netdev - Re: [PATCH net-next v6 02/10] eth: Move IPv4/IPv6 multicast address bases to their own symbols

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Message-ID: <8ff2275b53a542acf8c5a42b77621cbdc747e4a4.camel@redhat.com>
Date: Tue, 09 Apr 2024 16:30:20 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>, Diogo Ivo
	 <diogo.ivo@...mens.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
 netdev@...r.kernel.org, andrew@...n.ch, danishanwar@...com,
 rogerq@...nel.org,  vigneshr@...com, jan.kiszka@...mens.com
Subject: Re: [PATCH net-next v6 02/10] eth: Move IPv4/IPv6 multicast address
 bases to their own symbols

On Tue, 2024-04-09 at 13:00 +0200, Alexander Lobakin wrote:
> From: Diogo Ivo <diogo.ivo@...mens.com>
> Date: Tue, 9 Apr 2024 11:20:21 +0100
> 
> > On 4/9/24 10:07 AM, Alexander Lobakin wrote:
> > > From: Diogo Ivo <diogo.ivo@...mens.com>
> > > Date: Wed,  3 Apr 2024 11:48:12 +0100
> > > 
> > > > As these addresses can be useful outside of checking if an address
> > > > is a multicast address (for example in device drivers) make them
> > > > accessible to users of etherdevice.h to avoid code duplication.
> > > > 
> > > > Signed-off-by: Diogo Ivo <diogo.ivo@...mens.com>
> > > > Reviewed-by: MD Danish Anwar <danishanwar@...com>
> > > > ---
> > > > Changes in v5:
> > > >   - Added Reviewed-by tag from Danish
> > > > 
> > > >   include/linux/etherdevice.h | 12 ++++++++----
> > > >   1 file changed, 8 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
> > > > index 224645f17c33..8d6daf828427 100644
> > > > --- a/include/linux/etherdevice.h
> > > > +++ b/include/linux/etherdevice.h
> > > > @@ -71,6 +71,12 @@ static const u8 eth_reserved_addr_base[ETH_ALEN]
> > > > __aligned(2) =
> > > >   { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
> > > >   #define eth_stp_addr eth_reserved_addr_base
> > > >   +static const u8 eth_ipv4_mcast_addr_base[ETH_ALEN] __aligned(2) =
> > > > +{ 0x01, 0x00, 0x5e, 0x00, 0x00, 0x00 };
> > > > +
> > > > +static const u8 eth_ipv6_mcast_addr_base[ETH_ALEN] __aligned(2) =
> > > > +{ 0x33, 0x33, 0x00, 0x00, 0x00, 0x00 };
> > > 
> > > I see this is applied already, but I don't like static symbols in header
> > > files. This will make a local copy of every used symbol each time it's
> > > referenced.
> > > We usually make such symbols global consts and export them. Could you
> > > please send a follow-up?
> > 
> > I forgot to ask, should this exporting happen in
> > include/linux/etherdevice.h?
> 
> In etherdevice.h, you do
> 
> const u8 eth_ipv4_mcast_addr_base[ETH_ALEN];
> const u8 eth_ipv6_mcast_addr_base[ETH_ALEN];
> 
> Then, somewhere in, I guess, net/ethernet/eth.c, you do
> 
> const u8 eth_ipv4_mcast_addr_base[ETH_ALEN] __aligned(2) = {
> 	0x01, 0x00, 0x5e, 0x00, 0x00, 0x00
> };
> EXPORT_SYMBOL(eth_ipv4_mcast_addr_base);
> 
> const u8 eth_ipv6_mcast_addr_base[ETH_ALEN] __aligned(2) = {
> 	0x33, 0x33, 0x00, 0x00, 0x00, 0x00
> };
> EXPORT_SYMBOL(eth_ipv6_mcast_addr_base);

I think it would be good moving even eth_reserved_addr_base into eth.c

Thanks!

Paolo