[TCP]: Add Scalable TCP congestion control module.

This patch implements Tom Kelly's Scalable TCP congestion control algorithm 
for the modular framework.

The algorithm has some nice scaling properties, and has been used a fair bit 
in research, though is known to have significant fairness issues, so it's not 
really suitable for general purpose use.

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

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/
 
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