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 should consider 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           Note that some distributions enable it in startup scripts.
  53           For details about rp_filter strict and loose mode read
  54           <file:Documentation/networking/ip-sysctl.txt>.
  55
  56           If unsure, say N here.
  57
  58 config IP_FIB_TRIE_STATS
  59         bool "FIB TRIE statistics"
  60         depends on IP_ADVANCED_ROUTER
  61         ---help---
  62           Keep track of statistics on structure of FIB TRIE table.
  63           Useful for testing and measuring TRIE performance.
  64
  65 config IP_MULTIPLE_TABLES
  66         bool "IP: policy routing"
  67         depends on IP_ADVANCED_ROUTER
  68         select FIB_RULES
  69         ---help---
  70           Normally, a router decides what to do with a received packet based
  71           solely on the packet's final destination address. If you say Y here,
  72           the Linux router will also be able to take the packet's source
  73           address into account. Furthermore, the TOS (Type-Of-Service) field
  74           of the packet can be used for routing decisions as well.
  75
  76           If you are interested in this, please see the preliminary
  77           documentation at <http://www.compendium.com.ar/policy-routing.txt>
  78           and <ftp://post.tepkom.ru/pub/vol2/Linux/docs/advanced-routing.tex>.
  79           You will need supporting software from
  80           <ftp://ftp.tux.org/pub/net/ip-routing/>.
  81
  82           If unsure, say N.
  83
  84 config IP_ROUTE_MULTIPATH
  85         bool "IP: equal cost multipath"
  86         depends on IP_ADVANCED_ROUTER
  87         help
  88           Normally, the routing tables specify a single action to be taken in
  89           a deterministic manner for a given packet. If you say Y here
  90           however, it becomes possible to attach several actions to a packet
  91           pattern, in effect specifying several alternative paths to travel
  92           for those packets. The router considers all these paths to be of
  93           equal "cost" and chooses one of them in a non-deterministic fashion
  94           if a matching packet arrives.
  95
  96 config IP_ROUTE_VERBOSE
  97         bool "IP: verbose route monitoring"
  98         depends on IP_ADVANCED_ROUTER
  99         help
 100           If you say Y here, which is recommended, then the kernel will print
 101           verbose messages regarding the routing, for example warnings about
 102           received packets which look strange and could be evidence of an
 103           attack or a misconfigured system somewhere. The information is
 104           handled by the klogd daemon which is responsible for kernel messages
 105           ("man klogd").
 106
 107 config IP_ROUTE_CLASSID
 108         bool
 109
 110 config IP_PNP
 111         bool "IP: kernel level autoconfiguration"
 112         help
 113           This enables automatic configuration of IP addresses of devices and
 114           of the routing table during kernel boot, based on either information
 115           supplied on the kernel command line or by BOOTP or RARP protocols.
 116           You need to say Y only for diskless machines requiring network
 117           access to boot (in which case you want to say Y to "Root file system
 118           on NFS" as well), because all other machines configure the network
 119           in their startup scripts.
 120
 121 config IP_PNP_DHCP
 122         bool "IP: DHCP support"
 123         depends on IP_PNP
 124         ---help---
 125           If you want your Linux box to mount its whole root file system (the
 126           one containing the directory /) from some other computer over the
 127           net via NFS and you want the IP address of your computer to be
 128           discovered automatically at boot time using the DHCP protocol (a
 129           special protocol designed for doing this job), say Y here. In case
 130           the boot ROM of your network card was designed for booting Linux and
 131           does DHCP itself, providing all necessary information on the kernel
 132           command line, you can say N here.
