3 files changed, 78 insertions, 0 deletions

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 73a25b52bf7..690e88ba248 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -511,6 +511,15 @@ config TCP_CONG_VEGAS
         window. TCP Vegas should provide less packet loss, but it is
         not as aggressive as TCP Reno.
 
+config TCP_CONG_SCALABLE
+        tristate "Scalable TCP"
+        depends on INET && EXPERIMENTAL
+        default n
+        ---help---
+        Scalable TCP is a sender-side only change to TCP which uses a
+        MIMD congestion control algorithm which has some nice scaling
+        properties, though is known to have fairness issues.
+        See http://www-lce.eng.cam.ac.uk/~ctk21/scalable/
 
 endmenu
 
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index e96ed17deb9..5718cdb3a61 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
 obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
 obj-$(CONFIG_TCP_CONG_HTCP) += tcp_htcp.o
 obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
+obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
                       xfrm4_output.o
diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
new file mode 100644
index 00000000000..70e108e15c7
--- /dev/null
+++ b/net/ipv4/tcp_scalable.c
@@ -0,0 +1,68 @@
+/* Tom Kelly's Scalable TCP
+ *
+ * See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
+ *
+ * John Heffner <jheffner@sc.edu>
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <net/tcp.h>
+
+/* These factors derived from the recommended values in the aer:
+ * .01 and and 7/8. We use 50 instead of 100 to account for
+ * delayed ack.
+ */
+#define TCP_SCALABLE_AI_CNT     50U
+#define TCP_SCALABLE_MD_SCALE   3
+
+static void tcp_scalable_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
+                                    u32 in_flight, int flag)
+{
+        if (in_flight < tp->snd_cwnd)
+                return;
+
+        if (tp->snd_cwnd <= tp->snd_ssthresh) {
+                tp->snd_cwnd++;
+        } else {
+                tp->snd_cwnd_cnt++;
+                if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
+                        tp->snd_cwnd++;
+                        tp->snd_cwnd_cnt = 0;
+                }
+        }
+        tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
+        tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+static u32 tcp_scalable_ssthresh(struct tcp_sock *tp)
+{
+        return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
+}
+
+
+static struct tcp_congestion_ops tcp_scalable = {
+        .ssthresh       = tcp_scalable_ssthresh,
+        .cong_avoid     = tcp_scalable_cong_avoid,
+        .min_cwnd       = tcp_reno_min_cwnd,
+
+        .owner          = THIS_MODULE,
+        .name           = "scalable",
+};
+
+static int __init tcp_scalable_register(void)
+{
+        return tcp_register_congestion_control(&tcp_scalable);
+}
+
+static void __exit tcp_scalable_unregister(void)
+{
+        tcp_unregister_congestion_control(&tcp_scalable);
+}
+
+module_init(tcp_scalable_register);
+module_exit(tcp_scalable_unregister);
+
+MODULE_AUTHOR("John Heffner");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Scalable TCP");