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This work adds a generic facility for use from eBPF JIT compilers that allows for further hardening of JIT generated images through blinding constants. In response to the original work on BPF JIT spraying published by Keegan McAllister [1], most BPF JITs were changed to make images read-only and start at a randomized offset in the page, where the rest was filled with trap instructions. We have this nowadays in x86, arm, arm64 and s390 JIT compilers. Additionally, later work also made eBPF interpreter images read only for kernels supporting DEBUG_SET_MODULE_RONX, that is, x86, arm, arm64 and s390 archs as well currently. This is done by default for mentioned JITs when JITing is enabled. Furthermore, we had a generic and configurable constant blinding facility on our todo for quite some time now to further make spraying harder, and first implementation since around netconf 2016. We found that for systems where untrusted users can load cBPF/eBPF code where JIT is enabled, start offset randomization helps a bit to make jumps into crafted payload harder, but in case where larger programs that cross page boundary are injected, we again have some part of the program opcodes at a page start offset. With improved guessing and more reliable payload injection, chances can increase to jump into such payload. Elena Reshetova recently wrote a test case for it [2, 3]. Moreover, eBPF comes with 64 bit constants, which can leave some more room for payloads. Note that for all this, additional bugs in the kernel are still required to make the jump (and of course to guess right, to not jump into a trap) and naturally the JIT must be enabled, which is disabled by default. For helping mitigation, the general idea is to provide an option bpf_jit_harden that admins can tweak along with bpf_jit_enable, so that for cases where JIT should be enabled for performance reasons, the generated image can be further hardened with blinding constants for unpriviledged users (bpf_jit_harden == 1), with trading off performance for these, but not for privileged ones. We also added the option of blinding for all users (bpf_jit_harden == 2), which is quite helpful for testing f.e. with test_bpf.ko. There are no further e.g. hardening levels of bpf_jit_harden switch intended, rationale is to have it dead simple to use as on/off. Since this functionality would need to be duplicated over and over for JIT compilers to use, which are already complex enough, we provide a generic eBPF byte-code level based blinding implementation, which is then just transparently JITed. JIT compilers need to make only a few changes to integrate this facility and can be migrated one by one. This option is for eBPF JITs and will be used in x86, arm64, s390 without too much effort, and soon ppc64 JITs, thus that native eBPF can be blinded as well as cBPF to eBPF migrations, so that both can be covered with a single implementation. The rule for JITs is that bpf_jit_blind_constants() must be called from bpf_int_jit_compile(), and in case blinding is disabled, we follow normally with JITing the passed program. In case blinding is enabled and we fail during the process of blinding itself, we must return with the interpreter. Similarly, in case the JITing process after the blinding failed, we return normally to the interpreter with the non-blinded code. Meaning, interpreter doesn't change in any way and operates on eBPF code as usual. For doing this pre-JIT blinding step, we need to make use of a helper/auxiliary register, here BPF_REG_AX. This is strictly internal to the JIT and not in any way part of the eBPF architecture. Just like in the same way as JITs internally make use of some helper registers when emitting code, only that here the helper register is one abstraction level higher in eBPF bytecode, but nevertheless in JIT phase. That helper register is needed since f.e. manually written program can issue loads to all registers of eBPF architecture. The core concept with the additional register is: blind out all 32 and 64 bit constants by converting BPF_K based instructions into a small sequence from K_VAL into ((RND ^ K_VAL) ^ RND). Therefore, this is transformed into: BPF_REG_AX := (RND ^ K_VAL), BPF_REG_AX ^= RND, and REG <OP> BPF_REG_AX, so actual operation on the target register is translated from BPF_K into BPF_X one that is operating on BPF_REG_AX's content. During rewriting phase when blinding, RND is newly generated via prandom_u32() for each processed instruction. 