netlink: introduce NLA_POLICY_MAX_BE

netlink allows to specify allowed ranges for integer types.
Unfortunately, nfnetlink passes integers in big endian, so the existing
NLA_POLICY_MAX() cannot be used.

At the moment, nfnetlink users, such as nf_tables, need to resort to
programmatic checking via helpers such as nft_parse_u32_check().

This is both cumbersome and error prone.  This adds NLA_POLICY_MAX_BE
which adds range check support for BE16, BE32 and BE64 integers.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netlink.h

@@ -325,6 +325,7 @@ struct nla_policy {
  struct netlink_range_validation_signed *range_signed;
  struct {
  s16 min, max;
+ u8 network_byte_order:1;
  };
  int (*validate)(const struct nlattr *attr,
  struct netlink_ext_ack *extack);
@@ -418,6 +419,14 @@ struct nla_policy {
  .type = NLA_ENSURE_INT_OR_BINARY_TYPE(tp), \
  .validation_type = NLA_VALIDATE_MAX, \
  .max = _max, \
+ .network_byte_order = 0, \
+}
+
+#define NLA_POLICY_MAX_BE(tp, _max) { \
+ .type = NLA_ENSURE_UINT_TYPE(tp), \
+ .validation_type = NLA_VALIDATE_MAX, \
+ .max = _max, \
+ .network_byte_order = 1, \
 }
 
 #define NLA_POLICY_MASK(tp, _mask) { \

lib/nlattr.c

@@ -159,6 +159,31 @@ void nla_get_range_unsigned(const struct nla_policy *pt,
  }
 }
 
+static u64 nla_get_attr_bo(const struct nla_policy *pt,
+ const struct nlattr *nla)
+{
+ switch (pt->type) {
+ case NLA_U16:
+ if (pt->network_byte_order)
+ return ntohs(nla_get_be16(nla));
+
+ return nla_get_u16(nla);
+ case NLA_U32:
+ if (pt->network_byte_order)
+ return ntohl(nla_get_be32(nla));
+
+ return nla_get_u32(nla);
+ case NLA_U64:
+ if (pt->network_byte_order)
+ return be64_to_cpu(nla_get_be64(nla));
+
+ return nla_get_u64(nla);
+ }
+
+ WARN_ON_ONCE(1);
+ return 0;
+}
+
 static int nla_validate_range_unsigned(const struct nla_policy *pt,
  const struct nlattr *nla,
  struct netlink_ext_ack *extack,
@@ -172,12 +197,10 @@ static int nla_validate_range_unsigned(const struct nla_policy *pt,
  value = nla_get_u8(nla);
  break;
  case NLA_U16:
- value = nla_get_u16(nla);
- break;
  case NLA_U32:
- value = nla_get_u32(nla);
- break;
  case NLA_U64:
+ value = nla_get_attr_bo(pt, nla);
+ break;
  case NLA_MSECS:
  value = nla_get_u64(nla);
  break;