path: root/Documentation/networking
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authorYuchung Cheng <ycheng@google.com>2012-07-19 06:43:09 +0000
committerDavid S. Miller <davem@davemloft.net>2012-07-19 11:02:03 -0700
commitcf60af03ca4e71134206809ea892e49b92a88896 (patch)
tree478ee362f10d0737fbc4e6642e2966abe0cd1397 /Documentation/networking
parent8e4178c1c7b52f7c99f5fd22ef7af6b2bff409e3 (diff)
net-tcp: Fast Open client - sendmsg(MSG_FASTOPEN)
sendmsg() (or sendto()) with MSG_FASTOPEN is a combo of connect(2) and write(2). The application should replace connect() with it to send data in the opening SYN packet. For blocking socket, sendmsg() blocks until all the data are buffered locally and the handshake is completed like connect() call. It returns similar errno like connect() if the TCP handshake fails. For non-blocking socket, it returns the number of bytes queued (and transmitted in the SYN-data packet) if cookie is available. If cookie is not available, it transmits a data-less SYN packet with Fast Open cookie request option and returns -EINPROGRESS like connect(). Using MSG_FASTOPEN on connecting or connected socket will result in simlar errno like repeating connect() calls. Therefore the application should only use this flag on new sockets. The buffer size of sendmsg() is independent of the MSS of the connection. Signed-off-by: Yuchung Cheng <ycheng@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking')
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index e1e021594cf..03964e08818 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -468,6 +468,17 @@ tcp_syncookies - BOOLEAN
SYN flood warnings in logs not being really flooded, your server
is seriously misconfigured.
+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
+ Default: 0
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