diff mbox

[RFC,nf-next,1/1] netfilter: nft_payload: add packet mangling support

Message ID 1447078234-21628-2-git-send-email-kaber@trash.net
State Changes Requested
Delegated to: Pablo Neira
Headers show

Commit Message

Patrick McHardy Nov. 9, 2015, 2:10 p.m. UTC 
Add support for mangling packet payload. Checksum for the specified
base header is updated automatically, however no double updates (for
pseudo headers) are supported, meaning no stateless NAT is supported.

Signed-off-by: Patrick McHardy <kaber@trash.net>
---
 include/net/netfilter/nf_tables_core.h   |   1 +
 include/uapi/linux/netfilter/nf_tables.h |   4 ++
 net/netfilter/nft_payload.c              | 116 +++++++++++++++++++++++++++++--
 3 files changed, 115 insertions(+), 6 deletions(-)

Comments

Pablo Neira Ayuso Nov. 23, 2015, 12:31 p.m. UTC | #1 
On Mon, Nov 09, 2015 at 02:10:34PM +0000, Patrick McHardy wrote:
> Add support for mangling packet payload. Checksum for the specified
> base header is updated automatically, however no double updates (for
> pseudo headers) are supported, meaning no stateless NAT is supported.

Patrick, if you have no concerns, I'll pass this to David in the next
batch.

Thanks.
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Patrick McHardy Nov. 23, 2015, 12:45 p.m. UTC | #2 
On 23.11, Pablo Neira Ayuso wrote:
> On Mon, Nov 09, 2015 at 02:10:34PM +0000, Patrick McHardy wrote:
> > Add support for mangling packet payload. Checksum for the specified
> > base header is updated automatically, however no double updates (for
> > pseudo headers) are supported, meaning no stateless NAT is supported.
> 
> Patrick, if you have no concerns, I'll pass this to David in the next
> batch.

It needs a minor fix to work with link layer headers. I'll try to get it
ready tonight.
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diff mbox

Patch

diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h
index c6f400c..6d7a793 100644
--- a/include/net/netfilter/nf_tables_core.h
+++ b/include/net/netfilter/nf_tables_core.h
@@ -45,6 +45,7 @@  struct nft_payload {
 	u8			offset;
 	u8			len;
 	enum nft_registers	dreg:8;
+	u8			csum_offset;
 };
 
 extern const struct nft_expr_ops nft_payload_fast_ops;
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index d8c8a7c..56e1706 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -604,6 +604,8 @@  enum nft_payload_bases {
  * @NFTA_PAYLOAD_BASE: payload base (NLA_U32: nft_payload_bases)
  * @NFTA_PAYLOAD_OFFSET: payload offset relative to base (NLA_U32)
  * @NFTA_PAYLOAD_LEN: payload length (NLA_U32)
+ * @NFTA_PAYLOAD_SREG: source register to load data from (NLA_U32: nft_registers)
+ * @NFTA_PAYLOAD_CSUM_OFFSET: checksum offset relative to base (NLA_U32)
  */
 enum nft_payload_attributes {
 	NFTA_PAYLOAD_UNSPEC,
@@ -611,6 +613,8 @@  enum nft_payload_attributes {
 	NFTA_PAYLOAD_BASE,
 	NFTA_PAYLOAD_OFFSET,
 	NFTA_PAYLOAD_LEN,
+	NFTA_PAYLOAD_SREG,
+	NFTA_PAYLOAD_CSUM_OFFSET,
 	__NFTA_PAYLOAD_MAX
 };
 #define NFTA_PAYLOAD_MAX	(__NFTA_PAYLOAD_MAX - 1)
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 09b4b07..d04a31c 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -107,10 +107,12 @@  err:
 }
 
 static const struct nla_policy nft_payload_policy[NFTA_PAYLOAD_MAX + 1] = {
-	[NFTA_PAYLOAD_DREG]	= { .type = NLA_U32 },
-	[NFTA_PAYLOAD_BASE]	= { .type = NLA_U32 },
-	[NFTA_PAYLOAD_OFFSET]	= { .type = NLA_U32 },
-	[NFTA_PAYLOAD_LEN]	= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_SREG]		= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_DREG]		= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_BASE]		= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_OFFSET]		= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_LEN]		= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_CSUM_OFFSET]	= { .type = NLA_U32 },
 };
 
 static int nft_payload_init(const struct nft_ctx *ctx,
@@ -160,6 +162,100 @@  const struct nft_expr_ops nft_payload_fast_ops = {
 	.dump		= nft_payload_dump,
 };
 
