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Index: share/man/man4/blackhole.4
===================================================================
--- share/man/man4/blackhole.4
+++ share/man/man4/blackhole.4
@@ -12,24 +12,25 @@
.\"
.\"
.\" $FreeBSD$
-.Dd January 1, 2007
+.Dd August 29, 2015
.Dt BLACKHOLE 4
.Os
.Sh NAME
.Nm blackhole
.Nd a
.Xr sysctl 8
-MIB for manipulating behaviour in respect of refused TCP or UDP connection
+MIB for manipulating behaviour in respect of refused TCP, UDP, or SCTP connection
attempts
.Sh SYNOPSIS
-.Cd sysctl net.inet.tcp.blackhole[=[0 | 1 | 2]]
-.Cd sysctl net.inet.udp.blackhole[=[0 | 1]]
+.Cd sysctl net.inet.sctp.blackhole Ns [=[ 0 | 1 ]]
+.Cd sysctl net.inet.tcp.blackhole Ns [=[ 0 | 1 | 2 ]]
+.Cd sysctl net.inet.udp.blackhole Ns [=[ 0 | 1 ]]
.Sh DESCRIPTION
The
.Nm
.Xr sysctl 8
MIB is used to control system behaviour when connection requests
-are received on TCP or UDP ports where there is no socket listening.
+are received on TCP, UDP, or SCTP ports where there is no socket listening.
.Pp
Normal behaviour, when a TCP SYN segment is received on a port where
there is no socket accepting connections, is for the system to return
@@ -52,12 +53,17 @@
.Xr traceroute 8
to a system.
.Pp
+For SCTP, enabling blackhole behaviour turns off the sending of ABORT packets
+as follows: A MIB value of one will prevent sending an ABORT packet
+in response to an incoming INIT. A MIB value of two will do the same, but also
+prevent sending an ABORT packet when receiving packets out of the blue.
+.Pp
The blackhole behaviour is useful to slow down anyone who is port scanning
a system, attempting to detect vulnerable services on a system.
It could potentially also slow down someone who is attempting a denial
of service attack.
.Sh WARNING
-The TCP and UDP blackhole features should not be regarded as a replacement
+The SCTP, TCP, and UDP blackhole features should not be regarded as a replacement
for firewall solutions.
Better security would consist of the
.Nm
@@ -68,6 +74,7 @@
It should be used together with other security mechanisms.
.Sh SEE ALSO
.Xr ip 4 ,
+.Xr sctp 4 ,
.Xr tcp 4 ,
.Xr udp 4 ,
.Xr ipf 8 ,
@@ -80,5 +87,10 @@
MIBs
first appeared in
.Fx 4.0 .
+.Pp
+The SCTP
+.Nm
+MIB first appeared in
+.Fx 9.1 .
.Sh AUTHORS
.An Geoffrey M. Rehmet
Index: sys/netinet/sctp_sysctl.h
===================================================================
--- sys/netinet/sctp_sysctl.h
+++ sys/netinet/sctp_sysctl.h
@@ -545,7 +545,7 @@
#define SCTPCTL_RTTVAR_DCCCECN_MAX 1
#define SCTPCTL_RTTVAR_DCCCECN_DEFAULT 1 /* 0 means disable feature */
-#define SCTPCTL_BLACKHOLE_DESC "Enable SCTP blackholing"
+#define SCTPCTL_BLACKHOLE_DESC "Enable SCTP blackholing. See blackhole(4) man page for more details."
#define SCTPCTL_BLACKHOLE_MIN 0
#define SCTPCTL_BLACKHOLE_MAX 2
#define SCTPCTL_BLACKHOLE_DEFAULT SCTPCTL_BLACKHOLE_MIN

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