ddp.c

linux 内核源代码

			sum = atalk_sum_partial(vaddr + frag->page_offset +
						  offset - start, copy, sum);
			kunmap_skb_frag(vaddr);

			if (!(len -= copy))
				return sum;
			offset += copy;
		}
		start = end;
	}

	if (skb_shinfo(skb)->frag_list) {
		struct sk_buff *list = skb_shinfo(skb)->frag_list;

		for (; list; list = list->next) {
			int end;

			BUG_TRAP(start <= offset + len);

			end = start + list->len;
			if ((copy = end - offset) > 0) {
				if (copy > len)
					copy = len;
				sum = atalk_sum_skb(list, offset - start,
						    copy, sum);
				if ((len -= copy) == 0)
					return sum;
				offset += copy;
			}
			start = end;
		}
	}

	BUG_ON(len > 0);

	return sum;
}

static __be16 atalk_checksum(const struct sk_buff *skb, int len)
{
	unsigned long sum;

	/* skip header 4 bytes */
	sum = atalk_sum_skb(skb, 4, len-4, 0);

	/* Use 0xFFFF for 0. 0 itself means none */
	return sum ? htons((unsigned short)sum) : htons(0xFFFF);
}

static struct proto ddp_proto = {
	.name	  = "DDP",
	.owner	  = THIS_MODULE,
	.obj_size = sizeof(struct atalk_sock),
};

/*
 * Create a socket. Initialise the socket, blank the addresses
 * set the state.
 */
static int atalk_create(struct net *net, struct socket *sock, int protocol)
{
	struct sock *sk;
	int rc = -ESOCKTNOSUPPORT;

	if (net != &init_net)
		return -EAFNOSUPPORT;

	/*
	 * We permit SOCK_DGRAM and RAW is an extension. It is trivial to do
	 * and gives you the full ELAP frame. Should be handy for CAP 8)
	 */
	if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
		goto out;
	rc = -ENOMEM;
	sk = sk_alloc(net, PF_APPLETALK, GFP_KERNEL, &ddp_proto);
	if (!sk)
		goto out;
	rc = 0;
	sock->ops = &atalk_dgram_ops;
	sock_init_data(sock, sk);

	/* Checksums on by default */
	sock_set_flag(sk, SOCK_ZAPPED);
out:
	return rc;
}

/* Free a socket. No work needed */
static int atalk_release(struct socket *sock)
{
	struct sock *sk = sock->sk;

	if (sk) {
		sock_orphan(sk);
		sock->sk = NULL;
		atalk_destroy_socket(sk);
	}
	return 0;
}

/**
 * atalk_pick_and_bind_port - Pick a source port when one is not given
 * @sk - socket to insert into the tables
 * @sat - address to search for
 *
 * Pick a source port when one is not given. If we can find a suitable free
 * one, we insert the socket into the tables using it.
 *
 * This whole operation must be atomic.
 */
static int atalk_pick_and_bind_port(struct sock *sk, struct sockaddr_at *sat)
{
	int retval;

	write_lock_bh(&atalk_sockets_lock);

	for (sat->sat_port = ATPORT_RESERVED;
	     sat->sat_port < ATPORT_LAST;
	     sat->sat_port++) {
		struct sock *s;
		struct hlist_node *node;

		sk_for_each(s, node, &atalk_sockets) {
			struct atalk_sock *at = at_sk(s);

			if (at->src_net == sat->sat_addr.s_net &&
			    at->src_node == sat->sat_addr.s_node &&
			    at->src_port == sat->sat_port)
				goto try_next_port;
		}

		/* Wheee, it's free, assign and insert. */
		__atalk_insert_socket(sk);
		at_sk(sk)->src_port = sat->sat_port;
		retval = 0;
		goto out;

try_next_port:;
	}

	retval = -EBUSY;
out:
	write_unlock_bh(&atalk_sockets_lock);
	return retval;
}

static int atalk_autobind(struct sock *sk)
{
	struct atalk_sock *at = at_sk(sk);
	struct sockaddr_at sat;
	struct atalk_addr *ap = atalk_find_primary();
	int n = -EADDRNOTAVAIL;

	if (!ap || ap->s_net == htons(ATADDR_ANYNET))
		goto out;

	at->src_net  = sat.sat_addr.s_net  = ap->s_net;
	at->src_node = sat.sat_addr.s_node = ap->s_node;

	n = atalk_pick_and_bind_port(sk, &sat);
	if (!n)
		sock_reset_flag(sk, SOCK_ZAPPED);
out:
	return n;
}

