tcp: move ipv4_specific to tcp include file

Declare ipv4_specific once, in tcp.h were it belongs.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -907,6 +907,8 @@ static inline void tcp_skb_bpf_redirect_clear(struct sk_buff *skb)
 	TCP_SKB_CB(skb)->bpf.sk_redir = NULL;
 }
 
+extern const struct inet_connection_sock_af_ops ipv4_specific;
+
 #if IS_ENABLED(CONFIG_IPV6)
 /* This is the variant of inet6_iif() that must be used by TCP,
  * as TCP moves IP6CB into a different location in skb->cb[]

include/net/transp_v6.h

@@ -56,9 +56,6 @@ ip6_dgram_sock_seq_show(struct seq_file *seq, struct sock *sp, __u16 srcp,
 
 #define LOOPBACK4_IPV6 cpu_to_be32(0x7f000006)
 
-/* address family specific functions */
-extern const struct inet_connection_sock_af_ops ipv4_specific;
-
 void inet6_destroy_sock(struct sock *sk);
 
 #define IPV6_SEQ_DGRAM_HEADER					       \

net/mptcp/protocol.h

@@ -354,8 +354,6 @@ static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
 	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
 }
 
-extern const struct inet_connection_sock_af_ops ipv4_specific;
-
 void mptcp_proto_init(void);
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 int mptcp_proto_v6_init(void);