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/>. For most people, it's safe to say N.
  13
  14 config IP_ADVANCED_ROUTER
  15         bool "IP: advanced router"
  16         ---help---
  17           If you intend to run your Linux box mostly as a router, i.e. as a
  18           computer that forwards and redistributes network packets, say Y; you
  19           will then be presented with several options that allow more precise
  20           control about the routing process.
  21
  22           The answer to this question won't directly affect the kernel:
  23           answering N will just cause the configurator to skip all the
  24           questions about advanced routing.
  25
  26           Note that your box can only act as a router if you enable IP
  27           forwarding in your kernel; you can do that by saying Y to "/proc
  28           file system support" and "Sysctl support" below and executing the
  29           line
  30
  31           echo "1" > /proc/sys/net/ipv4/ip_forward
  32
  33           at boot time after the /proc file system has been mounted.
  34
  35           If you turn on IP forwarding, you should consider the rp_filter, which
  36           automatically rejects incoming packets if the routing table entry
  37           for their source address doesn't match the network interface they're
  38           arriving on. This has security advantages because it prevents the
  39           so-called IP spoofing, however it can pose problems if you use
  40           asymmetric routing (packets from you to a host take a different path
  41           than packets from that host to you) or if you operate a non-routing
  42           host which has several IP addresses on different interfaces. To turn
  43           rp_filter on use:
  44
  45           echo 1 > /proc/sys/net/ipv4/conf/<device>/rp_filter
  46            or
  47           echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter
  48
  49           Note that some distributions enable it in startup scripts.
  50           For details about rp_filter strict and loose mode read
  51           <file:Documentation/networking/ip-sysctl.txt>.
  52
  53           If unsure, say N here.
  54
  55 config IP_FIB_TRIE_STATS
  56         bool "FIB TRIE statistics"
  57         depends on IP_ADVANCED_ROUTER
  58         ---help---
  59           Keep track of statistics on structure of FIB TRIE table.
  60           Useful for testing and measuring TRIE performance.
  61
  62 config IP_MULTIPLE_TABLES
  63         bool "IP: policy routing"
  64         depends on IP_ADVANCED_ROUTER
  65         select FIB_RULES
  66         ---help---
  67           Normally, a router decides what to do with a received packet based
  68           solely on the packet's final destination address. If you say Y here,
  69           the Linux router will also be able to take the packet's source
  70           address into account. Furthermore, the TOS (Type-Of-Service) field
  71           of the packet can be used for routing decisions as well.
  72
  73           If you are interested in this, please see the preliminary
  74           documentation at <http://www.compendium.com.ar/policy-routing.txt>
  75           and <ftp://post.tepkom.ru/pub/vol2/Linux/docs/advanced-routing.tex>.
  76           You will need supporting software from
  77           <ftp://ftp.tux.org/pub/net/ip-routing/>.
  78
  79           If unsure, say N.
  80
  81 config IP_ROUTE_MULTIPATH
  82         bool "IP: equal cost multipath"
  83         depends on IP_ADVANCED_ROUTER
  84         help
  85           Normally, the routing tables specify a single action to be taken in
  86           a deterministic manner for a given packet. If you say Y here
  87           however, it becomes possible to attach several actions to a packet
  88           pattern, in effect specifying several alternative paths to travel
  89           for those packets. The router considers all these paths to be of
  90           equal "cost" and chooses one of them in a non-deterministic fashion
  91           if a matching packet arrives.
  92
  93 config IP_ROUTE_VERBOSE
  94         bool "IP: verbose route monitoring"
  95         depends on IP_ADVANCED_ROUTER
  96         help
  97           If you say Y here, which is recommended, then the kernel will print
  98           verbose messages regarding the routing, for example warnings about
  99           received packets which look strange and could be evidence of an
 100           attack or a misconfigured system somewhere. The information is
 101           handled by the klogd daemon which is responsible for kernel messages
 102           ("man klogd").
