sysctl.conf

# Kernel sysctl configuration file for Linux
#
# This file should be saved as /etc/sysctl.conf and can be activated using the command:
# sysctl -e -p /etc/sysctl.conf
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and sysctl.conf(5) for more details.
# ----------
# Credits:
# https://klaver.it/linux/sysctl.conf
# http://whatizee.blogspot.com/2015/02/webserverftpserver-sysctlconf-parameter.html
# https://easyengine.io/tutorials/linux/sysctl-conf/

###
### GENERAL SYSTEM SECURITY OPTIONS ###
###

# Controls the System Request debugging functionality of the kernel
kernel.sysrq=0

# Controls whether core dumps will append the PID to the core filename.
# Useful for debugging multi-threaded applications.
kernel.core_uses_pid=1

#Allow for more PIDs
kernel.pid_max=65535

#Enable ExecShield protection
# kernel.exec-shield = 1
kernel.randomize_va_space=2

# Controls the maximum size of a message, in bytes
kernel.msgmnb=65535

# Controls the default maxmimum size of a mesage queue
kernel.msgmax=65535

# Restrict core dumps
fs.suid_dumpable=0

# Hide exposed kernel pointers
kernel.kptr_restrict=1

###
### IMPROVE SYSTEM MEMORY MANAGEMENT ###
###

# Increase size of file handles and inode cache
fs.file-max=756024
fs.inotify.max_queued_events=2000000
fs.inotify.max_user_instances=512
fs.inotify.max_user_watches=4000000

# Do less swapping
vm.dirty_ratio=60
vm.swappiness=10
vm.dirty_background_ratio=2

# specifies the minimum virtual address that a process is allowed to mmap
vm.mmap_min_addr=4096

# Keep at least 64MB of free RAM space available
vm.min_free_kbytes=65535

###
### GENERAL NETWORK SECURITY OPTIONS ###
###

#Prevent SYN attack, enable SYNcookies (they will kick-in when the max_syn_backlog reached)
net.ipv4.tcp_syncookies=1
net.ipv4.tcp_syn_retries=2
net.ipv4.tcp_synack_retries=2
net.ipv4.tcp_max_syn_backlog=4096

# Disables packet forwarding
net.ipv4.ip_forward=0
net.ipv4.conf.all.forwarding=0
net.ipv4.conf.default.forwarding=0
net.ipv6.conf.all.forwarding=0
net.ipv6.conf.default.forwarding=0

# Disables IP source routing
net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.default.send_redirects=0
net.ipv4.conf.all.accept_source_route=0
net.ipv4.conf.default.accept_source_route=0
net.ipv6.conf.all.accept_source_route=0
net.ipv6.conf.default.accept_source_route=0

# Enable IP spoofing protection, turn on source route verification
net.ipv4.conf.all.rp_filter=1
net.ipv4.conf.default.rp_filter=1

# Disable ICMP Redirect Acceptance
net.ipv4.conf.all.accept_redirects=0
net.ipv4.conf.default.accept_redirects=0
net.ipv4.conf.all.secure_redirects=0
net.ipv4.conf.default.secure_redirects=0
net.ipv6.conf.all.accept_redirects=0
net.ipv6.conf.default.accept_redirects=0

# Enable Log Spoofed Packets, Source Routed Packets, Redirect Packets
net.ipv4.conf.all.log_martians=1
net.ipv4.conf.default.log_martians=1

# Decrease the time default value for tcp_fin_timeout connection
net.ipv4.tcp_fin_timeout=7

# Decrease the time default value for connections to keep alive
net.ipv4.tcp_keepalive_time=300
net.ipv4.tcp_keepalive_probes=5
net.ipv4.tcp_keepalive_intvl=15

# Don't relay bootp
net.ipv4.conf.all.bootp_relay=0

# Don't proxy arp for anyone
net.ipv4.conf.all.proxy_arp=0

# Turn on the tcp_timestamps, accurate timestamp make TCP congestion control algorithms work better
net.ipv4.tcp_timestamps=1

