net: sctp: dynamically enable or disable pf state

As we all know, the value of pf_retrans >= max_retrans_path can
disable pf state. The variables of pf_retrans and max_retrans_path
can be changed by the userspace application.

Sometimes the user expects to disable pf state while the 2
variables are changed to enable pf state. So it is necessary to
introduce a new variable to disable pf state.

According to the suggestions from Vlad Yasevich, extra1 and extra2
are removed. The initialization of pf_enable is added.

Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: Zhu Yanjun <zyjzyj2000@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netns/sctp.h b/include/net/netns/sctp.h
index 8ba379f..c501d67 100644
--- a/include/net/netns/sctp.h
+++ b/include/net/netns/sctp.h
@@ -89,6 +89,13 @@
 	int pf_retrans;
 
 	/*
+	 * Disable Potentially-Failed feature, the feature is enabled by default
+	 * pf_enable	-  0  : disable pf
+	 *		- >0  : enable pf
+	 */
+	int pf_enable;
+
+	/*
 	 * Policy for preforming sctp/socket accounting
 	 * 0   - do socket level accounting, all assocs share sk_sndbuf
 	 * 1   - do sctp accounting, each asoc may use sk_sndbuf bytes