 103
 104 config IP_ROUTE_CLASSID
 105         bool
 106
 107 config IP_PNP
 108         bool "IP: kernel level autoconfiguration"
 109         help
 110           This enables automatic configuration of IP addresses of devices and
 111           of the routing table during kernel boot, based on either information
 112           supplied on the kernel command line or by BOOTP or RARP protocols.
 113           You need to say Y only for diskless machines requiring network
 114           access to boot (in which case you want to say Y to "Root file system
 115           on NFS" as well), because all other machines configure the network
 116           in their startup scripts.
 117
 118 config IP_PNP_DHCP
 119         bool "IP: DHCP support"
 120         depends on IP_PNP
 121         ---help---
 122           If you want your Linux box to mount its whole root file system (the
 123           one containing the directory /) from some other computer over the
 124           net via NFS and you want the IP address of your computer to be
 125           discovered automatically at boot time using the DHCP protocol (a
 126           special protocol designed for doing this job), say Y here. In case
 127           the boot ROM of your network card was designed for booting Linux and
 128           does DHCP itself, providing all necessary information on the kernel
 129           command line, you can say N here.
 130
 131           If unsure, say Y. Note that if you want to use DHCP, a DHCP server
 132           must be operating on your network.  Read
 133           <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
 134
 135 config IP_PNP_BOOTP
 136         bool "IP: BOOTP support"
 137         depends on IP_PNP
 138         ---help---
 139           If you want your Linux box to mount its whole root file system (the
 140           one containing the directory /) from some other computer over the
 141           net via NFS and you want the IP address of your computer to be
 142           discovered automatically at boot time using the BOOTP protocol (a
 143           special protocol designed for doing this job), say Y here. In case
 144           the boot ROM of your network card was designed for booting Linux and
 145           does BOOTP itself, providing all necessary information on the kernel
 146           command line, you can say N here. If unsure, say Y. Note that if you
 147           want to use BOOTP, a BOOTP server must be operating on your network.
 148           Read <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
 149
 150 config IP_PNP_RARP
 151         bool "IP: RARP support"
 152         depends on IP_PNP
 153         help
 154           If you want your Linux box to mount its whole root file system (the
 155           one containing the directory /) from some other computer over the
 156           net via NFS and you want the IP address of your computer to be
 157           discovered automatically at boot time using the RARP protocol (an
 158           older protocol which is being obsoleted by BOOTP and DHCP), say Y
 159           here. Note that if you want to use RARP, a RARP server must be
 160           operating on your network. Read
 161           <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
 162
 163 config NET_IPIP
 164         tristate "IP: tunneling"
 165         select INET_TUNNEL
 166         select NET_IP_TUNNEL
 167         ---help---
 168           Tunneling means encapsulating data of one protocol type within
 169           another protocol and sending it over a channel that understands the
 170           encapsulating protocol. This particular tunneling driver implements
 171           encapsulation of IP within IP, which sounds kind of pointless, but
 172           can be useful if you want to make your (or some other) machine
 173           appear on a different network than it physically is, or to use
 174           mobile-IP facilities (allowing laptops to seamlessly move between
 175           networks without changing their IP addresses).
 176
 177           Saying Y to this option will produce two modules ( = code which can
 178           be inserted in and removed from the running kernel whenever you
 179           want). Most people won't need this and can say N.
 180
 181 config NET_IPGRE_DEMUX
 182         tristate "IP: GRE demultiplexer"
 183         help
 184          This is helper module to demultiplex GRE packets on GRE version field criteria.
 185          Required by ip_gre and pptp modules.
 186
 187 config NET_IP_TUNNEL
 188         tristate
 189         select DST_CACHE
 190         default n
 191
 192 config NET_IPGRE
 193         tristate "IP: GRE tunnels over IP"
 194         depends on (IPV6 || IPV6=n) && NET_IPGRE_DEMUX
 195         select NET_IP_TUNNEL
 196         help
 197           Tunneling means encapsulating data of one protocol type within
 198           another protocol and sending it over a channel that understands the
 199           encapsulating protocol. This particular tunneling driver implements
 200           GRE (Generic Routing Encapsulation) and at this time allows
 201           encapsulating of IPv4 or IPv6 over existing IPv4 infrastructure.
