[PATCH net-next v2 0/3]net: tcp: support probing OOM

[menglong8 . dong]

From: Menglong Dong <imagedong@xxxxxxxxxxx>

In this series, we make some small changes to make the tcp retransmission
become zero-window probes if the receiver drops the skb because of memory
pressure.

In the 1st patch, we reply a zero-window ACK if the skb is dropped
because out of memory, instead of dropping the skb silently.

In the 2nd patch, we allow a zero-window ACK to update the window.

In the 3rd patch, we check the timeout of a probing socket with
'(u32)icsk->icsk_timeout', instead of 'tcp_jiffies32'. This is more like
a bugfix.

After these changes, the tcp can probe the OOM of the receiver forever.

Changes since v1:
- send 0 rwin ACK for the receive queue empty case when necessary in the
  1st patch
- send the ACK immediately by using the ICSK_ACK_NOW flag in the 1st
  patch
- consider the case of the connection restart from idle, as Neal comment,
  in the 3rd patch

Menglong Dong (3):
  net: tcp: send zero-window ACK when no memory
  net: tcp: allow zero-window ACK update the window
  net: tcp: fix unexcepted socket die when snd_wnd is 0

 include/net/inet_connection_sock.h |  3 ++-
 net/ipv4/tcp_input.c               | 16 ++++++++++++----
 net/ipv4/tcp_output.c              | 14 +++++++++++---
 net/ipv4/tcp_timer.c               | 10 +++++++++-
 4 files changed, 34 insertions(+), 9 deletions(-)

-- 
2.40.1