net: Introduce sk_tx_queue_mapping

Introduce sk_tx_queue_mapping; and functions that set, test and
get this value. Reset sk_tx_queue_mapping to -1 whenever the dst
cache is set/reset, and in socket alloc. Setting txq to -1 and
using valid txq=<0 to n-1> allows the tx path to use the value
of sk_tx_queue_mapping directly instead of subtracting 1 on every
tx.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -107,6 +107,7 @@ struct net;
  *	@skc_node: main hash linkage for various protocol lookup tables
  *	@skc_nulls_node: main hash linkage for UDP/UDP-Lite protocol
  *	@skc_refcnt: reference count
+ *	@skc_tx_queue_mapping: tx queue number for this connection
  *	@skc_hash: hash value used with various protocol lookup tables
  *	@skc_family: network address family
  *	@skc_state: Connection state
@@ -128,6 +129,7 @@ struct sock_common {
 		struct hlist_nulls_node skc_nulls_node;
 	};
 	atomic_t		skc_refcnt;
+	int			skc_tx_queue_mapping;
 
 	unsigned int		skc_hash;
 	unsigned short		skc_family;
@@ -215,6 +217,7 @@ struct sock {
 #define sk_node			__sk_common.skc_node
 #define sk_nulls_node		__sk_common.skc_nulls_node
 #define sk_refcnt		__sk_common.skc_refcnt
+#define sk_tx_queue_mapping	__sk_common.skc_tx_queue_mapping
 
 #define sk_copy_start		__sk_common.skc_hash
 #define sk_hash			__sk_common.skc_hash
@@ -1094,8 +1097,29 @@ static inline void sock_put(struct sock *sk)
 extern int sk_receive_skb(struct sock *sk, struct sk_buff *skb,
 			  const int nested);
 
+static inline void sk_tx_queue_set(struct sock *sk, int tx_queue)
+{
+	sk->sk_tx_queue_mapping = tx_queue;
+}
+
+static inline void sk_tx_queue_clear(struct sock *sk)
+{
+	sk->sk_tx_queue_mapping = -1;
+}
+
+static inline int sk_tx_queue_get(const struct sock *sk)
+{
+	return sk->sk_tx_queue_mapping;
+}
+
+static inline bool sk_tx_queue_recorded(const struct sock *sk)
+{
+	return (sk && sk->sk_tx_queue_mapping >= 0);
+}
+
 static inline void sk_set_socket(struct sock *sk, struct socket *sock)
 {
+	sk_tx_queue_clear(sk);
 	sk->sk_socket = sock;
 }
 
@@ -1152,6 +1176,7 @@ __sk_dst_set(struct sock *sk, struct dst_entry *dst)
 {
 	struct dst_entry *old_dst;
 
+	sk_tx_queue_clear(sk);
 	old_dst = sk->sk_dst_cache;
 	sk->sk_dst_cache = dst;
 	dst_release(old_dst);
@@ -1170,6 +1195,7 @@ __sk_dst_reset(struct sock *sk)
 {
 	struct dst_entry *old_dst;
 
+	sk_tx_queue_clear(sk);
 	old_dst = sk->sk_dst_cache;
 	sk->sk_dst_cache = NULL;
 	dst_release(old_dst);

net/core/sock.c

@@ -357,6 +357,7 @@ struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie)
 	struct dst_entry *dst = sk->sk_dst_cache;
 
 	if (dst && dst->obsolete && dst->ops->check(dst, cookie) == NULL) {
+		sk_tx_queue_clear(sk);
 		sk->sk_dst_cache = NULL;
 		dst_release(dst);
 		return NULL;
@@ -953,7 +954,8 @@ static void sock_copy(struct sock *nsk, const struct sock *osk)
 	void *sptr = nsk->sk_security;
 #endif
 	BUILD_BUG_ON(offsetof(struct sock, sk_copy_start) !=
-		     sizeof(osk->sk_node) + sizeof(osk->sk_refcnt));
+		     sizeof(osk->sk_node) + sizeof(osk->sk_refcnt) +
+		     sizeof(osk->sk_tx_queue_mapping));
 	memcpy(&nsk->sk_copy_start, &osk->sk_copy_start,
 	       osk->sk_prot->obj_size - offsetof(struct sock, sk_copy_start));
 #ifdef CONFIG_SECURITY_NETWORK
@@ -997,6 +999,7 @@ static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority,
 
 		if (!try_module_get(prot->owner))
 			goto out_free_sec;
+		sk_tx_queue_clear(sk);
 	}
 
 	return sk;