veth.4: New page document veth virtual ethernet devices

Based on a page from Tomáš Pospíšek, with some clean-ups by mtk.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man4/veth.4

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+.\" Copyright (c) 2012 Tomáš Pospíšek (tpo_deb@sourcepole.ch),
+.\"     Fri, 03 Nov 2012 22:35:33 +0100
+.\"
+.\" This is free documentation; you can redistribute it and/or
+.\" modify it under the terms of the GNU General Public License as
+.\" published by the Free Software Foundation; either version 2 of
+.\" the License, or (at your option) any later version.
+.\"
+.\" The GNU General Public License's references to "object code"
+.\" and "executables" are to be interpreted as the output of any
+.\" document formatting or typesetting system, including
+.\" intermediate and printed output.
+.\"
+.\" This manual 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 General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU General Public
+.\" License along with this manual; if not, write to the Free
+.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
+.\" USA.
+.\"
+.\"
+.TH veth 4 2017-10-03 "Linux" "Linux Programmer's Manual"
+.SH NAME
+veth \- Virtual Ethernet Device
+.SH DESCRIPTION
+The
+.B veth
+devices are virtual Ethernet devices.
+.PP
+They can act as tunnels between network namespaces to create
+a bridge to a physical network device in another namespace, but
+can also be used as standalone network devices.
+.PP
+Because of their original purpose for tunneling
+.B veth
+devices are always created in pairs, that are
+interconnected with each other.
+When one
+.B veth
+end receives a packet it appears on its pair and vice versa.
+.PP
+.B Veth
+devices can be manipulated with the
+.BR ip (8)
+tool.
+See
+.I "ip link help"
+for more information.
+.PP
+.SH "SEE ALSO"
+.BR clone (2),
+.BR ip (8)