man7: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS

index 9bdf968..b6a13de 100644
@@ -303,6 +303,16 @@ The algorithm "reno" is always available,
 but additional choices may be available depending on kernel configuration.
 The default value for this file is set as part of kernel configuration.
 .TP
+.IR tcp_cookie_size " (integer; default: 0 (disabled); since Linux 2.6.33)"
+.\" The following is from 2.6.33-rc1: Documentation/networking/ip-sysctl.txt
+Default size of TCP Cookie Transactions (TCPCT) option,
+that may be overridden
+by the TCP_COOKIE_TRANSACTIONS socket option.
+Values greater than the maximum (16) are interpreted as the maximum.
+Values greater than zero and less than the minimum (8) are interpreted
+as the minimum.
+Odd values are interpreted as the next even value.
+.TP
 .IR tcp_dma_copybreak " (integer; default: 4096; since Linux 2.6.24)"
 Lower limit, in bytes, of the size of socket reads that will be
 offloaded to a DMA copy engine, if one is present in the system

@@ -822,6 +832,51 @@ For more information see
 .BR ip (7).
 .\" FIXME Document TCP_CONGESTION (new in 2.6.13)
 .TP
+.BR TCP_COOKIE_TRANSACTIONS " (since Linux 2.6.33)"
+If defined,
+this option can be used to override the system-wide setting in the file
+.I /proc/sys/net/ipv4/tcp_cookie_size
+for this socket.
+Passes \fIstruct tcp_cookie_transactions\fP
+as defined in the file
+.IR /usr/include/linux/tcp.h .
+Intended to be portable.
+.RS
+.TP
+.B tcpct_cookie_desired
+Send the Cookie option with the <SYN> on a per socket basis.
+Values: 0 (default), 8, 10, 12, 14, 16
+.TP
+.B tcpct_s_data_desired
+The maximum amount of data transmitted
+with the <SYN> or <SYN,ACK(SYN)>
+on a per socket basis.
+Wait for data before sending.
+.TP
+.B tcpct_used
+Alternatively,
+send a constant data string
+with the <SYN> or <SYN,ACK(SYN)>
+on a per socket basis.
+On receipt,
+returns cookie(s) exchanged.
+.TP
+.B TCP_COOKIE_IN_ALWAYS
+Silently discard any incoming <SYN> that is missing
+the Cookie option on a per socket basis.
+Default: off.
+.TP
+.B TCP_COOKIE_OUT_NEVER
+Refuse to send (override)
+the Cookie option on a per socket basis.
+Default: off.
+.TP
+.B TCP_EXTEND_TIMESTAMP
+If defined,
+may also send 64-bit timestamps extension.
+Default: off.
+.RE
+.TP
 .BR TCP_CORK " (since Linux 2.2)"
 .\" precisely: since 2.1.127
 If set, don't send out partial frames.