net: ip: make ip_route_input_noref() return drop reasons

In this commit, we make ip_route_input_noref() return drop reasons, which
come from ip_route_input_rcu().

We need adjust the callers of ip_route_input_noref() to make sure the
return value of ip_route_input_noref() is used properly.

The errno that ip_route_input_noref() returns comes from ip_route_input
and bpf_lwt_input_reroute in the origin logic, and we make them return
-EINVAL on error instead. In the following patch, we will make
ip_route_input() returns drop reasons too.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

3 files changed, 14 insertions, 11 deletions

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 48e2810f1f27..07036a2943c1 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -132,12 +132,12 @@ static bool frag_expire_skip_icmp(u32 user)
  */
 static void ip_expire(struct timer_list *t)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_FRAG_REASM_TIMEOUT;
 	struct inet_frag_queue *frag = from_timer(frag, t, timer);
 	const struct iphdr *iph;
 	struct sk_buff *head = NULL;
 	struct net *net;
 	struct ipq *qp;
-	int err;
 
 	qp = container_of(frag, struct ipq, q);
 	net = qp->q.fqdir->net;
@@ -175,14 +175,15 @@ static void ip_expire(struct timer_list *t)
 
 	/* skb has no dst, perform route lookup again */
 	iph = ip_hdr(head);
-	err = ip_route_input_noref(head, iph->daddr, iph->saddr, ip4h_dscp(iph),
-				   head->dev);
-	if (err)
+	reason = ip_route_input_noref(head, iph->daddr, iph->saddr,
+				      ip4h_dscp(iph), head->dev);
+	if (reason)
 		goto out;
 
 	/* Only an end host needs to send an ICMP
 	 * "Fragment Reassembly Timeout" message, per RFC792.
 	 */
+	reason = SKB_DROP_REASON_FRAG_REASM_TIMEOUT;
 	if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
 	    (skb_rtable(head)->rt_type != RTN_LOCAL))
 		goto out;
@@ -195,7 +196,7 @@ out:
 	spin_unlock(&qp->q.lock);
 out_rcu_unlock:
 	rcu_read_unlock();
-	kfree_skb_reason(head, SKB_DROP_REASON_FRAG_REASM_TIMEOUT);
+	kfree_skb_reason(head, reason);
 	ipq_put(qp);
 }
 
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index c40a26972884..513eb0c6435a 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -362,10 +362,11 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 	 *	how the packet travels inside Linux networking.
 	 */
 	if (!skb_valid_dst(skb)) {
-		err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
-					   ip4h_dscp(iph), dev);
-		if (unlikely(err))
+		drop_reason = ip_route_input_noref(skb, iph->daddr, iph->saddr,
+						   ip4h_dscp(iph), dev);
+		if (unlikely(drop_reason))
 			goto drop_error;
+		drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	} else {
 		struct in_device *in_dev = __in_dev_get_rcu(dev);
 
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 270bc8c96619..5a7edb66174a 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2500,8 +2500,9 @@ ip_route_input_rcu(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	return ip_route_input_slow(skb, daddr, saddr, dscp, dev, res);
 }
 
-int ip_route_input_noref(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-			 dscp_t dscp, struct net_device *dev)
+enum skb_drop_reason ip_route_input_noref(struct sk_buff *skb, __be32 daddr,
+					  __be32 saddr, dscp_t dscp,
+					  struct net_device *dev)
 {
 	enum skb_drop_reason reason;
 	struct fib_result res;
@@ -2510,7 +2511,7 @@ int ip_route_input_noref(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	reason = ip_route_input_rcu(skb, daddr, saddr, dscp, dev, &res);
 	rcu_read_unlock();
 
-	return reason ? -EINVAL : 0;
+	return reason;
 }
 EXPORT_SYMBOL(ip_route_input_noref);