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![Johannes Berg](/assets/img/avatar_default.png)
Wireless extensions have the unfortunate problem that events are multicast netlink messages, and are not independent of pointer size. Thus, currently 32-bit tasks on 64-bit platforms cannot properly receive events and fail with all kinds of strange problems, for instance wpa_supplicant never notices disassociations, due to the way the 64-bit event looks (to a 32-bit process), the fact that the address is all zeroes is lost, it thinks instead it is 00:00:00:00:01:00. The same problem existed with the ioctls, until David Miller fixed those some time ago in an heroic effort. A different problem caused by this is that we cannot send the ASSOCREQIE/ASSOCRESPIE events because sending them causes a 32-bit wpa_supplicant on a 64-bit system to overwrite its internal information, which is worse than it not getting the information at all -- so we currently resort to sending a custom string event that it then parses. This, however, has a severe size limitation we are frequently hitting with modern access points; this limitation would can be lifted after this patch by sending the correct binary, not custom, event. A similar problem apparently happens for some other netlink users on x86_64 with 32-bit tasks due to the alignment for 64-bit quantities. In order to fix these problems, I have implemented a way to send compat messages to tasks. When sending an event, we send the non-compat event data together with a compat event data in skb_shinfo(main_skb)->frag_list. Then, when the event is read from the socket, the netlink code makes sure to pass out only the skb that is compatible with the task. This approach was suggested by David Miller, my original approach required always sending two skbs but that had various small problems. To determine whether compat is needed or not, I have used the MSG_CMSG_COMPAT flag, and adjusted the call path for recv and recvfrom to include it, even if those calls do not have a cmsg parameter. I have not solved one small part of the problem, and I don't think it is necessary to: if a 32-bit application uses read() rather than any form of recvmsg() it will still get the wrong (64-bit) event. However, neither do applications actually do this, nor would it be a regression. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: David S. Miller <davem@davemloft.net>
279 lines
9.3 KiB
Text
279 lines
9.3 KiB
Text
#
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# Network configuration
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#
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menuconfig NET
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bool "Networking support"
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select NLATTR
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---help---
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Unless you really know what you are doing, you should say Y here.
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The reason is that some programs need kernel networking support even
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when running on a stand-alone machine that isn't connected to any
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other computer.
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If you are upgrading from an older kernel, you
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should consider updating your networking tools too because changes
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in the kernel and the tools often go hand in hand. The tools are
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contained in the package net-tools, the location and version number
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of which are given in <file:Documentation/Changes>.
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For a general introduction to Linux networking, it is highly
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recommended to read the NET-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>.
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if NET
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config WANT_COMPAT_NETLINK_MESSAGES
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bool
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help
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This option can be selected by other options that need compat
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netlink messages.
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config COMPAT_NETLINK_MESSAGES
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def_bool y
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depends on COMPAT
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depends on WIRELESS_EXT || WANT_COMPAT_NETLINK_MESSAGES
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help
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This option makes it possible to send different netlink messages
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to tasks depending on whether the task is a compat task or not. To
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achieve this, you need to set skb_shinfo(skb)->frag_list to the
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compat skb before sending the skb, the netlink code will sort out
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which message to actually pass to the task.
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Newly written code should NEVER need this option but do
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compat-independent messages instead!
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menu "Networking options"
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source "net/packet/Kconfig"
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source "net/unix/Kconfig"
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source "net/xfrm/Kconfig"
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source "net/iucv/Kconfig"
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config INET
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bool "TCP/IP networking"
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---help---
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These are the protocols used on the Internet and on most local
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Ethernets. It is highly recommended to say Y here (this will enlarge
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your kernel by about 400 KB), since some programs (e.g. the X window
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system) use TCP/IP even if your machine is not connected to any
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other computer. You will get the so-called loopback device which
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allows you to ping yourself (great fun, that!).
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For an excellent introduction to Linux networking, please read the
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Linux Networking HOWTO, available from
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<http://www.tldp.org/docs.html#howto>.
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If you say Y here and also to "/proc file system support" and
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"Sysctl support" below, you can change various aspects of the
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behavior of the TCP/IP code by writing to the (virtual) files in
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/proc/sys/net/ipv4/*; the options are explained in the file
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<file:Documentation/networking/ip-sysctl.txt>.
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Short answer: say Y.
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if INET
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source "net/ipv4/Kconfig"
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source "net/ipv6/Kconfig"
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source "net/netlabel/Kconfig"
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endif # if INET
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config NETWORK_SECMARK
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bool "Security Marking"
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help
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This enables security marking of network packets, similar
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to nfmark, but designated for security purposes.
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If you are unsure how to answer this question, answer N.
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menuconfig NETFILTER
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bool "Network packet filtering framework (Netfilter)"
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---help---
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Netfilter is a framework for filtering and mangling network packets
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that pass through your Linux box.
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The most common use of packet filtering is to run your Linux box as
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a firewall protecting a local network from the Internet. The type of
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firewall provided by this kernel support is called a "packet
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filter", which means that it can reject individual network packets
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based on type, source, destination etc. The other kind of firewall,
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a "proxy-based" one, is more secure but more intrusive and more
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bothersome to set up; it inspects the network traffic much more
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closely, modifies it and has knowledge about the higher level
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protocols, which a packet filter lacks. Moreover, proxy-based
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firewalls often require changes to the programs running on the local
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clients. Proxy-based firewalls don't need support by the kernel, but
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they are often combined with a packet filter, which only works if
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you say Y here.
