[13/23] netfilter: nft_payload: add packet mangling support

diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h
index c6f400c..4ff5424 100644
--- a/include/net/netfilter/nf_tables_core.h
+++ b/include/net/netfilter/nf_tables_core.h
@@ -47,6 +47,15 @@  struct nft_payload {
 	enum nft_registers	dreg:8;
 };
 
+struct nft_payload_set {
+	enum nft_payload_bases	base:8;
+	u8			offset;
+	u8			len;
+	enum nft_registers	sreg:8;
+	u8			csum_type;
+	u8			csum_offset;
+};
+
 extern const struct nft_expr_ops nft_payload_fast_ops;
 
 int nft_payload_module_init(void);
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index d8c8a7c..5f3ecec 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -598,12 +598,26 @@  enum nft_payload_bases {
 };
 
 /**
+ * enum nft_payload_csum_types - nf_tables payload expression checksum types
+ *
+ * @NFT_PAYLOAD_CSUM_NONE: no checksumming
+ * @NFT_PAYLOAD_CSUM_INET: internet checksum (RFC 791)
+ */
+enum nft_payload_csum_types {
+	NFT_PAYLOAD_CSUM_NONE,
+	NFT_PAYLOAD_CSUM_INET,
+};
+
+/**
  * enum nft_payload_attributes - nf_tables payload expression netlink attributes
  *
  * @NFTA_PAYLOAD_DREG: destination register to load data into (NLA_U32: nft_registers)
  * @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_TYPE: checksum type (NLA_U32)
+ * @NFTA_PAYLOAD_CSUM_OFFSET: checksum offset relative to base (NLA_U32)
  */
 enum nft_payload_attributes {
 	NFTA_PAYLOAD_UNSPEC,
@@ -611,6 +625,9 @@  enum nft_payload_attributes {
 	NFTA_PAYLOAD_BASE,
 	NFTA_PAYLOAD_OFFSET,
 	NFTA_PAYLOAD_LEN,
+	NFTA_PAYLOAD_SREG,
+	NFTA_PAYLOAD_CSUM_TYPE,
+	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..12cd4bf 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -107,10 +107,13 @@  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_TYPE]	= { .type = NLA_U32 },
+	[NFTA_PAYLOAD_CSUM_OFFSET]	= { .type = NLA_U32 },
 };
 
 static int nft_payload_init(const struct nft_ctx *ctx,
@@ -160,6 +163,118 @@  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_set *priv = nft_expr_priv(expr);
+	struct sk_buff *skb = pkt->skb;
+	const u32 *src = &regs->data[priv->sreg];
+	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->csum_type == NFT_PAYLOAD_CSUM_INET &&
+	    (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;
+
+		if (!skb_make_writable(skb, csum_offset + sizeof(sum)) ||
+		    skb_store_bits(skb, csum_offset, &sum, sizeof(sum)) < 0)
+			goto err;
+	}
+
+	if (!skb_make_writable(skb, max(offset + priv->len, 0)) ||
+	    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_set *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->sreg        = nft_parse_register(tb[NFTA_PAYLOAD_SREG]);
+
+	if (tb[NFTA_PAYLOAD_CSUM_TYPE])
+		priv->csum_type =
+			ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_TYPE]));
+	if (tb[NFTA_PAYLOAD_CSUM_OFFSET])
+		priv->csum_offset =
+			ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_OFFSET]));
+
+	switch (priv->csum_type) {
+	case NFT_PAYLOAD_CSUM_NONE:
+	case NFT_PAYLOAD_CSUM_INET:
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return nft_validate_register_load(priv->sreg, priv->len);
+}
+
+static int nft_payload_set_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_payload_set *priv = nft_expr_priv(expr);
+
+	if (nft_dump_register(skb, NFTA_PAYLOAD_SREG, priv->sreg) ||
+	    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_TYPE, htonl(priv->csum_type)) ||
+	    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_set)),
+	.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 +282,7 @@  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 +297,15 @@  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]));