 133
 134           If unsure, say Y. Note that if you want to use DHCP, a DHCP server
 135           must be operating on your network.  Read
 136           <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
 137
 138 config IP_PNP_BOOTP
 139         bool "IP: BOOTP support"
 140         depends on IP_PNP
 141         ---help---
 142           If you want your Linux box to mount its whole root file system (the
 143           one containing the directory /) from some other computer over the
 144           net via NFS and you want the IP address of your computer to be
 145           discovered automatically at boot time using the BOOTP protocol (a
 146           special protocol designed for doing this job), say Y here. In case
 147           the boot ROM of your network card was designed for booting Linux and
 148           does BOOTP itself, providing all necessary information on the kernel
 149           command line, you can say N here. If unsure, say Y. Note that if you
 150           want to use BOOTP, a BOOTP server must be operating on your network.
 151           Read <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
 152
 153 config IP_PNP_RARP
 154         bool "IP: RARP support"
 155         depends on IP_PNP
 156         help
 157           If you want your Linux box to mount its whole root file system (the
 158           one containing the directory /) from some other computer over the
 159           net via NFS and you want the IP address of your computer to be
 160           discovered automatically at boot time using the RARP protocol (an
 161           older protocol which is being obsoleted by BOOTP and DHCP), say Y
 162           here. Note that if you want to use RARP, a RARP server must be
 163           operating on your network. Read
 164           <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
 165
 166 config NET_IPIP
 167         tristate "IP: tunneling"
 168         select INET_TUNNEL
 169         select NET_IP_TUNNEL
 170         ---help---
 171           Tunneling means encapsulating data of one protocol type within
 172           another protocol and sending it over a channel that understands the
 173           encapsulating protocol. This particular tunneling driver implements
 174           encapsulation of IP within IP, which sounds kind of pointless, but
 175           can be useful if you want to make your (or some other) machine
 176           appear on a different network than it physically is, or to use
 177           mobile-IP facilities (allowing laptops to seamlessly move between
 178           networks without changing their IP addresses).
 179
 180           Saying Y to this option will produce two modules ( = code which can
 181           be inserted in and removed from the running kernel whenever you
 182           want). Most people won't need this and can say N.
 183
 184 config NET_IPGRE_DEMUX
 185         tristate "IP: GRE demultiplexer"
 186         help
 187          This is helper module to demultiplex GRE packets on GRE version field criteria.
 188          Required by ip_gre and pptp modules.
 189
 190 config NET_IP_TUNNEL
 191         tristate
 192         default n
 193
 194 config NET_IPGRE
 195         tristate "IP: GRE tunnels over IP"
 196         depends on (IPV6 || IPV6=n) && NET_IPGRE_DEMUX
 197         select NET_IP_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           GRE (Generic Routing Encapsulation) and at this time allows
 203           encapsulating of IPv4 or IPv6 over existing IPv4 infrastructure.
 204           This driver is useful if the other endpoint is a Cisco router: Cisco
 205           likes GRE much better than the other Linux tunneling driver ("IP
 206           tunneling" above). In addition, GRE allows multicast redistribution
 207           through the tunnel.
 208
 209 config NET_IPGRE_BROADCAST
 210         bool "IP: broadcast GRE over IP"
 211         depends on IP_MULTICAST && NET_IPGRE
 212         help
 213           One application of GRE/IP is to construct a broadcast WAN (Wide Area
 214           Network), which looks like a normal Ethernet LAN (Local Area
 215           Network), but can be distributed all over the Internet. If you want
 216           to do that, say Y here and to "IP multicast routing" below.
 217
 218 config IP_MROUTE
 219         bool "IP: multicast routing"
 220         depends on IP_MULTICAST
 221         help
 222           This is used if you want your machine to act as a router for IP
 223           packets that have several destination addresses. It is needed on the
 224           MBONE, a high bandwidth network on top of the Internet which carries
 225           audio and video broadcasts. In order to do that, you would most
 226           likely run the program mrouted. Information about the multicast
 227           capabilities of the various network cards is contained in
 228           <file:Documentation/networking/multicast.txt>. If you haven't heard
 229           about it, you don't need it.