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You should also say Y here if you intend to use your Linux box as
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the gateway to the Internet for a local network of machines without
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globally valid IP addresses. This is called "masquerading": if one
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of the computers on your local network wants to send something to
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the outside, your box can "masquerade" as that computer, i.e. it
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forwards the traffic to the intended outside destination, but
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modifies the packets to make it look like they came from the
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firewall box itself. It works both ways: if the outside host
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replies, the Linux box will silently forward the traffic to the
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correct local computer. This way, the computers on your local net
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are completely invisible to the outside world, even though they can
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reach the outside and can receive replies. It is even possible to
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run globally visible servers from within a masqueraded local network
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using a mechanism called portforwarding. Masquerading is also often
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called NAT (Network Address Translation).
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Another use of Netfilter is in transparent proxying: if a machine on
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the local network tries to connect to an outside host, your Linux
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box can transparently forward the traffic to a local server,
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typically a caching proxy server.
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Yet another use of Netfilter is building a bridging firewall. Using
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a bridge with Network packet filtering enabled makes iptables "see"
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the bridged traffic. For filtering on the lower network and Ethernet
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protocols over the bridge, use ebtables (under bridge netfilter
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configuration).
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Various modules exist for netfilter which replace the previous
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masquerading (ipmasqadm), packet filtering (ipchains), transparent
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proxying, and portforwarding mechanisms. Please see
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<file:Documentation/Changes> under "iptables" for the location of
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these packages.
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if NETFILTER
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config NETFILTER_DEBUG
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bool "Network packet filtering debugging"
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depends on NETFILTER
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help
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You can say Y here if you want to get additional messages useful in
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debugging the netfilter code.
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config NETFILTER_ADVANCED
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bool "Advanced netfilter configuration"
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depends on NETFILTER
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default y
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help
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If you say Y here you can select between all the netfilter modules.
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If you say N the more unusual ones will not be shown and the
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basic ones needed by most people will default to 'M'.
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If unsure, say Y.
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config BRIDGE_NETFILTER
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bool "Bridged IP/ARP packets filtering"
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depends on BRIDGE && NETFILTER && INET
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depends on NETFILTER_ADVANCED
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default y
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---help---
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Enabling this option will let arptables resp. iptables see bridged
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ARP resp. IP traffic. If you want a bridging firewall, you probably
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want this option enabled.
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Enabling or disabling this option doesn't enable or disable
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ebtables.
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If unsure, say N.
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source "net/netfilter/Kconfig"
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source "net/ipv4/netfilter/Kconfig"
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source "net/ipv6/netfilter/Kconfig"
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source "net/decnet/netfilter/Kconfig"
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source "net/bridge/netfilter/Kconfig"
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endif
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source "net/dccp/Kconfig"
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source "net/sctp/Kconfig"
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source "net/rds/Kconfig"
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source "net/tipc/Kconfig"
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source "net/atm/Kconfig"
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source "net/802/Kconfig"
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source "net/bridge/Kconfig"
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source "net/dsa/Kconfig"
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source "net/8021q/Kconfig"
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source "net/decnet/Kconfig"
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source "net/llc/Kconfig"
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source "net/ipx/Kconfig"
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source "drivers/net/appletalk/Kconfig"
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source "net/x25/Kconfig"
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source "net/lapb/Kconfig"
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source "net/econet/Kconfig"
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source "net/wanrouter/Kconfig"
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source "net/phonet/Kconfig"
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source "net/ieee802154/Kconfig"
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source "net/sched/Kconfig"
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source "net/dcb/Kconfig"
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menu "Network testing"
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config NET_PKTGEN
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tristate "Packet Generator (USE WITH CAUTION)"
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depends on PROC_FS
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---help---
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This module will inject preconfigured packets, at a configurable
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rate, out of a given interface. It is used for network interface
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stress testing and performance analysis. If you don't understand
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what was just said, you don't need it: say N.
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Documentation on how to use the packet generator can be found
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at <file:Documentation/networking/pktgen.txt>.
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To compile this code as a module, choose M here: the
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module will be called pktgen.
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config NET_TCPPROBE
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tristate "TCP connection probing"
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depends on INET && EXPERIMENTAL && PROC_FS && KPROBES
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---help---
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This module allows for capturing the changes to TCP connection
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state in response to incoming packets. It is used for debugging
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TCP congestion avoidance modules. If you don't understand
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what was just said, you don't need it: say N.
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Documentation on how to use TCP connection probing can be found
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at http://linux-net.osdl.org/index.php/TcpProbe
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To compile this code as a module, choose M here: the
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module will be called tcp_probe.
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config NET_DROP_MONITOR
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boolean "Network packet drop alerting service"
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depends on INET && EXPERIMENTAL && TRACEPOINTS
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---help---
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This feature provides an alerting service to userspace in the
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event that packets are discarded in the network stack. Alerts
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are broadcast via netlink socket to any listening user space
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process. If you don't need network drop alerts, or if you are ok
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just checking the various proc files and other utilities for
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drop statistics, say N here.
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endmenu
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endmenu
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source "net/ax25/Kconfig"
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source "net/can/Kconfig"
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source "net/irda/Kconfig"
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source "net/bluetooth/Kconfig"
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source "net/rxrpc/Kconfig"
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config FIB_RULES
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bool
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menuconfig WIRELESS
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bool "Wireless"
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depends on !S390
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default y
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if WIRELESS
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source "net/wireless/Kconfig"
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source "net/mac80211/Kconfig"
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endif # WIRELESS
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source "net/wimax/Kconfig"
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source "net/rfkill/Kconfig"
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source "net/9p/Kconfig"
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endif # if NET
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