Re: [PATCH] wifi: brcmfmac: keep ARP and ND offload off on the BCM4364

[Aditya Garg <aditya.garg@linux.dev>]

> On 4 Nov 2026, at 8:46 PM, Andre Eikmeyer <dev@deq.rocks> wrote:
> 
> brcmfmac enables the firmware's ARP and IPv6 ND offload (ndoe) whenever
> the interface is up and not promiscuous. On the Apple firmware for the
> BCM4364, ndoe makes IPv6 downloads collapse. IPv6 downloads topped out
> at 55 Mbit/s on a MacBookPro15,1 with the BCM4364/3 and on the
> MacBookPro16,1 with the later revision. The BCM4377 is not affected.
> 
> macOS enables ND offload for associated sleep only. A trace under
> macOS 26.6.1 on a MacBookPro16,2 shows nd_hostip_clear, ndoe=1 and the
> IPv6 addresses before sleep and ndoe cleared again on wake, see the
> first report below. Keep them off on the BCM4364.
> 
> Closes: https://github.com/t2linux/kernel/issues/34
> Closes: https://github.com/t2linux/T2-Debian-and-Ubuntu-Kernel/issues/227
> Tested-by: Yossef Osman <Yossef.Osman@proton.me>
> Tested-by: Aditya Garg <aditya.garg@linux.dev>
> Signed-off-by: Andre Eikmeyer <dev@deq.rocks>

The bug is present even in 6.18 LTS

Cc: stable@vger.kernel.org
> ---
> The KaiT2en community runs this patch with its kernels, no regression
> was reported.
> 
> .../net/wireless/broadcom/brcm80211/brcmfmac/core.c    | 10 ++++++++++
> 1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
> index 92ec269f43b..6eae7135aeb 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
> @@ -13,6 +13,7 @@
> #include <net/addrconf.h>
> #include <net/ieee80211_radiotap.h>
> #include <net/ipv6.h>
> +#include <brcm_hw_ids.h>
> #include <brcmu_utils.h>
> #include <brcmu_wifi.h>
> 
> @@ -103,6 +104,15 @@ void brcmf_configure_arp_nd_offload(struct brcmf_if *ifp, bool enable)
>        return;
>    }
> 
> +    /* With ND offload on while awake, the Apple firmware for the BCM4364
> +     * makes IPv6 downloads drop to low rates. macOS runs ARP and ND
> +     * offload only in sleep, keep both off on this chip.
> +     */
> +    if (enable && ifp->drvr->bus_if->chip == BRCM_CC_4364_CHIP_ID) {
> +        brcmf_dbg(TRACE, "Skip ARP/ND offload enable on BCM4364\n");
> +        enable = false;
> +    }
> +
>    if (enable)
>        mode = BRCMF_ARP_OL_AGENT | BRCMF_ARP_OL_PEER_AUTO_REPLY;
>    else
> 
> base-commit: 991a73f4909f1348ffb4b38765cdb522a775e4c2