 230
 231 config IP_MROUTE_MULTIPLE_TABLES
 232         bool "IP: multicast policy routing"
 233         depends on IP_MROUTE && IP_ADVANCED_ROUTER
 234         select FIB_RULES
 235         help
 236           Normally, a multicast router runs a userspace daemon and decides
 237           what to do with a multicast packet based on the source and
 238           destination addresses. If you say Y here, the multicast router
 239           will also be able to take interfaces and packet marks into
 240           account and run multiple instances of userspace daemons
 241           simultaneously, each one handling a single table.
 242
 243           If unsure, say N.
 244
 245 config IP_PIMSM_V1
 246         bool "IP: PIM-SM version 1 support"
 247         depends on IP_MROUTE
 248         help
 249           Kernel side support for Sparse Mode PIM (Protocol Independent
 250           Multicast) version 1. This multicast routing protocol is used widely
 251           because Cisco supports it. You need special software to use it
 252           (pimd-v1). Please see <http://netweb.usc.edu/pim/> for more
 253           information about PIM.
 254
 255           Say Y if you want to use PIM-SM v1. Note that you can say N here if
 256           you just want to use Dense Mode PIM.
 257
 258 config IP_PIMSM_V2
 259         bool "IP: PIM-SM version 2 support"
 260         depends on IP_MROUTE
 261         help
 262           Kernel side support for Sparse Mode PIM version 2. In order to use
 263           this, you need an experimental routing daemon supporting it (pimd or
 264           gated-5). This routing protocol is not used widely, so say N unless
 265           you want to play with it.
 266
 267 config ARPD
 268         bool "IP: ARP daemon support"
 269         ---help---
 270           The kernel maintains an internal cache which maps IP addresses to
 271           hardware addresses on the local network, so that Ethernet
 272           frames are sent to the proper address on the physical networking
 273           layer. Normally, kernel uses the ARP protocol to resolve these
 274           mappings.
 275
 276           Saying Y here adds support to have an user space daemon to do this
 277           resolution instead. This is useful for implementing an alternate
 278           address resolution protocol (e.g. NHRP on mGRE tunnels) and also for
 279           testing purposes.
 280
 281           If unsure, say N.
 282
 283 config SYN_COOKIES
 284         bool "IP: TCP syncookie support"
 285         ---help---
 286           Normal TCP/IP networking is open to an attack known as "SYN
 287           flooding". This denial-of-service attack prevents legitimate remote
 288           users from being able to connect to your computer during an ongoing
 289           attack and requires very little work from the attacker, who can
 290           operate from anywhere on the Internet.
 291
 292           SYN cookies provide protection against this type of attack. If you
 293           say Y here, the TCP/IP stack will use a cryptographic challenge
 294           protocol known as "SYN cookies" to enable legitimate users to
 295           continue to connect, even when your machine is under attack. There
 296           is no need for the legitimate users to change their TCP/IP software;
 297           SYN cookies work transparently to them. For technical information
 298           about SYN cookies, check out <http://cr.yp.to/syncookies.html>.
 299
 300           If you are SYN flooded, the source address reported by the kernel is
 301           likely to have been forged by the attacker; it is only reported as
 302           an aid in tracing the packets to their actual source and should not
 303           be taken as absolute truth.
 304
 305           SYN cookies may prevent correct error reporting on clients when the
 306           server is really overloaded. If this happens frequently better turn
 307           them off.
 308
 309           If you say Y here, you can disable SYN cookies at run time by
 310           saying Y to "/proc file system support" and
 311           "Sysctl support" below and executing the command
 312
 313           echo 0 > /proc/sys/net/ipv4/tcp_syncookies
 314
 315           after the /proc file system has been mounted.
