router: disable TCP offloading on all interfaces

It was already disabled on some bridges. This patch makes it for all
interfaces.

That might not be required with all network adapters/setups, but causing
trouble with mine.

router/files/if-up-disable-tcp-offloading

+#!/bin/bash
+#
+# Disables TCP offloading on all ifaces
+#
+# Inspired by: @Michelunik https://serverfault.com/a/422554/62953
+
+RUN=true
+case "${IF_NO_TOE,,}" in
+    no|off|false|disable|disabled)
+        RUN=false
+    ;;
+esac
+
+
+# Other offloading options that could be disabled (not TCP related):
+#  sg tso ufo gso gro lro rxvlan txvlan rxhash
+# see man ethtool
+
+if [ "$MODE" = start -a "$RUN" = true ]; then
+  TOE_OPTIONS="rx tx"
+  for TOE_OPTION in $TOE_OPTIONS; do
+    /sbin/ethtool --offload "$IFACE" "$TOE_OPTION" off &>/dev/null || true
+  done
+fi

router/tasks/main.yml

@@ -19,3 +19,14 @@
 - name: Set IPv6 firewall rules
   template: src=ip6tables.j2 dest=/etc/ip6tables
   notify: reload firewall rules
+
+# TCP offloading with e1000e module was buggy with errors like
+# e1000e 0000:00:19.0 eth0: Detected Hardware Unit Hang
+# ...
+# e1000e 0000:00:19.0 eth0: Reset adapter unexpectedly
+# See http://serverfault.com/questions/616485/
+- name: Disable TCP offloading features
+  copy:
+    src: files/if-up-disable-tcp-offloading
+    dest: /etc/network/if-up.d/disable-tcp-offloading
+    mode: 0744

router/templates/interfaces.j2

@@ -16,7 +16,6 @@ iface {{ dmz_iface }} inet static
 	bridge_fd 0
     bridge_stp off
     bridge_maxwait 0
-	post-up /sbin/ethtool -K {{ dmz_iface }} tx off rx off
     # That is ugly but needed : cant have 2 stanzas for same bridge
     # otherwise the up/down fails.
     up ip a a {{ dmz_ip6 }} dev {{ dmz_iface }}