af_ipx.c

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				break;
		}
		s = s->next;
	}

	/* skb was solely for us, and we did not make a copy, so free it. */
	if (!copy)
		kfree_skb(skb);

	ret = 0;
out:	spin_unlock_bh(&intrfc->if_sklist_lock);
	return ret;
}
#else
static struct sock *ncp_connection_hack(ipx_interface *intrfc,
					struct ipxhdr *ipx)
{
	/* The packet's target is a NCP connection handler. We want to hand it
	 * to the correct socket directly within the kernel, so that the
	 * mars_nwe packet distribution process does not have to do it. Here we
	 * only care about NCP and BURST packets.
	 *
	 * You might call this a hack, but believe me, you do not want a
	 * complete NCP layer in the kernel, and this is VERY fast as well. */
	struct sock *sk = NULL;
 	int connection = 0;
	u8 *ncphdr = (u8 *)(ipx + 1);

 	if (*ncphdr == 0x22 && *(ncphdr + 1) == 0x22) /* NCP request */
		connection = (((int) *(ncphdr + 5)) << 8) | (int) *(ncphdr + 3);
	else if (*ncphdr == 0x77 && *(ncphdr + 1) == 0x77) /* BURST packet */
		connection = (((int) *(ncphdr + 9)) << 8) | (int) *(ncphdr + 8);

	if (connection) {
		/* Now we have to look for a special NCP connection handling
		 * socket. Only these sockets have ipx_ncp_conn != 0, set by
		 * SIOCIPXNCPCONN. */
		spin_lock_bh(&intrfc->if_sklist_lock);
		for (sk = intrfc->if_sklist;
		     sk && sk->protinfo.af_ipx.ipx_ncp_conn != connection;
		     sk = sk->next);
		if (sk)
			sock_hold(sk);
		spin_unlock_bh(&intrfc->if_sklist_lock);
	}
	return sk;
}

static int ipxitf_demux_socket(ipx_interface *intrfc, struct sk_buff *skb,
				int copy)
{
	struct ipxhdr *ipx = skb->nh.ipxh;
	struct sock *sock1 = NULL, *sock2 = NULL;
	struct sk_buff *skb1 = NULL, *skb2 = NULL;
	int ret;

	if (intrfc == ipx_primary_net && ntohs(ipx->ipx_dest.sock) == 0x451)
		sock1 = ncp_connection_hack(intrfc, ipx);
        if (!sock1)
		/* No special socket found, forward the packet the normal way */
		sock1 = ipxitf_find_socket(intrfc, ipx->ipx_dest.sock);

	/*
	 * We need to check if there is a primary net and if
	 * this is addressed to one of the *SPECIAL* sockets because
	 * these need to be propagated to the primary net.
	 * The *SPECIAL* socket list contains: 0x452(SAP), 0x453(RIP) and
	 * 0x456(Diagnostic).
	 */

	if (ipx_primary_net && intrfc != ipx_primary_net) {
		const int dsock = ntohs(ipx->ipx_dest.sock);

		if (dsock == 0x452 || dsock == 0x453 || dsock == 0x456)
			/* The appropriate thing to do here is to dup the
			 * packet and route to the primary net interface via
			 * ipxitf_send; however, we'll cheat and just demux it
			 * here. */
			sock2 = ipxitf_find_socket(ipx_primary_net,
							ipx->ipx_dest.sock);
	}

	/*
	 * If there is nothing to do return. The kfree will cancel any charging.
	 */
	if (!sock1 && !sock2) {
		if (!copy)
			kfree_skb(skb);
		return 0;
	}

	/*
	 * This next segment of code is a little awkward, but it sets it up
	 * so that the appropriate number of copies of the SKB are made and
	 * that skb1 and skb2 point to it (them) so that it (they) can be
	 * demuxed to sock1 and/or sock2.  If we are unable to make enough
	 * copies, we do as much as is possible.
	 */

	if (copy)
		skb1 = skb_clone(skb, GFP_ATOMIC);
	else
		skb1 = skb;

	ret = -ENOMEM;
	if (!skb1)
		goto out;

