Subject: [PATCH stable 4.9 10/29] inet: frags: get rif of inet_frag_evicting()

From: Florian Fainelli <[email-masked]>
Date: Tue, 9 Oct 2018 15:49:05 -0700

From: Eric Dumazet <[email-masked]>

This refactors ip_expire() since one indentation level is removed.

Note: in the future, we should try hard to avoid the skb_clone()
since this is a serious performance cost.
Under DDOS, the ICMP message wont be sent because of rate limits.

Fact that ip6_expire_frag_queue() does not use skb_clone() is
disturbing too. Presumably IPv6 should have the same
issue than the one we fixed in commit ec4fbd64751d
("inet: frag: release spinlock before calling icmp_send()")

Signed-off-by: Eric Dumazet <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
(cherry picked from commit 399d1404be660d355192ff4df5ccc3f4159ec1e4)
---
 include/net/inet_frag.h |  5 ----
 net/ipv4/ip_fragment.c  | 65 ++++++++++++++++++++---------------------
 net/ipv6/reassembly.c   |  4 ---
 3 files changed, 32 insertions(+), 42 deletions(-)

diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index a49cdf25cef0..7e984045b2b7 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -118,11 +118,6 @@ static inline void inet_frag_put(struct inet_frag_queue *q)
 		inet_frag_destroy(q);
 }
 
-static inline bool inet_frag_evicting(struct inet_frag_queue *q)
-{
-	return false;
-}
-
 /* Memory Tracking Functions. */
 
 static inline int frag_mem_limit(struct netns_frags *nf)
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 8c4072b19296..308592a8ba97 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -141,8 +141,11 @@ static bool frag_expire_skip_icmp(u32 user)
  */
 static void ip_expire(unsigned long arg)
 {
-	struct ipq *qp;
+	struct sk_buff *clone, *head;
+	const struct iphdr *iph;
 	struct net *net;
+	struct ipq *qp;
+	int err;
 
 	qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
 	net = container_of(qp->q.net, struct net, ipv4.frags);
@@ -156,45 +159,41 @@ static void ip_expire(unsigned long arg)
 	ipq_kill(qp);
 	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
 
-	if (!inet_frag_evicting(&qp->q)) {
-		struct sk_buff *clone, *head = qp->q.fragments;
-		const struct iphdr *iph;
-		int err;
+	head = qp->q.fragments;
 
-		__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
+	__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
 
-		if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
-			goto out;
+	if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !head)
+		goto out;
 
-		head->dev = dev_get_by_index_rcu(net, qp->iif);
-		if (!head->dev)
-			goto out;
+	head->dev = dev_get_by_index_rcu(net, qp->iif);
+	if (!head->dev)
+		goto out;

-		/* skb has no dst, perform route lookup again */
-		iph = ip_hdr(head);
-		err = ip_route_input_noref(head, iph->daddr, iph->saddr,
+	/* skb has no dst, perform route lookup again */
+	iph = ip_hdr(head);
+	err = ip_route_input_noref(head, iph->daddr, iph->saddr,
 					   iph->tos, head->dev);
-		if (err)
-			goto out;
+	if (err)
+		goto out;
 
-		/* Only an end host needs to send an ICMP
-		 * "Fragment Reassembly Timeout" message, per RFC792.
-		 */
-		if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
-		    (skb_rtable(head)->rt_type != RTN_LOCAL))
-			goto out;
-
-		clone = skb_clone(head, GFP_ATOMIC);
-
-		/* Send an ICMP "Fragment Reassembly Timeout" message. */
-		if (clone) {
-			spin_unlock(&qp->q.lock);
-			icmp_send(clone, ICMP_TIME_EXCEEDED,
-				  ICMP_EXC_FRAGTIME, 0);
-			consume_skb(clone);
-			goto out_rcu_unlock;
-		}
+	/* Only an end host needs to send an ICMP
+	 * "Fragment Reassembly Timeout" message, per RFC792.
+	 */
+	if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
+	    (skb_rtable(head)->rt_type != RTN_LOCAL))
+		goto out;
+
+	clone = skb_clone(head, GFP_ATOMIC);
+
+	/* Send an ICMP "Fragment Reassembly Timeout" message. */
+	if (clone) {
+		spin_unlock(&qp->q.lock);
+		icmp_send(clone, ICMP_TIME_EXCEEDED,
+			  ICMP_EXC_FRAGTIME, 0);
+		consume_skb(clone);
+		goto out_rcu_unlock;
 	}
 out:
 	spin_unlock(&qp->q.lock);
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 8fe3836d1410..629a45a4c79f 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -106,10 +106,6 @@ void ip6_expire_frag_queue(struct net *net, struct frag_queue *fq)
 		goto out_rcu_unlock;
 
 	__IP6_INC_STATS(net, __in6_dev_get(dev), IPSTATS_MIB_REASMFAILS);
-
-	if (inet_frag_evicting(&fq->q))
-		goto out_rcu_unlock;
-
 	__IP6_INC_STATS(net, __in6_dev_get(dev), IPSTATS_MIB_REASMTIMEOUT);
 
 	/* Don't send error if the first segment did not arrive. */
-- 
2.17.1