[PATCH] man ip-link: Add more explanation about vlan reordering

[PATCH] man ip-link: Add more explanation about vlan reordering

[Vadim Kochan]

From: Vadim Kochan <vadim4j@gmail.com>

Add more explanation about VLAN reordering and what it affects.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
---
 man/man8/ip-link.8.in | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index df2fcce..b9137fb 100644
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -313,7 +313,31 @@ the following additional arguments are supported:
 - specifies the VLAN Identifer to use. Note that numbers with a leading " 0 " or " 0x " are interpreted as octal or hexadeimal, respectively.
 
 .BR reorder_hdr " { " on " | " off " } "
-- specifies whether ethernet headers are reordered or not.
+- specifies whether ethernet headers are reordered or not (default is
+.BR on ")."
+
+.in +4
+If
+.BR reorder_hdr " is " on
+then VLAN header will be not inserted immediately but only before passing to the
+physical device (if this device does not support VLAN offloading), the similar
+on the RX direction - by default the packet will be untagged before being
+received by VLAN device. Reordering allows to accelerate tagging on egress and
+to hide VLAN header on ingress so the packet looks like regular Ethernet packet,
+at the same time it might be confusing while the packet sniffing as the VLAN header
+does not exist within the packet.
+
+VLAN offloading can be checked by
+.BR ethtool "(8):"
+.in +4
+.sp
+.B ethtool -k
+<phy_dev> |
+.RB grep " tx-vlan-offload"
+.sp
+.in -4
+where <phy_dev> is the physical device to which VLAN device is bound.
+.in -4
 
 .BR gvrp " { " on " | " off " } "
 - specifies whether this VLAN should be registered using GARP VLAN Registration Protocol.
@@ -1065,7 +1089,8 @@ IEEE 802.15.4 device wpan0.
 .SH SEE ALSO
 .br
 .BR ip (8),
-.BR ip-netns (8)
+.BR ip-netns (8),
+.BR ethtool (8)
 
 .SH AUTHOR
 Original Manpage by Michail Litvak <mci@owl.openwall.com>
-- 
2.4.2

Re: [PATCH] man ip-link: Add more explanation about vlan reordering

[Jeremy Harris]

On 17/08/15 20:22, Vadim Kochan wrote:
> +.BR reorder_hdr " is " on
> +then VLAN header will be not inserted immediately but only before passing to the
> +physical device (if this device does not support VLAN offloading), the similar
> +on the RX direction - by default the packet will be untagged before being
> +received by VLAN device. Reordering allows to accelerate tagging on egress and
> +to hide VLAN header on ingress so the packet looks like regular Ethernet packet,
> +at the same time it might be confusing while the packet sniffing as the VLAN header
                                          ^^^^^^^^^^^^^^^^^^^^^^^^^

Does not read well.  "for packet capture" perhaps?
-- 
Jeremy

Re: [PATCH] man ip-link: Add more explanation about vlan reordering

[Vadim Kochan]

On Wed, Aug 26, 2015 at 04:27:48PM +0100, Jeremy Harris wrote:
> On 17/08/15 20:22, Vadim Kochan wrote:
> > +.BR reorder_hdr " is " on
> > +then VLAN header will be not inserted immediately but only before passing to the
> > +physical device (if this device does not support VLAN offloading), the similar
> > +on the RX direction - by default the packet will be untagged before being
> > +received by VLAN device. Reordering allows to accelerate tagging on egress and
> > +to hide VLAN header on ingress so the packet looks like regular Ethernet packet,
> > +at the same time it might be confusing while the packet sniffing as the VLAN header
>                                           ^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> Does not read well.  "for packet capture" perhaps?
> -- 
> Jeremy
> 
> 

Hi Jeremy,

Thanks for you comment, I have sent a patch, let me know if it is correct now.
And sorry for so late response.

Thanks,
Vadim Kochan