 316
 317           If unsure, say N.
 318
 319 config NET_IPVTI
 320         tristate "Virtual (secure) IP: tunneling"
 321         select INET_TUNNEL
 322         select NET_IP_TUNNEL
 323         depends on INET_XFRM_MODE_TUNNEL
 324         ---help---
 325           Tunneling means encapsulating data of one protocol type within
 326           another protocol and sending it over a channel that understands the
 327           encapsulating protocol. This can be used with xfrm mode tunnel to give
 328           the notion of a secure tunnel for IPSEC and then use routing protocol
 329           on top.
 330
 331 config INET_AH
 332         tristate "IP: AH transformation"
 333         select XFRM_ALGO
 334         select CRYPTO
 335         select CRYPTO_HMAC
 336         select CRYPTO_MD5
 337         select CRYPTO_SHA1
 338         ---help---
 339           Support for IPsec AH.
 340
 341           If unsure, say Y.
 342
 343 config INET_ESP
 344         tristate "IP: ESP transformation"
 345         select XFRM_ALGO
 346         select CRYPTO
 347         select CRYPTO_AUTHENC
 348         select CRYPTO_HMAC
 349         select CRYPTO_MD5
 350         select CRYPTO_CBC
 351         select CRYPTO_SHA1
 352         select CRYPTO_DES
 353         ---help---
 354           Support for IPsec ESP.
 355
 356           If unsure, say Y.
 357
 358 config INET_IPCOMP
 359         tristate "IP: IPComp transformation"
 360         select INET_XFRM_TUNNEL
 361         select XFRM_IPCOMP
 362         ---help---
 363           Support for IP Payload Compression Protocol (IPComp) (RFC3173),
 364           typically needed for IPsec.
 365
 366           If unsure, say Y.
 367
 368 config INET_XFRM_TUNNEL
 369         tristate
 370         select INET_TUNNEL
 371         default n
 372
 373 config INET_TUNNEL
 374         tristate
 375         default n
 376
 377 config INET_XFRM_MODE_TRANSPORT
 378         tristate "IP: IPsec transport mode"
 379         default y
 380         select XFRM
 381         ---help---
 382           Support for IPsec transport mode.
 383
 384           If unsure, say Y.
 385
 386 config INET_XFRM_MODE_TUNNEL
 387         tristate "IP: IPsec tunnel mode"
 388         default y
 389         select XFRM
 390         ---help---
 391           Support for IPsec tunnel mode.
 392
 393           If unsure, say Y.
 394
 395 config INET_XFRM_MODE_BEET
 396         tristate "IP: IPsec BEET mode"
 397         default y
 398         select XFRM
 399         ---help---
 400           Support for IPsec BEET mode.
 401
 402           If unsure, say Y.
 403
 404 config INET_LRO
 405         tristate "Large Receive Offload (ipv4/tcp)"
 406         default y
 407         ---help---
 408           Support for Large Receive Offload (ipv4/tcp).
 409
 410           If unsure, say Y.
 411
 412 config INET_DIAG
 413         tristate "INET: socket monitoring interface"
 414         default y
 415         ---help---
 416           Support for INET (TCP, DCCP, etc) socket monitoring interface used by
 417           native Linux tools such as ss. ss is included in iproute2, currently
 418           downloadable at:
 419
 420             http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2
 421
 422           If unsure, say Y.
 423
 424 config INET_TCP_DIAG
 425         depends on INET_DIAG
 426         def_tristate INET_DIAG
 427
 428 config INET_UDP_DIAG
 429         tristate "UDP: socket monitoring interface"
 430         depends on INET_DIAG && (IPV6 || IPV6=n)
 431         default n
 432         ---help---
 433           Support for UDP socket monitoring interface used by the ss tool.
 434           If unsure, say Y.
 435
 436 menuconfig TCP_CONG_ADVANCED
 437         bool "TCP: advanced congestion control"
 438         ---help---
 439           Support for selection of various TCP congestion control
 440           modules.
 441
 442           Nearly all users can safely say no here, and a safe default
 443           selection will be made (CUBIC with new Reno as a fallback).
