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netfilter: nft_hash: Add hash offset value

PATCH Superseded Laura Garcia Liebana 2 participants 4 messages Sep 5, 2016

Subsystems (2)
Networking netfilter

v1 of 2 Superseded Latest is v2 →

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Laura Garcia Liebana

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#0 lore raw

PATCH 1/1 netfilter: nft_hash: Add hash offset value

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 <[email protected]>
---
 include/uapi/linux/netfilter/nf_tables.h |  2 ++
 net/netfilter/nft_hash.c                 | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)
include/uapi/linux/netfilter/nf_tables.h +2 -0
index 4dbeeed..8026684 100644
@@ -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)
net/netfilter/nft_hash.c +11 -2
index b7e3b40..8ab04d9 100644
@@ -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:
Signature · 1 line
2.8.1
maintainer
#1 lore raw
Quoted 67 lines · Laura Garcia Liebana

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 <[email protected]>
---
 include/uapi/linux/netfilter/nf_tables.h |  2 ++
 net/netfilter/nft_hash.c                 | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)
include/uapi/linux/netfilter/nf_tables.h +2 -0
index 4dbeeed..8026684 100644
@@ -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)
net/netfilter/nft_hash.c +3 -1
index b7e3b40..8ab04d9 100644
@@ -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,

net/netfilter/nft_hash.c static int nft_hash_init(const struct nft_ctx *ctx, · line 68

Quoted 7 lines
net/netfilter/nft_hash.c +4 -0
@@ -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.

author
#2 lore raw
Quoted 79 lines · Pablo Neira Ayuso
Quoted 67 lines · Laura Garcia Liebana

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 <[email protected]>
---
 include/uapi/linux/netfilter/nf_tables.h |  2 ++
 net/netfilter/nft_hash.c                 | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)
include/uapi/linux/netfilter/nf_tables.h +2 -0
index 4dbeeed..8026684 100644
@@ -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)
net/netfilter/nft_hash.c +3 -1
index b7e3b40..8ab04d9 100644
@@ -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,

net/netfilter/nft_hash.c static int nft_hash_init(const struct nft_ctx *ctx, · line 68

Quoted 7 lines
net/netfilter/nft_hash.c +4 -0
@@ -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:

Quoted 5 lines
        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;
maintainer
#3 lore raw
Quoted 86 lines · Laura Garcia
Quoted 79 lines · Pablo Neira Ayuso
Quoted 67 lines · Laura Garcia Liebana

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 <[email protected]>
---
 include/uapi/linux/netfilter/nf_tables.h |  2 ++
 net/netfilter/nft_hash.c                 | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)
include/uapi/linux/netfilter/nf_tables.h +2 -0
index 4dbeeed..8026684 100644
@@ -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)
net/netfilter/nft_hash.c +3 -1
index b7e3b40..8ab04d9 100644
@@ -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,

net/netfilter/nft_hash.c static int nft_hash_init(const struct nft_ctx *ctx, · line 68

Quoted 7 lines
net/netfilter/nft_hash.c +4 -0
@@ -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:

Quoted 5 lines
        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.

Quoted 6 lines

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.