On Mon, Sep 05, 2016 at 10:36:57AM +0200, Laura Garcia Liebana wrote:
> Add support to pass through an offset to the hash value. With this
> feature, the sysadmin is able to generate a hash with a given
> offset value.
>
> Example:
>
> meta mark set jhash ip saddr mod 2 seed 0xabcd sum 100
>
> This option generates marks according to the source address from 100 to
> 101.
>
> Signed-off-by: Laura Garcia Liebana <nev...@gmail.com>
> ---
> include/uapi/linux/netfilter/nf_tables.h | 2 ++
> net/netfilter/nft_hash.c | 13 +++++++++++--
> 2 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/netfilter/nf_tables.h
> b/include/uapi/linux/netfilter/nf_tables.h
> index 4dbeeed..8026684 100644
> --- a/include/uapi/linux/netfilter/nf_tables.h
> +++ b/include/uapi/linux/netfilter/nf_tables.h
> @@ -764,6 +764,7 @@ enum nft_meta_keys {
> * @NFTA_HASH_LEN: source data length (NLA_U32)
> * @NFTA_HASH_MODULUS: modulus value (NLA_U32)
> * @NFTA_HASH_SEED: seed value (NLA_U32)
> + * @NFTA_HASH_SUM: Hash offset value (NLA_U32)
> */
> enum nft_hash_attributes {
> NFTA_HASH_UNSPEC,
> @@ -772,6 +773,7 @@ enum nft_hash_attributes {
> NFTA_HASH_LEN,
> NFTA_HASH_MODULUS,
> NFTA_HASH_SEED,
> + NFTA_HASH_SUM,
> __NFTA_HASH_MAX,
> };
> #define NFTA_HASH_MAX (__NFTA_HASH_MAX - 1)
> diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
> index b7e3b40..8ab04d9 100644
> --- a/net/netfilter/nft_hash.c
> +++ b/net/netfilter/nft_hash.c
> @@ -23,6 +23,7 @@ struct nft_hash {
> u8 len;
> u32 modulus;
> u32 seed;
> + u32 sum;
> };
>
> static void nft_hash_eval(const struct nft_expr *expr,
> @@ -35,7 +36,7 @@ static void nft_hash_eval(const struct nft_expr *expr,
>
> h = reciprocal_scale(jhash(data, priv->len, priv->seed), priv->modulus);
>
> - regs->data[priv->dreg] = h;
> + regs->data[priv->dreg] = priv->sum + h;
> }
>
> const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
> @@ -44,6 +45,7 @@ const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1]
> = {
> [NFTA_HASH_LEN] = { .type = NLA_U32 },
> [NFTA_HASH_MODULUS] = { .type = NLA_U32 },
> [NFTA_HASH_SEED] = { .type = NLA_U32 },
> + [NFTA_HASH_SUM] = { .type = NLA_U32 },
> };
>
> static int nft_hash_init(const struct nft_ctx *ctx,
> @@ -60,6 +62,11 @@ static int nft_hash_init(const struct nft_ctx *ctx,
> !tb[NFTA_HASH_MODULUS])
> return -EINVAL;
>
> + if (tb[NFTA_HASH_SUM])
> + priv->sum = ntohl(nla_get_be32(tb[NFTA_HASH_SUM]));
> + else
> + priv->sum = 0;
There is a corner case that we should reject from the kernel, I think
this is:
if (priv->sum + priv->modulus - 1 < priv->sum)
return -EOVERFLOW;
We'll handle this from userspace anyway too, but I think it's easy to
reject this crazy this.
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