linux-kernel - Re: [PATCH net-next v5 1/5] net: udp: add freebind option to udp_sock

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Message-ID: <d6e37117-4409-4ca5-ace6-7af1c9fc0cd9@gmail.com>
Date: Wed, 13 Aug 2025 17:10:47 +0200
From: Richard Gobert <richardbgobert@...il.com>
To: Ido Schimmel <idosch@...dia.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
 donald.hunter@...il.com, andrew+netdev@...n.ch, dsahern@...nel.org,
 shuah@...nel.org, daniel@...earbox.net, jacob.e.keller@...el.com,
 razor@...ckwall.org, petrm@...dia.com, menglong8.dong@...il.com,
 martin.lau@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 1/5] net: udp: add freebind option to
 udp_sock_create

Ido Schimmel wrote:
> On Tue, Aug 12, 2025 at 02:51:51PM +0200, Richard Gobert wrote:
>> udp_sock_create creates a UDP socket and binds it according to
>> udp_port_cfg.
>>
>> Add a freebind option to udp_port_cfg that allows a socket to be bound
>> as though IP_FREEBIND is set.
>>
>> This change is required for binding vxlan sockets to their local address
>> when the outgoing interface is down.
> 
> It's not necessarily the outgoing interface, but rather the interface to
> which the address is assigned.
> 
> Anyway, I'm not sure this change is actually necessary. It was only
> added in v4 because back then the default behavior was changed to bind
> the VXLAN socket to the local address and existing selftests do not
> necessarily configure the address before putting the VXLAN device up.
> 
> Given that in this version binding the VXLAN socket to the local address
> is opt-in, it seems legitimate to prevent user space from putting the
> VXLAN device up if the new option is enabled and the local address is
> not present. It can also be documented in the man page so that users are
> not surprised.

Sounds good, will change in v6.