1 files changed, 691 insertions, 0 deletions

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
new file mode 100644
index 0000000..7f68e27
--- /dev/null
+++ b/net/ipv4/ip_fragment.c
@@ -0,0 +1,691 @@
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		The IP fragmentation functionality.
+ *		
+ * Version:	$Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
+ *
+ * Authors:	Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
+ *		Alan Cox <Alan.Cox@linux.org>
+ *
+ * Fixes:
+ *		Alan Cox	:	Split from ip.c , see ip_input.c for history.
+ *		David S. Miller :	Begin massive cleanup...
+ *		Andi Kleen	:	Add sysctls.
+ *		xxxx		:	Overlapfrag bug.
+ *		Ultima          :       ip_expire() kernel panic.
+ *		Bill Hawes	:	Frag accounting and evictor fixes.
+ *		John McDonald	:	0 length frag bug.
+ *		Alexey Kuznetsov:	SMP races, threading, cleanup.
+ *		Patrick McHardy :	LRU queue of frag heads for evictor.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/jiffies.h>
+#include <linux/skbuff.h>
+#include <linux/list.h>
+#include <linux/ip.h>
+#include <linux/icmp.h>
+#include <linux/netdevice.h>
+#include <linux/jhash.h>
+#include <linux/random.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/checksum.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/inet.h>
+#include <linux/netfilter_ipv4.h>
+
+/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
+ * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
+ * as well. Or notify me, at least. --ANK
+ */
+
+/* Fragment cache limits. We will commit 256K at one time. Should we
+ * cross that limit we will prune down to 192K. This should cope with
+ * even the most extreme cases without allowing an attacker to measurably
+ * harm machine performance.
+ */
+int sysctl_ipfrag_high_thresh = 256*1024;
+int sysctl_ipfrag_low_thresh = 192*1024;
+
+/* Important NOTE! Fragment queue must be destroyed before MSL expires.
+ * RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
+ */
+int sysctl_ipfrag_time = IP_FRAG_TIME;
+
+struct ipfrag_skb_cb
+{
+	struct inet_skb_parm	h;
+	int			offset;
+};
+
+#define FRAG_CB(skb)	((struct ipfrag_skb_cb*)((skb)->cb))
+
+/* Describe an entry in the "incomplete datagrams" queue. */
+struct ipq {
+	struct ipq	*next;		/* linked list pointers			*/
+	struct list_head lru_list;	/* lru list member 			*/
+	u32		user;
+	u32		saddr;
+	u32		daddr;
+	u16		id;
+	u8		protocol;
+	u8		last_in;
+#define COMPLETE		4
+#define FIRST_IN		2
+#define LAST_IN			1
+
+	struct sk_buff	*fragments;	/* linked list of received fragments	*/
+	int		len;		/* total length of original datagram	*/
+	int		meat;
+	spinlock_t	lock;
+	atomic_t	refcnt;
+	struct timer_list timer;	/* when will this queue expire?		*/
+	struct ipq	**pprev;
+	int		iif;
+	struct timeval	stamp;
+};
+
+/* Hash table. */
+
+#define IPQ_HASHSZ	64
+
+/* Per-bucket lock is easy to add now. */
+static struct ipq *ipq_hash[IPQ_HASHSZ];
+static DEFINE_RWLOCK(ipfrag_lock);
+static u32 ipfrag_hash_rnd;
+static LIST_HEAD(ipq_lru_list);
+int ip_frag_nqueues = 0;
+
+static __inline__ void __ipq_unlink(struct ipq *qp)
+{
+	if(qp->next)