 444
 445           If unsure, say N.
 446
 447 if TCP_CONG_ADVANCED
 448
 449 config TCP_CONG_BIC
 450         tristate "Binary Increase Congestion (BIC) control"
 451         default m
 452         ---help---
 453         BIC-TCP is a sender-side only change that ensures a linear RTT
 454         fairness under large windows while offering both scalability and
 455         bounded TCP-friendliness. The protocol combines two schemes
 456         called additive increase and binary search increase. When the
 457         congestion window is large, additive increase with a large
 458         increment ensures linear RTT fairness as well as good
 459         scalability. Under small congestion windows, binary search
 460         increase provides TCP friendliness.
 461         See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/
 462
 463 config TCP_CONG_CUBIC
 464         tristate "CUBIC TCP"
 465         default y
 466         ---help---
 467         This is version 2.0 of BIC-TCP which uses a cubic growth function
 468         among other techniques.
 469         See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/cubic-paper.pdf
 470
 471 config TCP_CONG_WESTWOOD
 472         tristate "TCP Westwood+"
 473         default m
 474         ---help---
 475         TCP Westwood+ is a sender-side only modification of the TCP Reno
 476         protocol stack that optimizes the performance of TCP congestion
 477         control. It is based on end-to-end bandwidth estimation to set
 478         congestion window and slow start threshold after a congestion
 479         episode. Using this estimation, TCP Westwood+ adaptively sets a
 480         slow start threshold and a congestion window which takes into
 481         account the bandwidth used  at the time congestion is experienced.
 482         TCP Westwood+ significantly increases fairness wrt TCP Reno in
 483         wired networks and throughput over wireless links.
 484
 485 config TCP_CONG_HTCP
 486         tristate "H-TCP"
 487         default m
 488         ---help---
 489         H-TCP is a send-side only modifications of the TCP Reno
 490         protocol stack that optimizes the performance of TCP
 491         congestion control for high speed network links. It uses a
 492         modeswitch to change the alpha and beta parameters of TCP Reno
 493         based on network conditions and in a way so as to be fair with
 494         other Reno and H-TCP flows.
 495
 496 config TCP_CONG_HSTCP
 497         tristate "High Speed TCP"
 498         default n
 499         ---help---
 500         Sally Floyd's High Speed TCP (RFC 3649) congestion control.
 501         A modification to TCP's congestion control mechanism for use
 502         with large congestion windows. A table indicates how much to
 503         increase the congestion window by when an ACK is received.
 504         For more detail see http://www.icir.org/floyd/hstcp.html
 505
 506 config TCP_CONG_HYBLA
 507         tristate "TCP-Hybla congestion control algorithm"
 508         default n
 509         ---help---
 510         TCP-Hybla is a sender-side only change that eliminates penalization of
 511         long-RTT, large-bandwidth connections, like when satellite legs are
 512         involved, especially when sharing a common bottleneck with normal
 513         terrestrial connections.
 514
 515 config TCP_CONG_VEGAS
 516         tristate "TCP Vegas"
 517         default n
 518         ---help---
 519         TCP Vegas is a sender-side only change to TCP that anticipates
 520         the onset of congestion by estimating the bandwidth. TCP Vegas
 521         adjusts the sending rate by modifying the congestion
 522         window. TCP Vegas should provide less packet loss, but it is
 523         not as aggressive as TCP Reno.
 524
 525 config TCP_CONG_SCALABLE
 526         tristate "Scalable TCP"
 527         default n
 528         ---help---
 529         Scalable TCP is a sender-side only change to TCP which uses a
 530         MIMD congestion control algorithm which has some nice scaling
 531         properties, though is known to have fairness issues.
 532         See http://www.deneholme.net/tom/scalable/
 533
 534 config TCP_CONG_LP
 535         tristate "TCP Low Priority"
 536         default n
 537         ---help---
 538         TCP Low Priority (TCP-LP), a distributed algorithm whose goal is
 539         to utilize only the excess network bandwidth as compared to the
 540         ``fair share`` of bandwidth as targeted by TCP.
