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diff --git a/share/man/man4/tcp.4 b/share/man/man4/tcp.4
--- a/share/man/man4/tcp.4
+++ b/share/man/man4/tcp.4
@@ -34,7 +34,7 @@
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
-.Dd July 20, 2022
+.Dd August 1, 2022
.Dt TCP 4
.Os
.Sh NAME
@@ -203,12 +203,12 @@
To list the available TCP stacks, see
.Va functions_available
in the
-.Sx MIB Variables
+.Sx MIB (sysctl) Variables
section further down.
To list the default TCP stack, see
.Va functions_default
in the
-.Sx MIB Variables
+.Sx MIB (sysctl) Variables
section.
.It Dv TCP_KEEPINIT
This
@@ -221,7 +221,7 @@
For the global default in milliseconds see
.Va keepinit
in the
-.Sx MIB Variables
+.Sx MIB (sysctl) Variables
section further down.
.It Dv TCP_KEEPIDLE
This
@@ -237,7 +237,7 @@
For the global default in milliseconds see
.Va keepidle
in the
-.Sx MIB Variables
+.Sx MIB (sysctl) Variables
section further down.
.It Dv TCP_KEEPINTVL
This
@@ -252,7 +252,7 @@
For the global default in milliseconds see
.Va keepintvl
in the
-.Sx MIB Variables
+.Sx MIB (sysctl) Variables
section further down.
.It Dv TCP_KEEPCNT
This
@@ -267,7 +267,7 @@
For the global default see the
.Va keepcnt
in the
-.Sx MIB Variables
+.Sx MIB (sysctl) Variables
section further down.
.It Dv TCP_NODELAY
Under most circumstances,
@@ -413,14 +413,15 @@
Other congestion control algorithms can be made available using the
.Xr mod_cc 4
framework.
-.Ss MIB Variables
+.Ss MIB (sysctl) Variables
The
.Tn TCP
protocol implements a number of variables in the
.Va net.inet.tcp
branch of the
.Xr sysctl 3
-MIB.
+MIB, which can also be read or modified with
+.Xr sysctl 8 .
.Bl -tag -width ".Va v6pmtud_blackhole_mss"
.It Va always_keepalive
Assume that
@@ -432,13 +433,28 @@
is still up.
.It Va blackhole
If enabled, disable sending of RST when a connection is attempted
-to a port where there is not a socket accepting connections.
+to a port where there is no socket accepting connections.
See
.Xr blackhole 4 .
+.It Va blackhole_local
+See
+.Xr blackhole 4 .
+.It Va cc
+A number of variables for congestion control are under the
+.Va net.inet.tcp.cc
+node.
+See
+.Xr mod_cc 4 .
+.It Va cc.newreno
+Variables for NewReno congestion control are under the
+.Va net.inet.tcp.cc.newreno
+node.
+See
+.Xr cc_newreno 4 .
.It Va delacktime
Maximum amount of time, in milliseconds, before a delayed ACK is sent.
.It Va delayed_ack
-Delay ACK to try and piggyback it onto a data packet.
+Delay ACK to try and piggyback it onto a data packet or another ACK.
.It Va do_lrd
Enable Lost Retransmission Detection for SACK-enabled sessions, disabled by
default.
@@ -463,6 +479,8 @@
Flush packets in the
.Tn TCP
reassembly queue if the system is low on mbufs.
+.It Va drop_synfin
+Drop TCP packets with both SYN and FIN set.
.It Va ecn.enable
Enable support for TCP Explicit Congestion Notification (ECN).
ECN allows a TCP sender to reduce the transmission rate in order to
@@ -706,7 +724,7 @@
probe.
The default is 75000 msec (75K msec, 75 sec).
.It Va log_in_vain
-Log any connection attempts to ports where there is not a socket
+Log any connection attempts to ports where there is no socket
accepting connections.
The value of 1 limits the logging to
.Tn SYN
@@ -733,12 +751,15 @@
By default, it is initialized to
.Va kern.ipc.maxsockets
/ 5.
+.It Va minmss
+Minimum TCP Maximum Segment Size; used to prevent a denial of service attack
+from an unreasonably low MSS.
.It Va msl
The Maximum Segment Lifetime, in milliseconds, for a packet.
