Re: [PATCH v5 05/13] netlink: Return prefix length for IPv6 addresses in nl_addr_get()

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Feb 22, 2026 at 12:44:37PM -0500, Jon Maloy wrote:
> nl_addr_get() was not setting the prefix_len output parameter for
> IPv6 addresses, only for IPv4. This meant callers always got 0 for
> IPv6, forcing them to use a hardcoded default (64).
> 
> Fix by assigning *prefix_len in the IPv6 case, matching the IPv4
> behavior.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Moving this patch before 1/13 would address my comment there about the
never exercised check on the prefix_len from nl_addr_get().

> ---
>  conf.c    | 2 +-
>  netlink.c | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index f2ff8af..eb967c7 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -814,7 +814,7 @@ static unsigned int conf_ip6(struct ctx *c, unsigned int ifi)
>  	if (!e) {
>  		e = &c->addrs[c->addr_count++];
>  		e->addr = addr;
> -		e->prefix_len = prefix_len ? prefix_len : 64;
> +		e->prefix_len = prefix_len;
>  		e->flags = CONF_ADDR_HOST;
>  	}
>  
> diff --git a/netlink.c b/netlink.c
> index 82a2f0c..769cb23 100644
> --- a/netlink.c
> +++ b/netlink.c
> @@ -752,7 +752,7 @@ int nl_addr_set_ll_nodad(int s, unsigned int ifi)
>   * @ifi:	Interface index in outer network namespace
>   * @af:		Address family
>   * @addr:	Global address to fill
> - * @prefix_len:	Mask or prefix length, to fill (for IPv4)
> + * @prefix_len:	Mask or prefix length, to fill
>   * @addr_l:	Link-scoped address to fill (for IPv6)
>   *
>   * Return: 0 on success, negative error code on failure
> @@ -797,7 +797,7 @@ int nl_addr_get(int s, unsigned int ifi, sa_family_t af,
>  				   ifa->ifa_prefixlen > prefix_max) {
>  				memcpy(addr, RTA_DATA(rta), RTA_PAYLOAD(rta));
>  
> -				prefix_max = ifa->ifa_prefixlen;
> +				prefix_max = *prefix_len = ifa->ifa_prefixlen;
>  			}
>  
>  			if (addr_l &&
> -- 
> 2.52.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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