6lowpan: handling 6lowpan fragmentation via inet_frag api

This patch drops the current way of 6lowpan fragmentation on receiving
side and replace it with a implementation which use the inet_frag api.
The old fragmentation handling has some race conditions and isn't
rfc4944 compatible. Also adding support to match fragments on
destination address, source address, tag value and datagram_size
which is missing in the current implementation.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 564 insertions, 0 deletions

diff --git a/net/ieee802154/reassembly.c b/net/ieee802154/reassembly.c
new file mode 100644
index 000000000000..eb5995e74316
--- /dev/null
+++ b/net/ieee802154/reassembly.c
@@ -0,0 +1,564 @@
+/*	6LoWPAN fragment reassembly
+ *
+ *
+ *	Authors:
+ *	Alexander Aring		<aar@pengutronix.de>
+ *
+ *	Based on: net/ipv6/reassembly.c
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt) "6LoWPAN: " fmt
+
+#include <linux/net.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include <linux/random.h>
+#include <linux/jhash.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+
+#include <net/ieee802154_netdev.h>
+#include <net/ipv6.h>
+#include <net/inet_frag.h>
+
+#include "6lowpan.h"
+#include "reassembly.h"
+
+static struct inet_frags lowpan_frags;
+
+static int lowpan_frag_reasm(struct lowpan_frag_queue *fq,
+			     struct sk_buff *prev, struct net_device *dev);
+
+static unsigned int lowpan_hash_frag(__be16 tag, __be16 d_size,
+				     const struct ieee802154_addr *saddr,
+				     const struct ieee802154_addr *daddr)
+{
+	u32 c;
+
+	net_get_random_once(&lowpan_frags.rnd, sizeof(lowpan_frags.rnd));
+	c = jhash_3words(ieee802154_addr_hash(saddr),
+			 ieee802154_addr_hash(daddr),
+			 (__force u32)(tag + (d_size << 16)),
+			 lowpan_frags.rnd);
+
+	return c & (INETFRAGS_HASHSZ - 1);
+}
+
+static unsigned int lowpan_hashfn(struct inet_frag_queue *q)
+{
+	struct lowpan_frag_queue *fq;
+
+	fq = container_of(q, struct lowpan_frag_queue, q);
+	return lowpan_hash_frag(fq->tag, fq->d_size, &fq->saddr, &fq->daddr);
+}
+
+bool lowpan_frag_match(struct inet_frag_queue *q, void *a)
+{
+	struct lowpan_frag_queue *fq;
+	struct lowpan_create_arg *arg = a;
+
+	fq = container_of(q, struct lowpan_frag_queue, q);
+	return	fq->tag == arg->tag && fq->d_size == arg->d_size &&
+		ieee802154_addr_addr_equal(&fq->saddr, arg->src) &&
+		ieee802154_addr_addr_equal(&fq->daddr, arg->dst);
+}
+EXPORT_SYMBOL(lowpan_frag_match);
+
+void lowpan_frag_init(struct inet_frag_queue *q, void *a)
+{
+	struct lowpan_frag_queue *fq;
+	struct lowpan_create_arg *arg = a;
+
+	fq = container_of(q, struct lowpan_frag_queue, q);
+
+	fq->tag = arg->tag;
+	fq->d_size = arg->d_size;
+	fq->saddr = *arg->src;
+	fq->daddr = *arg->dst;
+}
+EXPORT_SYMBOL(lowpan_frag_init);
+
+void lowpan_expire_frag_queue(struct frag_queue *fq, struct inet_frags *frags)
+{
+	spin_lock(&fq->q.lock);
+
+	if (fq->q.last_in & INET_FRAG_COMPLETE)
+		goto out;
+
+	inet_frag_kill(&fq->q, frags);
+out:
+	spin_unlock(&fq->q.lock);
+	inet_frag_put(&fq->q, frags);
+}
+EXPORT_SYMBOL(lowpan_expire_frag_queue);
+
+static void lowpan_frag_expire(unsigned long data)
+{
+	struct frag_queue *fq;
+	struct net *net;
+
+	fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
+	net = container_of(fq->q.net, struct net, ieee802154_lowpan.frags);
+
+	lowpan_expire_frag_queue(fq, &lowpan_frags);
+}
+
+static inline struct lowpan_frag_queue *
+fq_find(struct net *net, const struct ieee802154_frag_info *frag_info,
+	const struct ieee802154_addr *src, const struct ieee802154_addr *dst)
+{
+	struct inet_frag_queue *q;
+	struct lowpan_create_arg arg;
+	unsigned int hash;
+
+	arg.tag = frag_info->d_tag;
+	arg.d_size = frag_info->d_size;
+	arg.src = src;
+	arg.dst = dst;
+
+	read_lock(&lowpan_frags.lock);
+	hash = lowpan_hash_frag(frag_info->d_tag, frag_info->d_size, src, dst);
+
+	q = inet_frag_find(&net->ieee802154_lowpan.frags,
+			   &lowpan_frags, &arg, hash);
+	if (IS_ERR_OR_NULL(q)) {
+		inet_frag_maybe_warn_overflow(q, pr_fmt());
+		return NULL;
+	}
+	return container_of(q, struct lowpan_frag_queue, q);
+}
+
+static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
+			     struct sk_buff *skb, const u8 frag_type)
+{
+	struct sk_buff *prev, *next;
+	struct net_device *dev;
+	int end, offset;
+
+	if (fq->q.last_in & INET_FRAG_COMPLETE)
+		goto err;
+
+	offset = mac_cb(skb)->frag_info.d_offset << 3;
+	end = mac_cb(skb)->frag_info.d_size;
+
+	/* Is this the final fragment? */
+	if (offset + skb->len == end) {
+		/* If we already have some bits beyond end
+		 * or have different end, the segment is corrupted.
