tcp:add sociopath

original source: @mlucy
https://github.com/mlucy/tcp_sociopath

Signed-off-by: HolyAngel <slverwolf@gmail.com>

net/ipv4/Kconfig

@@ -680,6 +680,13 @@ config TCP_CONG_BBR
 	bufferbloat, policers, or AQM schemes that do not provide a delay
 	signal. It requires the fq ("Fair Queue") pacing packet scheduler.
 
+config TCP_CONG_SOCIOPATH
+        tristate "TCP Sociopath"
+        default n
+        ---help---
+        This is basically TCP Reno with no slow start and a much more
+        aggressive ssthresh recalculation (lowers it by 5% instead of 50%).
+
 choice
 	prompt "Default TCP congestion control"
 	default DEFAULT_CUBIC
@@ -717,6 +724,9 @@ choice
 	config DEFAULT_BBR
 		bool "BBR" if TCP_CONG_BBR=y
 
+    config DEFAULT_SOCIOPATH
+		bool "Sociopath" if TCP_CONG_SOCIOPATH=y
+
 	config DEFAULT_RENO
 		bool "Reno"
 endchoice
@@ -741,6 +751,7 @@ config DEFAULT_TCP_CONG
 	default "dctcp" if DEFAULT_DCTCP
 	default "cdg" if DEFAULT_CDG
 	default "bbr" if DEFAULT_BBR
+    default "sociopath" if DEFAULT_SOCIOPATH
 	default "cubic"
 
 config TCP_MD5SIG

net/ipv4/Makefile

@@ -64,6 +64,7 @@ obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
 obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
 obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
+obj-$(CONFIG_TCP_CONG_SOCIOPATH) += tcp_sociopath.o
 obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \

net/ipv4/tcp_sociopath.c

@@ -0,0 +1,48 @@
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+#include <net/tcp.h>
+
+static int lambda = 20;
+module_param(lambda, int, 0644);
+MODULE_PARM_DESC(lambda, "degree of sociopathy");
+
+static u32 tcp_sociopath_ssthresh(struct sock *sk) {
+  u32 cwnd = tcp_sk(sk)->snd_cwnd;
+  return max(cwnd-(cwnd/lambda), 2U);
+}
+
+static void tcp_sociopath_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) {
+  struct tcp_sock *tp = tcp_sk(sk);
+  if (tp->snd_cwnd <= tp->snd_ssthresh) {
+    if (tp->snd_cwnd < lambda*10) tp->snd_cwnd = lambda*10;
+    tcp_reno_cong_avoid(sk, ack, in_flight);
+  } else {
+    tcp_reno_cong_avoid(sk, ack, in_flight);
+  }
+}
+
+static struct tcp_congestion_ops tcp_sociopath = {
+  .owner	= THIS_MODULE,
+  .name		= "sociopath",
+
+  .ssthresh	= tcp_sociopath_ssthresh,
+  .cong_avoid	= tcp_sociopath_cong_avoid
+};
+
+static int __init tcp_sociopath_register(void) {
+  tcp_register_congestion_control(&tcp_sociopath);
+  return 0;
+}
+
+static void __exit tcp_sociopath_unregister(void) {
+  tcp_unregister_congestion_control(&tcp_sociopath);
+}
+
+module_init(tcp_sociopath_register);
+module_exit(tcp_sociopath_unregister);
+
+MODULE_AUTHOR("Michael Lucy");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Sociopath");