f122668ddc
This will add eBPF JIT support to the 32-bit ARCv2 processors. The implementation is qualified by running the BPF tests on a Synopsys HSDK board with "ARC HS38 v2.1c at 500 MHz" as the 4-core CPU. The test_bpf.ko reports 2-10 fold improvements in execution time of its tests. For instance: test_bpf: #33 tcpdump port 22 jited:0 704 1766 2104 PASS test_bpf: #33 tcpdump port 22 jited:1 120 224 260 PASS test_bpf: #141 ALU_DIV_X: 4294967295 / 4294967295 = 1 jited:0 238 PASS test_bpf: #141 ALU_DIV_X: 4294967295 / 4294967295 = 1 jited:1 23 PASS test_bpf: #776 JMP32_JGE_K: all ... magnitudes jited:0 2034681 PASS test_bpf: #776 JMP32_JGE_K: all ... magnitudes jited:1 1020022 PASS Deployment and structure ------------------------ The related codes are added to "arch/arc/net": - bpf_jit.h -- The interface that a back-end translator must provide - bpf_jit_core.c -- Knows how to handle the input eBPF byte stream - bpf_jit_arcv2.c -- The back-end code that knows the translation logic The bpf_int_jit_compile() at the end of bpf_jit_core.c is the entrance to the whole process. Normally, the translation is done in one pass, namely the "normal pass". In case some relocations are not known during this pass, some data (arc_jit_data) is allocated for the next pass to come. This possible next (and last) pass is called the "extra pass". 1. Normal pass # The necessary pass 1a. Dry run # Get the whole JIT length, epilogue offset, etc. 1b. Emit phase # Allocate memory and start emitting instructions 2. Extra pass # Only needed if there are relocations to be fixed 2a. Patch relocations Support status -------------- The JIT compiler supports BPF instructions up to "cpu=v4". However, it does not yet provide support for: - Tail calls - Atomic operations - 64-bit division/remainder - BPF_PROBE_MEM* (exception table) The result of "test_bpf" test suite on an HSDK board is: hsdk-lnx# insmod test_bpf.ko test_suite=test_bpf test_bpf: Summary: 863 PASSED, 186 FAILED, [851/851 JIT'ed] All the failing test cases are due to the ones that were not JIT'ed. Categorically, they can be represented as: .-----------.------------.-------------. | test type | opcodes | # of cases | |-----------+------------+-------------| | atomic | 0xC3, 0xDB | 149 | | div64 | 0x37, 0x3F | 22 | | mod64 | 0x97, 0x9F | 15 | `-----------^------------+-------------| | (total) 186 | `-------------' Setup: build config ------------------- The following configs must be set to have a working JIT test: CONFIG_BPF_JIT=y CONFIG_BPF_JIT_ALWAYS_ON=y CONFIG_TEST_BPF=m The following options are not necessary for the tests module, but are good to have: CONFIG_DEBUG_INFO=y # prerequisite for below CONFIG_DEBUG_INFO_BTF=y # so bpftool can generate vmlinux.h CONFIG_FTRACE=y # CONFIG_BPF_SYSCALL=y # all these options lead to CONFIG_KPROBE_EVENTS=y # having CONFIG_BPF_EVENTS=y CONFIG_PERF_EVENTS=y # Some BPF programs provide data through /sys/kernel/debug: CONFIG_DEBUG_FS=y arc# mount -t debugfs debugfs /sys/kernel/debug Setup: elfutils --------------- The libdw.{so,a} library that is used by pahole for processing the final binary must come from elfutils 0.189 or newer. The support for ARCv2 [1] has been added since that version. [1] https://sourceware.org/git/?p=elfutils.git;a=commit;h=de3d46b3e7 Setup: pahole ------------- The line below in linux/scripts/Makefile.btf must be commented out: pahole-flags-$(call test-ge, $(pahole-ver), 121) += --btf_gen_floats Or else, the build will fail: $ make V=1 ... BTF .btf.vmlinux.bin.o pahole -J --btf_gen_floats \ -j --lang_exclude=rust \ --skip_encoding_btf_inconsistent_proto \ --btf_gen_optimized .tmp_vmlinux.btf Complex, interval and imaginary float types are not supported Encountered error while encoding BTF. ... BTFIDS vmlinux ./tools/bpf/resolve_btfids/resolve_btfids vmlinux libbpf: failed to find '.BTF' ELF section in vmlinux FAILED: load BTF from vmlinux: No data available This is due to the fact that the ARC toolchains generate "complex float" DIE entries in libgcc and at the moment, pahole can't handle such entries. Running the tests ----------------- host$ scp /bld/linux/lib/test_bpf.ko arc: arc # sysctl net.core.bpf_jit_enable=1 arc # insmod test_bpf.ko test_suite=test_bpf ... test_bpf: #1048 Staggered jumps: JMP32_JSLE_X jited:1 697811 PASS test_bpf: Summary: 863 PASSED, 186 FAILED, [851/851 JIT'ed] Acknowledgments --------------- - Claudiu Zissulescu for his unwavering support - Yuriy Kolerov for testing and troubleshooting - Vladimir Isaev for the pahole workaround - Sergey Matyukevich for paving the road by adding the interpreter support Signed-off-by: Shahab Vahedi <shahab@synopsys.com> Link: https://lore.kernel.org/r/20240430145604.38592-1-list+bpf@vahedi.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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================================
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Documentation for /proc/sys/net/
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================================
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Copyright
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Copyright (c) 1999
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- Terrehon Bowden <terrehon@pacbell.net>
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- Bodo Bauer <bb@ricochet.net>
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Copyright (c) 2000
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- Jorge Nerin <comandante@zaralinux.com>
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Copyright (c) 2009
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- Shen Feng <shen@cn.fujitsu.com>
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For general info and legal blurb, please look in index.rst.
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------------------------------------------------------------------------------
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This file contains the documentation for the sysctl files in
