bpf: Omit superfluous address family check in __bpf_skc_lookup

family is only set to either AF_INET or AF_INET6 based on len. In all
other cases we return early. Thus the check against AF_UNSPEC can be
omitted.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220630082618.15649-1-tklauser@distanz.ch

net/core/filter.c

@@ -6516,8 +6516,8 @@ __bpf_skc_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
 		 u64 flags)
 {
 	struct sock *sk = NULL;
-	u8 family = AF_UNSPEC;
 	struct net *net;
+	u8 family;
 	int sdif;
 
 	if (len == sizeof(tuple->ipv4))
@@ -6527,8 +6527,7 @@ __bpf_skc_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
 	else
 		return NULL;
 
-	if (unlikely(family == AF_UNSPEC || flags ||
-		     !((s32)netns_id < 0 || netns_id <= S32_MAX)))
+	if (unlikely(flags || !((s32)netns_id < 0 || netns_id <= S32_MAX)))
 		goto out;
 
 	if (family == AF_INET)