sysctl.conf

#
# /etc/sysctl.conf - Configuration file for setting system variables
# See /etc/sysctl.d/ for additional system variables.
# See sysctl.conf (5) for information.
#

#kernel.domainname = example.com

# Uncomment the following to stop low-level messages on console
#kernel.printk = 3 4 1 3

###################################################################
# Functions previously found in netbase
#

# Uncomment the next two lines to enable Spoof protection (reverse-path filter)
# Turn on Source Address Verification in all interfaces to
# prevent some spoofing attacks
#net.ipv4.conf.default.rp_filter=1
#net.ipv4.conf.all.rp_filter=1

# Uncomment the next line to enable TCP/IP SYN cookies
# See http://lwn.net/Articles/277146/
# Note: This may impact IPv6 TCP sessions too
#net.ipv4.tcp_syncookies=1

# Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.ip_forward=1

# Uncomment the next line to enable packet forwarding for IPv6
#  Enabling this option disables Stateless Address Autoconfiguration
#  based on Router Advertisements for this host
#net.ipv6.conf.all.forwarding=1


###################################################################
# Additional settings - these settings can improve the network
# security of the host and prevent against some network attacks
# including spoofing attacks and man in the middle attacks through
# redirection. Some network environments, however, require that these
# settings are disabled so review and enable them as needed.
#
# Do not accept ICMP redirects (prevent MITM attacks)
#net.ipv4.conf.all.accept_redirects = 0
#net.ipv4.conf.default.accept_redirects = 0
# _or_
# Accept ICMP redirects only for gateways listed in our default
# gateway list (enabled by default)
# net.ipv4.conf.all.secure_redirects = 1
#
# Do not send ICMP redirects (we are not a router)
#net.ipv4.conf.all.send_redirects = 0
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#

###################################################################
# Magic system request Key
# 0=disable, 1=enable all, >1 bitmask of sysrq functions
# See https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html
# for what other values do
#kernel.sysrq=438


# Network core settings
net.core.somaxconn = 65535
net.core.netdev_max_backlog = 65535
net.core.rmem_default = 87380
net.core.wmem_default = 65536
net.core.rmem_max = 134217728
net.core.wmem_max = 134217728

# TCP settings
net.ipv4.tcp_wmem = 4096 65536 134217728
net.ipv4.tcp_rmem = 4096 87380 134217728
net.ipv4.tcp_mem = 786432 1048576 26777216
net.ipv4.tcp_max_tw_buckets = 360000
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_fin_timeout = 15
net.ipv4.tcp_keepalive_time = 300
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_keepalive_intvl = 15
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_syn_backlog = 65535
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_congestion_control = bbr
net.ipv4.tcp_notsent_lowat = 16384
net.ipv4.tcp_slow_start_after_idle = 0
net.ipv4.tcp_mtu_probing = 1

# Connection tracking
net.netfilter.nf_conntrack_max = 262144
net.ipv4.netfilter.ip_conntrack_tcp_timeout_established = 86400

# IP settings
net.ipv4.ip_local_port_range = 1024 65535
net.ipv4.ip_forward = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.all.log_martians = 1

# File system
fs.file-max = 2097152
fs.nr_open = 2097152
fs.inotify.max_user_watches = 524288
fs.inotify.max_user_instances = 512

# Virtual memory
vm.swappiness = 10
vm.dirty_ratio = 15
vm.dirty_background_ratio = 5
vm.overcommit_memory = 1

# Security
kernel.randomize_va_space = 1
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1