IPsec AH.
 339
 340           If unsure, say Y.
 341
 342 config INET_ESP
 343         tristate "IP: ESP transformation"
 344         select XFRM
 345         select CRYPTO
 346         select CRYPTO_AUTHENC
 347         select CRYPTO_HMAC
 348         select CRYPTO_MD5
 349         select CRYPTO_CBC
 350         select CRYPTO_SHA1
 351         select CRYPTO_DES
 352         ---help---
 353           Support for IPsec ESP.
 354
 355           If unsure, say Y.
 356
 357 config INET_IPCOMP
 358         tristate "IP: IPComp transformation"
 359         select INET_XFRM_TUNNEL
 360         select XFRM_IPCOMP
 361         ---help---
 362           Support for IP Payload Compression Protocol (IPComp) (RFC3173),
 363           typically needed for IPsec.
 364
 365           If unsure, say Y.
 366
 367 config INET_XFRM_TUNNEL
 368         tristate
 369         select INET_TUNNEL
 370         default n
 371
 372 config INET_TUNNEL
 373         tristate
 374         default n
 375
 376 config INET_XFRM_MODE_TRANSPORT
 377         tristate "IP: IPsec transport mode"
 378         default y
 379         select XFRM
 380         ---help---
 381           Support for IPsec transport mode.
 382
 383           If unsure, say Y.
 384
 385 config INET_XFRM_MODE_TUNNEL
 386         tristate "IP: IPsec tunnel mode"
 387         default y
 388         select XFRM
 389         ---help---
 390           Support for IPsec tunnel mode.
 391
 392           If unsure, say Y.
 393
 394 config INET_XFRM_MODE_BEET
 395         tristate "IP: IPsec BEET mode"
 396         default y
 397         select XFRM
 398         ---help---
 399           Support for IPsec BEET mode.
 400
 401           If unsure, say Y.
 402
 403 config INET_LRO
 404         tristate "Large Receive Offload (ipv4/tcp)"
 405
 406         ---help---
 407           Support for Large Receive Offload (ipv4/tcp).
 408
 409           If unsure, say Y.
 410
 411 config INET_DIAG
 412         tristate "INET: socket monitoring interface"
 413         default y
 414         ---help---
 415           Support for INET (TCP, DCCP, etc) socket monitoring interface used by
 416           native Linux tools such as ss. ss is included in iproute2, currently
 417           downloadable at <http://linux-net.osdl.org/index.php/Iproute2>.
 418
 419           If unsure, say Y.
 420
 421 config INET_TCP_DIAG
 422         depends on INET_DIAG
 423         def_tristate INET_DIAG
 424
 425 menuconfig TCP_CONG_ADVANCED
 426         bool "TCP: advanced congestion control"
 427         ---help---
 428           Support for selection of various TCP congestion control
 429           modules.
 430
 431           Nearly all users can safely say no here, and a safe default
 432           selection will be made (CUBIC with new Reno as a fallback).
 433
 434           If unsure, say N.
 435
 436 if TCP_CONG_ADVANCED
 437
 438 config TCP_CONG_BIC
 439         tristate "Binary Increase Congestion (BIC) control"
 440         default m
 441         ---help---
 442         BIC-TCP is a sender-side only change that ensures a linear RTT
 443         fairness under large windows while offering both scalability and
 444         bounded TCP-friendliness. The protocol combines two schemes
 445         called additive increase and binary search increase. When the
 446         congestion window is large, additive increase with a large
 447         increment ensures linear RTT fairness as well as good
 448         scalability. Under small congestion windows, binary search
 449         increase provides TCP friendliness.
 450         See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/
 451
 452 config TCP_CONG_CUBIC
 453         tristate "CUBIC TCP"
 454         default y
 455         ---help---
 456         This is version 2.0 of BIC-TCP which uses a cubic growth function
 457         among other techniques.
 458         See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/cubic-paper.pdf
 459
 460 config TCP_CONG_WESTWOOD
 461         tristate "TCP Westwood+"
 462         default m
 463         ---help---
 464         TCP Westwood+ is a sender-side only modification of the TCP Reno
 465         protocol stack that optimizes the performance of TCP congestion
 466         control. It is based on end-to-end bandwidth estimation to set
 467         congestion window and slow start threshold after a congestion
 468         episode. Using this estimation, TCP Westwood+ adaptively sets a
 469         slow start threshold and a congestion window which takes into
 470         account the bandwidth used  at the time congestion is experienced.
 471         TCP Westwood+ significantly increases fairness wrt TCP Reno in
 472         wired networks and throughput over wireless links.
 473
 474 config TCP_CONG_HTCP
 475         tristate "H-TCP"
 476         default m
 477         ---help---
 478         H-TCP is a send-side only modifications of the TCP Reno
 479         protocol stack that optimizes the performance of TCP
 480         congestion control for high speed network links. It uses a
 481         modeswitch to change the alpha and beta parameters of TCP Reno
 482         based on network conditions and in a way so as to be fair with
 483         other Reno and H-TCP flows.
 484
 485 config TCP_CONG_HSTCP
 486         tristate "High Speed TCP"
 487         depends on EXPERIMENTAL
 488         default n
 489         ---help---
 490         Sally Floyd's High Speed TCP (RFC 3649) congestion control.
 491         A modification to TCP's congestion control mechanism for use
 492         with large congestion windows. A table indicates how much to
 493         increase the congestion window by when an ACK is received.
