Re: [PATCH net-next] net: ipv4: Add ability to have GRE ignore DF bit in IPv4 payloads

From: "Philip Prindeville" <redacted>
Date: Tue,  7 Jun 2016 13:48:46 -0600

From: Philip Prindeville <redacted>

In the presence of firewalls which improperly block ICMP Unreachable
(including Fragmentation Required) messages, Path MTU Discovery is
prevented from working.

A workaround is to handle IPv4 payloads opaquely, ignoring the DF bit--as
is done for other payloads like AppleTalk--and doing transparent
fragmentation and reassembly.

Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Philip Prindeville <redacted>

I think the feedback that this feature should be mutually exclusive
to pmtudisc is valid and you should address that.