Re: [dpdk-dev] [PATCH v2 1/3] net/af_packet: set_mtu() decrements sockaddr twice

[Kevin Traynor <ktraynor@redhat.com>]

On 11/20/2018 10:26 AM, Tiago Lam wrote:
> When setting the MTU, eth_dev_mtu_set() is called to validate the
> provided MTU. As part of that, it calculates the useful area to store
> data and compares it against the MTU, to guarantee that there's enough
> space to store the data. It calculates that as:
>     "tp_frame_size - TPACKET2_HDRLEN - sizeof(struct sockaddr_ll)"
> 
> However, the TPACKET2_HDRLEN macro already increaments sizeof(struct
> sockaddr_ll) internally, meaning the useuful area of data above will
> have sizeof(struct sockaddr_ll) decremented twice.
> 
> Instead, the useful area of data should be calculated as:
>     "tp_frame_size - TPACKET2_HDRLEN"
> 
> This makes sure that there's enough useful area to fit the provided MTU
> after excluding tpacket2_hdr and sockaddr_ll.
> 
> Fixes: cc68ac4 ("net/af_packet: support MTU change")
> 

It should be for stable also?

> Signed-off-by: Tiago Lam <tiago.lam@intel.com>
> ---
>  drivers/net/af_packet/rte_eth_af_packet.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/af_packet/rte_eth_af_packet.c b/drivers/net/af_packet/rte_eth_af_packet.c
> index 95a98c6..264cfc0 100644
> --- a/drivers/net/af_packet/rte_eth_af_packet.c
> +++ b/drivers/net/af_packet/rte_eth_af_packet.c
> @@ -433,8 +433,7 @@ eth_dev_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)
>  	int ret;
>  	int s;
>  	unsigned int data_size = internals->req.tp_frame_size -
> -				 TPACKET2_HDRLEN -
> -				 sizeof(struct sockaddr_ll);
> +				 TPACKET2_HDRLEN;
>  
>  	if (mtu > data_size)
>  		return -EINVAL;
>