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/proc/sys/net
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The interface to the networking parts of the kernel is located in
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/proc/sys/net. The following table shows all possible subdirectories. You may
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see only some of them, depending on your kernel's configuration.
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Table : Subdirectories in /proc/sys/net
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========= =================== = ========== ===================
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Directory Content Directory Content
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========= =================== = ========== ===================
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802 E802 protocol mptcp Multipath TCP
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appletalk Appletalk protocol netfilter Network Filter
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ax25 AX25 netrom NET/ROM
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bridge Bridging rose X.25 PLP layer
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core General parameter tipc TIPC
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ethernet Ethernet protocol unix Unix domain sockets
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ipv4 IP version 4 x25 X.25 protocol
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ipv6 IP version 6
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========= =================== = ========== ===================
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1. /proc/sys/net/core - Network core options
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============================================
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bpf_jit_enable
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--------------
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This enables the BPF Just in Time (JIT) compiler. BPF is a flexible
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and efficient infrastructure allowing to execute bytecode at various
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hook points. It is used in a number of Linux kernel subsystems such
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as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints)
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and security (e.g. seccomp). LLVM has a BPF back end that can compile
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restricted C into a sequence of BPF instructions. After program load
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through bpf(2) and passing a verifier in the kernel, a JIT will then
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translate these BPF proglets into native CPU instructions. There are
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two flavors of JITs, the newer eBPF JIT currently supported on:
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- x86_64
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- x86_32
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- arm64
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- arm32
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- ppc64
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- ppc32
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- sparc64
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- mips64
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- s390x
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- riscv64
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- riscv32
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- loongarch64
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- arc
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And the older cBPF JIT supported on the following archs:
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- mips
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- sparc
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eBPF JITs are a superset of cBPF JITs, meaning the kernel will
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migrate cBPF instructions into eBPF instructions and then JIT
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compile them transparently. Older cBPF JITs can only translate
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tcpdump filters, seccomp rules, etc, but not mentioned eBPF
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programs loaded through bpf(2).
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Values:
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- 0 - disable the JIT (default value)
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- 1 - enable the JIT
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- 2 - enable the JIT and ask the compiler to emit traces on kernel log.
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bpf_jit_harden
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--------------
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This enables hardening for the BPF JIT compiler. Supported are eBPF
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JIT backends. Enabling hardening trades off performance, but can
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mitigate JIT spraying.
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Values:
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- 0 - disable JIT hardening (default value)
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- 1 - enable JIT hardening for unprivileged users only
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- 2 - enable JIT hardening for all users
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where "privileged user" in this context means a process having
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CAP_BPF or CAP_SYS_ADMIN in the root user name space.