+		qp->next->pprev = qp->pprev;
+	*qp->pprev = qp->next;
+	list_del(&qp->lru_list);
+	ip_frag_nqueues--;
+}
+
+static __inline__ void ipq_unlink(struct ipq *ipq)
+{
+	write_lock(&ipfrag_lock);
+	__ipq_unlink(ipq);
+	write_unlock(&ipfrag_lock);
+}
+
+static unsigned int ipqhashfn(u16 id, u32 saddr, u32 daddr, u8 prot)
+{
+	return jhash_3words((u32)id << 16 | prot, saddr, daddr,
+			    ipfrag_hash_rnd) & (IPQ_HASHSZ - 1);
+}
+
+static struct timer_list ipfrag_secret_timer;
+int sysctl_ipfrag_secret_interval = 10 * 60 * HZ;
+
+static void ipfrag_secret_rebuild(unsigned long dummy)
+{
+	unsigned long now = jiffies;
+	int i;
+
+	write_lock(&ipfrag_lock);
+	get_random_bytes(&ipfrag_hash_rnd, sizeof(u32));
+	for (i = 0; i < IPQ_HASHSZ; i++) {
+		struct ipq *q;
+
+		q = ipq_hash[i];
+		while (q) {
+			struct ipq *next = q->next;
+			unsigned int hval = ipqhashfn(q->id, q->saddr,
+						      q->daddr, q->protocol);
+
+			if (hval != i) {
+				/* Unlink. */
+				if (q->next)
+					q->next->pprev = q->pprev;
+				*q->pprev = q->next;
+
+				/* Relink to new hash chain. */
+				if ((q->next = ipq_hash[hval]) != NULL)
+					q->next->pprev = &q->next;
+				ipq_hash[hval] = q;
+				q->pprev = &ipq_hash[hval];
+			}
+
+			q = next;
+		}
+	}
+	write_unlock(&ipfrag_lock);
+
+	mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval);
+}
+
+atomic_t ip_frag_mem = ATOMIC_INIT(0);	/* Memory used for fragments */
+
+/* Memory Tracking Functions. */
+static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
+{
+	if (work)
+		*work -= skb->truesize;
+	atomic_sub(skb->truesize, &ip_frag_mem);
+	kfree_skb(skb);
+}
+
+static __inline__ void frag_free_queue(struct ipq *qp, int *work)
+{
+	if (work)
+		*work -= sizeof(struct ipq);
+	atomic_sub(sizeof(struct ipq), &ip_frag_mem);
+	kfree(qp);
+}
+
+static __inline__ struct ipq *frag_alloc_queue(void)
+{
+	struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC);
+
+	if(!qp)
+		return NULL;
+	atomic_add(sizeof(struct ipq), &ip_frag_mem);
+	return qp;
+}
+
+
+/* Destruction primitives. */
+
+/* Complete destruction of ipq. */
+static void ip_frag_destroy(struct ipq *qp, int *work)
+{
+	struct sk_buff *fp;
+
+	BUG_TRAP(qp->last_in&COMPLETE);
+	BUG_TRAP(del_timer(&qp->timer) == 0);
+
+	/* Release all fragment data. */
+	fp = qp->fragments;
+	while (fp) {
+		struct sk_buff *xp = fp->next;
+
+		frag_kfree_skb(fp, work);
+		fp = xp;
+	}
+
+	/* Finally, release the queue descriptor itself. */
+	frag_free_queue(qp, work);
+}
+
+static __inline__ void ipq_put(struct ipq *ipq, int *work)
+{
+	if (atomic_dec_and_test(&ipq->refcnt))
+		ip_frag_destroy(ipq, work);
+}
+
+/* Kill ipq entry. It is not destroyed immediately,
+ * because caller (and someone more) holds reference count.
+ */
+static void ipq_kill(struct ipq *ipq)
+{
+	if (del_timer(&ipq->timer))
+		atomic_dec(&ipq->refcnt);
+
+	if (!(ipq->last_in & COMPLETE)) {
+		ipq_unlink(ipq);
+		atomic_dec(&ipq->refcnt);
+		ipq->last_in |= COMPLETE;
+	}
+}
+
+/* Memory limiting on fragments.  Evictor trashes the oldest 
+ * fragment queue until we are back under the threshold.
