ansible-personal/roles/common/templates/sysctl_Ubuntu.j2

#
# /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

##############################################################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.ipv6.conf.all.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
#
# Do not accept IP source route packets (we are not a router)
#net.ipv4.conf.all.accept_source_route = 0
#net.ipv6.conf.all.accept_source_route = 0
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#

# CIS Benchmark Adjustments
# See: https://github.com/alanorth/securekickstarts
kernel.randomize_va_space = 2 
net.ipv4.ip_forward = 0 
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.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.ipv4.conf.all.log_martians = 1 
net.ipv4.conf.default.log_martians = 1 
net.ipv4.icmp_echo_ignore_broadcasts = 1 
net.ipv4.icmp_ignore_bogus_error_responses = 1 
net.ipv4.conf.all.rp_filter = 1 
net.ipv4.conf.default.rp_filter = 1 
net.ipv4.tcp_syncookies = 1

# TCP stuff
# See: http://fasterdata.es.net/host-tuning/linux/
# increase TCP max buffer size settable using setsockopt()
net.core.rmem_max = 16777216 
net.core.wmem_max = 16777216 
# increase Linux autotuning TCP buffer limit 
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
# increase the length of the processor input queue
net.core.netdev_max_backlog = 30000
{# Linode kernels don't have htcp, and kernels after 2.6.32 don't have buggy cubic #}
{% if "linode" not in ansible_kernel and ansible_kernel < "2.6.33" %}
# recommended default congestion control is htcp 
net.ipv4.tcp_congestion_control=htcp
{% endif %}
# recommended for hosts with jumbo frames enabled
#net.ipv4.tcp_mtu_probing=1

# increase quadruplets (src ip, src port, dest ip, dest port)
# see: http://vincent.bernat.im/en/blog/2014-tcp-time-wait-state-linux.html
net.ipv4.ip_local_port_range = 10240 65535
# recommended for web servers, especially if running SPDY
# see: http://www.chromium.org/spdy/spdy-best-practices
net.ipv4.tcp_slow_start_after_idle = 0