	/* Do we need 2 SKBs? */
	if (sock1 && sock2)
		skb2 = skb_clone(skb1, GFP_ATOMIC);
	else
		skb2 = skb1;

	if (sock1)
		ipxitf_def_skb_handler(sock1, skb1);

	ret = -ENOMEM;
	if (!skb2)
		goto out;

	if (sock2)
		ipxitf_def_skb_handler(sock2, skb2);

	ret = 0;
out:	if (sock1)
		sock_put(sock1);
	if (sock2)
		sock_put(sock2);
	return ret;
}
#endif	/* CONFIG_IPX_INTERN */

static struct sk_buff *ipxitf_adjust_skbuff(ipx_interface *intrfc,
					    struct sk_buff *skb)
{
	struct sk_buff *skb2;
	int in_offset = skb->h.raw - skb->head;
	int out_offset = intrfc->if_ipx_offset;
	int len;

	/* Hopefully, most cases */
	if (in_offset >= out_offset)
		return skb;

	/* Need new SKB */
	len  = skb->len + out_offset;
	skb2 = alloc_skb(len, GFP_ATOMIC);
	if (skb2) {
		skb_reserve(skb2, out_offset);
		skb2->nh.raw = skb2->h.raw = skb_put(skb2, skb->len);
		memcpy(skb2->h.raw, skb->h.raw, skb->len);
		memcpy(skb2->cb, skb->cb, sizeof(skb->cb));
	}
	kfree_skb(skb);
	return skb2;
}

/* caller must hold a reference to intrfc and the skb has to be unshared */

static int ipxitf_send(ipx_interface *intrfc, struct sk_buff *skb, char *node)
{
	struct ipxhdr *ipx = skb->nh.ipxh;
	struct net_device *dev = intrfc->if_dev;
	struct datalink_proto *dl = intrfc->if_dlink;
	char dest_node[IPX_NODE_LEN];
	int send_to_wire = 1;
	int addr_len;

	ipx->ipx_tctrl = IPX_SKB_CB(skb)->ipx_tctrl;
	ipx->ipx_dest.net = IPX_SKB_CB(skb)->ipx_dest_net;
	ipx->ipx_source.net = IPX_SKB_CB(skb)->ipx_source_net;

	/* see if we need to include the netnum in the route list */
	if (IPX_SKB_CB(skb)->last_hop.index >= 0) {
		u32 *last_hop = (u32 *)(((u8 *) skb->data) +
				sizeof(struct ipxhdr) +
				IPX_SKB_CB(skb)->last_hop.index *
				sizeof(u32));
		*last_hop = IPX_SKB_CB(skb)->last_hop.netnum;
		IPX_SKB_CB(skb)->last_hop.index = -1;
	}
	
	/* 
	 * We need to know how many skbuffs it will take to send out this
	 * packet to avoid unnecessary copies.
	 */
	 
	if (!dl || !dev || dev->flags & IFF_LOOPBACK) 
		send_to_wire = 0;	/* No non looped */

	/*
	 * See if this should be demuxed to sockets on this interface 
	 *
	 * We want to ensure the original was eaten or that we only use
	 * up clones.
	 */
	 
	if (ipx->ipx_dest.net == intrfc->if_netnum) {
		/*
		 * To our own node, loop and free the original.
		 * The internal net will receive on all node address.
		 */
		if (intrfc == ipx_internal_net ||
		    !memcmp(intrfc->if_node, node, IPX_NODE_LEN)) {
			/* Don't charge sender */
			skb_orphan(skb);

			/* Will charge receiver */
			return ipxitf_demux_socket(intrfc, skb, 0);
		}

		/* Broadcast, loop and possibly keep to send on. */
		if (!memcmp(ipx_broadcast_node, node, IPX_NODE_LEN)) {
			if (!send_to_wire)
				skb_orphan(skb);
			ipxitf_demux_socket(intrfc, skb, send_to_wire);
			if (!send_to_wire)
				goto out;
		}
	}