+ */
+static void ip_evictor(void)
+{
+	struct ipq *qp;
+	struct list_head *tmp;
+	int work;
+
+	work = atomic_read(&ip_frag_mem) - sysctl_ipfrag_low_thresh;
+	if (work <= 0)
+		return;
+
+	while (work > 0) {
+		read_lock(&ipfrag_lock);
+		if (list_empty(&ipq_lru_list)) {
+			read_unlock(&ipfrag_lock);
+			return;
+		}
+		tmp = ipq_lru_list.next;
+		qp = list_entry(tmp, struct ipq, lru_list);
+		atomic_inc(&qp->refcnt);
+		read_unlock(&ipfrag_lock);
+
+		spin_lock(&qp->lock);
+		if (!(qp->last_in&COMPLETE))
+			ipq_kill(qp);
+		spin_unlock(&qp->lock);
+
+		ipq_put(qp, &work);
+		IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
+	}
+}
+
+/*
+ * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
+ */
+static void ip_expire(unsigned long arg)
+{
+	struct ipq *qp = (struct ipq *) arg;
+
+	spin_lock(&qp->lock);
+
+	if (qp->last_in & COMPLETE)
+		goto out;
+
+	ipq_kill(qp);
+
+	IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
+	IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
+
+	if ((qp->last_in&FIRST_IN) && qp->fragments != NULL) {
+		struct sk_buff *head = qp->fragments;
+		/* Send an ICMP "Fragment Reassembly Timeout" message. */
+		if ((head->dev = dev_get_by_index(qp->iif)) != NULL) {
+			icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
+			dev_put(head->dev);
+		}
+	}
+out:
+	spin_unlock(&qp->lock);
+	ipq_put(qp, NULL);
+}
+
+/* Creation primitives. */
+
+static struct ipq *ip_frag_intern(unsigned int hash, struct ipq *qp_in)
+{
+	struct ipq *qp;
+
+	write_lock(&ipfrag_lock);
+#ifdef CONFIG_SMP
+	/* With SMP race we have to recheck hash table, because
+	 * such entry could be created on other cpu, while we
+	 * promoted read lock to write lock.
+	 */
+	for(qp = ipq_hash[hash]; qp; qp = qp->next) {
+		if(qp->id == qp_in->id		&&
+		   qp->saddr == qp_in->saddr	&&
+		   qp->daddr == qp_in->daddr	&&
+		   qp->protocol == qp_in->protocol &&
+		   qp->user == qp_in->user) {
+			atomic_inc(&qp->refcnt);
+			write_unlock(&ipfrag_lock);
+			qp_in->last_in |= COMPLETE;
+			ipq_put(qp_in, NULL);
+			return qp;
+		}
+	}
+#endif
+	qp = qp_in;
+
+	if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time))
+		atomic_inc(&qp->refcnt);
+
+	atomic_inc(&qp->refcnt);
+	if((qp->next = ipq_hash[hash]) != NULL)
+		qp->next->pprev = &qp->next;
+	ipq_hash[hash] = qp;
+	qp->pprev = &ipq_hash[hash];
+	INIT_LIST_HEAD(&qp->lru_list);
+	list_add_tail(&qp->lru_list, &ipq_lru_list);
+	ip_frag_nqueues++;
+	write_unlock(&ipfrag_lock);
+	return qp;
+}
+
+/* Add an entry to the 'ipq' queue for a newly received IP datagram. */
+static struct ipq *ip_frag_create(unsigned hash, struct iphdr *iph, u32 user)
+{
+	struct ipq *qp;
+
+	if ((qp = frag_alloc_queue()) == NULL)
+		goto out_nomem;
+
+	qp->protocol = iph->protocol;
+	qp->last_in = 0;
+	qp->id = iph->id;
+	qp->saddr = iph->saddr;
+	qp->daddr = iph->daddr;
+	qp->user = user;
+	qp->len = 0;
+	qp->meat = 0;
+	qp->fragments = NULL;
+	qp->iif = 0;
+
+	/* Initialize a timer for this entry. */
+	init_timer(&qp->timer);
+	qp->timer.data = (unsigned long) qp;	/* pointer to queue	*/
+	qp->timer.function = ip_expire;		/* expire function	*/
+	spin_lock_init(&qp->lock);
+	atomic_set(&qp->refcnt, 1);
+
+	return ip_frag_intern(hash, qp);
+
+out_nomem:
+	NETDEBUG(if (net_ratelimit()) printk(KERN_ERR "ip_frag_create: no memory left !\n"));
+	return NULL;
+}
+
+/* Find the correct entry in the "incomplete datagrams" queue for
+ * this IP datagram, and create new one, if nothing is found.
