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- sysctl: name={{ item.name }} value={{ item.value }} sysctl_set=yes
with_items:
- { name: 'kernel.domainname', value: '{{ ansible_domain }}' }
# Networking. See
# https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
# Enable Spoof protection (reverse-path filter). Turn on Source
# Address Verification in all interfaces to prevent some spoofing
# attacks.
- { name: 'net.ipv4.conf.default.rp_filter', value: 1 }
- { name: 'net.ipv4.conf.all.rp_filter', value: 1 }
# Disable SYN cookies and improve SYN backlog handling, see tcp(7) and
# https://levelup.gitconnected.com/linux-kernel-tuning-for-high-performance-networking-high-volume-incoming-connections-196e863d458a
# TODO bullseye: remove net.core.somaxconn as 5.4 and later default to 4096
- { name: 'net.ipv4.tcp_syncookies', value: 0 }
- { name: 'net.ipv4.tcp_synack_retries', value: 1 }
- { name: 'net.ipv4.tcp_max_syn_backlog', value: 32768 }
- { name: 'net.core.somaxconn', value: 4096 }
# We rate-limit not only the default ICMP types 3, 4, 11 and 12
# (0x1818), but also types 0 and 8. See icmp(7).
- { name: 'net.ipv4.icmp_ratemask', value: 6425 }
- { name: 'net.ipv4.icmp_ratelimit', value: 1000 }
# Disable packet forwarding between interfaces (we are not a router).
- { name: 'net.ipv4.ip_forward', value: 0 }
- { name: 'net.ipv6.conf.all.forwarding', value: 0 }
# Do not accept ICMP redirects (prevent MITM attacks).
- { name: 'net.ipv4.conf.all.accept_redirects', value: 0 }
- { name: 'net.ipv6.conf.all.accept_redirects', value: 0 }
# Do not send ICMP redirects (we are not a router).
- { name: 'net.ipv4.conf.default.send_redirects', value: 0 }
- { name: 'net.ipv4.conf.all.send_redirects', value: 0 }
# Do not accept IP source route packets (we are not a router).
- { name: 'net.ipv4.conf.all.accept_source_route', value: 0 }
- { name: 'net.ipv6.conf.all.accept_source_route', value: 0 }
# Log Martian Packets.
- { name: 'net.ipv4.conf.all.log_martians', value: 1 }
# Ignore ICMP broadcasts.
- { name: 'net.ipv4.icmp_echo_ignore_broadcasts', value: 1 }
# Ignore bogus ICMP errors.
- { name: 'net.ipv4.icmp_ignore_bogus_error_responses', value: 1 }
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