Redirect isn't an error condition, it should leave
the error handler without touching the socket.
Signed-off-by: NDuan Jiong <duanj.fnst@cn.fujitsu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Redirect isn't an error condition, it should leave
the error handler without touching the socket.
Signed-off-by: NDuan Jiong <duanj.fnst@cn.fujitsu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If local fragmentation is allowed, then ip_select_ident() and
ip_select_ident_more() need to generate unique IDs to ensure
correct defragmentation on the peer.

For example, if IPsec (tunnel mode) has to encrypt large skbs
that have local_df bit set, then all IP fragments that belonged
to different ESP datagrams would have used the same identificator.
If one of these IP fragments would get lost or reordered, then
peer could possibly stitch together wrong IP fragments that did
not belong to the same datagram. This would lead to a packet loss
or data corruption.
Signed-off-by: NAnsis Atteka <aatteka@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

skb->data already points to IP header, but for the sake of
consistency we can also use ip_hdr() to retrieve it.
Signed-off-by: NAnsis Atteka <aatteka@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Commit 1b7fdd2a ("tcp: do not use cached RTT for RTT estimation")
did not correctly account for the fact that crtt is the RTT shifted
left 3 bits. Fix the calculation to consistently reflect this fact.
Signed-off-by: NNeal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Acked-By: NYuchung Cheng <ycheng@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

RESOURCE_MAX is far too general name, change it to RES_COUNTER_MAX.
Signed-off-by: NSha Zhengju <handai.szj@taobao.com>
Signed-off-by: NQiang Huang <h.huangqiang@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Jeff Liu <jeff.liu@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

TCP receive window handling is multi staged.

A socket has a memory budget, static or dynamic, in sk_rcvbuf.

Because we do not really know how this memory budget translates to
a TCP window (payload), TCP announces a small initial window
(about 20 MSS).

When a packet is received, we increase TCP rcv_win depending
on the payload/truesize ratio of this packet. Good citizen
packets give a hint that it's reasonable to have rcv_win = sk_rcvbuf/2

This heuristic takes place in tcp_grow_window()

Problem is : We currently call tcp_grow_window() only for in-order
packets.

This means that reorders or packet losses stop proper grow of
rcv_win, and senders are unable to benefit from fast recovery,
or proper reordering level detection.

Really, a packet being stored in OFO queue is not a bad citizen.
It should be part of the game as in-order packets.

In our traces, we very often see sender is limited by linux small
receive windows, even if linux hosts use autotuning (DRS) and should
allow rcv_win to grow to ~3MB.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In commit 0f7cc9a3 "tcp: increase throughput when reordering is high",
it only allows cwnd to increase in Open state. This mistakenly disables
slow start after timeout (CA_Loss). Moreover cwnd won't grow if the
state moves from Disorder to Open later in tcp_fastretrans_alert().

Therefore the correct logic should be to allow cwnd to grow as long
as the data is received in order in Open, Loss, or even Disorder state.
Signed-off-by: NYuchung Cheng <ycheng@google.com>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NDave Jones <davej@fedoraproject.org>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Commit 1b7fdd2a("tcp: do not use cached RTT for RTT estimation")
removes important comments on how RTO is initialized and updated.
Hopefully this patch puts those information back.
Signed-off-by: NYuchung Cheng <ycheng@google.com>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Packets reaching SYNPROXY were default dropped, as they were most
likely invalid (given the recommended state matching).  This
patch, changes SYNPROXY target to let packets, not consumed,
continue being processed by the stack.

This will be more in line other target modules. As it will allow
more flexible configurations of handling, logging or matching on
packets in INVALID states.
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Acked-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

Its seems Patrick missed to incoorporate some of my requested changes
during review v2 of SYNPROXY netfilter module.

Which were, to avoid SYN+ACK packets to enter the path, meant for the
ACK packet from the client (from the 3WHS).

Further there were a bug in ip6t_SYNPROXY.c, for matching SYN packets
that didn't exclude the ACK flag.

