net: Do delayed neigh confirmation.

When a dst_confirm() happens, mark the confirmation as pending in the
dst.  Then on the next packet out, when we have the neigh in-hand, do
the update.

This removes the dependency in dst_confirm() of dst's having an
attached neigh.

While we're here, remove the explicit 'dst' NULL check, all except 2
or 3 call sites ensure it's not NULL.  So just fix those cases up.

Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 38 insertions, 32 deletions

diff --git a/include/net/dst.h b/include/net/dst.h
index f0bf3b8d5911..84e7a3ff968d 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -51,7 +51,7 @@ struct dst_entry {
         int                     (*input)(struct sk_buff *);
         int                     (*output)(struct sk_buff *);
 
-        int                     flags;
+        unsigned short          flags;
 #define DST_HOST                0x0001
 #define DST_NOXFRM              0x0002
 #define DST_NOPOLICY            0x0004
@@ -62,6 +62,8 @@ struct dst_entry {
 #define DST_FAKE_RTABLE         0x0080
 #define DST_XFRM_TUNNEL         0x0100
 
+        unsigned short          pending_confirm;
+
         short                   error;
         short                   obsolete;
         unsigned short          header_len;     /* more space at head required */
@@ -371,7 +373,8 @@ static inline struct dst_entry *skb_dst_pop(struct sk_buff *skb)
 
 extern int dst_discard(struct sk_buff *skb);
 extern void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
-                       int initial_ref, int initial_obsolete, int flags);
+                       int initial_ref, int initial_obsolete,
+                       unsigned short flags);
 extern void __dst_free(struct dst_entry *dst);
 extern struct dst_entry *dst_destroy(struct dst_entry *dst);
 
@@ -395,14 +398,24 @@ static inline void dst_rcu_free(struct rcu_head *head)
 
 static inline void dst_confirm(struct dst_entry *dst)
 {
-        if (dst) {
-                struct neighbour *n;
+        dst->pending_confirm = 1;
+}
 
-                rcu_read_lock();
-                n = dst_get_neighbour_noref(dst);
-                neigh_confirm(n);
-                rcu_read_unlock();
+static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
+                                   struct sk_buff *skb)
+{
+        struct hh_cache *hh;
+
+        if (unlikely(dst->pending_confirm)) {
+                n->confirmed = jiffies;
+                dst->pending_confirm = 0;
         }
+
+        hh = &n->hh;
+        if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
+                return neigh_hh_output(hh, skb);
+        else
+                return n->output(n, skb);
 }
 
 static inline struct neighbour *dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index e1d18bdeebb8..344d8988842a 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -309,12 +309,6 @@ static inline struct neighbour * neigh_clone(struct neighbour *neigh)
 
 #define neigh_hold(n)   atomic_inc(&(n)->refcnt)
 
-static inline void neigh_confirm(struct neighbour *neigh)
-{
-        if (neigh)
-                neigh->confirmed = jiffies;
-}
-
 static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 {
         unsigned long now = jiffies;
@@ -358,15 +352,6 @@ static inline int neigh_hh_output(struct hh_cache *hh, struct sk_buff *skb)
         return dev_queue_xmit(skb);
 }
 
-static inline int neigh_output(struct neighbour *n, struct sk_buff *skb)
-{
-        struct hh_cache *hh = &n->hh;
-        if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
-                return neigh_hh_output(hh, skb);
-        else
-                return n->output(n, skb);
-}
-
 static inline struct neighbour *
 __neigh_lookup(struct neigh_table *tbl, const void *pkey, struct net_device *dev, int creat)
 {
diff --git a/net/core/dst.c b/net/core/dst.c
index 43d94cedbf7c..a6e19a23a745 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -152,7 +152,7 @@ EXPORT_SYMBOL(dst_discard);
 const u32 dst_default_metrics[RTAX_MAX];
 
 void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
-                int initial_ref, int initial_obsolete, int flags)
+                int initial_ref, int initial_obsolete, unsigned short flags)
 {
         struct dst_entry *dst;
 
@@ -188,6 +188,7 @@ void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
         dst->__use = 0;
         dst->lastuse = jiffies;
         dst->flags = flags;
+        dst->pending_confirm = 0;
         dst->next = NULL;
         if (!(flags & DST_NOCOUNT))
                 dst_entries_add(ops, 1);
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 6e9a266a0535..cc52679790b2 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -198,7 +198,7 @@ static inline int ip_finish_output2(struct sk_buff *skb)
         if (unlikely(!neigh))
                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
         if (neigh) {
-                int res = neigh_output(neigh, skb);
+                int res = dst_neigh_output(dst, neigh, skb);
 
                 rcu_read_unlock_bh();
                 return res;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8416f8a68e65..ca0d0e7c9778 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -740,13 +740,13 @@ void tcp_update_metrics(struct sock *sk)
         if (sysctl_tcp_nometrics_save)
                 return;
 
-        dst_confirm(dst);
-
         if (dst && (dst->flags & DST_HOST)) {
                 const struct inet_connection_sock *icsk = inet_csk(sk);
                 int m;
                 unsigned long rtt;
 
+                dst_confirm(dst);
+
                 if (icsk->icsk_backoff || !tp->srtt) {
                         /* This session failed to estimate rtt. Why?
                          * Probably, no packets returned in time.
@@ -3869,9 +3869,11 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
                         tcp_cong_avoid(sk, ack, prior_in_flight);
         }
 
-        if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
-                dst_confirm(__sk_dst_get(sk));
-
+        if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
+                struct dst_entry *dst = __sk_dst_get(sk);
+                if (dst)
+                        dst_confirm(dst);
+        }
         return 1;
 
 no_queue:
@@ -6140,9 +6142,14 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 
                 case TCP_FIN_WAIT1:
                         if (tp->snd_una == tp->write_seq) {
+                                struct dst_entry *dst;
+
                                 tcp_set_state(sk, TCP_FIN_WAIT2);
                                 sk->sk_shutdown |= SEND_SHUTDOWN;
-                                dst_confirm(__sk_dst_get(sk));
+
+                                dst = __sk_dst_get(sk);
+                                if (dst)
+                                        dst_confirm(dst);
 
                                 if (!sock_flag(sk, SOCK_DEAD))
                                         /* Wake up lingering close() */
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a233a7ccbc3a..c94e4aabe11b 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -125,7 +125,7 @@ static int ip6_finish_output2(struct sk_buff *skb)
         rcu_read_lock();
         neigh = dst_get_neighbour_noref(dst);
         if (neigh) {
-                int res = neigh_output(neigh, skb);
+                int res = dst_neigh_output(dst, neigh, skb);
 
                 rcu_read_unlock();
                 return res;