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bpf_jit_kallsyms
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----------------
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When BPF JIT compiler is enabled, then compiled images are unknown
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addresses to the kernel, meaning they neither show up in traces nor
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in /proc/kallsyms. This enables export of these addresses, which can
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be used for debugging/tracing. If bpf_jit_harden is enabled, this
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feature is disabled.
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Values :
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- 0 - disable JIT kallsyms export (default value)
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- 1 - enable JIT kallsyms export for privileged users only
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bpf_jit_limit
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-------------
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This enforces a global limit for memory allocations to the BPF JIT
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compiler in order to reject unprivileged JIT requests once it has
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been surpassed. bpf_jit_limit contains the value of the global limit
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in bytes.
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dev_weight
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----------
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The maximum number of packets that kernel can handle on a NAPI interrupt,
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it's a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware
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aggregated packet is counted as one packet in this context.
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Default: 64
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dev_weight_rx_bias
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------------------
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RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function
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of the driver for the per softirq cycle netdev_budget. This parameter influences
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the proportion of the configured netdev_budget that is spent on RPS based packet
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processing during RX softirq cycles. It is further meant for making current
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dev_weight adaptable for asymmetric CPU needs on RX/TX side of the network stack.
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(see dev_weight_tx_bias) It is effective on a per CPU basis. Determination is based
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on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias).
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Default: 1
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dev_weight_tx_bias
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------------------
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Scales the maximum number of packets that can be processed during a TX softirq cycle.
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Effective on a per CPU basis. Allows scaling of current dev_weight for asymmetric
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net stack processing needs. Be careful to avoid making TX softirq processing a CPU hog.
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Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias).
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Default: 1
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default_qdisc
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-------------
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The default queuing discipline to use for network devices. This allows
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overriding the default of pfifo_fast with an alternative. Since the default
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queuing discipline is created without additional parameters so is best suited
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to queuing disciplines that work well without configuration like stochastic
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fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use
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queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
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which require setting up classes and bandwidths. Note that physical multiqueue
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interfaces still use mq as root qdisc, which in turn uses this default for its
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leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
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default to noqueue.
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Default: pfifo_fast
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busy_read
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---------
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Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
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Approximate time in us to busy loop waiting for packets on the device queue.
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This sets the default value of the SO_BUSY_POLL socket option.
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Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
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which is the preferred method of enabling. If you need to enable the feature
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globally via sysctl, a value of 50 is recommended.
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Will increase power usage.
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Default: 0 (off)
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busy_poll
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----------------
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Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
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Approximate time in us to busy loop waiting for events.
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Recommended value depends on the number of sockets you poll on.
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For several sockets 50, for several hundreds 100.
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For more than that you probably want to use epoll.
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Note that only sockets with SO_BUSY_POLL set will be busy polled,
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so you want to either selectively set SO_BUSY_POLL on those sockets or set
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sysctl.net.busy_read globally.
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Will increase power usage.
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Default: 0 (off)
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mem_pcpu_rsv
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------------
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Per-cpu reserved forward alloc cache size in page units. Default 1MB per CPU.
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rmem_default
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------------
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The default setting of the socket receive buffer in bytes.
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rmem_max
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--------
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The maximum receive socket buffer size in bytes.
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rps_default_mask
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----------------
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The default RPS CPU mask used on newly created network devices. An empty
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mask means RPS disabled by default.
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tstamp_allow_data
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-----------------
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Allow processes to receive tx timestamps looped together with the original
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packet contents. If disabled, transmit timestamp requests from unprivileged
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processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
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Default: 1 (on)
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wmem_default
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------------
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The default setting (in bytes) of the socket send buffer.
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wmem_max
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--------
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The maximum send socket buffer size in bytes.
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message_burst and message_cost
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------------------------------
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These parameters are used to limit the warning messages written to the kernel
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log from the networking code. They enforce a rate limit to make a
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denial-of-service attack impossible. A higher message_cost factor, results in
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fewer messages that will be written. Message_burst controls when messages will
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be dropped. The default settings limit warning messages to one every five
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seconds.
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warnings
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--------
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This sysctl is now unused.
