1 files changed, 570 insertions, 0 deletions

diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
new file mode 100644
index 000000000..e0e8a65d5
--- /dev/null
+++ b/net/ipv4/inet_fragment.c
@@ -0,0 +1,570 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * inet fragments management
+ *
+ * 		Authors:	Pavel Emelyanov <xemul@openvz.org>
+ *				Started as consolidation of ipv4/ip_fragment.c,
+ *				ipv6/reassembly. and ipv6 nf conntrack reassembly
+ */
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/mm.h>
+#include <linux/random.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/slab.h>
+#include <linux/rhashtable.h>
+
+#include <net/sock.h>
+#include <net/inet_frag.h>
+#include <net/inet_ecn.h>
+#include <net/ip.h>
+#include <net/ipv6.h>
+
+/* Use skb->cb to track consecutive/adjacent fragments coming at
+ * the end of the queue. Nodes in the rb-tree queue will
+ * contain "runs" of one or more adjacent fragments.
+ *
+ * Invariants:
+ * - next_frag is NULL at the tail of a "run";
+ * - the head of a "run" has the sum of all fragment lengths in frag_run_len.
+ */
+struct ipfrag_skb_cb {
+	union {
+		struct inet_skb_parm	h4;
+		struct inet6_skb_parm	h6;
+	};
+	struct sk_buff		*next_frag;
+	int			frag_run_len;
+};
+
+#define FRAG_CB(skb)		((struct ipfrag_skb_cb *)((skb)->cb))
+
+static void fragcb_clear(struct sk_buff *skb)
+{
+	RB_CLEAR_NODE(&skb->rbnode);
+	FRAG_CB(skb)->next_frag = NULL;
+	FRAG_CB(skb)->frag_run_len = skb->len;
+}
+
+/* Append skb to the last "run". */
+static void fragrun_append_to_last(struct inet_frag_queue *q,
+				   struct sk_buff *skb)
+{
+	fragcb_clear(skb);
+
+	FRAG_CB(q->last_run_head)->frag_run_len += skb->len;
+	FRAG_CB(q->fragments_tail)->next_frag = skb;
+	q->fragments_tail = skb;
+}
+
+/* Create a new "run" with the skb. */
+static void fragrun_create(struct inet_frag_queue *q, struct sk_buff *skb)
+{
+	BUILD_BUG_ON(sizeof(struct ipfrag_skb_cb) > sizeof(skb->cb));
+	fragcb_clear(skb);
+
+	if (q->last_run_head)
+		rb_link_node(&skb->rbnode, &q->last_run_head->rbnode,
+			     &q->last_run_head->rbnode.rb_right);
+	else
+		rb_link_node(&skb->rbnode, NULL, &q->rb_fragments.rb_node);
+	rb_insert_color(&skb->rbnode, &q->rb_fragments);
+
+	q->fragments_tail = skb;
+	q->last_run_head = skb;
+}
+
+/* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
+ * Value : 0xff if frame should be dropped.
+ *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
+ */
+const u8 ip_frag_ecn_table[16] = {
+	/* at least one fragment had CE, and others ECT_0 or ECT_1 */
+	[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]			= INET_ECN_CE,
+	[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]			= INET_ECN_CE,
+	[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]	= INET_ECN_CE,
+
+	/* invalid combinations : drop frame */
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
+	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
+};
+EXPORT_SYMBOL(ip_frag_ecn_table);
+
+int inet_frags_init(struct inet_frags *f)
+{
+	f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
+					    NULL);
+	if (!f->frags_cachep)
+		return -ENOMEM;
+
+	refcount_set(&f->refcnt, 1);
+	init_completion(&f->completion);
+	return 0;
+}
+EXPORT_SYMBOL(inet_frags_init);
+
+void inet_frags_fini(struct inet_frags *f)
+{
+	if (refcount_dec_and_test(&f->refcnt))
+		complete(&f->completion);
+
+	wait_for_completion(&f->completion);
+
+	kmem_cache_destroy(f->frags_cachep);
+	f->frags_cachep = NULL;
+}
+EXPORT_SYMBOL(inet_frags_fini);
+
+/* called from rhashtable_free_and_destroy() at netns_frags dismantle */
+static void inet_frags_free_cb(void *ptr, void *arg)
+{
+	struct inet_frag_queue *fq = ptr;
+	int count;
+
+	count = del_timer_sync(&fq->timer) ? 1 : 0;
+
+	spin_lock_bh(&fq->lock);
+	if (!(fq->flags & INET_FRAG_COMPLETE)) {
+		fq->flags |= INET_FRAG_COMPLETE;
+		count++;
+	} else if (fq->flags & INET_FRAG_HASH_DEAD) {
+		count++;
+	}
+	spin_unlock_bh(&fq->lock);
+
+	if (refcount_sub_and_test(count, &fq->refcnt))
+		inet_frag_destroy(fq);
+}
+
+static void fqdir_work_fn(struct work_struct *work)
+{
+	struct fqdir *fqdir = container_of(work, struct fqdir, destroy_work);
+	struct inet_frags *f = fqdir->f;
+
+	rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL);
+
+	/* We need to make sure all ongoing call_rcu(..., inet_frag_destroy_rcu)
+	 * have completed, since they need to dereference fqdir.
