netdev - Re: [PATCHv2 net-next] sctp: add support for SCTP_REUSE

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Date:   Tue, 26 Jun 2018 12:41:23 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        Neil Horman <nhorman@...driver.com>,
        Michael Tuexen <tuexen@...muenster.de>,
        davem <davem@...emloft.net>
Subject: Re: [PATCHv2 net-next] sctp: add support for SCTP_REUSE_PORT sockopt

On Mon, Jun 25, 2018 at 9:30 PM, Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
> On Mon, Jun 25, 2018 at 10:06:46AM +0800, Xin Long wrote:
>> This feature is actually already supported by sk->sk_reuse which can be
>> set by socket level opt SO_REUSEADDR. But it's not working exactly as
>> RFC6458 demands in section 8.1.27, like:
>>
>>   - This option only supports one-to-one style SCTP sockets
>>   - This socket option must not be used after calling bind()
>>     or sctp_bindx().
>>
>> Besides, SCTP_REUSE_PORT sockopt should be provided for user's programs.
>> Otherwise, the programs with SCTP_REUSE_PORT from other systems will not
>> work in linux.
>>
>> To separate it from the socket level version, this patch adds 'reuse' in
>> sctp_sock and it works pretty much as sk->sk_reuse, but with some extra
>> setup limitations that are needed when it is being enabled.
>>
>> "It should be noted that the behavior of the socket-level socket option
>> to reuse ports and/or addresses for SCTP sockets is unspecified", so it
>> leaves SO_REUSEADDR as is for the compatibility.
>>
>> Note that the name SCTP_REUSE_PORT is kind of confusing, it is identical
>> to SO_REUSEADDR with some extra restriction, so here it uses 'reuse' in
>> sctp_sock instead of 'reuseport'. As for sk->sk_reuseport support for
>> SCTP, it will be added in another patch.
>
> To help changelog readers later, please update to something like:
>
> """\
> Note that the name SCTP_REUSE_PORT is somewhat confusing, as its
> functionality is nearly identical to SO_REUSEADDR, but with some
> extra restrictions. Here it uses 'reuse' in sctp_sock instead of
> 'reuseport'. As for sk->sk_reuseport support for SCTP, it will be
> added in another patch.
> """
>
> Makes sense, can you note the difference?
Sure, will post v3. thanks.