 494         For more detail see http://www.icir.org/floyd/hstcp.html
 495
 496 config TCP_CONG_HYBLA
 497         tristate "TCP-Hybla congestion control algorithm"
 498         depends on EXPERIMENTAL
 499         default n
 500         ---help---
 501         TCP-Hybla is a sender-side only change that eliminates penalization of
 502         long-RTT, large-bandwidth connections, like when satellite legs are
 503         involved, especially when sharing a common bottleneck with normal
 504         terrestrial connections.
 505
 506 config TCP_CONG_VEGAS
 507         tristate "TCP Vegas"
 508         depends on EXPERIMENTAL
 509         default n
 510         ---help---
 511         TCP Vegas is a sender-side only change to TCP that anticipates
 512         the onset of congestion by estimating the bandwidth. TCP Vegas
 513         adjusts the sending rate by modifying the congestion
 514         window. TCP Vegas should provide less packet loss, but it is
 515         not as aggressive as TCP Reno.
 516
 517 config TCP_CONG_SCALABLE
 518         tristate "Scalable TCP"
 519         depends on EXPERIMENTAL
 520         default n
 521         ---help---
 522         Scalable TCP is a sender-side only change to TCP which uses a
 523         MIMD congestion control algorithm which has some nice scaling
 524         properties, though is known to have fairness issues.
 525         See http://www.deneholme.net/tom/scalable/
 526
 527 config TCP_CONG_LP
 528         tristate "TCP Low Priority"
 529         depends on EXPERIMENTAL
 530         default n
 531         ---help---
 532         TCP Low Priority (TCP-LP), a distributed algorithm whose goal is
 533         to utilize only the excess network bandwidth as compared to the
 534         ``fair share`` of bandwidth as targeted by TCP.
 535         See http://www-ece.rice.edu/networks/TCP-LP/
 536
 537 config TCP_CONG_VENO
 538         tristate "TCP Veno"
 539         depends on EXPERIMENTAL
 540         default n
 541         ---help---
 542         TCP Veno is a sender-side only enhancement of TCP to obtain better
 543         throughput over wireless networks. TCP Veno makes use of state
 544         distinguishing to circumvent the difficult judgment of the packet loss
 545         type. TCP Veno cuts down less congestion window in response to random
 546         loss packets.
 547         See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf
 548
 549 config TCP_CONG_YEAH
 550         tristate "YeAH TCP"
 551         depends on EXPERIMENTAL
 552         select TCP_CONG_VEGAS
 553         default n
 554         ---help---
 555         YeAH-TCP is a sender-side high-speed enabled TCP congestion control
 556         algorithm, which uses a mixed loss/delay approach to compute the
 557         congestion window. It's design goals target high efficiency,
 558         internal, RTT and Reno fairness, resilience to link loss while
 559         keeping network elements load as low as possible.
 560
 561         For further details look here:
 562           http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
 563
 564 config TCP_CONG_ILLINOIS
 565         tristate "TCP Illinois"
 566         depends on EXPERIMENTAL
 567         default n
 568         ---help---
 569         TCP-Illinois is a sender-side modification of TCP Reno for
 570         high speed long delay links. It uses round-trip-time to
 571         adjust the alpha and beta parameters to achieve a higher average
 572         throughput and maintain fairness.
 573
 574         For further details see:
 575           http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html
 576
 577 choice
 578         prompt "Default TCP congestion control"
 579         default DEFAULT_CUBIC
 580         help
 581           Select the TCP congestion control that will be used by default
 582           for all connections.
 583
 584         config DEFAULT_BIC
 585                 bool "Bic" if TCP_CONG_BIC=y
 586
 587         config DEFAULT_CUBIC
 588                 bool "Cubic" if TCP_CONG_CUBIC=y
 589
 590         config DEFAULT_HTCP
 591                 bool "Htcp" if TCP_CONG_HTCP=y
 592
 593         config DEFAULT_VEGAS
 594                 bool "Vegas" if TCP_CONG_VEGAS=y
 595
 596         config DEFAULT_WESTWOOD
 597                 bool "Westwood" if TCP_CONG_WESTWOOD=y
 598
 599         config DEFAULT_RENO
 600                 bool "Reno"
 601
 602 endchoice
 603
 604 endif
 605
 606 config TCP_CONG_CUBIC
 607         tristate
 608         depends on !TCP_CONG_ADVANCED
 609         default y
 610
 611 config DEFAULT_TCP_CONG
 612         string
 613         default "bic" if DEFAULT_BIC
 614         default "cubic" if DEFAULT_CUBIC
 615         default "htcp" if DEFAULT_HTCP
 616         default "vegas" if DEFAULT_VEGAS
 617         default "westwood" if DEFAULT_WESTWOOD
 618         default "reno" if DEFAULT_RENO
 619         default "cubic"
 620
 621 config TCP_MD5SIG
 622         bool "TCP: MD5 Signature Option support (RFC2385) (EXPERIMENTAL)"
 623         depends on EXPERIMENTAL
 624         select CRYPTO
 625         select CRYPTO_MD5
 626         ---help---
 627           RFC2385 specifies a method of giving MD5 protection to TCP sessions.
 628           Its main (only?) use is to protect BGP sessions between core routers
 629           on the Internet.
 630
 631           If unsure, say N.
 632