net: Abstract away all dst_entry metrics accesses.

Use helper functions to hide all direct accesses, especially writes,
to dst_entry metrics values.

This will allow us to:

1) More easily change how the metrics are stored.

2) Implement COW for metrics.

In particular this will help us put metrics into the inetpeer
cache if that is what we end up doing.  We can make the _metrics
member a pointer instead of an array, initially have it point
at the read-only metrics in the FIB, and then on the first set
grab an inetpeer entry and point the _metrics member there.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6d8ab1c4efc..824e8c8a17a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -734,7 +734,7 @@ void tcp_update_metrics(struct sock *sk)
 			 * Reset our results.
 			 */
 			if (!(dst_metric_locked(dst, RTAX_RTT)))
-				dst->metrics[RTAX_RTT - 1] = 0;
+				dst_metric_set(dst, RTAX_RTT, 0);
 			return;
 		}
 
@@ -776,34 +776,38 @@ void tcp_update_metrics(struct sock *sk)
 			if (dst_metric(dst, RTAX_SSTHRESH) &&
 			    !dst_metric_locked(dst, RTAX_SSTHRESH) &&
 			    (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
-				dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
+				dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_cwnd >> 1);
 			if (!dst_metric_locked(dst, RTAX_CWND) &&
 			    tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
-				dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd;
+				dst_metric_set(dst, RTAX_CWND, tp->snd_cwnd);
 		} else if (tp->snd_cwnd > tp->snd_ssthresh &&
 			   icsk->icsk_ca_state == TCP_CA_Open) {
 			/* Cong. avoidance phase, cwnd is reliable. */
 			if (!dst_metric_locked(dst, RTAX_SSTHRESH))
-				dst->metrics[RTAX_SSTHRESH-1] =
-					max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
+				dst_metric_set(dst, RTAX_SSTHRESH,
+					       max(tp->snd_cwnd >> 1, tp->snd_ssthresh));
 			if (!dst_metric_locked(dst, RTAX_CWND))
-				dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1;
+				dst_metric_set(dst, RTAX_CWND,
+					       (dst_metric(dst, RTAX_CWND) +
+						tp->snd_cwnd) >> 1);
 		} else {
 			/* Else slow start did not finish, cwnd is non-sense,
 			   ssthresh may be also invalid.
 			 */
 			if (!dst_metric_locked(dst, RTAX_CWND))
-				dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1;
+				dst_metric_set(dst, RTAX_CWND,
+					       (dst_metric(dst, RTAX_CWND) +
+						tp->snd_ssthresh) >> 1);
 			if (dst_metric(dst, RTAX_SSTHRESH) &&
 			    !dst_metric_locked(dst, RTAX_SSTHRESH) &&
 			    tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH))
-				dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
+				dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_ssthresh);
 		}
 
 		if (!dst_metric_locked(dst, RTAX_REORDERING)) {
 			if (dst_metric(dst, RTAX_REORDERING) < tp->reordering &&
 			    tp->reordering != sysctl_tcp_reordering)
-				dst->metrics[RTAX_REORDERING-1] = tp->reordering;
+				dst_metric_set(dst, RTAX_REORDERING, tp->reordering);
 		}
 	}
 }