tcp: move tcp_out_of_memory() to net/ipv4/tcp.c

tcp_out_of_memory() has a single caller: tcp_check_oom().

Following patch will also make sk_memory_allocated()
not anymore visible from <net/sock.h> and <net/tcp.h>

Add const qualifier to sock argument of tcp_out_of_memory()
and tcp_check_oom().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240429134025.1233626-4-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/tcp.h

@@ -296,14 +296,6 @@ static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
 	return seq3 - seq2 >= seq1 - seq2;
 }
 
-static inline bool tcp_out_of_memory(struct sock *sk)
-{
-	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
-	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
-		return true;
-	return false;
-}
-
 static inline void tcp_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
 {
 	sk_wmem_queued_add(sk, -skb->truesize);
@@ -316,7 +308,7 @@ static inline void tcp_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
 
 void sk_forced_mem_schedule(struct sock *sk, int size);
 
-bool tcp_check_oom(struct sock *sk, int shift);
+bool tcp_check_oom(const struct sock *sk, int shift);
 
 
 extern struct proto tcp_prot;

net/ipv4/tcp.c

@@ -2752,7 +2752,15 @@ static bool tcp_too_many_orphans(int shift)
 		READ_ONCE(sysctl_tcp_max_orphans);
 }
 
-bool tcp_check_oom(struct sock *sk, int shift)
+static bool tcp_out_of_memory(const struct sock *sk)
+{
+	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
+	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
+		return true;
+	return false;
+}
+
+bool tcp_check_oom(const struct sock *sk, int shift)
 {
 	bool too_many_orphans, out_of_socket_memory;