.It Va mssdflt
-The default value used for the maximum segment size
+The default value used for the TCP Maximum Segment Size
.Pq Dq MSS
-when no advice to the contrary is received from MSS negotiation.
+for IPv4 when no advice to the contrary is received from MSS negotiation.
.It Va newcwd
Enable the New Congestion Window Validation mechanism as described in RFC 7661.
This gently reduces the congestion window during periods, where TCP is
@@ -766,6 +787,10 @@
template sampling rates when
.Xr stats 3
sampling is enabled.
+.It Va persmax
+Maximum persistence interval, msec.
+.It Va persmin
+Minimum persistence interval, msec.
.It Va pmtud_blackhole_detection
Enable automatic path MTU blackhole detection.
In case of retransmits of MSS sized segments,
@@ -808,10 +833,21 @@
The maximum limit on the total number of segments across all reassembly
queues.
The limit can be adjusted as a tunable.
+.It Va recvbuf_auto
+Enable automatic receive buffer sizing as a connection progresses.
+.It Va recvbuf_max
+Maximum size of automatic receive buffer.
.It Va recvspace
-Maximum
+Initial
.Tn TCP
-receive window.
+receive window (buffer size).
+.It Va require_unique_port
+Require unique ephemeral port for outgoing connections;
+otherwise, the 4-tuple of local and remote ports and addresses must be unique.
+Requiring a unique port limits the number of outgoing connections.
+.It Va rexmit_drop_options
+Drop TCP options from third and later retransmitted SYN segments
+of a connection.
.It Va rexmit_initial , rexmit_min , rexmit_slop
Adjust the retransmit timer calculation for
.Tn TCP .
@@ -857,6 +893,8 @@
which allows the receiver to inform the sender about all successfully
arrived segments, allowing the sender to retransmit the missing segments
only.
+.It Va sack.globalholes
+Global number of TCP SACK holes currently allocated.
.It Va sack.globalmaxholes
Maximum number of SACK holes per system, across all connections.
Defaults to 65536.
@@ -874,10 +912,24 @@
for a Retransmission timeout.
Finally, SACK loss recovery is also engaged, once two segments plus one byte are
SACKed - even if no traditional duplicate ACKs were observed.
+.It Va sendbuf_auto
+Enable automatic send buffer sizing.
+.It Va sendbuf_auto_lowat
+Modify threshold for auto send buffer growth to account for
+.Dv SO_SNDLOWAT .
+.It Va sendbuf_inc
+Incrementor step size of automatic send buffer.
+.It Va sendbuf_max
+Maximum size of automatic send buffer.
.It Va sendspace
-Maximum
+Initial
.Tn TCP
-send window.
+send window (buffer size).
+.It Va syncache
+Variables under the
+.Va net.inet.tcp.syncache
+node are documented in
+.Xr syncache 4 .
.It Va syncookies
Determines whether or not
.Tn SYN
@@ -890,6 +942,9 @@
flood attacks, and are enabled by default.
(See
.Xr syncookies 4 . )
+.It Va syncookies_only
+See
+.Xr syncookies 4 .
.It Va tcbhashsize
Size of the
.Tn TCP
@@ -916,6 +971,8 @@
When initializing the TCP timestamps, use a per connection offset instead of a
per host pair offset.
Default is to use per connection offsets as recommended in RFC 7323.
+.It Va tso
+Enable TCP Segmentation Offload.
.It Va udp_tunneling_overhead
The overhead taken into account when using UDP encapsulation.
Since MSS clamping by middleboxes will most likely not work, values larger than
@@ -926,6 +983,10 @@
The local UDP encapsulation port.
A value of 0 indicates that UDP encapsulation is disabled.
The default is 0.
+.It Va v6mssdflt
+The default value used for the TCP Maximum Segment Size
+.Pq Dq MSS
+for IPv6 when no advice to the contrary is received from MSS negotiation.
.It Va v6pmtud_blackhole_mss
MSS to try for IPv6 if PMTU blackhole detection is turned on.
See
@@ -981,6 +1042,7 @@
.Xr syncache 4 ,
.Xr tcp_bbr 4 ,
.Xr setkey 8 ,
+.Xr sysctl 8 ,
.Xr tcp_functions 9
.Rs
.%A "V. Jacobson"

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