netdev - Re: [PATCH net-next 03/10] ovpn: set skb->ignore_df = 1 before sending IPv6 packets out

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Message-ID: <fc07f58e-488e-490e-a33f-50f09163a0fb@redhat.com>
Date: Tue, 13 May 2025 09:37:33 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Antonio Quartulli <antonio@...nvpn.net>, netdev@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Sabrina Dubroca <sd@...asysnail.net>, Gert Doering <gert@...enie.muc.de>
Subject: Re: [PATCH net-next 03/10] ovpn: set skb->ignore_df = 1 before
 sending IPv6 packets out

On 5/9/25 4:26 PM, Antonio Quartulli wrote:
> IPv6 user packets (sent over the tunnel) may be larger than
> the outgoing interface MTU after encapsulation.
> When this happens ovpn should allow the kernel to fragment
> them because they are "locally generated".
> 
> To achieve the above, we must set skb->ignore_df = 1
> so that ip6_fragment() can be made aware of this decision.

Why the above applies only to IPv6? AFAICS the same could happen even
for IPv4.

/P