+	 * Would it not be nice to have kfree_rcu_barrier() ? :)
+	 */
+	rcu_barrier();
+
+	if (refcount_dec_and_test(&f->refcnt))
+		complete(&f->completion);
+
+	kfree(fqdir);
+}
+
+int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net)
+{
+	struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL);
+	int res;
+
+	if (!fqdir)
+		return -ENOMEM;
+	fqdir->f = f;
+	fqdir->net = net;
+	res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params);
+	if (res < 0) {
+		kfree(fqdir);
+		return res;
+	}
+	refcount_inc(&f->refcnt);
+	*fqdirp = fqdir;
+	return 0;
+}
+EXPORT_SYMBOL(fqdir_init);
+
+void fqdir_exit(struct fqdir *fqdir)
+{
+	INIT_WORK(&fqdir->destroy_work, fqdir_work_fn);
+	queue_work(system_wq, &fqdir->destroy_work);
+}
+EXPORT_SYMBOL(fqdir_exit);
+
+void inet_frag_kill(struct inet_frag_queue *fq)
+{
+	if (del_timer(&fq->timer))
+		refcount_dec(&fq->refcnt);
+
+	if (!(fq->flags & INET_FRAG_COMPLETE)) {
+		struct fqdir *fqdir = fq->fqdir;
+
+		fq->flags |= INET_FRAG_COMPLETE;
+		rcu_read_lock();
+		/* The RCU read lock provides a memory barrier
+		 * guaranteeing that if fqdir->dead is false then
+		 * the hash table destruction will not start until
+		 * after we unlock.  Paired with fqdir_pre_exit().
+		 */
+		if (!READ_ONCE(fqdir->dead)) {
+			rhashtable_remove_fast(&fqdir->rhashtable, &fq->node,
+					       fqdir->f->rhash_params);
+			refcount_dec(&fq->refcnt);
+		} else {
+			fq->flags |= INET_FRAG_HASH_DEAD;
+		}
+		rcu_read_unlock();
+	}
+}
+EXPORT_SYMBOL(inet_frag_kill);
+
+static void inet_frag_destroy_rcu(struct rcu_head *head)
+{
+	struct inet_frag_queue *q = container_of(head, struct inet_frag_queue,
+						 rcu);
+	struct inet_frags *f = q->fqdir->f;
+
+	if (f->destructor)
+		f->destructor(q);
+	kmem_cache_free(f->frags_cachep, q);
+}
+
+unsigned int inet_frag_rbtree_purge(struct rb_root *root)
+{
+	struct rb_node *p = rb_first(root);
+	unsigned int sum = 0;
+
+	while (p) {
+		struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);
+
+		p = rb_next(p);
+		rb_erase(&skb->rbnode, root);
+		while (skb) {
+			struct sk_buff *next = FRAG_CB(skb)->next_frag;
+
+			sum += skb->truesize;
+			kfree_skb(skb);
+			skb = next;
+		}
+	}
+	return sum;
+}
+EXPORT_SYMBOL(inet_frag_rbtree_purge);
+
+void inet_frag_destroy(struct inet_frag_queue *q)
+{
+	struct fqdir *fqdir;
+	unsigned int sum, sum_truesize = 0;
+	struct inet_frags *f;
+
+	WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
+	WARN_ON(del_timer(&q->timer) != 0);
+
+	/* Release all fragment data. */
+	fqdir = q->fqdir;
+	f = fqdir->f;
+	sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments);
+	sum = sum_truesize + f->qsize;
+
+	call_rcu(&q->rcu, inet_frag_destroy_rcu);
+
+	sub_frag_mem_limit(fqdir, sum);
+}
+EXPORT_SYMBOL(inet_frag_destroy);
+
+static struct inet_frag_queue *inet_frag_alloc(struct fqdir *fqdir,
+					       struct inet_frags *f,
+					       void *arg)
+{
+	struct inet_frag_queue *q;
+
+	q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
+	if (!q)
+		return NULL;
+
+	q->fqdir = fqdir;
+	f->constructor(q, arg);
+	add_frag_mem_limit(fqdir, f->qsize);
+
+	timer_setup(&q->timer, f->frag_expire, 0);
