netdev - Re: [PATCH net 2/2] packet: round up linear to header len

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Date:   Wed, 8 Feb 2017 07:34:54 -0800
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        eric.dumazet@...il.com, dvyukov@...gle.com,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net 2/2] packet: round up linear to header len

On (02/07/17 15:57), Willem de Bruijn wrote:
> @@ -2816,8 +2816,9 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
>  	err = -ENOBUFS;
>  	hlen = LL_RESERVED_SPACE(dev);
>  	tlen = dev->needed_tailroom;
> -	skb = packet_alloc_skb(sk, hlen + tlen, hlen, len,
> -			       __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len),
> +	linear = __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len);
> +	linear = max(linear, min_t(int, len, dev->hard_header_len));
> +	skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, linear,
>  			       msg->msg_flags & MSG_DONTWAIT, &err);

do we need a similar check in packet_sendsmg_spkt (even if it
is deprecated, would be better to get it to align with packet_snd?)

Also tpacket_fill_skb should ensure that copylen is set up like
the code above?

--Sowmini