net: filter: add jited flag to indicate jit compiled filters

This patch adds a jited flag into sk_filter struct in order to indicate
whether a filter is currently jited or not. The size of sk_filter is
not being expanded as the 32 bit 'len' member allows upper bits to be
reused since a filter can currently only grow as large as BPF_MAXINSNS.

Therefore, there's enough room also for other in future needed flags to
reuse 'len' field if necessary. The jited flag also allows for having
alternative interpreter functions running as currently, we can only
detect jit compiled filters by testing fp->bpf_func to not equal the
address of sk_run_filter().

Joint work with Alexei Starovoitov.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index e568c8ef896b..e65e23087367 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -25,7 +25,8 @@ struct sock;
 struct sk_filter
 {
 	atomic_t		refcnt;
-	unsigned int         	len;	/* Number of filter blocks */
+	u32			jited:1,	/* Is our filter JIT'ed? */
+				len:31;		/* Number of filter blocks */
 	struct rcu_head		rcu;
 	unsigned int		(*bpf_func)(const struct sk_buff *skb,
 					    const struct sock_filter *filter);