path: root/Documentation/networking
diff options
authorJerry Chu <hkchu@google.com>2012-08-31 12:29:11 +0000
committerDavid S. Miller <davem@davemloft.net>2012-08-31 20:02:18 -0400
commit1046716368979dee857a2b8a91c4a8833f21b9cb (patch)
treefdda70278e6fa56c27d242fb1a0ec9b7e3e81d38 /Documentation/networking
parent2a35cfa591ac63f17815c2d9432b799e37527980 (diff)
tcp: TCP Fast Open Server - header & support functions
This patch adds all the necessary data structure and support functions to implement TFO server side. It also documents a number of flags for the sysctl_tcp_fastopen knob, and adds a few Linux extension MIBs. In addition, it includes the following: 1. a new TCP_FASTOPEN socket option an application must call to supply a max backlog allowed in order to enable TFO on its listener. 2. A number of key data structures: "fastopen_rsk" in tcp_sock - for a big socket to access its request_sock for retransmission and ack processing purpose. It is non-NULL iff 3WHS not completed. "fastopenq" in request_sock_queue - points to a per Fast Open listener data structure "fastopen_queue" to keep track of qlen (# of outstanding Fast Open requests) and max_qlen, among other things. "listener" in tcp_request_sock - to point to the original listener for book-keeping purpose, i.e., to maintain qlen against max_qlen as part of defense against IP spoofing attack. 3. various data structure and functions, many in tcp_fastopen.c, to support server side Fast Open cookie operations, including /proc/sys/net/ipv4/tcp_fastopen_key to allow manual rekeying. Signed-off-by: H.K. Jerry Chu <hkchu@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Tom Herbert <therbert@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking')
1 files changed, 22 insertions, 7 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index d64e53124b8..c7fc1072494 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -467,16 +467,31 @@ 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