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From: "Robin Jarry" <rjarry@redhat.com>
To: "Thomas Monjalon" <thomas@monjalon.net>,
	"Christophe Fontaine" <cfontain@redhat.com>
Cc: "Stephen Hemminger" <stephen@networkplumber.org>,
	<stable@dpdk.org>, <dev@dpdk.org>
Subject: Re: [PATCH dpdk v2] net: ipv6 link local compliance with rfc 4291
Date: Wed, 19 Nov 2025 15:42:40 +0100	[thread overview]
Message-ID: <DECR1BBB72GY.3CA5B6PY8ORGW@redhat.com> (raw)
In-Reply-To: <4832942.kQq0lBPeGt@thomas>

Thomas Monjalon, Nov 19, 2025 at 01:27:
> After checking with Stephen, it appears that XOR is really desired.
> This bit must be inverted, so 0 is local and 1 is universal.
>
> Adding this comment in the code to avoid confusion in future:
>     /*
>      * The "u" bit (universal/local bit in IEEE EUI-64 terminology)
>      * must be inverted for IPv6 link local address.
>      * 0 means local scope, 1 means universal scope.
>      */
>
> Applied, thanks.

Thanks Thomas.

That XOR is described in the RFCs as "flipping the 'u' bit". I.e. the
bit should be 1 if the address is "global/universal" and 0 if the
address is "local/administratively configured".

Here's the corresponding code in Linux and BSD:

https://github.com/torvalds/linux/blob/v6.17/include/net/addrconf.h#L201

https://github.com/freebsd/freebsd-src/blob/release/14.3.0/sys/netinet6/in6_ifattach.c#L97

-- 
Robin

> No animals were injured.


      reply	other threads:[~2025-11-19 14:42 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-14 10:57 [PATCH dpdk] " Robin Jarry
2025-11-14 16:05 ` Stephen Hemminger
2025-11-14 16:08   ` Robin Jarry
2025-11-14 16:14   ` Morten Brørup
2025-11-14 16:46     ` Robin Jarry
2025-11-14 17:03       ` Stephen Hemminger
2025-11-15 17:57         ` Robin Jarry
2025-11-14 16:48     ` Stephen Hemminger
2025-11-14 16:08 ` Stephen Hemminger
2025-11-18 17:45 ` [PATCH dpdk v2] " Robin Jarry
2025-11-19  0:07   ` Thomas Monjalon
2025-11-19  0:27     ` Thomas Monjalon
2025-11-19 14:42       ` Robin Jarry [this message]

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