tcp: add helper for counter tweaking due mid-wq change

We need full-scale adjustment to fix a TCP miscount in the next
patch, so just move it into a helper and call for that from the
other places.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 34 insertions, 47 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index e54c76d75495..1b94b9bfe2dc 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -616,21 +616,6 @@ static inline int tcp_skb_mss(const struct sk_buff *skb)
         return skb_shinfo(skb)->gso_size;
 }
 
-static inline void tcp_dec_pcount_approx_int(__u32 *count, const int decr)
-{
-        if (*count) {
-                *count -= decr;
-                if ((int)*count < 0)
-                        *count = 0;
-        }
-}
-
-static inline void tcp_dec_pcount_approx(__u32 *count,
-                                         const struct sk_buff *skb)
-{
-        tcp_dec_pcount_approx_int(count, tcp_skb_pcount(skb));
-}
-
 /* Events passed to congestion control interface */
 enum tcp_ca_event {
         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index c1f259d2d33b..f1db89bb3aa7 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -754,6 +754,36 @@ static void tcp_adjust_fackets_out(struct sock *sk, struct sk_buff *skb,
                 tp->fackets_out -= decr;
 }
 
+/* Pcount in the middle of the write queue got changed, we need to do various
+ * tweaks to fix counters
+ */
+static void tcp_adjust_pcount(struct sock *sk, struct sk_buff *skb, int decr)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+
+        tp->packets_out -= decr;
+
+        if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
+                tp->sacked_out -= decr;
+        if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
+                tp->retrans_out -= decr;
+        if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
+                tp->lost_out -= decr;
+
+        /* Reno case is special. Sigh... */
+        if (tcp_is_reno(tp) && decr > 0)
+                tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
+
+        tcp_adjust_fackets_out(sk, skb, decr);
+
+        if (tp->lost_skb_hint &&
+            before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
+            (tcp_is_fack(tp) || TCP_SKB_CB(skb)->sacked))
+                tp->lost_cnt_hint -= decr;
+
+        tcp_verify_left_out(tp);
+}
+
 /* 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.
@@ -836,28 +866,8 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
                 int diff = old_factor - tcp_skb_pcount(skb) -
                         tcp_skb_pcount(buff);
 
-                tp->packets_out -= diff;
-
-                if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
-                        tp->sacked_out -= diff;
-                if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
-                        tp->retrans_out -= diff;
-
-                if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
-                        tp->lost_out -= 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(sk, skb, diff);
-
-                if (tp->lost_skb_hint &&
-                    before(TCP_SKB_CB(skb)->seq,
-                           TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
-                    (tcp_is_fack(tp) || TCP_SKB_CB(skb)->sacked))
-                        tp->lost_cnt_hint -= diff;
+                if (diff)
+                        tcp_adjust_pcount(sk, skb, diff);
         }
 
         /* Link BUFF into the send queue. */
@@ -1768,22 +1778,14 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
          * packet counting does not break.
          */
         TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
-        if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_RETRANS)
-                tp->retrans_out -= tcp_skb_pcount(next_skb);
-        if (TCP_SKB_CB(next_skb)->sacked & TCPCB_LOST)
-                tp->lost_out -= tcp_skb_pcount(next_skb);
-        /* Reno case is special. Sigh... */
-        if (tcp_is_reno(tp) && tp->sacked_out)
-                tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
-
-        tcp_adjust_fackets_out(sk, next_skb, tcp_skb_pcount(next_skb));
-        tp->packets_out -= tcp_skb_pcount(next_skb);
 
         /* changed transmit queue under us so clear hints */
         tcp_clear_retrans_hints_partial(tp);
         if (next_skb == tp->retransmit_skb_hint)
                 tp->retransmit_skb_hint = skb;
 
+        tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
+
         sk_wmem_free_skb(sk, next_skb);
 }