cgroups: add res_counter_write_u64() API

Extend the resource counter API with a mirror of res_counter_read_u64() to
make it handy to update a resource counter value from a cgroup subsystem
u64 value file.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
cgroups: new resource counter inheritance API

Provide an API to inherit a counter value from a parent.  This can be
useful to implement cgroup.clone_children on a resource counter.

Still the resources of the children are limited by those of the parent, so
this is only to provide a default setting behaviour when clone_children is
set.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
cgroups: ability to stop res charge propagation on bounded ancestor

Moving a task from a cgroup to another may require to substract its
resource charge from the old cgroup and add it to the new one.

For this to happen, the uncharge/charge propagation can just stop when we
reach the common ancestor for the two cgroups.  Further the performance
reasons, we also want to avoid to temporarily overload the common
ancestors with a non-accurate resource counter usage if we charge first
the new cgroup and uncharge the old one thereafter.  This is going to be a
requirement for the coming kcounter subsystem.

To solve this, provide a pair of new API that can charge/uncharge a
resource counter until we reach a given ancestor.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
cgroups: add res counter common ancestor searching

Add a new API to find the common ancestor between two resource counters.
This includes the passed resource counter themselves.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
res_counter: allow charge failure pointer to be null

So that callers of res_counter_charge() don't have to create and pass this
pointer even if they aren't interested in it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
cgroups: pull up res counter charge failure interpretation to caller

res_counter_charge() always returns -ENOMEM when the limit is reached and
the charge thus can't happen.

However it's up to the caller to interpret this failure and return the
appropriate error value.  The nproc counter of kcounter subsystem will need to
report the user that a fork() has been cancelled because of some limit reached,
not because we are too short on memory.

Fix this by returning -1 when res_counter_charge() fails.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
cgroups: allow subsystems to cancel a fork

Let the subsystem's fork callback return an error value so that they can cancel
a fork.  This is going to be used by the kcounter subsystem to implement the
nproc limit.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
cgroups: Add a kcounter subsystem

Add a new subsystem to limit usage of various types of resource
for a cgroup, by enforcing a upper bound upon the corresponding
resource counter. It behaves like the counterpart of user land
ulimit in the scope of a cgroup.

Currently nproc counter is the only consumer of kcounter
framework. For nproc counter, the user can set an upper bound
limit that is checked every time a task forks in a cgroup or is
moved into a cgroup with that subsystem binded.

The primary goal is to protect against forkbombs that explode
inside a container. The traditional NR_PROC rlimit is not
efficient in that case because if we run containers in parallel
under the same user, one of these could starve all the others
by spawning a high number of tasks close to the user wide limit.

This is a prevention against forkbombs, so it's not deemed to
cure the effects of a forkbomb when the system is in a state
where it's not responsive. It's aimed at preventing from ever
reaching that state and stop the spreading of tasks early.
While defining the limit on the allowed number of tasks, it's
up to the user to find the right balance between the resource
its containers may need and what it can afford to provide.

As it's totally dissociated from the rlimit NR_PROC, both
can be complementary: the cgroup nproc counter can set an upper
bound per container and the rlmit can be an upper bound on the
overall set of containers.

Also nproc counter can be used to kill all the tasks in a cgroup
without races against concurrent forks, by setting the limit of
tasks to 0, any further forks can be rejected. This is a good
way to kill a forkbomb in a container, or simply kill any container
without the need to retry an unbound number of times.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Reviewed-by: Zhi Yong Wu <zhiyong.wzy@alibaba-inc.com>
Merge pull request #64 from danielzhou82/ai-kcounter

Add kcounter cgroup subsys
config: enable kcounter cgroup subsys by default

Kcounter cgroup subsys is used to control resource usage of a cgroup by
enforcing an upper bound of resource counters. This is now required by AliIaaS
infrastructure to limit the tasks one cgroup can own.

Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Merge pull request #65 from danielzhou82/ai-kcounter

config: enable kcounter cgroup subsys by default
tcp: Handle CHECKSUM_PARTIAL for SYNACK packets for IPv4

tcp: Handle CHECKSUM_PARTIAL for SYNACK packets for IPv4

This patch moves the common code between tcp_v4_send_check and
tcp_v4_gso_send_check into a new function __tcp_v4_send_check.

