network-interfaces: Add the ability to create bond devices

This patch adds support for the creations of new bond devices, aggregate
pipes of physical devices for extra throughput or failover.

Additionally, add better correction at the startup of a bridge
of vlan interface (delete old, stale interfaces).

nixos/modules/services/networking/dhcpcd.nix

@@ -11,6 +11,7 @@ let
   ignoredInterfaces =
     map (i: i.name) (filter (i: i.ipAddress != null) (attrValues config.networking.interfaces))
     ++ concatLists (attrValues (mapAttrs (n: v: v.interfaces) config.networking.bridges))
+    ++ concatLists (attrValues (mapAttrs (n: v: v.interfaces) config.networking.bonds))
     ++ config.networking.dhcpcd.denyInterfaces;
 
   # Config file adapted from the one that ships with dhcpcd.

nixos/modules/tasks/network-interfaces.nix

@@ -7,6 +7,7 @@ let
   cfg = config.networking;
   interfaces = attrValues cfg.interfaces;
   hasVirtuals = any (i: i.virtual) interfaces;
+  hasBonds = cfg.bonds != { };
 
   interfaceOpts = { name, ... }: {
 
@@ -228,6 +229,60 @@ in
 
     };
 
+    networking.bonds = mkOption {
+      default = { };
+      example = {
+        bond0 = {
+          interfaces = [ "eth0" "wlan0" ];
+          miimon = 100;
+          mode = "active-backup";
+        };
+        fatpipe.interfaces = [ "enp4s0f0" "enp4s0f1" "enp5s0f0" "enp5s0f1" ];
+      };
+      description = ''
+        This option allows you to define bond devices that aggregate multiple,
+        underlying networking interfaces together. The value of this option is
+        an attribute set. Each attribute specifies a bond, with the attribute
+        name specifying the name of the bond's network interface
+      '';
+
+      type = types.attrsOf types.optionSet;
+
+      options = {
+
+        interfaces = mkOption {
+          example = [ "enp4s0f0" "enp4s0f1" "wlan0" ];
+          type = types.listOf types.string;
+          description = "The interfaces to bond together";
+        };
+
+        miimon = mkOption {
+          default = null;
+          example = 100;
+          type = types.nullOr types.int;
+          description = ''
+            Miimon is the number of millisecond in between each round of polling
+            by the device driver for failed links. By default polling is not
+            enabled and the driver is trusted to properly detect and handle
+            failure scenarios.
+          '';
+        };
+
+        mode = mkOption {
+          default = null;
+          example = "active-backup";
+          type = types.nullOr types.string;
+          description = ''
+            The mode which the bond will be running. The default mode for
+            the bonding driver is balance-rr, optimizing for throughput.
+            More information about valid modes can be found at
+            https://www.kernel.org/doc/Documentation/networking/bonding.txt
+          '';
+        };
+
+      };
+    };
+
     networking.vlans = mkOption {
       default = { };
       example = {
@@ -284,7 +339,15 @@ in
 
   config = {
 
-    boot.kernelModules = optional cfg.enableIPv6 "ipv6" ++ optional hasVirtuals "tun";
+    boot.kernelModules = [ ]
+      ++ optional cfg.enableIPv6 "ipv6"
+      ++ optional hasVirtuals "tun"
+      ++ optional hasBonds "bonding";
+
+    boot.extraModprobeConfig =
+      # This setting is intentional as it prevents default bond devices
+      # from being created.
+      optionalString hasBonds "options bonding max_bonds=0";
 
     environment.systemPackages =
       [ pkgs.host
@@ -450,6 +513,9 @@ in
             path = [ pkgs.bridge_utils pkgs.iproute ];
             script =
               ''
+                # Remove Dead Interfaces
+                ip link show "${n}" >/dev/null 2>&1 && ip link delete "${n}"
+
                 brctl addbr "${n}"
 
                 # Set bridge's hello time to 0 to avoid startup delays.
@@ -474,12 +540,50 @@ in
               '';
           };
 
+        createBondDevice = n: v:
+          let
+            deps = map (i: "sys-subsystem-net-devices-${i}.device") v.interfaces;
+          in
+          { description = "Bond Interface ${n}";
+            wantedBy = [ "network.target" "sys-subsystem-net-devices-${n}.device" ];
+            bindsTo = deps;
+            after = deps;
+            serviceConfig.Type = "oneshot";
+            serviceConfig.RemainAfterExit = true;
+            path = [ pkgs.ifenslave pkgs.iproute ];
+            script = ''
+              # Remove Dead Interfaces
+              ip link show "${n}" >/dev/null 2>&1 && ip link delete "${n}"
+
+              ip link add "${n}" type bond
+
+              # !!! There must be a better way to wait for the interface
+              while [ ! -d /sys/class/net/${n} ]; do sleep 0.1; done;
+
+              # Set the miimon and mode options
+              ${optionalString (v.miimon != null)
+                "echo ${toString v.miimon} > /sys/class/net/${n}/bonding/miimon"}
+              ${optionalString (v.mode != null)
+                "echo \"${v.mode}\" > /sys/class/net/${n}/bonding/mode"}
+
+              # Bring up the bridge and enslave the specified interfaces
+              ip link set "${n}" up
+              ${flip concatMapStrings v.interfaces (i: ''
+                ifenslave "${n}" "${i}"
+              '')}
+            '';
+            postStop = ''
+              ip link set "${n}" down
+              ifenslave -d "${n}"
+              ip link delete "${n}"
+            '';
+          };
+
         createVlanDevice = n: v:
           let
             deps = [ "sys-subsystem-net-devices-${v.interface}.device" ];
           in
-          {
+          { description = "Vlan Interface ${n}";
-            description = "Vlan Interface ${n}";
             wantedBy = [ "network.target" "sys-subsystem-net-devices-${n}.device" ];
             bindsTo = deps;
             after = deps;
@@ -487,6 +591,8 @@ in
             serviceConfig.RemainAfterExit = true;
             path = [ pkgs.iproute ];
             script = ''
+              # Remove Dead Interfaces
+              ip link show "${n}" >/dev/null 2>&1 && ip link delete "${n}"
               ip link add link "${v.interface}" "${n}" type vlan id "${toString v.id}"
               ip link set "${n}" up
             '';
@@ -499,6 +605,7 @@ in
            map configureInterface interfaces ++
            map createTunDevice (filter (i: i.virtual) interfaces))
          // mapAttrs createBridgeDevice cfg.bridges
+         // mapAttrs createBondDevice cfg.bonds
          // mapAttrs createVlanDevice cfg.vlans
          // { "network-setup" = networkSetup; };