debian-sysctl-performance-tunning-and-security

debian-sysctl-performance-tunning-and-security.md

### GENERAL SYSTEM SECURITY OPTIONS ###
###
# https://github.com/klaver/sysctl/blob/master/sysctl.conf
# https://github.com/sathrak/linux-sysctl.conf
# 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

# The contents of /proc/<pid>/maps and smaps files are only visible to
# readers that are allowed to ptrace() the process
kernel.maps_protect = 1

#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

###
### 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

# Decrease the time default value for tcp_fin_timeout connection
net.ipv4.tcp_fin_timeout = 3

# Decrease the time default value for connections to keep alive
net.ipv4.tcp_keepalive_time = 300
net.ipv4.tcp_keepalive_probes = 3
net.ipv4.tcp_keepalive_intvl = 15

# 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

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

# max open files
fs.file-max = 51200
# max read buffer
net.core.rmem_max = 67108864
# max write buffer
net.core.wmem_max = 67108864
# default read buffer
net.core.rmem_default = 65536
# default write buffer
net.core.wmem_default = 65536

# max processor input queue, increase number of incoming connections
net.core.netdev_max_backlog = 65530
# max backlog, increase number of incoming connections backlog
net.core.somaxconn = 65530

# resist SYN flood attacks
net.ipv4.tcp_syncookies = 1
# reuse timewait sockets when safe
net.ipv4.tcp_tw_reuse = 1
# turn off fast timewait sockets recycling
net.ipv4.tcp_tw_recycle = 0
# short FIN timeout
net.ipv4.tcp_fin_timeout = 30
# short keepalive time
net.ipv4.tcp_keepalive_time = 1200
# outbound port range
net.ipv4.ip_local_port_range = 2000 65500
# max SYN backlog
net.ipv4.tcp_max_syn_backlog = 4096
# max timewait sockets held by system simultaneously
net.ipv4.tcp_max_tw_buckets = 5000
# turn on TCP Fast Open on both client and server side
net.ipv4.tcp_fastopen = 3

# turn on path MTU discovery
net.ipv4.tcp_mtu_probing = 1

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

# Use BBR TCP congestion control and set tcp_notsent_lowat to 16384 to ensure HTTP/2 prioritization works optimally
# Do a 'modprobe tcp_bbr' first (kernel > 4.9)
# Fall-back to htcp if bbr is unavailable (older kernels)
net.ipv4.tcp_congestion_control = htcp
net.ipv4.tcp_congestion_control = bbr
net.ipv4.tcp_notsent_lowat = 16384

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

# Increase the read-buffer space allocatable
net.ipv4.tcp_rmem = 8192 87380 16777216
net.ipv4.udp_rmem_min = 16384
net.core.rmem_default = 262144
net.core.rmem_max = 16777216

# Increase the write-buffer-space allocatable
net.ipv4.tcp_wmem = 8192 65536 16777216
net.ipv4.udp_wmem_min = 16384
net.core.wmem_default = 262144
net.core.wmem_max = 16777216

# Increase number of incoming connections
net.core.somaxconn = 32768

# Increase number of incoming connections backlog
net.core.netdev_max_backlog = 16384
net.core.dev_weight = 64

# Increase the maximum amount of option memory buffers
#net.core.optmem_max = 65535
net.core.optmem_max = 25165824
# 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 the maximum memory used to reassemble IP fragments (CVE-2018-5391)
net.ipv4.ipfrag_low_thresh = 196608
net.ipv6.ip6frag_low_thresh = 196608
net.ipv4.ipfrag_high_thresh = 262144
net.ipv6.ip6frag_high_thresh = 262144

# 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

# Allow the TCP fastopen flag to be used, beware some firewalls do not like TFO! (kernel > 3.7)
net.ipv4.tcp_fastopen = 3

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


net.ipv4.tcp_mem = 25600 51200 102400
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv6.conf.all.accept_ra = 2
net.ipv6.conf.all.autoconf = 1
net.ipv6.conf.all.accept_ra = 2
net.ipv6.ip_forward = 1
net.ipv4.ip_forward = 1
net.ipv6.conf.all.proxy_ndp = 1
net.ipv6.route.max_size = 16384
net.ipv6.conf.all.forwarding = 1

net.core.default_qdisc = fq
net.ipv6.conf.all.accept_redirects = 1
net.ipv6.conf.all.accept_source_route = 1
net.ipv6.conf.all.disable_ipv6 = 0
net.netfilter.nf_conntrack_tcp_timeout_time_wait=30
net.netfilter.nf_conntrack_tcp_timeout_fin_wait=30

kernel.sched_min_granularity_ns = 10000000
kernel.sched_wakeup_granularity_ns = 15000000