[PATCH net-next 0/3] net: tcp: add support of window shrink

[menglong8.dong@gmail.com]

From: Menglong Dong <imagedong@tencent.com>

For now, skb will be dropped when no memory, which makes client keep
retrans util timeout and it's not friendly to the users.

Therefore, now we force to receive one packet on current socket when
the protocol memory is out of the limitation. Then, this socket will
stay in 'no mem' status, util protocol memory is available.

When a socket is in 'no mem' status, it's receive window will become
0, which means window shrink happens. For the sender, it need to
cover this case, and we turn it into zero-window probe status.

In the origin logic, 0 probe is triggered only when there is no any
data in the retrans queue and the receive window can't hold the data
of the 1th packet in the send queue.

Now, let's change it and trigger the 0 probe in such cases:

- if the retrans queue has data and the 1th packet in it is not within
  the receive window, which is for window shrink case, as the shrinked
  window may can't cover the data in retrans queue.
- no data in the retrans queue and the 1th packet in the send queue is
  out of the end of the receive window

And the sysctl 'tcp_wnd_shrink' is also introduced. In order to keep
safe, we disable this feature by default.

*** BLURB HERE ***

Menglong Dong (3):
  net: tcp: add sysctl for controling tcp window shrink
  net: tcp: send zero-window when no memory
  net: tcp: handle window shrink properly

 include/net/sock.h         |  1 +
 include/net/tcp.h          | 22 ++++++++++++++++
 net/ipv4/sysctl_net_ipv4.c |  9 +++++++
 net/ipv4/tcp.c             |  3 +++
 net/ipv4/tcp_input.c       | 53 ++++++++++++++++++++++++++++++++++++++
 net/ipv4/tcp_output.c      | 10 +++++--
 net/ipv4/tcp_timer.c       |  4 +--
 7 files changed, 97 insertions(+), 5 deletions(-)

-- 
2.40.1