+		 */
+		if (end < fq->q.len ||
+		    ((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len))
+			goto err;
+		fq->q.last_in |= INET_FRAG_LAST_IN;
+		fq->q.len = end;
+	} else {
+		if (end > fq->q.len) {
+			/* Some bits beyond end -> corruption. */
+			if (fq->q.last_in & INET_FRAG_LAST_IN)
+				goto err;
+			fq->q.len = end;
+		}
+	}
+
+	/* Find out which fragments are in front and at the back of us
+	 * in the chain of fragments so far.  We must know where to put
+	 * this fragment, right?
+	 */
+	prev = fq->q.fragments_tail;
+	if (!prev || mac_cb(prev)->frag_info.d_offset <
+		     mac_cb(skb)->frag_info.d_offset) {
+		next = NULL;
+		goto found;
+	}
+	prev = NULL;
+	for (next = fq->q.fragments; next != NULL; next = next->next) {
+		if (mac_cb(next)->frag_info.d_offset >=
+		    mac_cb(skb)->frag_info.d_offset)
+			break;	/* bingo! */
+		prev = next;
+	}
+
+found:
+	/* Insert this fragment in the chain of fragments. */
+	skb->next = next;
+	if (!next)
+		fq->q.fragments_tail = skb;
+	if (prev)
+		prev->next = skb;
+	else
+		fq->q.fragments = skb;
+
+	dev = skb->dev;
+	if (dev)
+		skb->dev = NULL;
+
+	fq->q.stamp = skb->tstamp;
+	if (frag_type == LOWPAN_DISPATCH_FRAG1) {
+		/* Calculate uncomp. 6lowpan header to estimate full size */
+		fq->q.meat += lowpan_uncompress_size(skb, NULL);
+		fq->q.last_in |= INET_FRAG_FIRST_IN;
+	} else {
+		fq->q.meat += skb->len;
+	}
+	add_frag_mem_limit(&fq->q, skb->truesize);
+
+	if (fq->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
+	    fq->q.meat == fq->q.len) {
+		int res;
+		unsigned long orefdst = skb->_skb_refdst;
+
+		skb->_skb_refdst = 0UL;
+		res = lowpan_frag_reasm(fq, prev, dev);
+		skb->_skb_refdst = orefdst;
+		return res;
+	}
+
+	inet_frag_lru_move(&fq->q);
+	return -1;
+err:
+	kfree_skb(skb);
+	return -1;
+}
+
+/*	Check if this packet is complete.
+ *	Returns NULL on failure by any reason, and pointer
+ *	to current nexthdr field in reassembled frame.
+ *
+ *	It is called with locked fq, and caller must check that
+ *	queue is eligible for reassembly i.e. it is not COMPLETE,
+ *	the last and the first frames arrived and all the bits are here.
+ */
+static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *prev,
+			     struct net_device *dev)
+{
+	struct sk_buff *fp, *head = fq->q.fragments;
+	int sum_truesize;
+
+	inet_frag_kill(&fq->q, &lowpan_frags);
+
+	/* Make the one we just received the head. */
+	if (prev) {
+		head = prev->next;
+		fp = skb_clone(head, GFP_ATOMIC);
+
+		if (!fp)
+			goto out_oom;
+
+		fp->next = head->next;
+		if (!fp->next)
+			fq->q.fragments_tail = fp;
+		prev->next = fp;
+
+		skb_morph(head, fq->q.fragments);
+		head->next = fq->q.fragments->next;
+
+		consume_skb(fq->q.fragments);
+		fq->q.fragments = head;
+	}
+
+	/* Head of list must not be cloned. */
+	if (skb_unclone(head, GFP_ATOMIC))
+		goto out_oom;
+
+	/* If the first fragment is fragmented itself, we split
+	 * it to two chunks: the first with data and paged part
+	 * and the second, holding only fragments.
