Re: git: 8f6561e8adbd - stable/15 - ixv: fix multicast address enumeration

Somewhat related: I'm concerned that ifmcstat(8) may not be reporting 
AF_LINK memberships in all cases, only the ones which were plumbed there 
by an upper layer (AF_INET, AF_INET6).

I noticed this when preparing "add that which was never ratified" for 
IPv6 sockets.

It's a potential issue for LLDP, Carrier Ethernet and IS-IS bring-up. 
Has anyone else observed this? Is anyone else actively using it, or 
using FreeBSD for these control plane protocols?

It may be a "bms@ ends up having to fix it again" issue because I merged 
ifmcstat(8) from NetBSD originally. #tragedyofthecommons

On 08/08/2026 01:38, Kevin Bowling wrote:
> The branch stable/15 has been updated by kbowling:
>
> URL: https://cgit.FreeBSD.org/src/commit/?id=8f6561e8adbd07f52278b5a404c72d5c9643b471
>
> commit 8f6561e8adbd07f52278b5a404c72d5c9643b471
> Author:     Kevin Bowling <kbowling@FreeBSD.org>
> AuthorDate: 2026-07-28 11:06:23 +0000
> Commit:     Kevin Bowling <kbowling@FreeBSD.org>
> CommitDate: 2026-08-08 00:34:24 +0000
>
>      ixv: fix multicast address enumeration
>      
>      if_foreach_llmaddr() adds each callback return value to its running
>      count.  Returning the incremented count made the address indices grow
>      as 0, 1, 3, 7, and so on, eventually writing beyond the multicast
>      address array.
>      
>      Return one address per callback and stop copying when the array is
>      full, matching the ixv-1.6.12 driver.
>      
>      Fixes:          ff06a8dbb677 ("Mechanically convert ixgbe(4) to IfAPI")
>      
>      (cherry picked from commit 6020de5ad154d54c8b9a838f28612c2182330c67)
> ---
>   sys/dev/ixgbe/if_ixv.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/sys/dev/ixgbe/if_ixv.c b/sys/dev/ixgbe/if_ixv.c
> index 8a1c1aae041d..24e6fa714a7b 100644
> --- a/sys/dev/ixgbe/if_ixv.c
> +++ b/sys/dev/ixgbe/if_ixv.c
> @@ -842,11 +842,14 @@ ixv_negotiate_api(struct ixgbe_softc *sc)
>   static u_int
>   ixv_if_multi_set_cb(void *cb_arg, struct sockaddr_dl *addr, u_int cnt)
>   {
> +	if (cnt >= MAX_NUM_MULTICAST_ADDRESSES)
> +		return (0);
> +
>   	bcopy(LLADDR(addr),
>   	    &((u8 *)cb_arg)[cnt * IXGBE_ETH_LENGTH_OF_ADDRESS],
>   	    IXGBE_ETH_LENGTH_OF_ADDRESS);
>   
> -	return (++cnt);
> +	return (1);
>   }
>   
>   /************************************************************************
> @@ -1982,4 +1985,3 @@ ixv_init_device_features(struct ixgbe_softc *sc)
>   	if (sc->feat_cap & IXGBE_FEATURE_NEEDS_CTXD)
>   		sc->feat_en |= IXGBE_FEATURE_NEEDS_CTXD;
>   } /* ixv_init_device_features */
> -
>