/* Set the address 'our end' of the connection */
static int atalk_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
	struct sockaddr_at *addr = (struct sockaddr_at *)uaddr;
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);

	if (!sock_flag(sk, SOCK_ZAPPED) ||
	    addr_len != sizeof(struct sockaddr_at))
		return -EINVAL;

	if (addr->sat_family != AF_APPLETALK)
		return -EAFNOSUPPORT;

	if (addr->sat_addr.s_net == htons(ATADDR_ANYNET)) {
		struct atalk_addr *ap = atalk_find_primary();

		if (!ap)
			return -EADDRNOTAVAIL;

		at->src_net  = addr->sat_addr.s_net = ap->s_net;
		at->src_node = addr->sat_addr.s_node= ap->s_node;
	} else {
		if (!atalk_find_interface(addr->sat_addr.s_net,
					  addr->sat_addr.s_node))
			return -EADDRNOTAVAIL;

		at->src_net  = addr->sat_addr.s_net;
		at->src_node = addr->sat_addr.s_node;
	}

	if (addr->sat_port == ATADDR_ANYPORT) {
		int n = atalk_pick_and_bind_port(sk, addr);

		if (n < 0)
			return n;
	} else {
		at->src_port = addr->sat_port;

		if (atalk_find_or_insert_socket(sk, addr))
			return -EADDRINUSE;
	}

	sock_reset_flag(sk, SOCK_ZAPPED);
	return 0;
}

/* Set the address we talk to */
static int atalk_connect(struct socket *sock, struct sockaddr *uaddr,
			 int addr_len, int flags)
{
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);
	struct sockaddr_at *addr;

	sk->sk_state   = TCP_CLOSE;
	sock->state = SS_UNCONNECTED;

	if (addr_len != sizeof(*addr))
		return -EINVAL;

	addr = (struct sockaddr_at *)uaddr;

	if (addr->sat_family != AF_APPLETALK)
		return -EAFNOSUPPORT;

	if (addr->sat_addr.s_node == ATADDR_BCAST &&
	    !sock_flag(sk, SOCK_BROADCAST)) {
#if 1
		printk(KERN_WARNING "%s is broken and did not set "
				    "SO_BROADCAST. It will break when 2.2 is "
				    "released.\n",
			current->comm);
#else
		return -EACCES;
#endif
	}

	if (sock_flag(sk, SOCK_ZAPPED))
		if (atalk_autobind(sk) < 0)
			return -EBUSY;

	if (!atrtr_get_dev(&addr->sat_addr))
		return -ENETUNREACH;

	at->dest_port = addr->sat_port;
	at->dest_net  = addr->sat_addr.s_net;
	at->dest_node = addr->sat_addr.s_node;

	sock->state  = SS_CONNECTED;
	sk->sk_state = TCP_ESTABLISHED;
	return 0;
}

/*
 * Find the name of an AppleTalk socket. Just copy the right
 * fields into the sockaddr.
 */
static int atalk_getname(struct socket *sock, struct sockaddr *uaddr,
			 int *uaddr_len, int peer)
{
	struct sockaddr_at sat;
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);

	if (sock_flag(sk, SOCK_ZAPPED))
		if (atalk_autobind(sk) < 0)
			return -ENOBUFS;

	*uaddr_len = sizeof(struct sockaddr_at);

	if (peer) {
		if (sk->sk_state != TCP_ESTABLISHED)
			return -ENOTCONN;

		sat.sat_addr.s_net  = at->dest_net;
		sat.sat_addr.s_node = at->dest_node;
		sat.sat_port	    = at->dest_port;
	} else {
		sat.sat_addr.s_net  = at->src_net;
		sat.sat_addr.s_node = at->src_node;
		sat.sat_port	    = at->src_port;
	}

	sat.sat_family = AF_APPLETALK;
	memcpy(uaddr, &sat, sizeof(sat));
	return 0;
}

#if defined(CONFIG_IPDDP) || defined(CONFIG_IPDDP_MODULE)
static __inline__ int is_ip_over_ddp(struct sk_buff *skb)
{
	return skb->data[12] == 22;
}

static int handle_ip_over_ddp(struct sk_buff *skb)
{
	struct net_device *dev = __dev_get_by_name(&init_net, "ipddp0");
	struct net_device_stats *stats;

	/* This needs to be able to handle ipddp"N" devices */
	if (!dev)
		return -ENODEV;

	skb->protocol = htons(ETH_P_IP);
	skb_pull(skb, 13);
	skb->dev   = dev;
	skb_reset_transport_header(skb);

	stats = dev->priv;
	stats->rx_packets++;
	stats->rx_bytes += skb->len + 13;
	netif_rx(skb);  /* Send the SKB up to a higher place. */
	return 0;
}
#else
/* make it easy for gcc to optimize this test out, i.e. kill the code */
#define is_ip_over_ddp(skb) 0
#define handle_ip_over_ddp(skb) 0
#endif

static void atalk_route_packet(struct sk_buff *skb, struct net_device *dev,
			       struct ddpehdr *ddp, __u16 len_hops,
			       int origlen)
{
	struct atalk_route *rt;
	struct atalk_addr ta;

