Add support for bonding / LAGs.

* Add a bond executor
  * Add mappings from ifupdown1/2
  * Add a detailed man page
  * Remove legacy compatiblity glue for setups with 'requires' only

  The current implementation has to work around the fact that member interfaces
  will be already up then the bond is created. This is simply done by downing
  them, adding them to the bundle and upping them again. This can possible be
  done in a nicer way after revisiting the ordering of plugin execution (#12).

  Closes #91

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

executor-scripts/linux/bond

@@ -0,0 +1,64 @@
+#!/bin/sh
+#
+# This executor is responsible for setting up bond/LAG interfaces.
+#
+# Sat, 03 Oct 2020 20:42:19 +0200
+#  -- Maximilian Wilhelm <max@sdn.clinic>
+#
+
+set -e
+
+[ -n "$VERBOSE" ] && set -x
+
+get_bond_options() {
+	env | while IFS="=" read opt value; do
+		# We only care for options of format IF_BOND_<OPTION_NAME>
+		if ! echo "${opt}" | grep -q '^IF_BOND_[A-Z0-9_]\+$'; then
+			continue
+		fi
+
+		# Members are handled seperately
+		if [ "${opt}" = "IF_BOND_MEMBERS" ]; then
+			continue
+		fi
+
+		# Convert options for the actual name
+		real_opt=$(echo "${opt}" | sed -e 's/^IF_BOND_\([A-Z0-9_]\+\)/\1/' | tr '[A-Z]' '[a-z]')
+
+		echo -n " ${real_opt} ${value}"
+	done
+}
+
+case "$PHASE" in
+	depend)
+		echo "${IF_BOND_MEMBERS}"
+		;;
+
+	create)
+		if [ -d "/sys/class/net/${IFACE}" ]; then
+			exit 0
+		fi
+
+		# Gather bonding options for this interface
+		options=$(get_bond_options)
+
+		# Create bond
+		${MOCK} ip link add "${IFACE}" type bond ${options}
+
+		# Add members to bundle
+		for member_iface in ${IF_BOND_MEMBERS}; do
+			# Work around the current execution order
+			ip link set "${member_iface}" down
+			ip link set master "${IFACE}" "${member_iface}"
+			ip link set "${member_iface}" up
+		done
+		;;
+
+	destroy)
+		if [ -z "${MOCK}" -a ! -d "/sys/class/net/${IFACE}" ]; then
+			exit 0
+		fi
+
+		${MOCK} ip link del "${IFACE}"
+		;;
+esac