Remove address from non tagged interface:

Boots send kernel command line parameter "ip=dhcp",
this causes the system to configure the network interface(s) with DHCP.
When an environment's network configuration has this machine connected a
trunked interface with a default/native VLAN, the interface will be configured
on the default/native VLAN because we haven't yet configured the VLAN interface.
Boots will respond to this DHCP request because in this scenario it is not
VLAN aware. Also in this scenario, the machine will end up being configured
with 2 default routes. To resolve this, we remove the default route and IP
that kernel added and let the dhcpcd handle setting the route.

Signed-off-by: Jacob Weinstock <jakobweinstock@gmail.com>

Author: jacobweinstock

files/dhcp.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+
+# This script will run the dhcp client. If `vlan_id=` in `/proc/cmdline` has a value, it will run the dhcp client only on the
+# VLAN interface.
+# This script accepts an input parameter of true or false.
+# true: run the dhcp client with the one shot option
+# false: run the dhcp client as a service
+set -x
+
+run_dhcp_client() {
+  one_shot="$1"
+  al="eth*"
+
+  # shellcheck disable=SC2013
+  for x in $(cat /proc/cmdline); do
+    # shellcheck disable=SC2022
+    echo "$x" | grep -qe 'vlan_id*' || continue
+    vlan_id="${x#vlan_id=}"
+    if [ -n "$vlan_id" ]; then
+       al="eth*.*"
+    fi
+  done
+
+  # Boots send kernel command line parameter "ip=dhcp", this causes the system to configure the network interface(s) with DHCP.
+  # When an environment's network configuration has this machine connected a trunked interface with a default/native VLAN, the
+  # interface will be configured on the default/native VLAN because we haven't yet configured the VLAN interface. Boots will respond
+  # to this DHCP request because in this scenario it is not VLAN aware. Also in this scenario, the machine will end up being configured
+  # with 2 default routes. To resolve this, we remove the default route and IP that kernel added and let the dhcpcd handle setting the route. 
+  ip route del default || true
+  ipa=$(ip -4 -o addr show dev eth0 | awk '{print $4}')
+  ip addr del dev eth0 "$ipa" || true
+
+  if [ "$one_shot" = "true" ]; then
+    /sbin/dhcpcd --nobackground -f /dhcpcd.conf --allowinterfaces "${al}" -1
+  else
+    /sbin/dhcpcd --nobackground -f /dhcpcd.conf --allowinterfaces "${al}"
+  fi
+  
+  
+}
+
+# we always return true so that a failure here doesn't block the next container service from starting. Ideally, we always
+# want the getty service to start so we can debug failures.
+run_dhcp_client "$1" || true

files/dhcpcd.conf

@@ -0,0 +1,15 @@
+# Default values for dhcpcd from linuxkit/dhcpcd:v0.8 with `allowinterfaces eth*` removed
+# This allows the `--allowinterfaces` flag of dhcpcd to specify the allowinterfaces.
+hostname
+clientid
+persistent
+option rapid_commit
+option domain_name_servers, domain_name, domain_search, host_name
+option classless_static_routes
+option ntp_servers
+option interface_mtu
+require dhcp_server_identifier
+slaac private
+nodelay
+noarp
+waitip 4

files/vlan.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+# This script will set up VLAN interfaces if `vlan_id=` in `/proc/cmdline` has a value
+set -x
+
+add_vlan_interface() {
+  # shellcheck disable=SC2013
+  for param in $(cat /proc/cmdline); do
+    # shellcheck disable=SC2022
+    echo "$param" | grep -qe 'vlan_id*' || continue
+    vlan_id="${param#vlan_id=}"
+    if [ -n "$vlan_id" ]; then
+      for ifname in $(ip -4 -o link show | awk -F': ' '{print $2}'); do
+        [ "$ifname" = "lo" ] && continue
+        [ "$ifname" = "docker0" ] && continue
+        ip link add link "$ifname" name "$ifname.$vlan_id" type vlan id "$vlan_id"
+        ip link set "$ifname.$vlan_id" up
+      done
+      return
+    fi
+  done
+}
+
+# we always return true so that a failure here doesn't block the next container service from starting. Ideally, we always
+# want the getty service to start so we can debug failures.
+add_vlan_interface || true

hook.yaml

@@ -23,10 +23,12 @@ onboot:
 
   - name: dhcpcd
     image: linuxkit/dhcpcd:v0.8
-    command: ["/sbin/dhcpcd", "--nobackground", "-f", "/dhcpcd.conf", "-1"]
+    command: ["/etc/ip/dhcp.sh", "true"]
     binds.add:
       - /var/lib/dhcpcd:/var/lib/dhcpcd
       - /run:/run
+      - /etc/ip/dhcp.sh:/etc/ip/dhcp.sh
+      - /dhcpcd.conf:/dhcpcd.conf
     runtime:
       mkdir:
         - /var/lib/dhcpcd
@@ -44,9 +46,12 @@ services:
 
   - name: dhcpcd
     image: linuxkit/dhcpcd:v0.8
+    command: ["/etc/ip/dhcp.sh", "false"]
     binds.add:
       - /var/lib/dhcpcd:/var/lib/dhcpcd
       - /run:/run
+      - /etc/ip/dhcp.sh:/etc/ip/dhcp.sh
+      - /dhcpcd.conf:/dhcpcd.conf
     runtime:
       mkdir:
         - /var/lib/dhcpcd
@@ -104,26 +109,17 @@ files:
     mode: "0644"
 
   - path: etc/ip/vlan.sh
-    contents: |
-      #!/bin/sh
-      # This script will set up VLAN interfaces if `vlan_id=` in `/proc/cmdline` has a value
-      set -x
-
-      for x in $(cat /proc/cmdline); do
-        echo "$x" | grep -qe 'vlan_id*' || continue
-        vlan_id="${x#vlan_id=}"
-        if [ ! -z "$vlan_id" ]; then
-          for x in $(ip -4 -o link show | awk -F': ' '{print $2}'); do
-            [ "$x" == "lo" ] && continue
-            [ "$x" == "docker0" ] && continue
-            ip link add link "$x" name "$x.$vlan_id" type vlan id "$vlan_id"
-            ip link set "$x.$vlan_id" up
-          done
-          exit 0
-        fi
-      done
+    source: "files/vlan.sh"
+    mode: "0777"
+
+  - path: etc/ip/dhcp.sh
+    source: "files/dhcp.sh"
     mode: "0777"
 
+  - path: dhcpcd.conf
+    source: "files/dhcpcd.conf"
+    mode: "0644"
+
 #dbg  - path: root/.ssh/authorized_keys
 #dbg    source: ~/.ssh/id_rsa.pub
 #dbg    mode: "0600"