	/*
	 * Don't route multicast, etc., packets, or packets sent to "this
	 * network"
	 */
	if (skb->pkt_type != PACKET_HOST || !ddp->deh_dnet) {
		/*
		 * FIXME:
		 *
		 * Can it ever happen that a packet is from a PPP iface and
		 * needs to be broadcast onto the default network?
		 */
		if (dev->type == ARPHRD_PPP)
			printk(KERN_DEBUG "AppleTalk: didn't forward broadcast "
					  "packet received from PPP iface\n");
		goto free_it;
	}

	ta.s_net  = ddp->deh_dnet;
	ta.s_node = ddp->deh_dnode;

	/* Route the packet */
	rt = atrtr_find(&ta);
	/* increment hops count */
	len_hops += 1 << 10;
	if (!rt || !(len_hops & (15 << 10)))
		goto free_it;

	/* FIXME: use skb->cb to be able to use shared skbs */

	/*
	 * Route goes through another gateway, so set the target to the
	 * gateway instead.
	 */

	if (rt->flags & RTF_GATEWAY) {
		ta.s_net  = rt->gateway.s_net;
		ta.s_node = rt->gateway.s_node;
	}

	/* Fix up skb->len field */
	skb_trim(skb, min_t(unsigned int, origlen,
			    (rt->dev->hard_header_len +
			     ddp_dl->header_length + (len_hops & 1023))));

	/* FIXME: use skb->cb to be able to use shared skbs */
	ddp->deh_len_hops = htons(len_hops);

	/*
	 * Send the buffer onwards
	 *
	 * Now we must always be careful. If it's come from LocalTalk to
	 * EtherTalk it might not fit
	 *
	 * Order matters here: If a packet has to be copied to make a new
	 * headroom (rare hopefully) then it won't need unsharing.
	 *
	 * Note. ddp-> becomes invalid at the realloc.
	 */
	if (skb_headroom(skb) < 22) {
		/* 22 bytes - 12 ether, 2 len, 3 802.2 5 snap */
		struct sk_buff *nskb = skb_realloc_headroom(skb, 32);
		kfree_skb(skb);
		if (!nskb)
			goto out;
		skb = nskb;
	} else
		skb = skb_unshare(skb, GFP_ATOMIC);

	/*
	 * If the buffer didn't vanish into the lack of space bitbucket we can
	 * send it.
	 */
	if (skb && aarp_send_ddp(rt->dev, skb, &ta, NULL) == -1)
		goto free_it;
out:
	return;
free_it:
	kfree_skb(skb);
}

/**
 *	atalk_rcv - Receive a packet (in skb) from device dev
 *	@skb - packet received
 *	@dev - network device where the packet comes from
 *	@pt - packet type
 *
 *	Receive a packet (in skb) from device dev. This has come from the SNAP
 *	decoder, and on entry skb->transport_header is the DDP header, skb->len
 *	is the DDP header, skb->len is the DDP length. The physical headers
 *	have been extracted. PPP should probably pass frames marked as for this
 *	layer.  [ie ARPHRD_ETHERTALK]
 */
static int atalk_rcv(struct sk_buff *skb, struct net_device *dev,
		     struct packet_type *pt, struct net_device *orig_dev)
{
	struct ddpehdr *ddp;
	struct sock *sock;
	struct atalk_iface *atif;
	struct sockaddr_at tosat;
	int origlen;
	__u16 len_hops;

	if (dev->nd_net != &init_net)
		goto freeit;

	/* Don't mangle buffer if shared */
	if (!(skb = skb_share_check(skb, GFP_ATOMIC)))
		goto out;

	/* Size check and make sure header is contiguous */
	if (!pskb_may_pull(skb, sizeof(*ddp)))
		goto freeit;

	ddp = ddp_hdr(skb);

	len_hops = ntohs(ddp->deh_len_hops);

	/* Trim buffer in case of stray trailing data */
	origlen = skb->len;
	skb_trim(skb, min_t(unsigned int, skb->len, len_hops & 1023));

	/*
	 * Size check to see if ddp->deh_len was crap
	 * (Otherwise we'll detonate most spectacularly
	 * in the middle of atalk_checksum() or recvmsg()).
	 */
	if (skb->len < sizeof(*ddp) || skb->len < (len_hops & 1023)) {
		pr_debug("AppleTalk: dropping corrupted frame (deh_len=%u, "
			 "skb->len=%u)\n", len_hops & 1023, skb->len);
		goto freeit;
	}

	/*
	 * Any checksums. Note we don't do htons() on this == is assumed to be
	 * valid for net byte orders all over the networking code...
	 */
	if (ddp->deh_sum &&
	    atalk_checksum(skb, len_hops & 1023) != ddp->deh_sum)
		/* Not a valid AppleTalk frame - dustbin time */
		goto freeit;

	/* Check the packet is aimed at us */
	if (!ddp->deh_dnet)	/* Net 0 is 'this network' */
		atif = atalk_find_anynet(ddp->deh_dnode, dev);
	else
		atif = atalk_find_interface(ddp->deh_dnet, ddp->deh_dnode);

	if (!atif) {
		/* Not ours, so we route the packet via the correct
		 * AppleTalk iface
		 */
		atalk_route_packet(skb, dev, ddp, len_hops, origlen);