From: Eyal Birger <eyal.birger@xxxxxxxxx> Date: Sat, 28 Feb 2015 21:39:34 +0200 > On Sat, Feb 28, 2015 at 9:21 PM, David Miller <davem@xxxxxxxxxxxxx> wrote: >> From: Eyal Birger <eyal.birger@xxxxxxxxx> >> Date: Thu, 26 Feb 2015 21:07:01 +0200 >> >>> As part of an effort to move skb->dropcount to skb->cb[], 4 bytes >>> of additional room are needed in skb->cb[] in packet sockets. >>> >>> Store the skb original length in skb->dev instead of skb->cb[] for >>> this purpose. >>> >>> Signed-off-by: Eyal Birger <eyal.birger@xxxxxxxxx> >> >> I'm a little confused, why is this even needed? >> >> packet_skb_cb is 24 bytes by my calculations, which is much >> smaller than the cb[] size which is 48 bytes. > > Note the BUILD_BUG_ON in packet_rcv(). > > packet_skb_cb may contain an address as large as MAX_ADDR_LEN (32) > Therefore the required space is sizeof(packet_skb_cb) + MAX_ADDR_LEN - 8 > which is 48 bytes before this change. So let's take a step back. What link layer we support has 32-byte hardware addresses? If the answer is lower than 32, we should use that value instead. -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