+static void nft_payload_set_eval(const struct nft_expr *expr,
+				 struct nft_regs *regs,
+				 const struct nft_pktinfo *pkt)
+{
+	const struct nft_payload *priv = nft_expr_priv(expr);
+	struct sk_buff *skb = pkt->skb;
+	const u32 *src = &regs->data[priv->dreg];
+	int offset, csum_offset;
+	__wsum fsum, tsum;
+	__sum16 sum;
+
+	switch (priv->base) {
+	case NFT_PAYLOAD_LL_HEADER:
+		if (!skb_mac_header_was_set(skb))
+			goto err;
+		offset = skb_mac_header(skb) - skb->data;
+		break;
+	case NFT_PAYLOAD_NETWORK_HEADER:
+		offset = skb_network_offset(skb);
+		break;
+	case NFT_PAYLOAD_TRANSPORT_HEADER:
+		offset = pkt->xt.thoff;
+		break;
+	default:
+		BUG();
+	}
+
+	csum_offset = offset + priv->csum_offset;
+	offset += priv->offset;
+
+	if (priv->base != NFT_PAYLOAD_TRANSPORT_HEADER ||
+	    skb->ip_summed != CHECKSUM_PARTIAL) {
+		if (skb_copy_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
+			goto err;
+
+		fsum = skb_checksum(skb, offset, priv->len, 0);
+		tsum = csum_partial(src, priv->len, 0);
+		sum = csum_fold(csum_add(csum_sub(~csum_unfold(sum), fsum),
+					 tsum));
+		if (sum == 0)
+			sum = CSUM_MANGLED_0;
+
+		skb_store_bits(skb, csum_offset, &sum, sizeof(sum));
+	}
+
+	if (!skb_make_writable(skb, offset + priv->len) ||
+	    skb_store_bits(skb, offset, src, priv->len) < 0)
+		goto err;
+
+	return;
+err:
+	regs->verdict.code = NFT_BREAK;
+}
+
+
+static int nft_payload_set_init(const struct nft_ctx *ctx,
+				const struct nft_expr *expr,
+				const struct nlattr * const tb[])
+{
+	struct nft_payload *priv = nft_expr_priv(expr);
+
+	priv->base        = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
+	priv->offset      = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
+	priv->len         = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
+	priv->csum_offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_OFFSET]));
+	priv->dreg        = nft_parse_register(tb[NFTA_PAYLOAD_SREG]);
+
+	return nft_validate_register_load(priv->dreg, priv->len);
+}
+
+static int nft_payload_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_payload *priv = nft_expr_priv(expr);
+
+	if (nft_dump_register(skb, NFTA_PAYLOAD_SREG, priv->dreg) ||
+	    nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
+	    nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
+	    nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)) ||
+	    nla_put_be32(skb, NFTA_PAYLOAD_CSUM_OFFSET, htonl(priv->csum_offset)))
+		goto nla_put_failure;
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static const struct nft_expr_ops nft_payload_set_ops = {
+	.type		= &nft_payload_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_payload)),
+	.eval		= nft_payload_set_eval,
+	.init		= nft_payload_set_init,
+	.dump		= nft_payload_set_dump,
+};
+
 static const struct nft_expr_ops *
 nft_payload_select_ops(const struct nft_ctx *ctx,
 		       const struct nlattr * const tb[])
@@ -167,8 +263,7 @@  nft_payload_select_ops(const struct nft_ctx *ctx,
 	enum nft_payload_bases base;
 	unsigned int offset, len;
 
-	if (tb[NFTA_PAYLOAD_DREG] == NULL ||
-	    tb[NFTA_PAYLOAD_BASE] == NULL ||
+	if (tb[NFTA_PAYLOAD_BASE] == NULL ||
 	    tb[NFTA_PAYLOAD_OFFSET] == NULL ||
 	    tb[NFTA_PAYLOAD_LEN] == NULL)
 		return ERR_PTR(-EINVAL);
@@ -183,6 +278,15 @@  nft_payload_select_ops(const struct nft_ctx *ctx,
 		return ERR_PTR(-EOPNOTSUPP);
 	}
 
+	if (tb[NFTA_PAYLOAD_SREG] != NULL) {
+		if (tb[NFTA_PAYLOAD_DREG] != NULL)
+			return ERR_PTR(-EINVAL);
+		return &nft_payload_set_ops;
+	}
+
+	if (tb[NFTA_PAYLOAD_DREG] == NULL)
+		return ERR_PTR(-EINVAL);
+
 	offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 	len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));