[TCP] Westwood: fix first sample

Need to update send sequence number tracking after first ack.
Rework of patch from Luca De Cicco.

Signed-off-by: Stephen Hemminger <shemminger@dxpl.pdx.osdl.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 1 deletions

diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index 29eb258b6d82..62a96b71b0dd 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -22,6 +22,7 @@ struct westwood {
         u32    accounted;
         u32    rtt;
         u32    rtt_min;          /* minimum observed RTT */
+        u8     first_ack;        /* flag which infers that this is the first ack */
 };
 
 
@@ -52,6 +53,7 @@ static void tcp_westwood_init(struct sock *sk)
         w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT;
         w->rtt_win_sx = tcp_time_stamp;
         w->snd_una = tcp_sk(sk)->snd_una;
+        w->first_ack = 1;
 }
 
 /*
@@ -91,6 +93,15 @@ static void westwood_update_window(struct sock *sk)
         struct westwood *w = inet_csk_ca(sk);
         s32 delta = tcp_time_stamp - w->rtt_win_sx;
 
+        /* Initialise w->snd_una with the first acked sequence number in order
+         * to fix mismatch between tp->snd_una and w->snd_una for the first
+         * bandwidth sample
+         */
+        if (w->first_ack) {
+                w->snd_una = tcp_sk(sk)->snd_una;
+                w->first_ack = 0;
+        }
+
         /*
          * See if a RTT-window has passed.
          * Be careful since if RTT is less than
@@ -180,7 +191,7 @@ static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         struct westwood *w = inet_csk_ca(sk);
-
+        
         switch(event) {
         case CA_EVENT_FAST_ACK:
                 westwood_fast_bw(sk);