[PATCH 2.6] BIC tcp congestion calculation timestamp

[Stephen Hemminger <shemminger@xxxxxxxx>]

Small change to bictcp based on the BIC 1.1 patches for web100.
Keep track of last time congestion was computed, and recompute
if cwnd changes or every 1/32 of a second.

Also changes the initialization location for the parameters.

Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxx>

diff -urN -X dontdiff linux-2.6/include/linux/tcp.h tcp-2.6/include/linux/tcp.h
--- linux-2.6/include/linux/tcp.h       2004-06-23 09:29:47.000000000 -0700
+++ tcp-2.6/include/linux/tcp.h 2004-07-27 10:26:52.000000000 -0700
@@ -420,6 +420,7 @@
                __u32   cnt;            /* increase cwnd by 1 after this number 
of ACKs */
                __u32   last_max_cwnd;  /* last maximium snd_cwnd */
                __u32   last_cwnd;      /* the last snd_cwnd */
+               __u32   last_stamp;     /* time when updated last_cwnd */
        } bictcp;
 };
 
diff -urN -X dontdiff linux-2.6/net/ipv4/tcp_input.c 
tcp-2.6/net/ipv4/tcp_input.c
--- linux-2.6/net/ipv4/tcp_input.c      2004-07-23 09:36:18.000000000 -0700
+++ tcp-2.6/net/ipv4/tcp_input.c        2004-07-28 13:52:50.000000000 -0700
@@ -330,6 +330,15 @@
        tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
+static void init_bictcp(struct tcp_opt *tp)
+{
+       tp->bictcp.cnt = 0;
+
+       tp->bictcp.last_max_cwnd = 0;
+       tp->bictcp.last_cwnd = 0;
+       tp->bictcp.last_stamp = 0;
+}
+
 /* 5. Recalculate window clamp after socket hit its memory bounds. */
 static void tcp_clamp_window(struct sock *sk, struct tcp_opt *tp)
 {
@@ -1233,6 +1242,8 @@
        tcp_set_ca_state(tp, TCP_CA_Loss);
        tp->high_seq = tp->frto_highmark;
        TCP_ECN_queue_cwr(tp);
+
+       init_bictcp(tp);
 }
 
 void tcp_clear_retrans(struct tcp_opt *tp)
@@ -2011,10 +2022,12 @@
        if (!sysctl_tcp_bic)
                return tp->snd_cwnd;
 
-       if (tp->bictcp.last_cwnd == tp->snd_cwnd)
-               return tp->bictcp.cnt; /*  same cwnd, no update */
-      
+       if (tp->bictcp.last_cwnd == tp->snd_cwnd &&
+          (s32)(tcp_time_stamp - tp->bictcp.last_stamp) <= (HZ>>5))
+               return tp->bictcp.cnt;
+
        tp->bictcp.last_cwnd = tp->snd_cwnd;
+       tp->bictcp.last_stamp = tcp_time_stamp;
       
        /* start off normal */
        if (tp->snd_cwnd <= sysctl_tcp_bic_low_window)
@@ -4612,6 +4625,7 @@
                                return 1;
 
                        init_westwood(sk);
+                       init_bictcp(tp);
 
                        /* Now we have several options: In theory there is 
                         * nothing else in the frame. KA9Q has an option to 
@@ -4635,6 +4649,7 @@
 
        case TCP_SYN_SENT:
                init_westwood(sk);
+               init_bictcp(tp);
 
                queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
                if (queued >= 0)
diff -urN -X dontdiff linux-2.6/net/ipv4/tcp_minisocks.c 
tcp-2.6/net/ipv4/tcp_minisocks.c
--- linux-2.6/net/ipv4/tcp_minisocks.c  2004-07-23 09:36:18.000000000 -0700
+++ tcp-2.6/net/ipv4/tcp_minisocks.c    2004-07-23 09:48:07.000000000 -0700
@@ -767,9 +767,6 @@
                newtp->snd_cwnd = 2;
                newtp->snd_cwnd_cnt = 0;
 
-               newtp->bictcp.cnt = 0;
-               newtp->bictcp.last_max_cwnd = newtp->bictcp.last_cwnd = 0;
-
                newtp->frto_counter = 0;
                newtp->frto_highmark = 0;