 202           This driver is useful if the other endpoint is a Cisco router: Cisco
 203           likes GRE much better than the other Linux tunneling driver ("IP
 204           tunneling" above). In addition, GRE allows multicast redistribution
 205           through the tunnel.
 206
 207 config NET_IPGRE_BROADCAST
 208         bool "IP: broadcast GRE over IP"
 209         depends on IP_MULTICAST && NET_IPGRE
 210         help
 211           One application of GRE/IP is to construct a broadcast WAN (Wide Area
 212           Network), which looks like a normal Ethernet LAN (Local Area
 213           Network), but can be distributed all over the Internet. If you want
 214           to do that, say Y here and to "IP multicast routing" below.
 215
 216 config IP_MROUTE
 217         bool "IP: multicast routing"
 218         depends on IP_MULTICAST
 219         help
 220           This is used if you want your machine to act as a router for IP
 221           packets that have several destination addresses. It is needed on the
 222           MBONE, a high bandwidth network on top of the Internet which carries
 223           audio and video broadcasts. In order to do that, you would most
 224           likely run the program mrouted. If you haven't heard about it, you
 225           don't need it.
 226
 227 config IP_MROUTE_MULTIPLE_TABLES
 228         bool "IP: multicast policy routing"
 229         depends on IP_MROUTE && IP_ADVANCED_ROUTER
 230         select FIB_RULES
 231         help
 232           Normally, a multicast router runs a userspace daemon and decides
 233           what to do with a multicast packet based on the source and
 234           destination addresses. If you say Y here, the multicast router
 235           will also be able to take interfaces and packet marks into
 236           account and run multiple instances of userspace daemons
 237           simultaneously, each one handling a single table.
 238
 239           If unsure, say N.
 240
 241 config IP_PIMSM_V1
 242         bool "IP: PIM-SM version 1 support"
 243         depends on IP_MROUTE
 244         help
 245           Kernel side support for Sparse Mode PIM (Protocol Independent
 246           Multicast) version 1. This multicast routing protocol is used widely
 247           because Cisco supports it. You need special software to use it
 248           (pimd-v1). Please see <http://netweb.usc.edu/pim/> for more
 249           information about PIM.
 250
 251           Say Y if you want to use PIM-SM v1. Note that you can say N here if
 252           you just want to use Dense Mode PIM.
 253
 254 config IP_PIMSM_V2
 255         bool "IP: PIM-SM version 2 support"
 256         depends on IP_MROUTE
 257         help
 258           Kernel side support for Sparse Mode PIM version 2. In order to use
 259           this, you need an experimental routing daemon supporting it (pimd or
 260           gated-5). This routing protocol is not used widely, so say N unless
 261           you want to play with it.
 262
 263 config SYN_COOKIES
 264         bool "IP: TCP syncookie support"
 265         ---help---
 266           Normal TCP/IP networking is open to an attack known as "SYN
 267           flooding". This denial-of-service attack prevents legitimate remote
 268           users from being able to connect to your computer during an ongoing
 269           attack and requires very little work from the attacker, who can
 270           operate from anywhere on the Internet.
 271
 272           SYN cookies provide protection against this type of attack. If you
 273           say Y here, the TCP/IP stack will use a cryptographic challenge
 274           protocol known as "SYN cookies" to enable legitimate users to
 275           continue to connect, even when your machine is under attack. There
 276           is no need for the legitimate users to change their TCP/IP software;
 277           SYN cookies work transparently to them. For technical information
 278           about SYN cookies, check out <http://cr.yp.to/syncookies.html>.
