netdev - Re: [PATCH net-next] gre/sit: Don't generate link-local addr if addr_gen_mode is IN6_ADDR_GEN_MODE

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Date:   Thu, 21 Oct 2021 14:52:44 +0200
From:   Antonio Quartulli <a@...table.cc>
To:     Stephen Suryaputra <ssuryaextr@...il.com>, netdev@...r.kernel.org
Cc:     kuba@...nel.org, davem@...emloft.net
Subject: Re: [PATCH net-next] gre/sit: Don't generate link-local addr if
 addr_gen_mode is IN6_ADDR_GEN_MODE_NONE

Hi,

On 20/10/2021 22:06, Stephen Suryaputra wrote:
> When addr_gen_mode is set to IN6_ADDR_GEN_MODE_NONE, the link-local addr
> should not be generated. But it isn't the case for GRE (as well as GRE6)
> and SIT tunnels. Make it so that tunnels consider the addr_gen_mode,
> especially for IN6_ADDR_GEN_MODE_NONE.
> 
> Do this in add_v4_addrs() to cover both GRE and SIT only if the addr
> scope is link.
> 
> Signed-off-by: Stephen Suryaputra <ssuryaextr@...il.com>
> ---
>  net/ipv6/addrconf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index d4fae16deec4..9e1463a2acae 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -3110,6 +3110,9 @@ static void add_v4_addrs(struct inet6_dev *idev)
>  	memcpy(&addr.s6_addr32[3], idev->dev->dev_addr + offset, 4);
>  
>  	if (idev->dev->flags&IFF_POINTOPOINT) {
> +		if (idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_NONE)
> +			return;
> +

Maybe I am missing something, but why checking the mode only for
pointtopoint? If mode is NONE shouldn't this routine just abort
regardless of the interface setup?

Cheers,

>  		addr.s6_addr32[0] = htonl(0xfe800000);
>  		scope = IFA_LINK;
>  		plen = 64;
> 

-- 
Antonio Quartulli