[PATCH bpf-next V3 6/6] net: inline and splitup is_skb_forwardable

[Jesper Dangaard Brouer <brouer@xxxxxxxxxx>]

The BPF-helper bpf_skb_fib_lookup() use is_skb_forwardable() that
also checks if net_device is "up", which is unnecessary for this
helper. This patch splitup is_skb_forwardable() into is_skb_fwd_size_ok()
such that the helper can use this instead.

This change also cause is_skb_forwardable() to be inlined in the
existing call sites. Most importantly in dev_forward_skb().

Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
---
 include/linux/netdevice.h |   27 +++++++++++++++++++++++++--
 net/core/dev.c            |   21 ---------------------
 net/core/filter.c         |    2 +-
 3 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 58fb7b4869ba..4857c54590b5 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3862,8 +3862,31 @@ int xdp_umem_query(struct net_device *dev, u16 queue_id);
 
 int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
 int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
-bool is_skb_forwardable(const struct net_device *dev,
-			const struct sk_buff *skb);
+
+static __always_inline bool is_skb_fwd_size_ok(const struct net_device *dev,
+					       const struct sk_buff *skb)
+{
+	const u32 vlan_hdr_len = 4; /* VLAN_HLEN */
+	unsigned int mtu = dev->mtu + dev->hard_header_len + vlan_hdr_len;
+
+	/* Assumes SKB length at L2 */
+	if (likely(skb->len <= mtu))
+		return true;
+
+	/* If TSO is enabled, we don't care about the length as the packet
+	 * could be forwarded without being segmented before.
+	 */
+	return skb_is_gso(skb);
+}
+
+static __always_inline bool is_skb_forwardable(const struct net_device *dev,
+					       const struct sk_buff *skb)
+{
+	if (unlikely(!(dev->flags & IFF_UP)))
+		return false;
+
+	return is_skb_fwd_size_ok(dev, skb);
+}
 
 static __always_inline int ____dev_forward_skb(struct net_device *dev,
 					       struct sk_buff *skb,
diff --git a/net/core/dev.c b/net/core/dev.c
index 96b455f15872..21b62bda0ef9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2186,27 +2186,6 @@ static inline void net_timestamp_set(struct sk_buff *skb)
 			__net_timestamp(SKB);			\
 	}							\
 
-bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb)
-{
-	unsigned int len;
-
-	if (!(dev->flags & IFF_UP))
-		return false;
-
-	len = dev->mtu + dev->hard_header_len + VLAN_HLEN;
-	if (skb->len <= len)
-		return true;
-
-	/* if TSO is enabled, we don't care about the length as the packet
-	 * could be forwarded without being segmented before
-	 */
-	if (skb_is_gso(skb))
-		return true;
-
-	return false;
-}
-EXPORT_SYMBOL_GPL(is_skb_forwardable);
-
 int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
 {
 	int ret = ____dev_forward_skb(dev, skb, true);
diff --git a/net/core/filter.c b/net/core/filter.c
index a8e24092e4f5..14e6b93757d4 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5502,7 +5502,7 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
 		struct net_device *dev;
 
 		dev = dev_get_by_index_rcu(net, params->ifindex);
-		if (!is_skb_forwardable(dev, skb))
+		if (!is_skb_fwd_size_ok(dev, skb))
 			rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
 
 		params->mtu = dev->mtu; /* union with tot_len */