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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Bart Groeneveld' <avi@bartavi.nl>,
        Patches internal <patches.internal@link.bartavi.nl>
CC:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2] net: Use standardized (IANA) local port range
Thread-Topic: [PATCH v2] net: Use standardized (IANA) local port range
Thread-Index: AQHWfXt8zR3om+J6ikuVkMpiekBWLKlPFWkw
Date:   Sat, 29 Aug 2020 13:37:01 +0000
Message-ID: <30c8e904e2114204a4381034e7ee06c7@AcuMS.aculab.com>
References: <20200821142533.45694-1-avi@bartavi.nl>
 <20200828203959.32010-1-avi@bartavi.nl>
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From: Bart Groeneveld
> Sent: 28 August 2020 21:40
> 
> IANA specifies User ports as 1024-49151,
> and Private ports (local/ephemeral/dynamic/w/e) as 49152-65535 [1].
> 
> This means Linux uses 32768-49151 'illegally'.
> This is not just a matter of following specifications:
> IANA actually assigns numbers in this range [1].

Linux is using the 'historic' values.
IANA shouldn't really have 'grabbed' half the port number space.
Really the 'problem' of TCP port numbers identifying the service
as well as the connection should have been addresses by some other
means (eg using port 1023 and a TCP option to select the serivce).

Changing the default base from 32k to 48k will break some existing
systems if/when a kernel upgrade is installed.

You are also changing the numbers for UDP.
Anyone doing a lot of RTP (which typically requires 2 adjacent
UDP ports) is already constrained by the availability or ports.

	David

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