Re: [PATCH v3 net-next 3/6] net: Add SW fallback infrastructure for offloaded sockets

Offloaded sockets rely on the netdev to transform the transmitted
packets before sending them over the network.
When a packet from an offloaded socket is looped back or
rerouted to a different device we need to detect it and
do the transformation in software

Signed-off-by: Ilya Lesokhin <redacted>
Signed-off-by: Boris Pismenny <redacted>
---
 include/net/sock.h | 17 +++++++++++++++++
 net/core/dev.c     |  4 ++++
 2 files changed, 21 insertions(+)

diff --git a/include/net/sock.h b/include/net/sock.h
index 9a9047268d37..5397307603ec 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h

@@ -479,6 +479,9 @@ struct sock {
 	void			(*sk_error_report)(struct sock *sk);
 	int			(*sk_backlog_rcv)(struct sock *sk,
 						  struct sk_buff *skb);
+	struct sk_buff*		(*sk_offload_check)(struct sock *sk,
+						    struct net_device *dev,
+						    struct sk_buff *skb);
 	void                    (*sk_destruct)(struct sock *sk);
 	struct sock_reuseport __rcu	*sk_reuseport_cb;
 	struct rcu_head		sk_rcu;

@@ -2324,6 +2327,20 @@ static inline bool sk_fullsock(const struct sock *sk)
 	return (1 << sk->sk_state) & ~(TCPF_TIME_WAIT | TCPF_NEW_SYN_RECV);
 }
 
+/* Checks if this SKB belongs to an HW offloaded socket
+ * and whether any SW fallbacks are required based on dev.
+ */
+static inline struct sk_buff *skb_offload_check(struct sk_buff *skb,
+						struct net_device *dev)
+{
+	struct sock *sk = skb->sk;
+
+	if (sk && sk_fullsock(sk) && sk->sk_offload_check)

+		skb = sk->sk_offload_check(sk, dev, skb);
+
+	return skb;
+}
+
 /* This helper checks if a socket is a LISTEN or NEW_SYN_RECV
  * SYNACK messages can be attached to either ones (depending on SYNCOOKIE)
  */

diff --git a/net/core/dev.c b/net/core/dev.c
index b0eee49a2489..6a78d9046674 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -3051,6 +3051,10 @@ static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device
 	if (unlikely(!skb))
 		goto out_null;
 
+	skb = skb_offload_check(skb, dev);
+	if (!skb)
+		goto out_null;
+
 	if (netif_needs_gso(skb, features)) {
 		struct sk_buff *segs;
 

-- 
2.15.0.317.g14c63a9