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-rw-r--r--Documentation/networking/ip-sysctl.txt37
1 files changed, 28 insertions, 9 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ca447b35b833..c7fc10724948 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -439,7 +439,9 @@ tcp_stdurg - BOOLEAN
tcp_synack_retries - INTEGER
Number of times SYNACKs for a passive TCP connection attempt will
be retransmitted. Should not be higher than 255. Default value
- is 5, which corresponds to ~180seconds.
+ is 5, which corresponds to 31seconds till the last retransmission
+ with the current initial RTO of 1second. With this the final timeout
+ for a passive TCP connection will happen after 63seconds.
tcp_syncookies - BOOLEAN
Only valid when the kernel was compiled with CONFIG_SYNCOOKIES
@@ -465,20 +467,37 @@ tcp_syncookies - BOOLEAN
tcp_fastopen - INTEGER
Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data
in the opening SYN packet. To use this feature, the client application
- must not use connect(). Instead, it should use sendmsg() or sendto()
- with MSG_FASTOPEN flag which performs a TCP handshake automatically.
-
- The values (bitmap) are:
- 1: Enables sending data in the opening SYN on the client
- 5: Enables sending data in the opening SYN on the client regardless
- of cookie availability.
+ must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than
+ connect() to perform a TCP handshake automatically.
+
+ The values (bitmap) are
+ 1: Enables sending data in the opening SYN on the client.
+ 2: Enables TCP Fast Open on the server side, i.e., allowing data in
+ a SYN packet to be accepted and passed to the application before
+ 3-way hand shake finishes.
+ 4: Send data in the opening SYN regardless of cookie availability and
+ without a cookie option.
+ 0x100: Accept SYN data w/o validating the cookie.
+ 0x200: Accept data-in-SYN w/o any cookie option present.
+ 0x400/0x800: Enable Fast Open on all listeners regardless of the
+ TCP_FASTOPEN socket option. The two different flags designate two
+ different ways of setting max_qlen without the TCP_FASTOPEN socket
+ option.
Default: 0
+ Note that the client & server side Fast Open flags (1 and 2
+ respectively) must be also enabled before the rest of flags can take
+ effect.
+
+ See include/net/tcp.h and the code for more details.
+
tcp_syn_retries - INTEGER
Number of times initial SYNs for an active TCP connection attempt
will be retransmitted. Should not be higher than 255. Default value
- is 5, which corresponds to ~180seconds.
+ is 6, which corresponds to 63seconds till the last restransmission
+ with the current initial RTO of 1second. With this the final timeout
+ for an active TCP connection attempt will happen after 127seconds.
tcp_timestamps - BOOLEAN
Enable timestamps as defined in RFC1323.