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-rw-r--r--roles/common/tasks/sysctl.yml12
1 files changed, 9 insertions, 3 deletions
diff --git a/roles/common/tasks/sysctl.yml b/roles/common/tasks/sysctl.yml
index 3bf3b4f..f95b7fa 100644
--- a/roles/common/tasks/sysctl.yml
+++ b/roles/common/tasks/sysctl.yml
@@ -11,10 +11,16 @@
- { name: 'net.ipv4.conf.default.rp_filter', value: 1 }
- { name: 'net.ipv4.conf.all.rp_filter', value: 1 }
- # Enable TCP/IP SYN cookies to avoid TCP SYN flood attacks. We
- # rate-limit not only the default ICMP types 3, 4, 11 and 12
+ # 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.tcp_syncookies', value: 1 }
- { name: 'net.ipv4.icmp_ratemask', value: 6425 }
- { name: 'net.ipv4.icmp_ratelimit', value: 1000 }