+ */
+static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
+{
+	__u16 id = iph->id;
+	__u32 saddr = iph->saddr;
+	__u32 daddr = iph->daddr;
+	__u8 protocol = iph->protocol;
+	unsigned int hash = ipqhashfn(id, saddr, daddr, protocol);
+	struct ipq *qp;
+
+	read_lock(&ipfrag_lock);
+	for(qp = ipq_hash[hash]; qp; qp = qp->next) {
+		if(qp->id == id		&&
+		   qp->saddr == saddr	&&
+		   qp->daddr == daddr	&&
+		   qp->protocol == protocol &&
+		   qp->user == user) {
+			atomic_inc(&qp->refcnt);
+			read_unlock(&ipfrag_lock);
+			return qp;
+		}
+	}
+	read_unlock(&ipfrag_lock);
+
+	return ip_frag_create(hash, iph, user);
+}
+
+/* Add new segment to existing queue. */
+static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
+{
+	struct sk_buff *prev, *next;
+	int flags, offset;
+	int ihl, end;
+
+	if (qp->last_in & COMPLETE)
+		goto err;
+
+ 	offset = ntohs(skb->nh.iph->frag_off);
+	flags = offset & ~IP_OFFSET;
+	offset &= IP_OFFSET;
+	offset <<= 3;		/* offset is in 8-byte chunks */
+ 	ihl = skb->nh.iph->ihl * 4;
+
+	/* Determine the position of this fragment. */
+ 	end = offset + skb->len - ihl;
+
+	/* Is this the final fragment? */
+	if ((flags & IP_MF) == 0) {
+		/* If we already have some bits beyond end
+		 * or have different end, the segment is corrrupted.
+		 */
+		if (end < qp->len ||
+		    ((qp->last_in & LAST_IN) && end != qp->len))
+			goto err;
+		qp->last_in |= LAST_IN;
+		qp->len = end;
+	} else {
+		if (end&7) {
+			end &= ~7;
+			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
+				skb->ip_summed = CHECKSUM_NONE;
+		}
+		if (end > qp->len) {
+			/* Some bits beyond end -> corruption. */
+			if (qp->last_in & LAST_IN)
+				goto err;
+			qp->len = end;
+		}
+	}
+	if (end == offset)
+		goto err;
+
+	if (pskb_pull(skb, ihl) == NULL)
+		goto err;
+	if (pskb_trim(skb, end-offset))
+		goto err;
+
+	/* 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 = NULL;
+	for(next = qp->fragments; next != NULL; next = next->next) {
+		if (FRAG_CB(next)->offset >= offset)
+			break;	/* bingo! */
+		prev = next;
+	}
+
+	/* We found where to put this one.  Check for overlap with
+	 * preceding fragment, and, if needed, align things so that
+	 * any overlaps are eliminated.
+	 */
+	if (prev) {
+		int i = (FRAG_CB(prev)->offset + prev->len) - offset;
+
+		if (i > 0) {
+			offset += i;
+			if (end <= offset)
+				goto err;
+			if (!pskb_pull(skb, i))
+				goto err;
+			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
+				skb->ip_summed = CHECKSUM_NONE;
+		}
+	}
+
+	while (next && FRAG_CB(next)->offset < end) {
+		int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
+
+		if (i < next->len) {
+			/* Eat head of the next overlapped fragment
+			 * and leave the loop. The next ones cannot overlap.
+			 */
+			if (!pskb_pull(next, i))
+				goto err;
+			FRAG_CB(next)->offset += i;
+			qp->meat -= i;
+			if (next->ip_summed != CHECKSUM_UNNECESSARY)
+				next->ip_summed = CHECKSUM_NONE;
+			break;
+		} else {
+			struct sk_buff *free_it = next;
+
+			/* Old fragmnet is completely overridden with
+			 * new one drop it.