	/*
	 * If the originating net is not equal to our net; this is routed
	 * We are still charging the sender. Which is right - the driver
	 * free will handle this fairly.
	 */
	if (ipx->ipx_source.net != intrfc->if_netnum) {
		/*
		 * Unshare the buffer before modifying the count in
		 * case its a flood or tcpdump
		 */
		skb = skb_unshare(skb, GFP_ATOMIC);
		if (!skb)
			goto out;
		if (++ipx->ipx_tctrl > ipxcfg_max_hops)
			send_to_wire = 0;
	}

	if (!send_to_wire) {
		kfree_skb(skb);
		goto out;
	}

	/* Determine the appropriate hardware address */
	addr_len = dev->addr_len;
	if (!memcmp(ipx_broadcast_node, node, IPX_NODE_LEN))
		memcpy(dest_node, dev->broadcast, addr_len);
	else
		memcpy(dest_node, &(node[IPX_NODE_LEN-addr_len]), addr_len);

	/* Make any compensation for differing physical/data link size */
	skb = ipxitf_adjust_skbuff(intrfc, skb);
	if (!skb)
		goto out;

	/* set up data link and physical headers */
	skb->dev	= dev;
	skb->protocol	= __constant_htons(ETH_P_IPX);
	dl->datalink_header(dl, skb, dest_node);

	/* Send it out */
	dev_queue_xmit(skb);
out:	return 0;
}

static int ipxrtr_add_route(__u32, ipx_interface *, unsigned char *);

static int ipxitf_add_local_route(ipx_interface *intrfc)
{
	return ipxrtr_add_route(intrfc->if_netnum, intrfc, NULL);
}

static const char * ipx_frame_name(unsigned short);
static const char * ipx_device_name(ipx_interface *);
static void ipxitf_discover_netnum(ipx_interface *intrfc, struct sk_buff *skb);
static int ipxitf_pprop(ipx_interface *intrfc, struct sk_buff *skb);

static int ipxitf_rcv(ipx_interface *intrfc, struct sk_buff *skb)
{
	struct ipxhdr	*ipx = skb->nh.ipxh;
	int ret = 0;

	ipxitf_hold(intrfc);

	/* See if we should update our network number */
	if (!intrfc->if_netnum) /* net number of intrfc not known yet */
 		ipxitf_discover_netnum(intrfc, skb);
	
	IPX_SKB_CB(skb)->last_hop.index = -1;
	if (ipx->ipx_type == IPX_TYPE_PPROP) {
		ret = ipxitf_pprop(intrfc, skb);
		if (ret)
			goto out_free_skb;
	}

	/* local processing follows */
	if (!IPX_SKB_CB(skb)->ipx_dest_net)
		IPX_SKB_CB(skb)->ipx_dest_net = intrfc->if_netnum;
	if (!IPX_SKB_CB(skb)->ipx_source_net)
		IPX_SKB_CB(skb)->ipx_source_net = intrfc->if_netnum;

	/* it doesn't make sense to route a pprop packet, there's no meaning
	 * in the ipx_dest_net for such packets */
	if (ipx->ipx_type != IPX_TYPE_PPROP &&
	    intrfc->if_netnum != IPX_SKB_CB(skb)->ipx_dest_net) {
		/* We only route point-to-point packets. */
		if (skb->pkt_type == PACKET_HOST) {
			skb = skb_unshare(skb, GFP_ATOMIC);
			if (skb)
				ret = ipxrtr_route_skb(skb);
			goto out_intrfc;
		}

		goto out_free_skb;
	}

	/* see if we should keep it */
	if (!memcmp(ipx_broadcast_node, ipx->ipx_dest.node, IPX_NODE_LEN) ||
	    !memcmp(intrfc->if_node, ipx->ipx_dest.node, IPX_NODE_LEN)) {
		ret = ipxitf_demux_socket(intrfc, skb, 0);
		goto out_intrfc;
	}