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This was used to control console messages from the networking stack that
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occur because of problems on the network like duplicate address or bad
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checksums.
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These messages are now emitted at KERN_DEBUG and can generally be enabled
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and controlled by the dynamic_debug facility.
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netdev_budget
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-------------
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Maximum number of packets taken from all interfaces in one polling cycle (NAPI
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poll). In one polling cycle interfaces which are registered to polling are
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probed in a round-robin manner. Also, a polling cycle may not exceed
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netdev_budget_usecs microseconds, even if netdev_budget has not been
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exhausted.
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netdev_budget_usecs
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---------------------
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Maximum number of microseconds in one NAPI polling cycle. Polling
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will exit when either netdev_budget_usecs have elapsed during the
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poll cycle or the number of packets processed reaches netdev_budget.
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netdev_max_backlog
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------------------
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Maximum number of packets, queued on the INPUT side, when the interface
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receives packets faster than kernel can process them.
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netdev_rss_key
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--------------
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RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
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randomly generated.
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Some user space might need to gather its content even if drivers do not
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provide ethtool -x support yet.
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::
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myhost:~# cat /proc/sys/net/core/netdev_rss_key
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84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8: ... (52 bytes total)
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File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
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Note:
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/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
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but most drivers only use 40 bytes of it.
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::
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myhost:~# ethtool -x eth0
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RX flow hash indirection table for eth0 with 8 RX ring(s):
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0: 0 1 2 3 4 5 6 7
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RSS hash key:
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84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89
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netdev_tstamp_prequeue
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----------------------
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If set to 0, RX packet timestamps can be sampled after RPS processing, when
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the target CPU processes packets. It might give some delay on timestamps, but
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permit to distribute the load on several cpus.
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If set to 1 (default), timestamps are sampled as soon as possible, before
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queueing.
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netdev_unregister_timeout_secs
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------------------------------
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Unregister network device timeout in seconds.
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This option controls the timeout (in seconds) used to issue a warning while
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waiting for a network device refcount to drop to 0 during device
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unregistration. A lower value may be useful during bisection to detect
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a leaked reference faster. A larger value may be useful to prevent false
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warnings on slow/loaded systems.
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Default value is 10, minimum 1, maximum 3600.
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skb_defer_max
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-------------
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Max size (in skbs) of the per-cpu list of skbs being freed
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by the cpu which allocated them. Used by TCP stack so far.
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Default: 64
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optmem_max
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----------
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Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
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of struct cmsghdr structures with appended data. TCP tx zerocopy also uses
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optmem_max as a limit for its internal structures.
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Default : 128 KB
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fb_tunnels_only_for_init_net
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----------------------------
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Controls if fallback tunnels (like tunl0, gre0, gretap0, erspan0,
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sit0, ip6tnl0, ip6gre0) are automatically created. There are 3 possibilities
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(a) value = 0; respective fallback tunnels are created when module is
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loaded in every net namespaces (backward compatible behavior).
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(b) value = 1; [kcmd value: initns] respective fallback tunnels are
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created only in init net namespace and every other net namespace will
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not have them.
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(c) value = 2; [kcmd value: none] fallback tunnels are not created
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when a module is loaded in any of the net namespace. Setting value to
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"2" is pointless after boot if these modules are built-in, so there is
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a kernel command-line option that can change this default. Please refer to
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Documentation/admin-guide/kernel-parameters.txt for additional details.
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Not creating fallback tunnels gives control to userspace to create
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whatever is needed only and avoid creating devices which are redundant.
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Default : 0 (for compatibility reasons)
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devconf_inherit_init_net
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------------------------
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Controls if a new network namespace should inherit all current
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settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By
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default, we keep the current behavior: for IPv4 we inherit all current
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settings from init_net and for IPv6 we reset all settings to default.
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If set to 1, both IPv4 and IPv6 settings are forced to inherit from
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current ones in init_net. If set to 2, both IPv4 and IPv6 settings are
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forced to reset to their default values. If set to 3, both IPv4 and IPv6
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settings are forced to inherit from current ones in the netns where this
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new netns has been created.
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Default : 0 (for compatibility reasons)
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txrehash
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--------
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Controls default hash rethink behaviour on socket when SO_TXREHASH option is set
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to SOCK_TXREHASH_DEFAULT (i. e. not overridden by setsockopt).
