sock_diag: add SK_MEMINFO_BACKLOG

Adding socket backlog len in INET_DIAG_SKMEMINFO is really useful to
diagnose various TCP problems.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/sock_diag.h

@@ -18,6 +18,7 @@ enum {
 	SK_MEMINFO_FWD_ALLOC,
 	SK_MEMINFO_WMEM_QUEUED,
 	SK_MEMINFO_OPTMEM,
+	SK_MEMINFO_BACKLOG,
 
 	SK_MEMINFO_VARS,
 };

net/core/sock_diag.c

@@ -46,6 +46,7 @@ int sock_diag_put_meminfo(struct sock *sk, struct sk_buff *skb, int attrtype)
 	mem[SK_MEMINFO_FWD_ALLOC] = sk->sk_forward_alloc;
 	mem[SK_MEMINFO_WMEM_QUEUED] = sk->sk_wmem_queued;
 	mem[SK_MEMINFO_OPTMEM] = atomic_read(&sk->sk_omem_alloc);
+	mem[SK_MEMINFO_BACKLOG] = sk->sk_backlog.len;
 
 	return 0;