[X25]: Selective sub-address matching with call user data.

From: Shaun Pereira <[e-mail]>

This is the first (independent of the second) patch of two that I am
working on with x25 on linux (tested with xot on a cisco router). Details
are as follows.

Current state of module:

A server using the current implementation (2.6.11.7) of the x25 module will
accept a call request/ incoming call packet at the listening x.25 address,
from all callers to that address, as long as NO call user data is present
in the packet header.

If the server needs to choose to accept a particular call request/ incoming
call packet arriving at its listening x25 address, then the kernel has to
allow a match of call user data present in the call request packet with its
own. This is required when multiple servers listen at the same x25 address
and device interface. The kernel currently matches ALL call user data, if
present.

Current Changes:

This patch is a follow up to the patch submitted previously by Andrew
Hendry, and allows the user to selectively control the number of octets of
call user data in the call request packet, that the kernel will match. By
default no call user data is matched, even if call user data is present.
To allow call user data matching, a cudmatchlength > 0 has to be passed
into the kernel after which the passed number of octets will be matched.
Otherwise the kernel behavior is exactly as the original implementation.

This patch also ensures that as is normally the case, no call user data
will be present in the Call accepted / call connected packet sent back to
the caller

Future Changes on next patch:

There are cases however when call user data may be present in the call
accepted packet. According to the X.25 recommendation (ITU-T 10/96)
section 5.2.3.2 call user data may be present in the call accepted packet
provided the fast select facility is used. My next patch will include this
fast select utility and the ability to send up to 128 octets call user data
in the call accepted packet provided the fast select facility is used. I
am currently testing this, again with xot on linux and cisco.

Signed-off-by: Shaun Pereira <[e-mail]>

(With a fix from Alexey Dobriyan <[e-mail]>)
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/x25.h

···
  * 	History
  *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities 
  *					  negotiation.
+ *	apr/02/05	Shaun Pereira Selective sub address matching with
+ *					call user data
  */
 
 #ifndef	X25_KERNEL_H
···
 #define	SIOCX25GCALLUSERDATA	(SIOCPROTOPRIVATE + 4)
 #define	SIOCX25SCALLUSERDATA	(SIOCPROTOPRIVATE + 5)
 #define	SIOCX25GCAUSEDIAG	(SIOCPROTOPRIVATE + 6)
+#define SIOCX25SCUDMATCHLEN	(SIOCPROTOPRIVATE + 7)
 
 /*
  *	Values for {get,set}sockopt.
···
 struct x25_causediag {
 	unsigned char	cause;
 	unsigned char	diagnostic;
+};
+
+/*
+ *	Further optional call user data match length selection
+ */
+struct x25_subaddr {
+	unsigned int cudmatchlength;
 };
 
 #endif

include/net/x25.h

···
 	struct sock		sk;
 	struct x25_address	source_addr, dest_addr;
 	struct x25_neigh	*neighbour;
-	unsigned int		lci;
+	unsigned int		lci, cudmatchlength;
 	unsigned char		state, condition, qbitincl, intflag;
 	unsigned short		vs, vr, va, vl;
 	unsigned long		t2, t21, t22, t23;
···
 extern void x25_write_internal(struct sock *, int);
 extern int  x25_decode(struct sock *, struct sk_buff *, int *, int *, int *, int *, int *);
 extern void x25_disconnect(struct sock *, int, unsigned char, unsigned char);
-extern int x25_check_calluserdata(struct x25_calluserdata *,struct x25_calluserdata *);
 
 /* x25_timer.c */
 extern void x25_start_heartbeat(struct sock *);

net/x25/af_x25.c

···
  *	2000-11-14	Henner Eisen    Closing datalink from NETDEV_GOING_DOWN
  *	2002-10-06	Arnaldo C. Melo Get rid of cli/sti, move proc stuff to
  *					x25_proc.c, using seq_file
+ *	2005-04-02	Shaun Pereira	Selective sub address matching
+ *					with call user data
  */
 
 #include <linux/config.h>
···
  *	Note: if a listening socket has cud set it must only get calls
  *	with matching cud.
  */
-static struct sock *x25_find_listener(struct x25_address *addr, struct x25_calluserdata *calluserdata)
+static struct sock *x25_find_listener(struct x25_address *addr,
+					struct sk_buff *skb)
 {
 	struct sock *s;
 	struct sock *next_best;
···
 
