[PATCH net-next v2 6/7] net: ip: make ip_route_input_noref() return drop reasons

[Menglong Dong]

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 in the origin logic is
returned by ip_route_input and bpf_lwt_input_reroute, 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@xxxxxxxxxxxxxxx>
---
 include/net/route.h    | 15 ++++++++-------
 net/core/lwt_bpf.c     |  1 +
 net/ipv4/ip_fragment.c | 12 +++++++-----
 net/ipv4/ip_input.c    |  7 ++++---
 net/ipv4/route.c       |  7 ++++---
 5 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/include/net/route.h b/include/net/route.h
index 35bc12146960..c0b1b5fb9b59 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -202,8 +202,9 @@ enum skb_drop_reason
 ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		      u8 tos, struct net_device *dev,
 		      struct in_device *in_dev, u32 *itag);
-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);
 int ip_route_use_hint(struct sk_buff *skb, __be32 dst, __be32 src,
 		      u8 tos, struct net_device *devin,
 		      const struct sk_buff *hint);
@@ -211,18 +212,18 @@ int ip_route_use_hint(struct sk_buff *skb, __be32 dst, __be32 src,
 static inline int ip_route_input(struct sk_buff *skb, __be32 dst, __be32 src,
 				 dscp_t dscp, struct net_device *devin)
 {
-	int err;
+	enum skb_drop_reason reason;
 
 	rcu_read_lock();
-	err = ip_route_input_noref(skb, dst, src, dscp, devin);
-	if (!err) {
+	reason = ip_route_input_noref(skb, dst, src, dscp, devin);
+	if (!reason) {
 		skb_dst_force(skb);
 		if (!skb_dst(skb))
-			err = -EINVAL;
+			reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	}
 	rcu_read_unlock();
 
-	return err;
+	return reason ? -EINVAL : 0;
 }
 
 void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu, int oif,
diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c
index e0ca24a58810..a4652f2a103a 100644
--- a/net/core/lwt_bpf.c
+++ b/net/core/lwt_bpf.c
@@ -98,6 +98,7 @@ static int bpf_lwt_input_reroute(struct sk_buff *skb)
 		skb_dst_drop(skb);
 		err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
 					   ip4h_dscp(iph), dev);
+		err = err ? -EINVAL : 0;
 		dev_put(dev);
 	} else if (skb->protocol == htons(ETH_P_IPV6)) {
 		skb_dst_drop(skb);
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 48e2810f1f27..52b991e976ba 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;
@@ -175,10 +175,12 @@ 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;
+	else
+		reason = SKB_DROP_REASON_FRAG_REASM_TIMEOUT;
 
 	/* Only an end host needs to send an ICMP
 	 * "Fragment Reassembly Timeout" message, per RFC792.
@@ -195,7 +197,7 @@ static void ip_expire(struct timer_list *t)
 	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 a6f5bfc274ee..aeb71675052c 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 56a1ebddde24..6baaaf0bcb3e 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2492,8 +2492,9 @@ 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;
@@ -2502,7 +2503,7 @@ 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);
 
-- 
2.39.5