tor: sysctl tuning

modules/tor/default.nix

@@ -24,6 +24,67 @@
     };
   };
 
+  # https://support.torproject.org/relay-operators/#relay-operators_relay-bridge-overloaded
+  # https://lists.torproject.org/pipermail/tor-talk/2012-August/025296.html
+  # https://www.ibm.com/docs/en/linux-on-systems?topic=recommendations-network-performance-tuning
+  # https://github.com/Enkidu-6/tor-ddos
+  boot.kernel.sysctl = {
+    # Increase the maximum size of the network interface's receive queue, used
+    # to store received frames after removing them from the network adapter's
+    # ring buffer. High speed adapters should use a high value to prevent the
+    # queue from becoming full and dropping packets causing retransmits.
+    "net.core.netdev_max_backlog" = 262144;
+    # Increase TCP read/write buffers to enable scaling to a larger window
+    # size. Larger windows increase the amount of data to be transferred before
+    # an acknowledgement (ACK) is required. This reduces overall latencies and
+    # results in increased throughput.
+    "net.core.rmem_max" = 33554432;
+    "net.core.wmem_max" = 33554432;
+    "net.ipv4.tcp_rmem" = "4096 131072 33554432";
+    "net.ipv4.tcp_wmem" = "4096 65536 33554432";
+    # Reduce the length of time an orphaned connection will wait before it is
+    # aborted. For workloads or systems that generate or support high levels of
+    # network traffic, it can be advantageous to more aggressively reclaim dead
+    # or stale resources.
+    "net.ipv4.tcp_fin_timeout" = 10;
+    # Maximal number of TCP sockets not attached to any user file handle, held
+    # by system. If this number is exceeded orphaned connections are reset
+    # immediately and warning is printed. This limit exists only to prevent
+    # simple DoS attacks, you _must_ not rely on this or lower the limit
+    # artificially, but rather increase it (probably, after increasing
+    # installed memory), if network conditions require more than default value,
+    # and tune network services to linger and kill such states more
+    # aggressively. Let me to remind again: each orphan eats up to ~64K of
+    # unswappable memory.
+    "net.ipv4.tcp_max_orphans" = 262144;
+    # Maximal number of timewait sockets held by system simultaneously. If this
+    # number is exceeded time-wait socket is immediately destroyed and warning
+    # is printed. This limit exists only to prevent simple DoS attacks, you
+    # _must_ not lower the limit artificially, but rather increase it
+    # (probably, after increasing installed memory), if network conditions
+    # require more than default value.
+    "net.ipv4.tcp_max_tw_buckets" = 2097152;
+    # In high traffic environments, sockets are created and destroyed at very
+    # high rates. This parameter, when set, allows "no longer needed" and
+    # "about to be destroyed" sockets to be used for new connections. When
+    # enabled, this parameter can bypass the allocation and initialization
+    # overhead normally associated with socket creation saving CPU cycles,
+    # system load and time.
+    "net.ipv4.tcp_tw_reuse" = 1;
+    # Aggressivelly check for and close broken connections
+    "net.ipv4.tcp_keepalive_time" = 60;
+    "net.ipv4.tcp_keepalive_probes" = 3;
+    "net.ipv4.tcp_keepalive_intvl" = 10;
+    # Increase the length of the SYN queue and socket listen() backlog to
+    # accommodate more connections waiting to connect.
+    "net.ipv4.tcp_max_syn_backlog" = 262144;
+    "net.core.somaxconn" = 32768;
+    # Expand local port range used for outgoing connections
+    "net.ipv4.ip_local_port_range" = "1025 65530";
+    # Disable RFC1323 timestamps (TODO: why?)
+    "net.ipv4.tcp_timestamps" = 0;
+  };
+
   environment.systemPackages = with pkgs; [
     nyx # Command-line monitor for Tor
   ];