Subject: Re: [PATCH net] geneve: initialize needed_headroom

From: Hannes Frederic Sowa <[email-masked]>
Date: Wed, 23 Dec 2015 16:35:13 +0100

On 23.12.2015 16:21, Paolo Abeni wrote:
> Currently the needed_headroom field for the geneve device is left
> to the default value.
> 
> This patch set it to space required for basic geneve encapsulation,
> so that we can avoid the skb head re-allocation on xmit.
> 
> This give a 6% speedup for unsegment traffic on geneve tunnel.
> 
> Signed-off-by: Paolo Abeni <[email-masked]>
> Acked-by: Hannes Frederic Sowa <[email-masked]>

(Sorry, just saw this.)

> ---
>  drivers/net/geneve.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
> index c2b79f5..bb3e6ed 100644
> --- a/drivers/net/geneve.c
> +++ b/drivers/net/geneve.c
> @@ -1155,7 +1155,7 @@ static int geneve_configure(struct net *net, struct net_device *dev,
>  	struct geneve_net *gn = net_generic(net, geneve_net_id);
>  	struct geneve_dev *t, *geneve = netdev_priv(dev);
>  	bool tun_collect_md, tun_on_same_port;
> -	int err;
> +	int err, encap_len;
>  
>  	if (!remote)
>  		return -EINVAL;
> @@ -1187,6 +1187,14 @@ static int geneve_configure(struct net *net, struct net_device *dev,
>  	if (t)
>  		return -EBUSY;
>  
> +	/* make enough headroom for basic scenario */
> +	encap_len = GENEVE_BASE_HLEN + ETH_HLEN;
> +	if (remote->sa.sa_family == AF_INET)
> +		encap_len += sizeof(struct iphdr);
> +	else
> +		encap_len += sizeof(struct ipv6hdr);
> +	dev->needed_headroom = encap_len;
> +

We are missing one time ETH_HLEN or hard_header_len of the lower_dev (if
available) in here AFAIK.

Thanks,
Hannes