 541         See http://www-ece.rice.edu/networks/TCP-LP/
 542
 543 config TCP_CONG_VENO
 544         tristate "TCP Veno"
 545         default n
 546         ---help---
 547         TCP Veno is a sender-side only enhancement of TCP to obtain better
 548         throughput over wireless networks. TCP Veno makes use of state
 549         distinguishing to circumvent the difficult judgment of the packet loss
 550         type. TCP Veno cuts down less congestion window in response to random
 551         loss packets.
 552         See <http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1177186>
 553
 554 config TCP_CONG_YEAH
 555         tristate "YeAH TCP"
 556         select TCP_CONG_VEGAS
 557         default n
 558         ---help---
 559         YeAH-TCP is a sender-side high-speed enabled TCP congestion control
 560         algorithm, which uses a mixed loss/delay approach to compute the
 561         congestion window. It's design goals target high efficiency,
 562         internal, RTT and Reno fairness, resilience to link loss while
 563         keeping network elements load as low as possible.
 564
 565         For further details look here:
 566           http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
 567
 568 config TCP_CONG_ILLINOIS
 569         tristate "TCP Illinois"
 570         default n
 571         ---help---
 572         TCP-Illinois is a sender-side modification of TCP Reno for
 573         high speed long delay links. It uses round-trip-time to
 574         adjust the alpha and beta parameters to achieve a higher average
 575         throughput and maintain fairness.
 576
 577         For further details see:
 578           http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html
 579
 580 choice
 581         prompt "Default TCP congestion control"
 582         default DEFAULT_CUBIC
 583         help
 584           Select the TCP congestion control that will be used by default
 585           for all connections.
 586
 587         config DEFAULT_BIC
 588                 bool "Bic" if TCP_CONG_BIC=y
 589
 590         config DEFAULT_CUBIC
 591                 bool "Cubic" if TCP_CONG_CUBIC=y
 592
 593         config DEFAULT_HTCP
 594                 bool "Htcp" if TCP_CONG_HTCP=y
 595
 596         config DEFAULT_HYBLA
 597                 bool "Hybla" if TCP_CONG_HYBLA=y
 598
 599         config DEFAULT_VEGAS
 600                 bool "Vegas" if TCP_CONG_VEGAS=y
 601
 602         config DEFAULT_VENO
 603                 bool "Veno" if TCP_CONG_VENO=y
 604
 605         config DEFAULT_WESTWOOD
 606                 bool "Westwood" if TCP_CONG_WESTWOOD=y
 607
 608         config DEFAULT_RENO
 609                 bool "Reno"
 610
 611 endchoice
 612
 613 endif
 614
 615 config TCP_CONG_CUBIC
 616         tristate
 617         depends on !TCP_CONG_ADVANCED
 618         default y
 619
 620 config DEFAULT_TCP_CONG
 621         string
 622         default "bic" if DEFAULT_BIC
 623         default "cubic" if DEFAULT_CUBIC
 624         default "htcp" if DEFAULT_HTCP
 625         default "hybla" if DEFAULT_HYBLA
 626         default "vegas" if DEFAULT_VEGAS
 627         default "westwood" if DEFAULT_WESTWOOD
 628         default "veno" if DEFAULT_VENO
 629         default "reno" if DEFAULT_RENO
 630         default "cubic"
 631
 632 config TCP_MD5SIG
 633         bool "TCP: MD5 Signature Option support (RFC2385)"
 634         select CRYPTO
 635         select CRYPTO_MD5
 636         ---help---
 637           RFC2385 specifies a method of giving MD5 protection to TCP sessions.
 638           Its main (only?) use is to protect BGP sessions between core routers
 639           on the Internet.
 640
 641           If unsure, say N.