64 bit loads are split into two 32 bit loads to make translation and patching not too complex. Only basic thing required by JITs is to call the helper bpf_jit_blind_constants()/bpf_jit_prog_release_other() pair, and to map BPF_REG_AX into an unused register. Small bpf_jit_disasm extract from [2] when applied to x86 JIT: echo 0 > /proc/sys/net/core/bpf_jit_harden ffffffffa034f5e9 + <x>: [...] 39: mov $0xa8909090,%eax 3e: mov $0xa8909090,%eax 43: mov $0xa8ff3148,%eax 48: mov $0xa89081b4,%eax 4d: mov $0xa8900bb0,%eax 52: mov $0xa810e0c1,%eax 57: mov $0xa8908eb4,%eax 5c: mov $0xa89020b0,%eax [...] echo 1 > /proc/sys/net/core/bpf_jit_harden ffffffffa034f1e5 + <x>: [...] 39: mov $0xe1192563,%r10d 3f: xor $0x4989b5f3,%r10d 46: mov %r10d,%eax 49: mov $0xb8296d93,%r10d 4f: xor $0x10b9fd03,%r10d 56: mov %r10d,%eax 59: mov $0x8c381146,%r10d 5f: xor $0x24c7200e,%r10d 66: mov %r10d,%eax 69: mov $0xeb2a830e,%r10d 6f: xor $0x43ba02ba,%r10d 76: mov %r10d,%eax 79: mov $0xd9730af,%r10d 7f: xor $0xa5073b1f,%r10d 86: mov %r10d,%eax 89: mov $0x9a45662b,%r10d 8f: xor $0x325586ea,%r10d 96: mov %r10d,%eax [...] As can be seen, original constants that carry payload are hidden when enabled, actual operations are transformed from constant-based to register-based ones, making jumps into constants ineffective. Above extract/example uses single BPF load instruction over and over, but of course all instructions with constants are blinded. Performance wise, JIT with blinding performs a bit slower than just JIT and faster than interpreter case. This is expected, since we still get all the performance benefits from JITing and in normal use-cases not every single instruction needs to be blinded. Summing up all 296 test cases averaged over multiple runs from test_bpf.ko suite, interpreter was 55% slower than JIT only and JIT with blinding was 8% slower than JIT only. Since there are also some extremes in the test suite, I expect for ordinary workloads that the performance for the JIT with blinding case is even closer to JIT only case, f.e. nmap test case from suite has averaged timings in ns 29 (JIT), 35 (+ blinding), and 151 (interpreter). BPF test suite, seccomp test suite, eBPF sample code and various bigger networking eBPF programs have been tested with this and were running fine. For testing purposes, I also adapted interpreter and redirected blinded eBPF image to interpreter and also here all tests pass. [1] http://mainisusuallyafunction.blogspot.com/2012/11/attacking-hardened-linux-systems-with.html [2] https://github.com/01org/jit-spray-poc-for-ksp/ [3] http://www.openwall.com/lists/kernel-hardening/2016/05/03/5 Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Elena Reshetova <elena.reshetova@intel.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
436 lines
13 KiB
Plaintext
436 lines
13 KiB
Plaintext
#
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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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select GENERIC_NET_UTILS
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select BPF
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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 WEXT_CORE || 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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config NET_INGRESS
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bool
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config NET_EGRESS
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bool
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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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select CRYPTO
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select CRYPTO_AES
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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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config NET_PTP_CLASSIFY
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def_bool n
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config NETWORK_PHY_TIMESTAMPING
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bool "Timestamping in PHY devices"
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select NET_PTP_CLASSIFY
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help
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This allows timestamping of network packets by PHYs with
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hardware timestamping capabilities. This option adds some
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overhead in the transmit and receive paths.
