[PATCH v3] options: make `tun` the default for `--dev`

From: Antonio Quartulli <[email protected]>

With this change, OpenVPN can be launched without specifying
any --dev option and it will start a `tun` (L3) tunnel with the
interface named `tunX`.
As before, this behaviour can be changed using --dev or --dev-type.

Existing configs won't see any behavioural change as they all
had to contain at least one --dev directive.

Change-Id: I0ca7b5b7ec1a01acaad222c99db137c94c88555a
Signed-off-by: Antonio Quartulli <[email protected]>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1537
---

This change was reviewed on Gerrit and approved by at least one
developer. I request to merge it to master.

Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1537
This mail reflects revision 3 of this Change.

Acked-by according to Gerrit (reflected above):

        
diff --git a/doc/man-sections/examples.rst b/doc/man-sections/examples.rst
index 80ef2df..416e576 100644
--- a/doc/man-sections/examples.rst
+++ b/doc/man-sections/examples.rst
@@ -63,6 +63,10 @@
 Example 1: A simple tunnel without security (not recommended)
 -------------------------------------------------------------
 
+Since :code:`tun` is the default device type, ``--dev`` is optional; when it
+is omitted OpenVPN creates a dynamically-named ``tunX`` device. The examples
+below still name the device (``--dev tun1``) explicitly for clarity.
+
 On bob::
 
    openvpn --remote alice.example.com --dev tun1 \
diff --git a/doc/man-sections/vpn-network-options.rst b/doc/man-sections/vpn-network-options.rst
index 33ebedb..960c6ad 100644
--- a/doc/man-sections/vpn-network-options.rst
+++ b/doc/man-sections/vpn-network-options.rst
@@ -50,6 +50,10 @@
   :code:`null` or an arbitrary name string (:code:`X` can be omitted for
   a dynamic device.)
 
+  If neither ``--dev`` nor ``--dev-type`` is specified, OpenVPN defaults to
+  :code:`tun`, i.e. it creates a dynamically-named :code:`tunX` device and
+  runs a layer-3 tunnel.
+
   See examples section below for an example on setting up a TUN device.
 
   You must use either tun devices on both ends of the connection or tap
diff --git a/sample/sample-config-files/client.conf b/sample/sample-config-files/client.conf
index 53b8027..1806b24 100644
--- a/sample/sample-config-files/client.conf
+++ b/sample/sample-config-files/client.conf
@@ -20,6 +20,8 @@
 # On most systems, the VPN will not function
 # unless you partially or fully disable
 # the firewall for the TUN/TAP interface.
+# "tun" is the default device type, so the
+# "dev tun" line below is optional.
 ;dev tap
 dev tun
 
diff --git a/sample/sample-config-files/server.conf b/sample/sample-config-files/server.conf
index 8943c34..924fb96 100644
--- a/sample/sample-config-files/server.conf
+++ b/sample/sample-config-files/server.conf
@@ -49,6 +49,8 @@
 # On most systems, the VPN will not function
 # unless you partially or fully disable/open
 # the firewall for the TUN/TAP interface.
+# "tun" is the default device type, so the
+# "dev tun" line below is optional.
 ;dev tap
 dev tun
 
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 87218d4..d4cc158 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -189,7 +189,8 @@
     " or --socks-proxy"
     " is used).\n"
     "--nobind        : Do not bind to local address and port.\n"
-    "--dev tunX|tapX : tun/tap device (X can be omitted for dynamic device.\n"
+    "--dev tunX|tapX : tun/tap device (X can be omitted for dynamic device).\n"
+    "                  Defaults to \"tun\" if neither --dev nor --dev-type is given.\n"
     "--dev-type dt   : Which device type are we using? (dt = tun or tap) Use\n"
     "                  this option only if the tun/tap device used with --dev\n"
     "                  does not begin with \"tun\" or \"tap\".\n"
@@ -801,6 +802,7 @@
     gc_init(&o->dns_options.gc);
 
     o->mode = MODE_POINT_TO_POINT;
+    o->dev = "tun";
     o->topology = TOP_UNDEF;
     o->ce.proto = PROTO_UDP;
     o->ce.af = AF_UNSPEC;