Re: [RFC 01/12] ip: Introduce multi-address data structures for IPv4 and IPv6

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

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On Sun, Dec 14, 2025 at 08:54:30PM -0500, Jon Maloy wrote:
> As preparation for supporting multiple addresses per interface, we
> replace the single addr/prefix_len fields with arrays.
> 
> - We add an ip4_addr_entry and an ip6_addr_entry struct containing
>   address and prefix length.
> 
> - We set the array sizes to IP4_MAX_ADDRS=8 and IP6_MAX_ADDRS=16,
>   respectively.
> 
> The only functional change is that the IPv6 prefix length now is
> properly stored instead of being hardcoded to 64 even when set
> via the -a option.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> ---
>  arp.c    |  4 +--
>  conf.c   | 97 +++++++++++++++++++++++++++++++++-----------------------
>  dhcp.c   |  8 ++---
>  dhcpv6.c |  6 ++--
>  fwd.c    | 12 +++----
>  ip.h     | 26 +++++++++++++++
>  ndp.c    |  6 ++--
>  passt.h  | 16 ++++++----
>  pasta.c  | 12 ++++---
>  tap.c    |  4 +--
>  util.h   |  1 +
>  11 files changed, 122 insertions(+), 70 deletions(-)
> 
> diff --git a/arp.c b/arp.c
> index bb042e9..7eaf517 100644
> --- a/arp.c
> +++ b/arp.c
> @@ -54,7 +54,7 @@ static bool ignore_arp(const struct ctx *c,
>  		return true;
>  
>  	/* Don't resolve the guest's assigned address, either. */
> -	if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip)))
> +	if (!memcmp(am->tip, &c->ip4.addrs[0].addr, sizeof(am->tip)))
>  		return true;

Sorry, missed this on my first pass.  This needs to skip *all* of the
guest addresses, not just the first one.  Otherwise passt will respond
to arps for the guest's other addresses with its own MAC which will
break everything.

-- 
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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