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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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tristate "Bridged IP/ARP packets filtering"
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depends on BRIDGE
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depends on NETFILTER && INET
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depends on NETFILTER_ADVANCED
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default m
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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/l2tp/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/phonet/Kconfig"
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source "net/6lowpan/Kconfig"
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source "net/ieee802154/Kconfig"
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source "net/mac802154/Kconfig"
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source "net/sched/Kconfig"
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source "net/dcb/Kconfig"
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source "net/dns_resolver/Kconfig"
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source "net/batman-adv/Kconfig"
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source "net/openvswitch/Kconfig"
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source "net/vmw_vsock/Kconfig"
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source "net/netlink/Kconfig"
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source "net/mpls/Kconfig"
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source "net/hsr/Kconfig"
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source "net/switchdev/Kconfig"
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source "net/l3mdev/Kconfig"
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source "net/qrtr/Kconfig"
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config RPS
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bool
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depends on SMP && SYSFS
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default y
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config RFS_ACCEL
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bool
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depends on RPS
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select CPU_RMAP
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default y
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config XPS
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bool
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depends on SMP
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default y
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config HWBM
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bool
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config SOCK_CGROUP_DATA
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bool
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default n
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config CGROUP_NET_PRIO
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bool "Network priority cgroup"
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depends on CGROUPS
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select SOCK_CGROUP_DATA
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---help---
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Cgroup subsystem for use in assigning processes to network priorities on
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a per-interface basis.
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config CGROUP_NET_CLASSID
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bool "Network classid cgroup"
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depends on CGROUPS
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select SOCK_CGROUP_DATA
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---help---
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Cgroup subsystem for use as general purpose socket classid marker that is
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being used in cls_cgroup and for netfilter matching.
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config NET_RX_BUSY_POLL
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bool
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default y
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config BQL
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bool
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depends on SYSFS
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select DQL
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default y
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config BPF_JIT
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bool "enable BPF Just In Time compiler"
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depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
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depends on MODULES
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---help---
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Berkeley Packet Filter filtering capabilities are normally handled
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by an interpreter. This option allows kernel to generate a native
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code when filter is loaded in memory. This should speedup
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packet sniffing (libpcap/tcpdump).
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Note, admin should enable this feature changing:
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/proc/sys/net/core/bpf_jit_enable
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/proc/sys/net/core/bpf_jit_harden (optional)
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config NET_FLOW_LIMIT
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bool
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depends on RPS
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default y
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---help---
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The network stack has to drop packets when a receive processing CPU's
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backlog reaches netdev_max_backlog. If a few out of many active flows
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generate the vast majority of load, drop their traffic earlier to
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maintain capacity for the other flows. This feature provides servers
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with many clients some protection against DoS by a single (spoofed)
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flow that greatly exceeds average workload.
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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 INET && 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 && 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:
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http://www.linuxfoundation.org/collaborate/workgroups/networking/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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tristate "Network packet drop alerting service"
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depends on INET && 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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source "net/kcm/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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source "net/caif/Kconfig"
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source "net/ceph/Kconfig"
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source "net/nfc/Kconfig"
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config LWTUNNEL
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bool "Network light weight tunnels"
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---help---
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This feature provides an infrastructure to support light weight
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tunnels like mpls. There is no netdevice associated with a light
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weight tunnel endpoint. Tunnel encapsulation parameters are stored
|
|
with light weight tunnel state associated with fib routes.
|
|
|
|
config DST_CACHE
|
|
bool
|
|
default n
|
|
|
|
config NET_DEVLINK
|
|
tristate "Network physical/parent device Netlink interface"
|
|
help
|
|
Network physical/parent device Netlink interface provides
|
|
infrastructure to support access to physical chip-wide config and
|
|
monitoring.
|
|
|
|
config MAY_USE_DEVLINK
|
|
tristate
|
|
default m if NET_DEVLINK=m
|
|
default y if NET_DEVLINK=y || NET_DEVLINK=n
|
|
help
|
|
Drivers using the devlink infrastructure should have a dependency
|
|
on MAY_USE_DEVLINK to ensure they do not cause link errors when
|
|
devlink is a loadable module and the driver using it is built-in.
|
|
|
|
endif # if NET
|
|
|
|
# Used by archs to tell that they support BPF JIT compiler plus which flavour.
|
|
# Only one of the two can be selected for a specific arch since eBPF JIT supersedes
|
|
# the cBPF JIT.
|
|
|
|
# Classic BPF JIT (cBPF)
|
|
config HAVE_CBPF_JIT
|
|
bool
|
|
|
|
# Extended BPF JIT (eBPF)
|
|
config HAVE_EBPF_JIT
|
|
bool
|