X25: Enable setting of cause and diagnostic fields

Adds SIOCX25SCAUSEDIAG, allowing X.25 programs to set the cause and
diagnostic fields.

Normally used to indicate status upon closing connections.
Signed-off-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/x25.h

@@ -25,6 +25,7 @@
 #define SIOCX25SENDCALLACCPT    (SIOCPROTOPRIVATE + 9)
 #define SIOCX25GDTEFACILITIES (SIOCPROTOPRIVATE + 10)
 #define SIOCX25SDTEFACILITIES (SIOCPROTOPRIVATE + 11)
+#define SIOCX25SCAUSEDIAG	(SIOCPROTOPRIVATE + 12)
 
 /*
  *	Values for {get,set}sockopt.

net/x25/af_x25.c

@@ -1471,6 +1471,17 @@ static int x25_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 			break;
 		}
 
+		case SIOCX25SCAUSEDIAG: {
+			struct x25_causediag causediag;
+			rc = -EFAULT;
+			if (copy_from_user(&causediag, argp, sizeof(causediag)))
+				break;
+			x25->causediag = causediag;
+			rc = 0;
+			break;
+
+		}
+
 		case SIOCX25SCUDMATCHLEN: {
 			struct x25_subaddr sub_addr;
 			rc = -EINVAL;
@@ -1639,6 +1650,7 @@ static int compat_x25_ioctl(struct socket *sock, unsigned int cmd,
 	case SIOCX25GCALLUSERDATA:
 	case SIOCX25SCALLUSERDATA:
 	case SIOCX25GCAUSEDIAG:
+	case SIOCX25SCAUSEDIAG:
 	case SIOCX25SCUDMATCHLEN:
 	case SIOCX25CALLACCPTAPPRV:
 	case SIOCX25SENDCALLACCPT:

net/x25/x25_subr.c

@@ -225,6 +225,12 @@ void x25_write_internal(struct sock *sk, int frametype)
 			break;
 
 		case X25_CLEAR_REQUEST:
+			dptr    = skb_put(skb, 3);
+			*dptr++ = frametype;
+			*dptr++ = x25->causediag.cause;
+			*dptr++ = x25->causediag.diagnostic;
+			break;
+
 		case X25_RESET_REQUEST:
 			dptr    = skb_put(skb, 3);
 			*dptr++ = frametype;