inet_diag: Move the INET_DIAG_REQ_BYTECODE nlattr to cb->data

The INET_DIAG_REQ_BYTECODE nlattr is currently re-found every time when
the "dump()" is re-started.

In a latter patch, it will also need to parse the new
INET_DIAG_REQ_SK_BPF_STORAGES nlattr to learn the map_fds. Thus, this
patch takes this chance to store the parsed nlattr in cb->data
during the "start" time of a dump.

By doing this, the "bc" argument also becomes unnecessary
and is removed.  Also, the two copies of the INET_DIAG_REQ_BYTECODE
parsing-audit logic between compat/current version can be
consolidated to one.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200225230415.1975555-1-kafai@fb.com
diff --git a/net/ipv4/raw_diag.c b/net/ipv4/raw_diag.c
index a2933ee..d19cce3 100644
--- a/net/ipv4/raw_diag.c
+++ b/net/ipv4/raw_diag.c
@@ -138,17 +138,21 @@ static int sk_diag_dump(struct sock *sk, struct sk_buff *skb,
 }
 
 static void raw_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
-			  const struct inet_diag_req_v2 *r, struct nlattr *bc)
+			  const struct inet_diag_req_v2 *r)
 {
 	bool net_admin = netlink_net_capable(cb->skb, CAP_NET_ADMIN);
 	struct raw_hashinfo *hashinfo = raw_get_hashinfo(r);
 	struct net *net = sock_net(skb->sk);
+	struct inet_diag_dump_data *cb_data;
 	int num, s_num, slot, s_slot;
 	struct sock *sk = NULL;
+	struct nlattr *bc;
 
 	if (IS_ERR(hashinfo))
 		return;
 
+	cb_data = cb->data;
+	bc = cb_data->inet_diag_nla_bc;
 	s_slot = cb->args[0];
 	num = s_num = cb->args[1];