+	spin_lock_init(&q->lock);
+	refcount_set(&q->refcnt, 3);
+
+	return q;
+}
+
+static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir,
+						void *arg,
+						struct inet_frag_queue **prev)
+{
+	struct inet_frags *f = fqdir->f;
+	struct inet_frag_queue *q;
+
+	q = inet_frag_alloc(fqdir, f, arg);
+	if (!q) {
+		*prev = ERR_PTR(-ENOMEM);
+		return NULL;
+	}
+	mod_timer(&q->timer, jiffies + fqdir->timeout);
+
+	*prev = rhashtable_lookup_get_insert_key(&fqdir->rhashtable, &q->key,
+						 &q->node, f->rhash_params);
+	if (*prev) {
+		q->flags |= INET_FRAG_COMPLETE;
+		inet_frag_kill(q);
+		inet_frag_destroy(q);
+		return NULL;
+	}
+	return q;
+}
+
+/* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
+struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key)
+{
+	/* This pairs with WRITE_ONCE() in fqdir_pre_exit(). */
+	long high_thresh = READ_ONCE(fqdir->high_thresh);
+	struct inet_frag_queue *fq = NULL, *prev;
+
+	if (!high_thresh || frag_mem_limit(fqdir) > high_thresh)
+		return NULL;
+
+	rcu_read_lock();
+
+	prev = rhashtable_lookup(&fqdir->rhashtable, key, fqdir->f->rhash_params);
+	if (!prev)
+		fq = inet_frag_create(fqdir, key, &prev);
+	if (!IS_ERR_OR_NULL(prev)) {
+		fq = prev;
+		if (!refcount_inc_not_zero(&fq->refcnt))
+			fq = NULL;
+	}
+	rcu_read_unlock();
+	return fq;
+}
+EXPORT_SYMBOL(inet_frag_find);
+
+int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb,
+			   int offset, int end)
+{
+	struct sk_buff *last = q->fragments_tail;
+
+	/* RFC5722, Section 4, amended by Errata ID : 3089
+	 *                          When reassembling an IPv6 datagram, if
+	 *   one or more its constituent fragments is determined to be an
+	 *   overlapping fragment, the entire datagram (and any constituent
+	 *   fragments) MUST be silently discarded.
+	 *
+	 * Duplicates, however, should be ignored (i.e. skb dropped, but the
+	 * queue/fragments kept for later reassembly).
+	 */
+	if (!last)
+		fragrun_create(q, skb);  /* First fragment. */
+	else if (last->ip_defrag_offset + last->len < end) {
+		/* This is the common case: skb goes to the end. */
+		/* Detect and discard overlaps. */
+		if (offset < last->ip_defrag_offset + last->len)
+			return IPFRAG_OVERLAP;
+		if (offset == last->ip_defrag_offset + last->len)
+			fragrun_append_to_last(q, skb);
+		else
+			fragrun_create(q, skb);
+	} else {
+		/* Binary search. Note that skb can become the first fragment,
+		 * but not the last (covered above).
+		 */
+		struct rb_node **rbn, *parent;
+
+		rbn = &q->rb_fragments.rb_node;
+		do {
+			struct sk_buff *curr;
+			int curr_run_end;
+
+			parent = *rbn;
+			curr = rb_to_skb(parent);
+			curr_run_end = curr->ip_defrag_offset +
+					FRAG_CB(curr)->frag_run_len;
+			if (end <= curr->ip_defrag_offset)
+				rbn = &parent->rb_left;
+			else if (offset >= curr_run_end)
+				rbn = &parent->rb_right;
+			else if (offset >= curr->ip_defrag_offset &&
+				 end <= curr_run_end)
+				return IPFRAG_DUP;
+			else
+				return IPFRAG_OVERLAP;
+		} while (*rbn);
+		/* Here we have parent properly set, and rbn pointing to
+		 * one of its NULL left/right children. Insert skb.