	/* we couldn't pawn it off so unload it */
out_free_skb:
	kfree_skb(skb);
out_intrfc:
	ipxitf_put(intrfc);
	return ret;
}

static void ipxitf_discover_netnum(ipx_interface *intrfc, struct sk_buff *skb)
{ 
	const struct ipx_cb *cb = IPX_SKB_CB(skb);

	/* see if this is an intra packet: source_net == dest_net */
	if (cb->ipx_source_net == cb->ipx_dest_net && cb->ipx_source_net) {
		ipx_interface *i = ipxitf_find_using_net(cb->ipx_source_net);
		/* NB: NetWare servers lie about their hop count so we
		 * dropped the test based on it. This is the best way
		 * to determine this is a 0 hop count packet. */
		if (!i) {
			intrfc->if_netnum = cb->ipx_source_net;
			ipxitf_add_local_route(intrfc);
		} else {
			printk(KERN_WARNING "IPX: Network number collision "
				"%lx\n        %s %s and %s %s\n",
				(unsigned long) htonl(cb->ipx_source_net),
				ipx_device_name(i),
				ipx_frame_name(i->if_dlink_type),
				ipx_device_name(intrfc),
				ipx_frame_name(intrfc->if_dlink_type));
			ipxitf_put(i);
		}
	}
}

/**
 * ipxitf_pprop - Process packet propagation IPX packet type 0x14, used for
 * 		  NetBIOS broadcasts
 * @intrfc: IPX interface receiving this packet
 * @skb: Received packet
 *
 * Checks if packet is valid: if its more than %IPX_MAX_PPROP_HOPS hops or if it
 * is smaller than a IPX header + the room for %IPX_MAX_PPROP_HOPS hops we drop
 * it, not even processing it locally, if it has exact %IPX_MAX_PPROP_HOPS we
 * don't broadcast it, but process it locally. See chapter 5 of Novell's "IPX
 * RIP and SAP Router Specification", Part Number 107-000029-001.
 * 
 * If it is valid, check if we have pprop broadcasting enabled by the user,
 * if not, just return zero for local processing.
 *
 * If it is enabled check the packet and don't broadcast it if we have already
 * seen this packet.
 *
 * Broadcast: send it to the interfaces that aren't on the packet visited nets
 * array, just after the IPX header.
 *
 * Returns -EINVAL for invalid packets, so that the calling function drops
 * the packet without local processing. 0 if packet is to be locally processed.
 */
static int ipxitf_pprop(ipx_interface *intrfc, struct sk_buff *skb)
{
	struct ipxhdr *ipx = skb->nh.ipxh;
	int i, ret = -EINVAL;
	ipx_interface *ifcs;
	char *c;
	u32 *l;

	/* Illegal packet - too many hops or too short */
	/* We decide to throw it away: no broadcasting, no local processing.
	 * NetBIOS unaware implementations route them as normal packets -
	 * tctrl <= 15, any data payload... */
	if (IPX_SKB_CB(skb)->ipx_tctrl > IPX_MAX_PPROP_HOPS ||
	    ntohs(ipx->ipx_pktsize) < sizeof(struct ipxhdr) +
	    				IPX_MAX_PPROP_HOPS * sizeof(u32))
		goto out;
	/* are we broadcasting this damn thing? */
	ret = 0;
	if (!sysctl_ipx_pprop_broadcasting)
		goto out;
	/* We do broadcast packet on the IPX_MAX_PPROP_HOPS hop, but we
	 * process it locally. All previous hops broadcasted it, and process it
	 * locally. */
	if (IPX_SKB_CB(skb)->ipx_tctrl == IPX_MAX_PPROP_HOPS)
		goto out;
	
	c = ((u8 *) ipx) + sizeof(struct ipxhdr);
	l = (u32 *) c;