It then uses the new function in tcp_v4_send_synack so that it
handles CHECKSUM_PARTIAL properly.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Yinghai <yinghai.lu@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
tcp: Set CHECKSUM_UNNECESSARY in tcp_init_nondata_skb

Back in commit 04a0551c87363f100b04d28d7a15a632b70e18e7
("loopback: Drop obsolete ip_summed setting") we stopped
setting CHECKSUM_UNNECESSARY in the loopback xmit.

This is because such a setting was a lie since it implies that the
checksum field of the packet is properly filled in.

Instead what happens normally is that CHECKSUM_PARTIAL is set and
skb->csum is calculated as needed.

But this was only happening for TCP data packets (via the
skb->ip_summed assignment done in tcp_sendmsg()).  It doesn't
happen for non-data packets like ACKs etc.

Fix this by setting skb->ip_summed in the common non-data packet
constructor.  It already is setting skb->csum to zero.

But this reminds us that we still have things like ip_output.c's
ip_dev_loopback_xmit() which sets skb->ip_summed to the value
CHECKSUM_UNNECESSARY, which Herbert's patch teaches us is not
valid.  So we'll have to address that at some point too.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
net-tcp: Fast Open base

This patch impelements the common code for both the client and server.

1. TCP Fast Open option processing. Since Fast Open does not have an
   option number assigned by IANA yet, it shares the experiment option
   code 254 by implementing draft-ietf-tcpm-experimental-options
   with a 16 bits magic number 0xF989. This enables global experiments
   without clashing the scarce(2) experimental options available for TCP.

   When the draft status becomes standard (maybe), the client should
   switch to the new option number assigned while the server supports
   both numbers for transistion.

2. The new sysctl tcp_fastopen

3. A place holder init function

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
net-tcp: Fast Open client - cookie cache

With help from Eric Dumazet, add Fast Open metrics in tcp metrics cache.
The basic ones are MSS and the cookies. Later patch will cache more to
handle unfriendly middleboxes.

[Note from Zheng Liu]
In this commit we add a hash table for tcp fast open because of some
missing patches.  This hash table is similar with hash table in net/ipv4
/tcp_metrics.c.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
net-tcp: Fast Open client - sending SYN-data

This patch implements sending SYN-data in tcp_connect(). The data is
from tcp_sendmsg() with flag MSG_FASTOPEN (implemented in a later patch).

The length of the cookie in tcp_fastopen_req, init'd to 0, controls the
type of the SYN. If the cookie is not cached (len==0), the host sends
data-less SYN with Fast Open cookie request option to solicit a cookie
from the remote. If cookie is not available (len > 0), the host sends
a SYN-data with Fast Open cookie option. If cookie length is negative,
  the SYN will not include any Fast Open option (for fall back operations).

To deal with middleboxes that may drop SYN with data or experimental TCP
option, the SYN-data is only sent once. SYN retransmits do not include
data or Fast Open options. The connection will fall back to regular TCP
handshake.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
net-tcp: Fast Open client - receiving SYN-ACK

On receiving the SYN-ACK after SYN-data, the client needs to
a) update the cached MSS and cookie (if included in SYN-ACK)
b) retransmit the data not yet acknowledged by the SYN-ACK in the final ACK of
   the handshake.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
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>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
net-tcp: Fast Open client - detecting SYN-data drops

On paths with firewalls dropping SYN with data or experimental TCP options,
Fast Open connections will have experience SYN timeout and bad performance.
The solution is to track such incidents in the cookie cache and disables
Fast Open temporarily.

Since only the original SYN includes data and/or Fast Open option, the
SYN-ACK has some tell-tale sign (tcp_rcv_fastopen_synack()) to detect
such drops. If a path has recurring Fast Open SYN drops, Fast Open is
disabled for 2^(recurring_losses) minutes starting from four minutes up to
roughly one and half day. sendmsg with MSG_FASTOPEN flag will succeed but
it behaves as connect() then write().

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
net-tcp: Fast Open client - cookie-less mode

In trusted networks, e.g., intranet, data-center, the client does not
need to use Fast Open cookie to mitigate DoS attacks. In cookie-less
mode, sendmsg() with MSG_FASTOPEN flag will send SYN-data regardless
of cookie availability.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>