03f5781be2
The JIT compiler emits ia32 bit instructions. Currently, It supports eBPF
only. Classic BPF is supported because of the conversion by BPF core.
Almost all instructions from eBPF ISA supported except the following:
BPF_ALU64 | BPF_DIV | BPF_K
BPF_ALU64 | BPF_DIV | BPF_X
BPF_ALU64 | BPF_MOD | BPF_K
BPF_ALU64 | BPF_MOD | BPF_X
BPF_STX | BPF_XADD | BPF_W
BPF_STX | BPF_XADD | BPF_DW
It doesn't support BPF_JMP|BPF_CALL with BPF_PSEUDO_CALL at the moment.
IA32 has few general purpose registers, EAX|EDX|ECX|EBX|ESI|EDI. I use
EAX|EDX|ECX|EBX as temporary registers to simulate instructions in eBPF
ISA, and allocate ESI|EDI to BPF_REG_AX for constant blinding, all others
eBPF registers, R0-R10, are simulated through scratch space on stack.
The reasons behind the hardware registers allocation policy are:
1:MUL need EAX:EDX, shift operation need ECX, so they aren't fit
for general eBPF 64bit register simulation.
2:We need at least 4 registers to simulate most eBPF ISA operations
on registers operands instead of on register&memory operands.
3:We need to put BPF_REG_AX on hardware registers, or constant blinding
will degrade jit performance heavily.
Tested on PC (Intel(R) Core(TM) i5-5200U CPU).
Testing results on i5-5200U:
1) test_bpf: Summary: 349 PASSED, 0 FAILED, [319/341 JIT'ed]
2) test_progs: Summary: 83 PASSED, 0 FAILED.
3) test_lpm: OK
4) test_lru_map: OK
5) test_verifier: Summary: 828 PASSED, 0 FAILED.
Above tests are all done in following two conditions separately:
1:bpf_jit_enable=1 and bpf_jit_harden=0
2:bpf_jit_enable=1 and bpf_jit_harden=2
Below are some numbers for this jit implementation:
Note:
I run test_progs in kselftest 100 times continuously for every condition,
the numbers are in format: total/times=avg.
The numbers that test_bpf reports show almost the same relation.
a:jit_enable=0 and jit_harden=0 b:jit_enable=1 and jit_harden=0
test_pkt_access:PASS:ipv4:15622/100=156 test_pkt_access:PASS:ipv4:10674/100=106
test_pkt_access:PASS:ipv6:9130/100=91 test_pkt_access:PASS:ipv6:4855/100=48
test_xdp:PASS:ipv4:240198/100=2401 test_xdp:PASS:ipv4:138912/100=1389
test_xdp:PASS:ipv6:137326/100=1373 test_xdp:PASS:ipv6:68542/100=685
test_l4lb:PASS:ipv4:61100/100=611 test_l4lb:PASS:ipv4:37302/100=373
test_l4lb:PASS:ipv6:101000/100=1010 test_l4lb:PASS:ipv6:55030/100=550
c:jit_enable=1 and jit_harden=2
test_pkt_access:PASS:ipv4:10558/100=105
test_pkt_access:PASS:ipv6:5092/100=50
test_xdp:PASS:ipv4:131902/100=1319
test_xdp:PASS:ipv6:77932/100=779
test_l4lb:PASS:ipv4:38924/100=389
test_l4lb:PASS:ipv6:57520/100=575
The numbers show we get 30%~50% improvement.
See Documentation/networking/filter.txt for more information.
Changelog:
Changes v5-v6:
1:Add do {} while (0) to RETPOLINE_RAX_BPF_JIT for
consistence reason.
2:Clean up non-standard comments, reported by Daniel Borkmann.
3:Fix a memory leak issue, repoted by Daniel Borkmann.
Changes v4-v5:
1:Delete is_on_stack, BPF_REG_AX is the only one
on real hardware registers, so just check with
it.
2:Apply commit 1612a981b7 ("bpf, x64: fix JIT emission
for dead code"), suggested by Daniel Borkmann.
Changes v3-v4:
1:Fix changelog in commit.
I install llvm-6.0, then test_progs willn't report errors.
I submit another patch:
"bpf: fix misaligned access for BPF_PROG_TYPE_PERF_EVENT program type on x86_32 platform"
to fix another problem, after that patch, test_verifier willn't report errors too.
2:Fix clear r0[1] twice unnecessarily in *BPF_IND|BPF_ABS* simulation.
Changes v2-v3:
1:Move BPF_REG_AX to real hardware registers for performance reason.
3:Using bpf_load_pointer instead of bpf_jit32.S, suggested by Daniel Borkmann.
4:Delete partial codes in 1c2a088a66, suggested by Daniel Borkmann.
5:Some bug fixes and comments improvement.
Changes v1-v2:
1:Fix bug in emit_ia32_neg64.
