[TCP]: Appropriate Byte Count support

This is an updated version of the RFC3465 ABC patch originally
for Linux 2.6.11-rc4 by Yee-Ting Li. ABC is a way of counting
bytes ack'd rather than packets when updating congestion control.

The orignal ABC described in the RFC applied to a Reno style
algorithm. For advanced congestion control there is little
change after leaving slow start.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e43065654930..4cb5e6f408dc 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -89,6 +89,7 @@ int sysctl_tcp_frto;
 int sysctl_tcp_nometrics_save;
 
 int sysctl_tcp_moderate_rcvbuf = 1;
+int sysctl_tcp_abc = 1;
 
 #define FLAG_DATA               0x01 /* Incoming frame contained data.          */
 #define FLAG_WIN_UPDATE         0x02 /* Incoming ACK was a window update.       */
@@ -1247,6 +1248,7 @@ void tcp_enter_loss(struct sock *sk, int how)
         tp->snd_cwnd_cnt   = 0;
         tp->snd_cwnd_stamp = tcp_time_stamp;
 
+        tp->bytes_acked = 0;
         tcp_clear_retrans(tp);
 
         /* Push undo marker, if it was plain RTO and nothing
@@ -1904,6 +1906,7 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
                         TCP_ECN_queue_cwr(tp);
                 }
 
+                tp->bytes_acked = 0;
                 tp->snd_cwnd_cnt = 0;
                 tcp_set_ca_state(sk, TCP_CA_Recovery);
         }
@@ -2310,6 +2313,9 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
         if (before(ack, prior_snd_una))
                 goto old_ack;
 
+        if (sysctl_tcp_abc && icsk->icsk_ca_state < TCP_CA_CWR)
+                tp->bytes_acked += ack - prior_snd_una;
+
         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
                 /* Window is constant, pure forward advance.
                  * No more checks are required.
@@ -4370,6 +4376,7 @@ discard:
 
 EXPORT_SYMBOL(sysctl_tcp_ecn);
 EXPORT_SYMBOL(sysctl_tcp_reordering);
+EXPORT_SYMBOL(sysctl_tcp_abc);
 EXPORT_SYMBOL(tcp_parse_options);
 EXPORT_SYMBOL(tcp_rcv_established);
 EXPORT_SYMBOL(tcp_rcv_state_process);