 279
 280           If you are SYN flooded, the source address reported by the kernel is
 281           likely to have been forged by the attacker; it is only reported as
 282           an aid in tracing the packets to their actual source and should not
 283           be taken as absolute truth.
 284
 285           SYN cookies may prevent correct error reporting on clients when the
 286           server is really overloaded. If this happens frequently better turn
 287           them off.
 288
 289           If you say Y here, you can disable SYN cookies at run time by
 290           saying Y to "/proc file system support" and
 291           "Sysctl support" below and executing the command
 292
 293           echo 0 > /proc/sys/net/ipv4/tcp_syncookies
 294
 295           after the /proc file system has been mounted.
 296
 297           If unsure, say N.
 298
 299 config NET_IPVTI
 300         tristate "Virtual (secure) IP: tunneling"
 301         select INET_TUNNEL
 302         select NET_IP_TUNNEL
 303         depends on INET_XFRM_MODE_TUNNEL
 304         ---help---
 305           Tunneling means encapsulating data of one protocol type within
 306           another protocol and sending it over a channel that understands the
 307           encapsulating protocol. This can be used with xfrm mode tunnel to give
 308           the notion of a secure tunnel for IPSEC and then use routing protocol
 309           on top.
 310
 311 config NET_UDP_TUNNEL
 312         tristate
 313         select NET_IP_TUNNEL
 314         default n
 315
 316 config NET_FOU
 317         tristate "IP: Foo (IP protocols) over UDP"
 318         select XFRM
 319         select NET_UDP_TUNNEL
 320         ---help---
 321           Foo over UDP allows any IP protocol to be directly encapsulated
 322           over UDP include tunnels (IPIP, GRE, SIT). By encapsulating in UDP
 323           network mechanisms and optimizations for UDP (such as ECMP
 324           and RSS) can be leveraged to provide better service.
 325
 326 config NET_FOU_IP_TUNNELS
 327         bool "IP: FOU encapsulation of IP tunnels"
 328         depends on NET_IPIP || NET_IPGRE || IPV6_SIT
 329         select NET_FOU
 330         ---help---
 331           Allow configuration of FOU or GUE encapsulation for IP tunnels.
 332           When this option is enabled IP tunnels can be configured to use
 333           FOU or GUE encapsulation.
 334
 335 config INET_AH
 336         tristate "IP: AH transformation"
 337         select XFRM_ALGO
 338         select CRYPTO
 339         select CRYPTO_HMAC
 340         select CRYPTO_MD5
 341         select CRYPTO_SHA1
 342         ---help---
 343           Support for IPsec AH.
 344
 345           If unsure, say Y.
 346
 347 config INET_ESP
 348         tristate "IP: ESP transformation"
 349         select XFRM_ALGO
 350         select CRYPTO
 351         select CRYPTO_AUTHENC
 352         select CRYPTO_HMAC
 353         select CRYPTO_MD5
 354         select CRYPTO_CBC
 355         select CRYPTO_SHA1
 356         select CRYPTO_DES
 357         select CRYPTO_ECHAINIV
 358         ---help---
 359           Support for IPsec ESP.
 360
 361           If unsure, say Y.
 362
 363 config INET_IPCOMP
 364         tristate "IP: IPComp transformation"
 365         select INET_XFRM_TUNNEL
 366         select XFRM_IPCOMP
 367         ---help---
 368           Support for IP Payload Compression Protocol (IPComp) (RFC3173),
 369           typically needed for IPsec.