+	 */
+	if (skb_has_frag_list(head)) {
+		struct sk_buff *clone;
+		int i, plen = 0;
+
+		clone = alloc_skb(0, GFP_ATOMIC);
+		if (!clone)
+			goto out_oom;
+		clone->next = head->next;
+		head->next = clone;
+		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
+		skb_frag_list_init(head);
+		for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
+			plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
+		clone->len = head->data_len - plen;
+		clone->data_len = clone->len;
+		head->data_len -= clone->len;
+		head->len -= clone->len;
+		add_frag_mem_limit(&fq->q, clone->truesize);
+	}
+
+	WARN_ON(head == NULL);
+
+	sum_truesize = head->truesize;
+	for (fp = head->next; fp;) {
+		bool headstolen;
+		int delta;
+		struct sk_buff *next = fp->next;
+
+		sum_truesize += fp->truesize;
+		if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
+			kfree_skb_partial(fp, headstolen);
+		} else {
+			if (!skb_shinfo(head)->frag_list)
+				skb_shinfo(head)->frag_list = fp;
+			head->data_len += fp->len;
+			head->len += fp->len;
+			head->truesize += fp->truesize;
+		}
+		fp = next;
+	}
+	sub_frag_mem_limit(&fq->q, sum_truesize);
+
+	head->next = NULL;
+	head->dev = dev;
+	head->tstamp = fq->q.stamp;
+
+	fq->q.fragments = NULL;
+	fq->q.fragments_tail = NULL;
+
+	return 1;
+out_oom:
+	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
+	return -1;
+}
+
+static int lowpan_get_frag_info(struct sk_buff *skb, const u8 frag_type,
+				struct ieee802154_frag_info *frag_info)
+{
+	bool fail;
+	u8 pattern = 0, low = 0;
+
+	fail = lowpan_fetch_skb(skb, &pattern, 1);
+	fail |= lowpan_fetch_skb(skb, &low, 1);
+	frag_info->d_size = (pattern & 7) << 8 | low;
+	fail |= lowpan_fetch_skb(skb, &frag_info->d_tag, 2);
+
+	if (frag_type == LOWPAN_DISPATCH_FRAGN) {
+		fail |= lowpan_fetch_skb(skb, &frag_info->d_offset, 1);
+	} else {
+		skb_reset_network_header(skb);
+		frag_info->d_offset = 0;
+	}
+
+	if (unlikely(fail))
+		return -EIO;
+
+	return 0;
+}
+
+int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type)
+{
+	struct lowpan_frag_queue *fq;
+	struct net *net = dev_net(skb->dev);
+	struct ieee802154_frag_info *frag_info = &mac_cb(skb)->frag_info;
+	int err;
+
+	err = lowpan_get_frag_info(skb, frag_type, frag_info);
+	if (err < 0)
+		goto err;
+
+	if (frag_info->d_size > net->ieee802154_lowpan.max_dsize)
+		goto err;
+
+	inet_frag_evictor(&net->ieee802154_lowpan.frags, &lowpan_frags, false);
+
+	fq = fq_find(net, frag_info, &mac_cb(skb)->sa, &mac_cb(skb)->da);
+	if (fq != NULL) {
+		int ret;
+		spin_lock(&fq->q.lock);
+		ret = lowpan_frag_queue(fq, skb, frag_type);
+		spin_unlock(&fq->q.lock);
+
+		inet_frag_put(&fq->q, &lowpan_frags);
+		return ret;
+	}
+
+err:
+	kfree_skb(skb);
+	return -1;
+}
+EXPORT_SYMBOL(lowpan_frag_rcv);
+
+#ifdef CONFIG_SYSCTL
+static struct ctl_table lowpan_frags_ns_ctl_table[] = {
+	{
+		.procname	= "6lowpanfrag_high_thresh",
+		.data		= &init_net.ieee802154_lowpan.frags.high_thresh,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{
+		.procname	= "6lowpanfrag_low_thresh",
+		.data		= &init_net.ieee802154_lowpan.frags.low_thresh,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{
+		.procname	= "6lowpanfrag_time",
+		.data		= &init_net.ieee802154_lowpan.frags.timeout,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
+	{
+		.procname	= "6lowpanfrag_max_datagram_size",
+		.data		= &init_net.ieee802154_lowpan.max_dsize,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{ }
+};
+
+static struct ctl_table lowpan_frags_ctl_table[] = {
+	{
+		.procname	= "6lowpanfrag_secret_interval",
