RE: [PATCH net-next 08/10] hv_netvsc: Don't ask for additional head room in the skb

From: KY Srinivasan
Date: Tue Nov 24 2015 - 11:28:00 EST




> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Tuesday, November 24, 2015 12:56 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: davem@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx;
> apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx
> Subject: Re: [PATCH net-next 08/10] hv_netvsc: Don't ask for additional head
> room in the skb
>
> "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx> writes:
>
> > The rndis header is 116 bytes big and can be placed in the default
> > head room that will be available in the skb.
>
> We have the following in include/linux/netdevice.h:
>
> #if defined(CONFIG_WLAN) || IS_ENABLED(CONFIG_AX25)
> # if defined(CONFIG_MAC80211_MESH)
> # define LL_MAX_HEADER 128
> # else
> # define LL_MAX_HEADER 96
> # endif
> #else
> # define LL_MAX_HEADER 32
> #endif
>
> In case someone disables MAC80211_MESH in his kernel config we're in
> troubles again. I suggest we add additional patch here making sure it is
> 128 bytes for Hyper-V:
>
> #if defined(CONFIG_HYPERV_NET)
> # define LL_MAX_HEADER 128
> #elseif defined(CONFIG_WLAN) || IS_ENABLED(CONFIG_AX25)
> ...

Thanks Vitaly; will do.

K. Y
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