 370
 371           If unsure, say Y.
 372
 373 config INET_XFRM_TUNNEL
 374         tristate
 375         select INET_TUNNEL
 376         default n
 377
 378 config INET_TUNNEL
 379         tristate
 380         default n
 381
 382 config INET_XFRM_MODE_TRANSPORT
 383         tristate "IP: IPsec transport mode"
 384         default y
 385         select XFRM
 386         ---help---
 387           Support for IPsec transport mode.
 388
 389           If unsure, say Y.
 390
 391 config INET_XFRM_MODE_TUNNEL
 392         tristate "IP: IPsec tunnel mode"
 393         default y
 394         select XFRM
 395         ---help---
 396           Support for IPsec tunnel mode.
 397
 398           If unsure, say Y.
 399
 400 config INET_XFRM_MODE_BEET
 401         tristate "IP: IPsec BEET mode"
 402         default y
 403         select XFRM
 404         ---help---
 405           Support for IPsec BEET mode.
 406
 407           If unsure, say Y.
 408
 409 config INET_DIAG
 410         tristate "INET: socket monitoring interface"
 411         default y
 412         ---help---
 413           Support for INET (TCP, DCCP, etc) socket monitoring interface used by
 414           native Linux tools such as ss. ss is included in iproute2, currently
 415           downloadable at:
 416
 417             http://www.linuxfoundation.org/collaborate/workgroups/networking/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 config INET_UDP_DIAG
 426         tristate "UDP: socket monitoring interface"
 427         depends on INET_DIAG && (IPV6 || IPV6=n)
 428         default n
 429         ---help---
 430           Support for UDP socket monitoring interface used by the ss tool.
 431           If unsure, say Y.
 432
 433 config INET_DIAG_DESTROY
 434         bool "INET: allow privileged process to administratively close sockets"
 435         depends on INET_DIAG
 436         default n
 437         ---help---
 438           Provides a SOCK_DESTROY operation that allows privileged processes
 439           (e.g., a connection manager or a network administration tool such as
 440           ss) to close sockets opened by other processes. Closing a socket in
 441           this way interrupts any blocking read/write/connect operations on
 442           the socket and causes future socket calls to behave as if the socket
 443           had been disconnected.
 444           If unsure, say N.
 445
 446 menuconfig TCP_CONG_ADVANCED
 447         bool "TCP: advanced congestion control"
 448         ---help---
 449           Support for selection of various TCP congestion control
 450           modules.
 451
 452           Nearly all users can safely say no here, and a safe default
 453           selection will be made (CUBIC with new Reno as a fallback).
 454
 455           If unsure, say N.
 456
 457 if TCP_CONG_ADVANCED
 458
 459 config TCP_CONG_BIC
 460         tristate "Binary Increase Congestion (BIC) control"
 461         default m
 462         ---help---
 463         BIC-TCP is a sender-side only change that ensures a linear RTT
 464         fairness under large windows while offering both scalability and
 465         bounded TCP-friendliness. The protocol combines two schemes
 466         called additive increase and binary search increase. When the
 467         congestion window is large, additive increase with a large
 468         increment ensures linear RTT fairness as well as good
 469         scalability. Under small congestion windows, binary search
 470         increase provides TCP friendliness.
 471         See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/
 472
 473 config TCP_CONG_CUBIC
 474         tristate "CUBIC TCP"
 475         default y
 476         ---help---
 477         This is version 2.0 of BIC-TCP which uses a cubic growth function
 478         among other techniques.
 479         See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/cubic-paper.pdf
 480
 481 config TCP_CONG_WESTWOOD
 482         tristate "TCP Westwood+"
 483         default m
 484         ---help---
 485         TCP Westwood+ is a sender-side only modification of the TCP Reno
 486         protocol stack that optimizes the performance of TCP congestion
 487         control. It is based on end-to-end bandwidth estimation to set
 488         congestion window and slow start threshold after a congestion
 489         episode. Using this estimation, TCP Westwood+ adaptively sets a
 490         slow start threshold and a congestion window which takes into
 491         account the bandwidth used  at the time congestion is experienced.
 492         TCP Westwood+ significantly increases fairness wrt TCP Reno in
 493         wired networks and throughput over wireless links.
 494
 495 config TCP_CONG_HTCP
 496         tristate "H-TCP"
 497         default m
 498         ---help---
 499         H-TCP is a send-side only modifications of the TCP Reno
 500         protocol stack that optimizes the performance of TCP
 501         congestion control for high speed network links. It uses a
 502         modeswitch to change the alpha and beta parameters of TCP Reno
 503         based on network conditions and in a way so as to be fair with
 504         other Reno and H-TCP flows.