+		 */
+		fragcb_clear(skb);
+		rb_link_node(&skb->rbnode, parent, rbn);
+		rb_insert_color(&skb->rbnode, &q->rb_fragments);
+	}
+
+	skb->ip_defrag_offset = offset;
+
+	return IPFRAG_OK;
+}
+EXPORT_SYMBOL(inet_frag_queue_insert);
+
+void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb,
+			      struct sk_buff *parent)
+{
+	struct sk_buff *fp, *head = skb_rb_first(&q->rb_fragments);
+	struct sk_buff **nextp;
+	int delta;
+
+	if (head != skb) {
+		fp = skb_clone(skb, GFP_ATOMIC);
+		if (!fp)
+			return NULL;
+		FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag;
+		if (RB_EMPTY_NODE(&skb->rbnode))
+			FRAG_CB(parent)->next_frag = fp;
+		else
+			rb_replace_node(&skb->rbnode, &fp->rbnode,
+					&q->rb_fragments);
+		if (q->fragments_tail == skb)
+			q->fragments_tail = fp;
+		skb_morph(skb, head);
+		FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag;
+		rb_replace_node(&head->rbnode, &skb->rbnode,
+				&q->rb_fragments);
+		consume_skb(head);
+		head = skb;
+	}
+	WARN_ON(head->ip_defrag_offset != 0);
+
+	delta = -head->truesize;
+
+	/* Head of list must not be cloned. */
+	if (skb_unclone(head, GFP_ATOMIC))
+		return NULL;
+
+	delta += head->truesize;
+	if (delta)
+		add_frag_mem_limit(q->fqdir, delta);
+
+	/* 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)
+			return NULL;
+		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->data_len = head->data_len - plen;
+		clone->len = clone->data_len;
+		head->truesize += clone->truesize;
+		clone->csum = 0;
+		clone->ip_summed = head->ip_summed;
+		add_frag_mem_limit(q->fqdir, clone->truesize);
+		skb_shinfo(head)->frag_list = clone;
+		nextp = &clone->next;
+	} else {
+		nextp = &skb_shinfo(head)->frag_list;
+	}
+
+	return nextp;
+}
+EXPORT_SYMBOL(inet_frag_reasm_prepare);
+
+void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head,
+			    void *reasm_data, bool try_coalesce)
+{
+	struct sk_buff **nextp = (struct sk_buff **)reasm_data;
+	struct rb_node *rbn;
+	struct sk_buff *fp;
+	int sum_truesize;
+
+	skb_push(head, head->data - skb_network_header(head));
+
+	/* Traverse the tree in order, to build frag_list. */
+	fp = FRAG_CB(head)->next_frag;
+	rbn = rb_next(&head->rbnode);
+	rb_erase(&head->rbnode, &q->rb_fragments);
+
+	sum_truesize = head->truesize;
+	while (rbn || fp) {
+		/* fp points to the next sk_buff in the current run;
+		 * rbn points to the next run.
+		 */
+		/* Go through the current run. */
+		while (fp) {
+			struct sk_buff *next_frag = FRAG_CB(fp)->next_frag;
+			bool stolen;
+			int delta;
+
+			sum_truesize += fp->truesize;
+			if (head->ip_summed != fp->ip_summed)
+				head->ip_summed = CHECKSUM_NONE;
+			else if (head->ip_summed == CHECKSUM_COMPLETE)
+				head->csum = csum_add(head->csum, fp->csum);
+
+			if (try_coalesce && skb_try_coalesce(head, fp, &stolen,
+							     &delta)) {
+				kfree_skb_partial(fp, stolen);
+			} else {
+				fp->prev = NULL;
+				memset(&fp->rbnode, 0, sizeof(fp->rbnode));
+				fp->sk = NULL;
+
+				head->data_len += fp->len;
+				head->len += fp->len;
+				head->truesize += fp->truesize;
+
+				*nextp = fp;
+				nextp = &fp->next;
+			}
+
+			fp = next_frag;
+		}
+		/* Move to the next run. */
+		if (rbn) {
+			struct rb_node *rbnext = rb_next(rbn);
+
+			fp = rb_to_skb(rbn);
+			rb_erase(rbn, &q->rb_fragments);
+			rbn = rbnext;
+		}
+	}
+	sub_frag_mem_limit(q->fqdir, sum_truesize);
+
+	*nextp = NULL;
+	skb_mark_not_on_list(head);
+	head->prev = NULL;
+	head->tstamp = q->stamp;
+}
+EXPORT_SYMBOL(inet_frag_reasm_finish);
+
+struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q)
+{
+	struct sk_buff *head, *skb;
+
+	head = skb_rb_first(&q->rb_fragments);
+	if (!head)
+		return NULL;
+	skb = FRAG_CB(head)->next_frag;
+	if (skb)
+		rb_replace_node(&head->rbnode, &skb->rbnode,
+				&q->rb_fragments);
+	else
+		rb_erase(&head->rbnode, &q->rb_fragments);
+	memset(&head->rbnode, 0, sizeof(head->rbnode));
+	barrier();
+
+	if (head == q->fragments_tail)
+		q->fragments_tail = NULL;
+
+	sub_frag_mem_limit(q->fqdir, head->truesize);
+
+	return head;
+}
+EXPORT_SYMBOL(inet_frag_pull_head);