+			 */
+			next = next->next;
+
+			if (prev)
+				prev->next = next;
+			else
+				qp->fragments = next;
+
+			qp->meat -= free_it->len;
+			frag_kfree_skb(free_it, NULL);
+		}
+	}
+
+	FRAG_CB(skb)->offset = offset;
+
+	/* Insert this fragment in the chain of fragments. */
+	skb->next = next;
+	if (prev)
+		prev->next = skb;
+	else
+		qp->fragments = skb;
+
+ 	if (skb->dev)
+ 		qp->iif = skb->dev->ifindex;
+	skb->dev = NULL;
+	qp->stamp = skb->stamp;
+	qp->meat += skb->len;
+	atomic_add(skb->truesize, &ip_frag_mem);
+	if (offset == 0)
+		qp->last_in |= FIRST_IN;
+
+	write_lock(&ipfrag_lock);
+	list_move_tail(&qp->lru_list, &ipq_lru_list);
+	write_unlock(&ipfrag_lock);
+
+	return;
+
+err:
+	kfree_skb(skb);
+}
+
+
+/* Build a new IP datagram from all its fragments. */
+
+static struct sk_buff *ip_frag_reasm(struct ipq *qp, struct net_device *dev)
+{
+	struct iphdr *iph;
+	struct sk_buff *fp, *head = qp->fragments;
+	int len;
+	int ihlen;
+
+	ipq_kill(qp);
+
+	BUG_TRAP(head != NULL);
+	BUG_TRAP(FRAG_CB(head)->offset == 0);
+
+	/* Allocate a new buffer for the datagram. */
+	ihlen = head->nh.iph->ihl*4;
+	len = ihlen + qp->len;
+
+	if(len > 65535)
+		goto out_oversize;
+
+	/* Head of list must not be cloned. */
+	if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
+		goto out_nomem;
+
+	/* 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_shinfo(head)->frag_list) {
+		struct sk_buff *clone;
+		int i, plen = 0;
+
+		if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
+			goto out_nomem;
+		clone->next = head->next;
+		head->next = clone;
+		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
+		skb_shinfo(head)->frag_list = NULL;
+		for (i=0; i<skb_shinfo(head)->nr_frags; i++)
+			plen += skb_shinfo(head)->frags[i].size;
+		clone->len = clone->data_len = head->data_len - plen;
+		head->data_len -= clone->len;
+		head->len -= clone->len;
+		clone->csum = 0;
+		clone->ip_summed = head->ip_summed;
+		atomic_add(clone->truesize, &ip_frag_mem);
+	}
+
+	skb_shinfo(head)->frag_list = head->next;
+	skb_push(head, head->data - head->nh.raw);
+	atomic_sub(head->truesize, &ip_frag_mem);
+
+	for (fp=head->next; fp; fp = fp->next) {
+		head->data_len += fp->len;
+		head->len += fp->len;
+		if (head->ip_summed != fp->ip_summed)
+			head->ip_summed = CHECKSUM_NONE;
+		else if (head->ip_summed == CHECKSUM_HW)
+			head->csum = csum_add(head->csum, fp->csum);
+		head->truesize += fp->truesize;
+		atomic_sub(fp->truesize, &ip_frag_mem);
+	}
+
+	head->next = NULL;
+	head->dev = dev;
+	head->stamp = qp->stamp;
+
+	iph = head->nh.iph;
+	iph->frag_off = 0;
+	iph->tot_len = htons(len);
+	IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
+	qp->fragments = NULL;
+	return head;
+
+out_nomem:
+ 	NETDEBUG(if (net_ratelimit())
+	         printk(KERN_ERR 
+			"IP: queue_glue: no memory for gluing queue %p\n",
+			qp));
+	goto out_fail;
+out_oversize:
+	if (net_ratelimit())
+		printk(KERN_INFO
+			"Oversized IP packet from %d.%d.%d.%d.\n",
+			NIPQUAD(qp->saddr));
+out_fail:
+	IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
+	return NULL;
+}
+
+/* Process an incoming IP datagram fragment. */
+struct sk_buff *ip_defrag(struct sk_buff *skb, u32 user)
+{
+	struct iphdr *iph = skb->nh.iph;
+	struct ipq *qp;
+	struct net_device *dev;
+	
+	IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
+
+	/* Start by cleaning up the memory. */
+	if (atomic_read(&ip_frag_mem) > sysctl_ipfrag_high_thresh)
+		ip_evictor();
+
+	dev = skb->dev;
+
+	/* Lookup (or create) queue header */
+	if ((qp = ip_find(iph, user)) != NULL) {
+		struct sk_buff *ret = NULL;
+
+		spin_lock(&qp->lock);
+
+		ip_frag_queue(qp, skb);
+
+		if (qp->last_in == (FIRST_IN|LAST_IN) &&
+		    qp->meat == qp->len)
+			ret = ip_frag_reasm(qp, dev);
+
+		spin_unlock(&qp->lock);
+		ipq_put(qp, NULL);
+		return ret;
+	}
+
+	IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
+	kfree_skb(skb);
+	return NULL;
+}
+
+void ipfrag_init(void)
+{
+	ipfrag_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
+				 (jiffies ^ (jiffies >> 6)));
+
+	init_timer(&ipfrag_secret_timer);
+	ipfrag_secret_timer.function = ipfrag_secret_rebuild;
+	ipfrag_secret_timer.expires = jiffies + sysctl_ipfrag_secret_interval;
+	add_timer(&ipfrag_secret_timer);
+}
+
+EXPORT_SYMBOL(ip_defrag);