 505
 506 config TCP_CONG_HSTCP
 507         tristate "High Speed TCP"
 508         default n
 509         ---help---
 510         Sally Floyd's High Speed TCP (RFC 3649) congestion control.
 511         A modification to TCP's congestion control mechanism for use
 512         with large congestion windows. A table indicates how much to
 513         increase the congestion window by when an ACK is received.
 514         For more detail see http://www.icir.org/floyd/hstcp.html
 515
 516 config TCP_CONG_HYBLA
 517         tristate "TCP-Hybla congestion control algorithm"
 518         default n
 519         ---help---
 520         TCP-Hybla is a sender-side only change that eliminates penalization of
 521         long-RTT, large-bandwidth connections, like when satellite legs are
 522         involved, especially when sharing a common bottleneck with normal
 523         terrestrial connections.
 524
 525 config TCP_CONG_VEGAS
 526         tristate "TCP Vegas"
 527         default n
 528         ---help---
 529         TCP Vegas is a sender-side only change to TCP that anticipates
 530         the onset of congestion by estimating the bandwidth. TCP Vegas
 531         adjusts the sending rate by modifying the congestion
 532         window. TCP Vegas should provide less packet loss, but it is
 533         not as aggressive as TCP Reno.
 534
 535 config TCP_CONG_SCALABLE
 536         tristate "Scalable TCP"
 537         default n
 538         ---help---
 539         Scalable TCP is a sender-side only change to TCP which uses a
 540         MIMD congestion control algorithm which has some nice scaling
 541         properties, though is known to have fairness issues.
 542         See http://www.deneholme.net/tom/scalable/
 543
 544 config TCP_CONG_LP
 545         tristate "TCP Low Priority"
 546         default n
 547         ---help---
 548         TCP Low Priority (TCP-LP), a distributed algorithm whose goal is
 549         to utilize only the excess network bandwidth as compared to the
 550         ``fair share`` of bandwidth as targeted by TCP.
 551         See http://www-ece.rice.edu/networks/TCP-LP/
 552
 553 config TCP_CONG_VENO
 554         tristate "TCP Veno"
 555         default n
 556         ---help---
 557         TCP Veno is a sender-side only enhancement of TCP to obtain better
 558         throughput over wireless networks. TCP Veno makes use of state
 559         distinguishing to circumvent the difficult judgment of the packet loss
 560         type. TCP Veno cuts down less congestion window in response to random
 561         loss packets.
 562         See <http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1177186>
 563
 564 config TCP_CONG_YEAH
 565         tristate "YeAH TCP"
 566         select TCP_CONG_VEGAS
 567         default n
 568         ---help---
 569         YeAH-TCP is a sender-side high-speed enabled TCP congestion control
 570         algorithm, which uses a mixed loss/delay approach to compute the
 571         congestion window. It's design goals target high efficiency,
 572         internal, RTT and Reno fairness, resilience to link loss while
 573         keeping network elements load as low as possible.
 574
 575         For further details look here:
 576           http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
 577
 578 config TCP_CONG_ILLINOIS
 579         tristate "TCP Illinois"
 580         default n
 581         ---help---
 582         TCP-Illinois is a sender-side modification of TCP Reno for
 583         high speed long delay links. It uses round-trip-time to
 584         adjust the alpha and beta parameters to achieve a higher average
 585         throughput and maintain fairness.
 586
 587         For further details see:
 588           http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html
 589
 590 config TCP_CONG_DCTCP
 591         tristate "DataCenter TCP (DCTCP)"
 592         default n
 593         ---help---
 594         DCTCP leverages Explicit Congestion Notification (ECN) in the network to
 595         provide multi-bit feedback to the end hosts. It is designed to provide:
 596
 597         - High burst tolerance (incast due to partition/aggregate),
 598         - Low latency (short flows, queries),
 599         - High throughput (continuous data updates, large file transfers) with
 600           commodity, shallow-buffered switches.
