Re: [PATCH] net/mlx5: IPSec, fix 64-bit division correctly

[Joe Perches <joe@perches.com>]

On Mon, 2017-07-10 at 10:24 +0000, Ilan Tayari wrote:
> > -----Original Message-----
> > From: Arnd Bergmann [mailto:arnd@arndb.de]
> > Subject: [PATCH] net/mlx5: IPSec, fix 64-bit division correctly
> > 
> > The new IPSec offload code introduced a build error:
> > 
> > drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.o: In function
> > `mlx5e_ipsec_build_inverse_table':
> > ipsec_rxtx.c:(.text+0x556): undefined reference
> > 
> > Another patch was added on top to fix the build error, but
> > that introduced a new bug, as we now use the remainder of
> > the division rather than the result.

Is it possible to return noise in mlx5e_ipsec_mss_inv ?

What clamps skb_shinfo(skb)->gso_size to MAX_LSO
(the size of inverse_table)?

#define MAX_LSO_MSS 2048
static __be16 mlx5e_ipsec_inverse_table[MAX_LSO_MSS];

static inline __be16 mlx5e_ipsec_mss_inv(struct sk_buff *skb)
{
	return mlx5e_ipsec_inverse_table[skb_shinfo(skb)->gso_size];
}