refactor: split sysctl file

common/nixos/sysctl/networking/net.nix

@@ -0,0 +1,21 @@
+{
+  config,
+  pkgs,
+  ...
+}: {
+  boot.kernel.sysctl = {
+    # increase the maximum length of processor input queues
+    "net.core.netdev_max_backlog" = 250000;
+
+    # enable BPF JIT hardening for all users
+    # this trades off performance, but can mitigate JIT spraying
+    "net.core.bpf_jit_harden" = 2;
+
+    # increase TCP max buffer size setable using setsockopt()
+    "net.core.rmem_max" = 8388608;
+    "net.core.wmem_max" = 8388608;
+    "net.core.rmem_default" = 8388608;
+    "net.core.wmem_default" = 8388608;
+    #net.core.optmem_max = 40960
+  };
+}