 601
 602         All switches in the data center network running DCTCP must support
 603         ECN marking and be configured for marking when reaching defined switch
 604         buffer thresholds. The default ECN marking threshold heuristic for
 605         DCTCP on switches is 20 packets (30KB) at 1Gbps, and 65 packets
 606         (~100KB) at 10Gbps, but might need further careful tweaking.
 607
 608         For further details see:
 609           http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf
 610
 611 config TCP_CONG_CDG
 612         tristate "CAIA Delay-Gradient (CDG)"
 613         default n
 614         ---help---
 615         CAIA Delay-Gradient (CDG) is a TCP congestion control that modifies
 616         the TCP sender in order to:
 617
 618           o Use the delay gradient as a congestion signal.
 619           o Back off with an average probability that is independent of the RTT.
 620           o Coexist with flows that use loss-based congestion control.
 621           o Tolerate packet loss unrelated to congestion.
 622
 623         For further details see:
 624           D.A. Hayes and G. Armitage. "Revisiting TCP congestion control using
 625           delay gradients." In Networking 2011. Preprint: http://goo.gl/No3vdg
 626
 627 choice
 628         prompt "Default TCP congestion control"
 629         default DEFAULT_CUBIC
 630         help
 631           Select the TCP congestion control that will be used by default
 632           for all connections.
 633
 634         config DEFAULT_BIC
 635                 bool "Bic" if TCP_CONG_BIC=y
 636
 637         config DEFAULT_CUBIC
 638                 bool "Cubic" if TCP_CONG_CUBIC=y
 639
 640         config DEFAULT_HTCP
 641                 bool "Htcp" if TCP_CONG_HTCP=y
 642
 643         config DEFAULT_HYBLA
 644                 bool "Hybla" if TCP_CONG_HYBLA=y
 645
 646         config DEFAULT_VEGAS
 647                 bool "Vegas" if TCP_CONG_VEGAS=y
 648
 649         config DEFAULT_VENO
 650                 bool "Veno" if TCP_CONG_VENO=y
 651
 652         config DEFAULT_WESTWOOD
 653                 bool "Westwood" if TCP_CONG_WESTWOOD=y
 654
 655         config DEFAULT_DCTCP
 656                 bool "DCTCP" if TCP_CONG_DCTCP=y
 657
 658         config DEFAULT_CDG
 659                 bool "CDG" if TCP_CONG_CDG=y
 660
 661         config DEFAULT_RENO
 662                 bool "Reno"
 663 endchoice
 664
 665 endif
 666
 667 config TCP_CONG_CUBIC
 668         tristate
 669         depends on !TCP_CONG_ADVANCED
 670         default y
 671
 672 config DEFAULT_TCP_CONG
 673         string
 674         default "bic" if DEFAULT_BIC
 675         default "cubic" if DEFAULT_CUBIC
 676         default "htcp" if DEFAULT_HTCP
 677         default "hybla" if DEFAULT_HYBLA
 678         default "vegas" if DEFAULT_VEGAS
 679         default "westwood" if DEFAULT_WESTWOOD
 680         default "veno" if DEFAULT_VENO
 681         default "reno" if DEFAULT_RENO
 682         default "dctcp" if DEFAULT_DCTCP
 683         default "cdg" if DEFAULT_CDG
 684         default "cubic"
 685
 686 config TCP_MD5SIG
 687         bool "TCP: MD5 Signature Option support (RFC2385)"
 688         select CRYPTO
 689         select CRYPTO_MD5
 690         ---help---
 691           RFC2385 specifies a method of giving MD5 protection to TCP sessions.
 692           Its main (only?) use is to protect BGP sessions between core routers
 693           on the Internet.
 694
 695           If unsure, say N.