	/* Don't broadcast packet if already seen this net */
	for (i = 0; i < IPX_SKB_CB(skb)->ipx_tctrl; i++)
		if (*l++ == intrfc->if_netnum)
			goto out;

	/* < IPX_MAX_PPROP_HOPS hops && input interface not in list. Save the
	 * position where we will insert recvd netnum into list, later on,
	 * in ipxitf_send */
	IPX_SKB_CB(skb)->last_hop.index = i;
	IPX_SKB_CB(skb)->last_hop.netnum = intrfc->if_netnum;
	/* xmit on all other interfaces... */
	spin_lock_bh(&ipx_interfaces_lock);
	for (ifcs = ipx_interfaces; ifcs; ifcs = ifcs->if_next) {
		/* Except unconfigured interfaces */
		if (!ifcs->if_netnum)
			continue;
					
		/* That aren't in the list */
		if (ifcs == intrfc)
			continue;
		l = (__u32 *) c;
		/* don't consider the last entry in the packet list,
		 * it is our netnum, and it is not there yet */
		for (i = 0; i < IPX_SKB_CB(skb)->ipx_tctrl; i++)
			if (ifcs->if_netnum == *l++)
				break;
		if (i == IPX_SKB_CB(skb)->ipx_tctrl) {
			struct sk_buff *s = skb_copy(skb, GFP_ATOMIC);

			if (s) {
				IPX_SKB_CB(s)->ipx_dest_net = ifcs->if_netnum;
				ipxrtr_route_skb(s);
			}
		}
	}
	spin_unlock_bh(&ipx_interfaces_lock);
out:	return ret;
}

static void ipxitf_insert(ipx_interface *intrfc)
{
	intrfc->if_next = NULL;
	spin_lock_bh(&ipx_interfaces_lock);
	if (!ipx_interfaces)
		ipx_interfaces = intrfc;
	else {
		ipx_interface *i = ipx_interfaces;
		while (i->if_next)
			i = i->if_next;
		i->if_next = intrfc;
	}
	spin_unlock_bh(&ipx_interfaces_lock);

	if (ipxcfg_auto_select_primary && !ipx_primary_net)
		ipx_primary_net = intrfc;
}

static ipx_interface *ipxitf_alloc(struct net_device *dev, __u32 netnum,
				   unsigned short dlink_type,
				   struct datalink_proto *dlink,
				   unsigned char internal, int ipx_offset)
{
	ipx_interface *intrfc = kmalloc(sizeof(*intrfc), GFP_ATOMIC);

	if (intrfc) {
		intrfc->if_dev		= dev;
		intrfc->if_netnum	= netnum;
		intrfc->if_dlink_type 	= dlink_type;
		intrfc->if_dlink 	= dlink;
		intrfc->if_internal 	= internal;
		intrfc->if_ipx_offset 	= ipx_offset;
		intrfc->if_sknum 	= IPX_MIN_EPHEMERAL_SOCKET;
		intrfc->if_sklist 	= NULL;
		atomic_set(&intrfc->refcnt, 1);
		spin_lock_init(&intrfc->if_sklist_lock);
		MOD_INC_USE_COUNT;
	}

	return intrfc;
}

static int ipxitf_create_internal(ipx_interface_definition *idef)
{
	ipx_interface *intrfc;
	int ret = -EEXIST;

	/* Only one primary network allowed */
	if (ipx_primary_net)
		goto out;

	/* Must have a valid network number */
	ret = -EADDRNOTAVAIL;
	if (!idef->ipx_network)
		goto out;
	intrfc = ipxitf_find_using_net(idef->ipx_network);
	ret = -EADDRINUSE;
	if (intrfc) {
		ipxitf_put(intrfc);
		goto out;
	}
	intrfc = ipxitf_alloc(NULL, idef->ipx_network, 0, NULL, 1, 0);
	ret = -EAGAIN;