+		.data		= &lowpan_frags.secret_interval,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
+	{ }
+};
+
+static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
+{
+	struct ctl_table *table;
+	struct ctl_table_header *hdr;
+
+	table = lowpan_frags_ns_ctl_table;
+	if (!net_eq(net, &init_net)) {
+		table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
+				GFP_KERNEL);
+		if (table == NULL)
+			goto err_alloc;
+
+		table[0].data = &net->ieee802154_lowpan.frags.high_thresh;
+		table[1].data = &net->ieee802154_lowpan.frags.low_thresh;
+		table[2].data = &net->ieee802154_lowpan.frags.timeout;
+		table[2].data = &net->ieee802154_lowpan.max_dsize;
+
+		/* Don't export sysctls to unprivileged users */
+		if (net->user_ns != &init_user_ns)
+			table[0].procname = NULL;
+	}
+
+	hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
+	if (hdr == NULL)
+		goto err_reg;
+
+	net->ieee802154_lowpan.sysctl.frags_hdr = hdr;
+	return 0;
+
+err_reg:
+	if (!net_eq(net, &init_net))
+		kfree(table);
+err_alloc:
+	return -ENOMEM;
+}
+
+static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
+{
+	struct ctl_table *table;
+
+	table = net->ieee802154_lowpan.sysctl.frags_hdr->ctl_table_arg;
+	unregister_net_sysctl_table(net->ieee802154_lowpan.sysctl.frags_hdr);
+	if (!net_eq(net, &init_net))
+		kfree(table);
+}
+
+static struct ctl_table_header *lowpan_ctl_header;
+
+static int lowpan_frags_sysctl_register(void)
+{
+	lowpan_ctl_header = register_net_sysctl(&init_net,
+						"net/ieee802154/6lowpan",
+						lowpan_frags_ctl_table);
+	return lowpan_ctl_header == NULL ? -ENOMEM : 0;
+}
+
+static void lowpan_frags_sysctl_unregister(void)
+{
+	unregister_net_sysctl_table(lowpan_ctl_header);
+}
+#else
+static inline int lowpan_frags_ns_sysctl_register(struct net *net)
+{
+	return 0;
+}
+
+static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
+{
+}
+
+static inline int lowpan_frags_sysctl_register(void)
+{
+	return 0;
+}
+
+static inline void lowpan_frags_sysctl_unregister(void)
+{
+}
+#endif
+
+static int __net_init lowpan_frags_init_net(struct net *net)
+{
+	net->ieee802154_lowpan.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
+	net->ieee802154_lowpan.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
+	net->ieee802154_lowpan.frags.timeout = IPV6_FRAG_TIMEOUT;
+	net->ieee802154_lowpan.max_dsize = 0xFFFF;
+
+	inet_frags_init_net(&net->ieee802154_lowpan.frags);
+
+	return lowpan_frags_ns_sysctl_register(net);
+}
+
+static void __net_exit lowpan_frags_exit_net(struct net *net)
+{
+	lowpan_frags_ns_sysctl_unregister(net);
+	inet_frags_exit_net(&net->ieee802154_lowpan.frags, &lowpan_frags);
+}
+
+static struct pernet_operations lowpan_frags_ops = {
+	.init = lowpan_frags_init_net,
+	.exit = lowpan_frags_exit_net,
+};
+
+int __init lowpan_net_frag_init(void)
+{
+	int ret;
+
+	ret = lowpan_frags_sysctl_register();
+	if (ret)
+		goto out;
+
+	ret = register_pernet_subsys(&lowpan_frags_ops);
+	if (ret)
+		goto err_pernet;
+
+	lowpan_frags.hashfn = lowpan_hashfn;
+	lowpan_frags.constructor = lowpan_frag_init;
+	lowpan_frags.destructor = NULL;
+	lowpan_frags.skb_free = NULL;
+	lowpan_frags.qsize = sizeof(struct frag_queue);
+	lowpan_frags.match = lowpan_frag_match;
+	lowpan_frags.frag_expire = lowpan_frag_expire;
+	lowpan_frags.secret_interval = 10 * 60 * HZ;
+	inet_frags_init(&lowpan_frags);
+err_pernet:
+	lowpan_frags_sysctl_unregister();
+out:
+	return ret;
+}
+
+void lowpan_net_frag_exit(void)
+{
+	inet_frags_fini(&lowpan_frags);
+	lowpan_frags_sysctl_unregister();
+	unregister_pernet_subsys(&lowpan_frags_ops);
+}