T4825: Add interface type veth

Add interface type veth (Virtual ethernet)
One of the usecases it's interconnect different vrf's and
default vrf via bridge

set interfaces virtual-ethernet veth0 peer-name 'veth1010'
set interfaces virtual-ethernet veth1010 address '10.0.0.10/24'
set interfaces virtual-ethernet veth1010 peer-name 'veth0'
set interfaces virtual-ethernet veth1010 vrf 'foo'
set interfaces bridge br0 address '10.0.0.1/24'
set interfaces bridge br0 member interface veth0

vyos@r1:~$ ping 10.0.0.10 count 1
PING 10.0.0.10 (10.0.0.10) 56(84) bytes of data.
64 bytes from 10.0.0.10: icmp_seq=1 ttl=64 time=0.082 ms

2 files changed, 55 insertions, 0 deletions

diff --git a/python/vyos/ifconfig/__init__.py b/python/vyos/ifconfig/__init__.py
index c5d83d24b..a18e315db 100644
--- a/python/vyos/ifconfig/__init__.py
+++ b/python/vyos/ifconfig/__init__.py
@@ -36,4 +36,5 @@ from vyos.ifconfig.pppoe import PPPoEIf
 from vyos.ifconfig.wireless import WiFiIf
 from vyos.ifconfig.l2tpv3 import L2TPv3If
 from vyos.ifconfig.macsec import MACsecIf
+from vyos.ifconfig.veth import VethIf
 from vyos.ifconfig.wwan import WWANIf
diff --git a/python/vyos/ifconfig/veth.py b/python/vyos/ifconfig/veth.py
new file mode 100644
index 000000000..aafbf226a
--- /dev/null
+++ b/python/vyos/ifconfig/veth.py
@@ -0,0 +1,54 @@
+# Copyright 2022 VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+from vyos.ifconfig.interface import Interface
+
+
+@Interface.register
+class VethIf(Interface):
+    """
+    Abstraction of a Linux veth interface
+    """
+    iftype = 'veth'
+    definition = {
+        **Interface.definition,
+        **{
+            'section': 'virtual-ethernet',
+            'prefixes': ['veth', ],
+            'bridgeable': True,
+        },
+    }
+
+    def _create(self):
+        """
+        Create veth interface in OS kernel. Interface is administrative
+        down by default.
+        """
+        # check before create, as we have 2 veth interfaces in our CLI
+        # interface virtual-ethernet veth0 peer-name 'veth1'
+        # interface virtual-ethernet veth1 peer-name 'veth0'
+        #
+        # but iproute2 creates the pair with one command:
+        # ip link add vet0 type veth peer name veth1
+        if self.exists(self.config['peer_name']):
+            return
+
+        # create virtual-ethernet interface
+        cmd = 'ip link add {ifname} type {type}'.format(**self.config)
+        cmd += f' peer name {self.config["peer_name"]}'
+        self._cmd(cmd)
+
+        # interface is always A/D down. It needs to be enabled explicitly
+        self.set_admin_state('down')