net: dropreason: add SKB_DROP_REASON_FRAG_REASM_TIMEOUT

Used to track skbs freed after a timeout happened
in a reassmbly unit.

Passing a @reason argument to inet_frag_rbtree_purge()
allows to use correct consumed status for frags
that have been successfully re-assembled.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/dropreason.h

@@ -69,6 +69,7 @@
 	FN(IP_INNOROUTES)		\
 	FN(PKT_TOO_BIG)			\
 	FN(DUP_FRAG)			\
+	FN(FRAG_REASM_TIMEOUT)		\
 	FNe(MAX)
 
 /**
@@ -303,6 +304,8 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_PKT_TOO_BIG,
 	/** @SKB_DROP_REASON_DUP_FRAG: duplicate fragment */
 	SKB_DROP_REASON_DUP_FRAG,
+	/** @SKB_DROP_REASON_FRAG_REASM_TIMEOUT: fragment reassembly timeout */
+	SKB_DROP_REASON_FRAG_REASM_TIMEOUT,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be
 	 * used as a real 'reason'

include/net/inet_frag.h

@@ -7,6 +7,7 @@
 #include <linux/in6.h>
 #include <linux/rbtree_types.h>
 #include <linux/refcount.h>
+#include <net/dropreason.h>
 
 /* Per netns frag queues directory */
 struct fqdir {
@@ -34,12 +35,14 @@ struct fqdir {
  * @INET_FRAG_LAST_IN: final fragment has arrived
  * @INET_FRAG_COMPLETE: frag queue has been processed and is due for destruction
  * @INET_FRAG_HASH_DEAD: inet_frag_kill() has not removed fq from rhashtable
+ * @INET_FRAG_DROP: if skbs must be dropped (instead of being consumed)
  */
 enum {
 	INET_FRAG_FIRST_IN	= BIT(0),
 	INET_FRAG_LAST_IN	= BIT(1),
 	INET_FRAG_COMPLETE	= BIT(2),
 	INET_FRAG_HASH_DEAD	= BIT(3),
+	INET_FRAG_DROP		= BIT(4),
 };
 
 struct frag_v4_compare_key {
@@ -139,7 +142,8 @@ void inet_frag_destroy(struct inet_frag_queue *q);
 struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key);
 
 /* Free all skbs in the queue; return the sum of their truesizes. */
-unsigned int inet_frag_rbtree_purge(struct rb_root *root);
+unsigned int inet_frag_rbtree_purge(struct rb_root *root,
+				    enum skb_drop_reason reason);
 
 static inline void inet_frag_put(struct inet_frag_queue *q)
 {

include/net/ipv6_frag.h

@@ -76,6 +76,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
 	if (fq->q.flags & INET_FRAG_COMPLETE)
 		goto out;
 
+	fq->q.flags |= INET_FRAG_DROP;
 	inet_frag_kill(&fq->q);
 
 	dev = dev_get_by_index_rcu(net, fq->iif);
@@ -101,7 +102,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
 	spin_unlock(&fq->q.lock);
 
 	icmpv6_send(head, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0);
-	kfree_skb(head);
+	kfree_skb_reason(head, SKB_DROP_REASON_FRAG_REASM_TIMEOUT);
 	goto out_rcu_unlock;
 
 out:

net/ipv4/inet_fragment.c

@@ -133,6 +133,7 @@ static void inet_frags_free_cb(void *ptr, void *arg)
 	count = del_timer_sync(&fq->timer) ? 1 : 0;
 
 	spin_lock_bh(&fq->lock);
+	fq->flags |= INET_FRAG_DROP;
 	if (!(fq->flags & INET_FRAG_COMPLETE)) {
 		fq->flags |= INET_FRAG_COMPLETE;
 		count++;
@@ -260,7 +261,8 @@ static void inet_frag_destroy_rcu(struct rcu_head *head)
 	kmem_cache_free(f->frags_cachep, q);
 }
 
-unsigned int inet_frag_rbtree_purge(struct rb_root *root)
+unsigned int inet_frag_rbtree_purge(struct rb_root *root,
+				    enum skb_drop_reason reason)
 {
 	struct rb_node *p = rb_first(root);
 	unsigned int sum = 0;
@@ -274,7 +276,7 @@ unsigned int inet_frag_rbtree_purge(struct rb_root *root)
 			struct sk_buff *next = FRAG_CB(skb)->next_frag;
 
 			sum += skb->truesize;
-			kfree_skb(skb);
+			kfree_skb_reason(skb, reason);
 			skb = next;
 		}
 	}
@@ -284,17 +286,21 @@ EXPORT_SYMBOL(inet_frag_rbtree_purge);
 
 void inet_frag_destroy(struct inet_frag_queue *q)
 {
-	struct fqdir *fqdir;
 	unsigned int sum, sum_truesize = 0;
+	enum skb_drop_reason reason;
 	struct inet_frags *f;
+	struct fqdir *fqdir;
 
 	WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
+	reason = (q->flags & INET_FRAG_DROP) ?
+			SKB_DROP_REASON_FRAG_REASM_TIMEOUT :
+			SKB_CONSUMED;
 	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_truesize = inet_frag_rbtree_purge(&q->rb_fragments, reason);
 	sum = sum_truesize + f->qsize;
 
 	call_rcu(&q->rcu, inet_frag_destroy_rcu);

net/ipv4/ip_fragment.c

@@ -153,6 +153,7 @@ static void ip_expire(struct timer_list *t)
 	if (qp->q.flags & INET_FRAG_COMPLETE)
 		goto out;
 
+	qp->q.flags |= INET_FRAG_DROP;
 	ipq_kill(qp);
 	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
 	__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
@@ -194,7 +195,7 @@ static void ip_expire(struct timer_list *t)
 	spin_unlock(&qp->q.lock);
 out_rcu_unlock:
 	rcu_read_unlock();
-	kfree_skb(head);
+	kfree_skb_reason(head, SKB_DROP_REASON_FRAG_REASM_TIMEOUT);
 	ipq_put(qp);
 }
 
@@ -254,7 +255,8 @@ static int ip_frag_reinit(struct ipq *qp)
 		return -ETIMEDOUT;
 	}
 
-	sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments);
+	sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments,
+					      SKB_DROP_REASON_NOT_SPECIFIED);
 	sub_frag_mem_limit(qp->q.fqdir, sum_truesize);
 
 	qp->q.flags = 0;