unix_diag: Report memory usage info

index 3f7afb0..d62e562 100644
@@ -16,6 +16,7 @@ struct unix_diag_req {
 #define UDIAG_SHOW_PEER		0x00000004	/* show peer socket info */
 #define UDIAG_SHOW_ICONS	0x00000008	/* show pending connections */
 #define UDIAG_SHOW_RQLEN	0x00000010	/* show skb receive queue len */
+#define UDIAG_SHOW_MEMINFO	0x00000020
 
 struct unix_diag_msg {
 	__u8	udiag_family;

@@ -33,6 +34,7 @@ enum {
 	UNIX_DIAG_PEER,
 	UNIX_DIAG_ICONS,
 	UNIX_DIAG_RQLEN,
+	UNIX_DIAG_MEMINFO,
 
 	UNIX_DIAG_MAX,
 };

@@ -42,4 +44,9 @@ struct unix_diag_vfs {
 	__u32	udiag_vfs_dev;
 };
 
+struct unix_diag_meminfo {
+	__u32	udiag_len;
+	__u32	udiag_limit;
+};
+
 #endif

index c5bdbcb..dbae8a4 100644
@@ -108,6 +108,20 @@ rtattr_failure:
 	return -EMSGSIZE;
 }
 
+static int sk_diag_show_meminfo(struct sock *sk, struct sk_buff *nlskb)
+{
+	struct unix_diag_meminfo *mi;
+
+	mi = UNIX_DIAG_PUT(nlskb, UNIX_DIAG_MEMINFO, sizeof(*mi));
+	mi->udiag_len = sk_wmem_alloc_get(sk);
+	mi->udiag_limit = sk->sk_sndbuf;
+
+	return 0;
+
+rtattr_failure:
+	return -EMSGSIZE;
+}
+
 static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req,
 		u32 pid, u32 seq, u32 flags, int sk_ino)
 {

@@ -146,6 +160,10 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r
 			sk_diag_show_rqlen(sk, skb))
 		goto nlmsg_failure;
 
+	if ((req->udiag_show & UDIAG_SHOW_MEMINFO) &&
+			sk_diag_show_meminfo(sk, skb))
+		goto nlmsg_failure;
+
 	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 	return skb->len;