add interfaces --> settings

source/interfaces.rst

@@ -16,3 +16,5 @@ All traffic flowing through your appliance is using (virtual) interfaces, this i
    :titlesonly:
 
    manual/interfaces
+   manual/diagnostics
+   manual/interfaces_settings

source/manual/interfaces_settings.rst

@@ -0,0 +1,66 @@
+=========================
+Settings
+=========================
+
+There are some advanced settings, which you can alter in :menuselection:`Interfaces --> Settings`, most of the time
+you should leave these settings default, but advanced scenarios may require specific settings.
+
+The settings on this page will be applied after reboot or a reconfiguration of each interface.
+
+--------------------
+Hardware CRC
+--------------------
+Disable hardware checksum offloading, which is checked by default, controls if user-configurable checksum offloading might be handled by the network card.
+Not all technologies support this (IPS for example) and some drivers have issues when enabled. We generally advise to keep this disabled, the
+performance gain is debatable as well.
+
+(the :code:`ifconfig` settings in the OS related to this setting are :code:`txcsum` , :code:`rxcsum` , :code:`txcsum6` , :code:`rxcsum6`)
+
+
+--------------------
+Hardware TSO
+--------------------
+Disable hardware TCP segmentation offload, also checked by default, prevents the system to offload packet segmentation to the network card.
+This option is incompatible with IPS in OPNsense and is broken in some network cards.
+
+(the :code:`ifconfig` settings in the OS related to this setting are :code:`tso` ,  :code:`tso4` , :code:`tso6`)
+
+--------------------
+Hardware LRO
+--------------------
+Disable hardware large receive offload, which is checked by default, prevents the network card from aggregating incoming packets
+into a larger buffer before passing it further on the network stack (in order to decrease the number of packets to process).
+
+For routing traffic its usually advisable to disable options which queue traffic in the network card to prevent additional latency.
+
+Enabling LRO might degrade routing performance or for some drivers is incompatible with packet-forwarding at all.
+
+(the :code:`ifconfig` setting in the OS related to this setting is :code:`lro`)
+
+
+-------------------------
+VLAN Hardware Filtering
+-------------------------
+
+Set usage of VLAN hardware filtering.
+This hardware acceleration may be broken in some device drivers, our advice is to keep this setting on "Leave default".
+In some cases we have seen random disconnects when the driver is forced into a mode it was not set at by default.
+
+
+(the :code:`ifconfig` settings in the OS related to this setting are :code:`vlanhwtag` ,  :code:`vlanhwfilter` , :code:`vlanhwtso`)
+
+--------------------------
+ARP Handling
+--------------------------
+By default the kernel logs movement of ip addresses from one hardware address to another and when an arp request is received on the
+wrong interface. When checking this option, it will stop doing so, which is practical if multiple interfaces reside on the same broadcast domain.
+
+(for a more detailed description, see :code:`man arp` and search :code:`log_arp_wrong_iface` and  :code:`log_arp_movements`)
+
+--------------------------
+DHCP Unique Identifier
+--------------------------
+This option can be used to enter an explicit DUID for use by IPv6 DHCP clients, the different types are detailed in
+`section 11 of rfc8415 <https://tools.ietf.org/html/rfc8415#section-11>`__
+
+When not set, the dhcp v6 client (:code:`dhcp6c`) will assign one automatically.