2:Fix bug in emit_ia32_arsh_r64.
3:Delete filename in top level comment, suggested by Thomas Gleixner.
4:Delete unnecessary boiler plate text, suggested by Thomas Gleixner.
5:Rewrite some words in changelog.
6:CodingSytle improvement and a little more comments.
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
399 lines
14 KiB
Text
399 lines
14 KiB
Text
Documentation for /proc/sys/net/*
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(c) 1999 Terrehon Bowden <terrehon@pacbell.net>
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Bodo Bauer <bb@ricochet.net>
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(c) 2000 Jorge Nerin <comandante@zaralinux.com>
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(c) 2009 Shen Feng <shen@cn.fujitsu.com>
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For general info and legal blurb, please look in README.
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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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core General parameter appletalk Appletalk protocol
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unix Unix domain sockets netrom NET/ROM
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802 E802 protocol ax25 AX25
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ethernet Ethernet protocol rose X.25 PLP layer
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ipv4 IP version 4 x25 X.25 protocol
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ipx IPX token-ring IBM token ring
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bridge Bridging decnet DEC net
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ipv6 IP version 6 tipc TIPC
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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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- sparc64
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- mips64
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- s390x
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And the older cBPF JIT supported on the following archs:
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- mips
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- ppc
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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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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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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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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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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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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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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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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.
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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 when a new
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network namespace is created, if corresponding tunnel is present
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in initial network namespace.
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If set to 1, these devices are not automatically created, and
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user space is responsible for creating them if needed.
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Default : 0 (for compatibility reasons)
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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.
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unix_dgram_qlen limits the max number of datagrams queued in Unix domain
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socket's buffer. It will not take effect unless PF_UNIX flag is specified.
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3. /proc/sys/net/ipv4 - IPV4 settings
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-------------------------------------------------------
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Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
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descriptions of these entries.
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4. Appletalk
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-------------------------------------------------------
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The /proc/sys/net/appletalk directory holds the Appletalk configuration data
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when Appletalk is loaded. The configurable parameters are:
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aarp-expiry-time
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----------------
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The amount of time we keep an ARP entry before expiring it. Used to age out
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old hosts.
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aarp-resolve-time
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-----------------
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The amount of time we will spend trying to resolve an Appletalk address.
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aarp-retransmit-limit
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---------------------
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The number of times we will retransmit a query before giving up.
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aarp-tick-time
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--------------
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Controls the rate at which expires are checked.
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The directory /proc/net/appletalk holds the list of active Appletalk sockets
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on a machine.
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The fields indicate the DDP type, the local address (in network:node format)
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the remote address, the size of the transmit pending queue, the size of the
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received queue (bytes waiting for applications to read) the state and the uid
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owning the socket.
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/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
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shows the name of the interface, its Appletalk address, the network range on
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that address (or network number for phase 1 networks), and the status of the
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interface.
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/proc/net/atalk_route lists each known network route. It lists the target
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(network) that the route leads to, the router (may be directly connected), the
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route flags, and the device the route is using.
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5. IPX
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-------------------------------------------------------
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The IPX protocol has no tunable values in proc/sys/net.
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The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
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socket giving the local and remote addresses in Novell format (that is
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network:node:port). In accordance with the strange Novell tradition,
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everything but the port is in hex. Not_Connected is displayed for sockets that
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are not tied to a specific remote address. The Tx and Rx queue sizes indicate
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the number of bytes pending for transmission and reception. The state
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indicates the state the socket is in and the uid is the owning uid of the
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socket.
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The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
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it gives the network number, the node number, and indicates if the network is
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the primary network. It also indicates which device it is bound to (or
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Internal for internal networks) and the Frame Type if appropriate. Linux
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supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
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IPX.
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The /proc/net/ipx_route table holds a list of IPX routes. For each route it
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gives the destination network, the router node (or Directly) and the network
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address of the router (or Connected) for internal networks.
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6. TIPC
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-------------------------------------------------------
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tipc_rmem
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----------
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The TIPC protocol now has a tunable for the receive memory, similar to the
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tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
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# cat /proc/sys/net/tipc/tipc_rmem
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4252725 34021800 68043600
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#
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The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
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are scaled (shifted) versions of that same value. Note that the min value
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is not at this point in time used in any meaningful way, but the triplet is
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preserved in order to be consistent with things like tcp_rmem.
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named_timeout
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--------------
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TIPC name table updates are distributed asynchronously in a cluster, without
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any form of transaction handling. This means that different race scenarios are
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possible. One such is that a name withdrawal sent out by one node and received
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by another node may arrive after a second, overlapping name publication already
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has been accepted from a third node, although the conflicting updates
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originally may have been issued in the correct sequential order.
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If named_timeout is nonzero, failed topology updates will be placed on a defer
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queue until another event arrives that clears the error, or until the timeout
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expires. Value is in milliseconds.
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