[TCP]: Make fackets_out accurate
Substraction for fackets_out is unconditional when snd_una
advances, thus there's no need to do it inside the loop. Just
make sure correct bounds are honored.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9df5b2a..cbe8bf6 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -652,6 +652,26 @@
}
}
+/* When a modification to fackets out becomes necessary, we need to check
+ * skb is counted to fackets_out or not. Another important thing is to
+ * tweak SACK fastpath hint too as it would overwrite all changes unless
+ * hint is also changed.
+ */
+static void tcp_adjust_fackets_out(struct tcp_sock *tp, struct sk_buff *skb,
+ int decr)
+{
+ if (!tp->sacked_out)
+ return;
+
+ if (!before(tp->highest_sack, TCP_SKB_CB(skb)->seq))
+ tp->fackets_out -= decr;
+
+ /* cnt_hint is "off-by-one" compared with fackets_out (see sacktag) */
+ if (tp->fastpath_skb_hint != NULL &&
+ after(TCP_SKB_CB(tp->fastpath_skb_hint)->seq, TCP_SKB_CB(skb)->seq))
+ tp->fastpath_cnt_hint -= decr;
+}
+
/* Function to create two new TCP segments. Shrinks the given segment
* to the specified size and appends a new segment with the rest of the
* packet to the list. This won't be called frequently, I hope.
@@ -746,21 +766,12 @@
if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
tp->lost_out -= diff;
- if (diff > 0) {
- /* Adjust Reno SACK estimate. */
- if (tcp_is_reno(tp)) {
- tcp_dec_pcount_approx_int(&tp->sacked_out, diff);
- tcp_verify_left_out(tp);
- }
-
- tcp_dec_pcount_approx_int(&tp->fackets_out, diff);
- /* SACK fastpath might overwrite it unless dealt with */
- if (tp->fastpath_skb_hint != NULL &&
- after(TCP_SKB_CB(tp->fastpath_skb_hint)->seq,
- TCP_SKB_CB(skb)->seq)) {
- tcp_dec_pcount_approx_int(&tp->fastpath_cnt_hint, diff);
- }
+ /* Adjust Reno SACK estimate. */
+ if (tcp_is_reno(tp) && diff > 0) {
+ tcp_dec_pcount_approx_int(&tp->sacked_out, diff);
+ tcp_verify_left_out(tp);
}
+ tcp_adjust_fackets_out(tp, skb, diff);
}
/* Link BUFF into the send queue. */
@@ -1746,10 +1757,7 @@
if (tcp_is_reno(tp) && tp->sacked_out)
tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
- /* Not quite right: it can be > snd.fack, but
- * it is better to underestimate fackets.
- */
- tcp_dec_pcount_approx(&tp->fackets_out, next_skb);
+ tcp_adjust_fackets_out(tp, skb, tcp_skb_pcount(next_skb));
tp->packets_out -= tcp_skb_pcount(next_skb);
sk_stream_free_skb(sk, next_skb);
}