# Don't ignore directed pings
net.ipv4.icmp_echo_ignore_all=0

# Enable ignoring broadcasts request
net.ipv4.icmp_echo_ignore_broadcasts=1

# Enable bad error message Protection
net.ipv4.icmp_ignore_bogus_error_responses=1

# Allowed local port range
net.ipv4.ip_local_port_range=16384 65535

# Enable a fix for RFC1337 - time-wait assassination hazards in TCP
net.ipv4.tcp_rfc1337=1

# Do not auto-configure IPv6
net.ipv6.conf.all.autoconf=0
net.ipv6.conf.all.accept_ra=0
net.ipv6.conf.default.autoconf=0
net.ipv6.conf.default.accept_ra=0

###
### TUNING NETWORK PERFORMANCE ###
###

# Turn on the tcp_window_scaling
net.ipv4.tcp_window_scaling=1

# Default Socket Receive Buffer
net.core.rmem_default=31457280

# Maximum Socket Receive Buffer
net.core.rmem_max=12582912

# Default Socket Send Buffer
net.core.wmem_default=31457280

# Maximum Socket Send Buffer
net.core.wmem_max=12582912

# Increase number of incoming connections
net.core.somaxconn=4096

# Increase number of incoming connections backlog
net.core.netdev_max_backlog=65536

# Increase the maximum amount of option memory buffers
net.core.optmem_max=25165824

# Increase the maximum total buffer-space allocatable
# This is measured in units of pages (4096 bytes)
net.ipv4.tcp_mem=65536 131072 262144
net.ipv4.udp_mem=65536 131072 262144

# Increase the read-buffer space allocatable
net.ipv4.tcp_rmem=8192 87380 16777216
net.ipv4.udp_rmem_min=16384

# Increase the write-buffer-space allocatable
net.ipv4.tcp_wmem=8192 65536 16777216
net.ipv4.udp_wmem_min=16384


# Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks
net.ipv4.tcp_max_tw_buckets=1440000

# try to reuse time-wait connections, but don't recycle them (recycle can break clients behind NAT)
net.ipv4.tcp_tw_recycle=0
net.ipv4.tcp_tw_reuse=1

# Limit number of orphans, each orphan can eat up to 16M (max wmem) of unswappable memory
net.ipv4.tcp_max_orphans=16384
net.ipv4.tcp_orphan_retries=0

# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save=1
net.ipv4.tcp_moderate_rcvbuf=1

# Increase size of RPC datagram queue length
net.unix.max_dgram_qlen=50

# Don't allow the arp table to become bigger than this
net.ipv4.neigh.default.gc_thresh3=2048

# Tell the gc when to become aggressive with arp table cleaning.
# Adjust this based on size of the LAN. 1024 is suitable for most /24 networks
net.ipv4.neigh.default.gc_thresh2=1024

# Adjust where the gc will leave arp table alone - set to 32.
net.ipv4.neigh.default.gc_thresh1=32

# Adjust to arp table gc to clean-up more often
net.ipv4.neigh.default.gc_interval=30

# Increase TCP queue length
net.ipv4.neigh.default.proxy_qlen=96
net.ipv4.neigh.default.unres_qlen=6

# Enable Explicit Congestion Notification (RFC 3168), disable it if it doesn't work for you
net.ipv4.tcp_ecn=1
net.ipv4.tcp_reordering=3

# How many times to retry killing an alive TCP connection
net.ipv4.tcp_retries2=15
net.ipv4.tcp_retries1=3

# Avoid falling back to slow start after a connection goes idle
# keeps our cwnd large with the keep alive connections (kernel > 3.6)
net.ipv4.tcp_slow_start_after_idle=0

# This will enusre that immediatly subsequent connections use the new values
net.ipv4.route.flush=1
net.ipv6.route.flush=1