netfilter: nft_hash: Add hash offset value
diff mbox

Message ID 20160905083655.GA15395@sonyv
State Changes Requested
Delegated to: Pablo Neira
Headers show

Commit Message

Laura Garcia Liebana Sept. 5, 2016, 8:36 a.m. UTC
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 <nevola@gmail.com>
---
 include/uapi/linux/netfilter/nf_tables.h |  2 ++
 net/netfilter/nft_hash.c                 | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

Comments

Pablo Neira Ayuso Sept. 5, 2016, 9:10 a.m. UTC | #1
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 <nevola@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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Laura Garcia Liebana Sept. 5, 2016, 9:58 a.m. UTC | #2
On Mon, Sep 05, 2016 at 11:10:28AM +0200, Pablo Neira Ayuso wrote:
> 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 <nevola@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.

Such case shouldn't happen cause the modulus must be > 1. The init()
provides:

        priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
        if (priv->modulus <= 1)
                return -ERANGE;


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Pablo Neira Ayuso Sept. 5, 2016, 10:09 a.m. UTC | #3
On Mon, Sep 05, 2016 at 11:58:24AM +0200, Laura Garcia wrote:
> On Mon, Sep 05, 2016 at 11:10:28AM +0200, Pablo Neira Ayuso wrote:
> > 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 <nevola@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.
> 
> Such case shouldn't happen cause the modulus must be > 1. The init()
> provides:
> 
>         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
>         if (priv->modulus <= 1)
>                 return -ERANGE;

I don't see how this is preventing an overflow of hash(x) + sum.
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Patch
diff mbox

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;
+
 	priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
 	if (priv->sreg < 0)
 		return -ERANGE;
@@ -99,7 +106,9 @@  static int nft_hash_dump(struct sk_buff *skb,
 		goto nla_put_failure;
 	if (nft_dump_register(skb, NFTA_HASH_SEED, priv->seed))
 		goto nla_put_failure;
-
+	if (priv->sum != 0)
+		if (nft_dump_register(skb, NFTA_HASH_SUM, priv->sum))
+			goto nla_put_failure;
 	return 0;
 
 nla_put_failure: