Re: [PATCH 1/3] tcp: TCP Fast Open Server - header & support functions

On Thu, 2012-08-30 at 16:39 -0700, H.K. Jerry Chu wrote:

From: Jerry Chu <redacted>

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 <redacted>
Cc: Yuchung Cheng <redacted>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <redacted>
---
 Documentation/networking/ip-sysctl.txt |   29 ++++++++---
 include/linux/snmp.h                   |    4 ++
 include/linux/tcp.h                    |   45 ++++++++++++++++-
 include/net/request_sock.h             |   36 ++++++++++++++
 include/net/tcp.h                      |   46 +++++++++++++++---
 net/ipv4/proc.c                        |    4 ++
 net/ipv4/sysctl_net_ipv4.c             |   45 +++++++++++++++++
 net/ipv4/tcp_fastopen.c                |   83 +++++++++++++++++++++++++++++++-
 net/ipv4/tcp_input.c                   |    4 +-
 9 files changed, 276 insertions(+), 20 deletions(-)

There are two very small points that can be addressed later, or in next
iteration if there is one.

static inline bool fastopen_cookie_present(struct tcp_fastopen_cookie *foc)
{
       return (foc)->len != -1;
}

should be :

static inline bool fastopen_cookie_present(const struct tcp_fastopen_cookie *foc)
{
       return foc->len != -1;
}

And we should add a BUILD_BUG_ON(TCP_FASTOPEN_KEY_LENGTH != 4*sizeof(u32));
in proc_tcp_fastopen_key().

Acked-by: Eric Dumazet <edumazet@google.com>