 	sk_for_each(s, node, &x25_list)
 		if ((!strcmp(addr->x25_addr,
-			     x25_sk(s)->source_addr.x25_addr) ||
-		     !strcmp(addr->x25_addr,
-			     null_x25_address.x25_addr)) &&
-		     s->sk_state == TCP_LISTEN) {
-
+			x25_sk(s)->source_addr.x25_addr) ||
+				!strcmp(addr->x25_addr,
+					null_x25_address.x25_addr)) &&
+					s->sk_state == TCP_LISTEN) {
 			/*
 			 * Found a listening socket, now check the incoming
 			 * call user data vs this sockets call user data
 			 */
-			if (x25_check_calluserdata(&x25_sk(s)->calluserdata, calluserdata)) {
-				sock_hold(s);
-				goto found;
-			}
-			if (x25_sk(s)->calluserdata.cudlength == 0) {
+			if(skb->len > 0 && x25_sk(s)->cudmatchlength > 0) {
+			 	if((memcmp(x25_sk(s)->calluserdata.cuddata,
+			 		skb->data,
+					x25_sk(s)->cudmatchlength)) == 0) {
+					sock_hold(s);
+					goto found;
+				 }
+			} else
 				next_best = s;
-			}
 		}
 	if (next_best) {
 		s = next_best;
···
 	x25->t23   = sysctl_x25_clear_request_timeout;
 	x25->t2    = sysctl_x25_ack_holdback_timeout;
 	x25->state = X25_STATE_0;
+	x25->cudmatchlength = 0;
 
 	x25->facilities.winsize_in  = X25_DEFAULT_WINDOW_SIZE;
 	x25->facilities.winsize_out = X25_DEFAULT_WINDOW_SIZE;
···
 	x25->t2         = ox25->t2;
 	x25->facilities = ox25->facilities;
 	x25->qbitincl   = ox25->qbitincl;
+	x25->cudmatchlength = ox25->cudmatchlength;
 
 	x25_init_timers(sk);
 out:
···
 	struct x25_sock *makex25;
 	struct x25_address source_addr, dest_addr;
 	struct x25_facilities facilities;
-	struct x25_calluserdata calluserdata;
 	int len, rc;
 
 	/*
···
 	skb_pull(skb,len);
 
 	/*
-	 *	Incoming Call User Data.
-	 */
-	if (skb->len >= 0) {
-		memcpy(calluserdata.cuddata, skb->data, skb->len);
-		calluserdata.cudlength = skb->len;
-	}
-
-	skb_push(skb,len);
-
-	/*
 	 *	Find a listener for the particular address/cud pair.
 	 */
-	sk = x25_find_listener(&source_addr,&calluserdata);
+	sk = x25_find_listener(&source_addr,skb);
+	skb_push(skb,len);
 
 	/*
 	 *	We can't accept the Call Request.
···
 	makex25->neighbour     = nb;
 	makex25->facilities    = facilities;
 	makex25->vc_facil_mask = x25_sk(sk)->vc_facil_mask;
-	makex25->calluserdata  = calluserdata;
+	/* ensure no reverse facil on accept */
+	makex25->vc_facil_mask &= ~X25_MASK_REVERSE;
+	makex25->cudmatchlength = x25_sk(sk)->cudmatchlength;
 
 	x25_write_internal(make, X25_CALL_ACCEPTED);
 
 	makex25->state = X25_STATE_3;
+
+	/*
+	 *	Incoming Call User Data.
+	 */
+	if (skb->len >= 0) {
+		memcpy(makex25->calluserdata.cuddata, skb->data, skb->len);
+		makex25->calluserdata.cudlength = skb->len;
+	}
 
 	sk->sk_ack_backlog++;
 
···
 			causediag = x25->causediag;
 			rc = copy_to_user(argp, &causediag,
 					  sizeof(causediag)) ? -EFAULT : 0;
+			break;
+		}
+
+		case SIOCX25SCUDMATCHLEN: {
+			struct x25_subaddr sub_addr;
+			rc = -EINVAL;
+			if(sk->sk_state != TCP_CLOSE)
+				break;
+			rc = -EFAULT;
+			if (copy_from_user(&sub_addr, argp,
+					sizeof(sub_addr)))
+				break;
+		 	rc = -EINVAL;
+			if(sub_addr.cudmatchlength > X25_MAX_CUD_LEN)
+				break;
+			x25->cudmatchlength = sub_addr.cudmatchlength;
+			rc = 0;
 			break;
 		}
 

net/x25/x25_subr.c

···
 	}
 }
 
-/*
- * Compare 2 calluserdata structures, used to find correct listening sockets
- * when call user data is used.
- */
-int x25_check_calluserdata(struct x25_calluserdata *ours, struct x25_calluserdata *theirs)
-{
-	int i;
-	if (ours->cudlength != theirs->cudlength)
-		return 0;
-
-	for (i=0;i<ours->cudlength;i++) {
-		if (ours->cuddata[i] != theirs->cuddata[i]) {
-			return 0;
-		}
-	}
-	return 1;
-}
-