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If set to 1 (default), hash rethink is performed on listening socket.
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If set to 0, hash rethink is not performed.
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gro_normal_batch
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----------------
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Maximum number of the segments to batch up on output of GRO. When a packet
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exits GRO, either as a coalesced superframe or as an original packet which
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GRO has decided not to coalesce, it is placed on a per-NAPI list. This
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list is then passed to the stack when the number of segments reaches the
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gro_normal_batch limit.
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high_order_alloc_disable
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------------------------
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By default the allocator for page frags tries to use high order pages (order-3
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on x86). While the default behavior gives good results in most cases, some users
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might have hit a contention in page allocations/freeing. This was especially
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true on older kernels (< 5.14) when high-order pages were not stored on per-cpu
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lists. This allows to opt-in for order-0 allocation instead but is now mostly of
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historical importance.
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Default: 0
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2. /proc/sys/net/unix - Parameters for Unix domain sockets
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----------------------------------------------------------
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There is only one file in this directory.
|
|
unix_dgram_qlen limits the max number of datagrams queued in Unix domain
|
|
socket's buffer. It will not take effect unless PF_UNIX flag is specified.
|
|
|
|
|
|
3. /proc/sys/net/ipv4 - IPV4 settings
|
|
-------------------------------------
|
|
Please see: Documentation/networking/ip-sysctl.rst and
|
|
Documentation/admin-guide/sysctl/net.rst for descriptions of these entries.
|
|
|
|
|
|
4. Appletalk
|
|
------------
|
|
|
|
The /proc/sys/net/appletalk directory holds the Appletalk configuration data
|
|
when Appletalk is loaded. The configurable parameters are:
|
|
|
|
aarp-expiry-time
|
|
----------------
|
|
|
|
The amount of time we keep an ARP entry before expiring it. Used to age out
|
|
old hosts.
|
|
|
|
aarp-resolve-time
|
|
-----------------
|
|
|
|
The amount of time we will spend trying to resolve an Appletalk address.
|
|
|
|
aarp-retransmit-limit
|
|
---------------------
|
|
|
|
The number of times we will retransmit a query before giving up.
|
|
|
|
aarp-tick-time
|
|
--------------
|
|
|
|
Controls the rate at which expires are checked.
|
|
|
|
The directory /proc/net/appletalk holds the list of active Appletalk sockets
|
|
on a machine.
|
|
|
|
The fields indicate the DDP type, the local address (in network:node format)
|
|
the remote address, the size of the transmit pending queue, the size of the
|
|
received queue (bytes waiting for applications to read) the state and the uid
|
|
owning the socket.
|
|
|
|
/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
|
|
shows the name of the interface, its Appletalk address, the network range on
|
|
that address (or network number for phase 1 networks), and the status of the
|
|
interface.
|
|
|
|
/proc/net/atalk_route lists each known network route. It lists the target
|
|
(network) that the route leads to, the router (may be directly connected), the
|
|
route flags, and the device the route is using.
|
|
|
|
5. TIPC
|
|
-------
|
|
|
|
tipc_rmem
|
|
---------
|
|
|
|
The TIPC protocol now has a tunable for the receive memory, similar to the
|
|
tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
|
|
|
|
::
|
|
|
|
# cat /proc/sys/net/tipc/tipc_rmem
|
|
4252725 34021800 68043600
|
|
#
|
|
|
|
The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
|
|
are scaled (shifted) versions of that same value. Note that the min value
|
|
is not at this point in time used in any meaningful way, but the triplet is
|
|
preserved in order to be consistent with things like tcp_rmem.
|
|
|
|
named_timeout
|
|
-------------
|
|
|
|
TIPC name table updates are distributed asynchronously in a cluster, without
|
|
any form of transaction handling. This means that different race scenarios are
|
|
possible. One such is that a name withdrawal sent out by one node and received
|
|
by another node may arrive after a second, overlapping name publication already
|
|
has been accepted from a third node, although the conflicting updates
|
|
originally may have been issued in the correct sequential order.
|
|
If named_timeout is nonzero, failed topology updates will be placed on a defer
|
|
queue until another event arrives that clears the error, or until the timeout
|
|
expires. Value is in milliseconds.
|