netfilter: nft_payload: extend offset to 65535 bytes

In some situations 255 bytes offset is not enough to match or manipulate
the desired packet field. Increase the offset limit to 65535 or U16_MAX.

In addition, the nla policy maximum value is not set anymore as it is
limited to s16. Instead, the maximum value is checked during the payload
expression initialization function.

Tested with the nft command line tool.

table ip filter {
chain output {
@nh,2040,8 set 0xff
@nh,524280,8 set 0xff
@nh,524280,8 0xff
@nh,2040,8 0xff
}
}

Signed-off-by: Fernando Fernandez Mancera <[e-mail]>
Signed-off-by: Florian Westphal <[e-mail]>

include/net/netfilter/nf_tables_core.h

···
 
 struct nft_payload {
 	enum nft_payload_bases	base:8;
-	u8			offset;
+	u16			offset;
 	u8			len;
 	u8			dreg;
 };

net/netfilter/nft_payload.c

···
 
 /* add vlan header into the user buffer for if tag was removed by offloads */
 static bool
-nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u8 offset, u8 len)
+nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u16 offset, u8 len)
 {
 	int mac_off = skb_mac_header(skb) - skb->data;
 	u8 *vlanh, *dst_u8 = (u8 *) d;
···
 	[NFTA_PAYLOAD_SREG]		= { .type = NLA_U32 },
 	[NFTA_PAYLOAD_DREG]		= { .type = NLA_U32 },
 	[NFTA_PAYLOAD_BASE]		= { .type = NLA_U32 },
-	[NFTA_PAYLOAD_OFFSET]		= NLA_POLICY_MAX(NLA_BE32, 255),
+	[NFTA_PAYLOAD_OFFSET]		= { .type = NLA_BE32 },
 	[NFTA_PAYLOAD_LEN]		= NLA_POLICY_MAX(NLA_BE32, 255),
 	[NFTA_PAYLOAD_CSUM_TYPE]	= { .type = NLA_U32 },
 	[NFTA_PAYLOAD_CSUM_OFFSET]	= NLA_POLICY_MAX(NLA_BE32, 255),
···
 
 struct nft_payload_set {
 	enum nft_payload_bases	base:8;
-	u8			offset;
+	u16			offset;
 	u8			len;
 	u8			sreg;
 	u8			csum_type;
···
 };
 
 static bool
-nft_payload_set_vlan(const u32 *src, struct sk_buff *skb, u8 offset, u8 len,
+nft_payload_set_vlan(const u32 *src, struct sk_buff *skb, u16 offset, u8 len,
 		     int *vlan_hlen)
 {
 	struct nft_payload_vlan_hdr *vlanh;
···
 				const struct nft_expr *expr,
 				const struct nlattr * const tb[])
 {
+	u32 csum_offset, offset, csum_type = NFT_PAYLOAD_CSUM_NONE;
 	struct nft_payload_set *priv = nft_expr_priv(expr);
-	u32 csum_offset, csum_type = NFT_PAYLOAD_CSUM_NONE;
 	int err;
 
 	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]));
+
+	err = nft_parse_u32_check(tb[NFTA_PAYLOAD_OFFSET], U16_MAX, &offset);
+	if (err < 0)
+		return err;
+	priv->offset = offset;
 
 	if (tb[NFTA_PAYLOAD_CSUM_TYPE])
 		csum_type = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_CSUM_TYPE]));
···
 	if (tb[NFTA_PAYLOAD_DREG] == NULL)
 		return ERR_PTR(-EINVAL);
 
-	err = nft_parse_u32_check(tb[NFTA_PAYLOAD_OFFSET], U8_MAX, &offset);
+	err = nft_parse_u32_check(tb[NFTA_PAYLOAD_OFFSET], U16_MAX, &offset);
 	if (err < 0)
 		return ERR_PTR(err);