Go a step further with SYN packet/flag matching by excluding flags
ACK+FIN+RST, in both IPv4 and IPv6 modules.

The intented usage of SYNPROXY is as follows:
(gracefully describing usage in commit)

 iptables -t raw -A PREROUTING -i eth0 -p tcp --dport 80 --syn -j NOTRACK
 iptables -A INPUT -i eth0 -p tcp --dport 80 -m state UNTRACKED,INVALID \
         -j SYNPROXY --sack-perm --timestamp --mss 1480 --wscale 7 --ecn

 echo 0 > /proc/sys/net/netfilter/nf_conntrack_tcp_loose

This does filter SYN flags early, for packets in the UNTRACKED state,
but packets in the INVALID state with other TCP flags could still
reach the module, thus this stricter flag matching is still needed.
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Acked-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

tcp_rcv_established() returns only one value namely 0. We change the return
value to void (as suggested by David Miller).

After commit 0c24604b (tcp: implement RFC 5961 4.2), we no longer send RSTs in
response to SYNs. We can remove the check and processing on the return value of
tcp_rcv_established().

We also fix jtcp_rcv_established() in tcp_probe.c to match that of
tcp_rcv_established().
Signed-off-by: NVijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

With recent changes in tcp_probe module (e.g. f925d0a6 ("net: tcp_probe:
add IPv6 support")) we also need to take into account that tbuf needs to
be updated as format string will be further expanded. tbuf sits on the stack
in tcpprobe_read() function that is invoked when user space reads procfs
file /proc/net/tcpprobe, hence not fast path as in jtcp_rcv_established().
Having a size similarly as in sctp_probe module of 256 bytes is fully
sufficient for that, we need theoretical maximum of 252 bytes otherwise we
could get truncated.
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The goal of this patch is to harmonize cleanup done on a skbuff on rx path.
Before this patch, behaviors were different depending of the tunnel type.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The goal of this patch is to harmonize cleanup done on a skbuff on xmit path.
Before this patch, behaviors were different depending of the tunnel type.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This function was only used when a packet was sent to another netns. Now, it can
also be used after tunnel encapsulation or decapsulation.

Only skb_orphan() should not be done when a packet is not crossing netns.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This argument is not used, let's remove it.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This config option is superfluous in that it only guards a call
to neigh_app_ns(). Enabling CONFIG_ARPD by default has no
change in behavior. There will now be call to __neigh_notify()
for each ARP resolution, which has no impact unless there is a
user space daemon waiting to receive the notification, i.e.,
the case for which CONFIG_ARPD was designed anyways.
Suggested-by: NEric W. Biederman <ebiederm@xmission.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Gao feng <gaofeng@cn.fujitsu.com>
Cc: Joe Perches <joe@perches.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: NTim Gardner <tim.gardner@canonical.com>
Reviewed-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Fengguang reported:

   net/built-in.o: In function `in6_dev_finish_destroy':
   (.text+0x4ca7d): undefined reference to `snmp_mib_free'

this is due to snmp_mib_free() is defined when CONFIG_INET is enabled,
but in6_dev_finish_destroy() is now moved to core kernel.

I think snmp_mib_free() is small enough to be inlined, so just make it
static inline.
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NCong Wang <amwang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

As suggested by Pravin, we can unify the code in case of duplicated
code.

Cc: Pravin Shelar <pshelar@nicira.com>
Signed-off-by: NCong Wang <amwang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Since commit 3d7b46cd (ip_tunnel: push generic protocol handling to
ip_tunnel module.), an Oops is triggered when an xfrm policy is configured on
an IPv4 over IPv4 tunnel.

xfrm4_policy_check() calls __xfrm_policy_check2(), which uses skb_dst(skb). But
this field is NULL because iptunnel_pull_header() calls skb_dst_drop(skb).
Signed-off-by: NLi Hongjun <hongjun.li@6wind.com>
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In commit 90ba9b19 (tcp: tcp_make_synack() can use alloc_skb()), Eric changed
the call to sock_wmalloc in tcp_make_synack to alloc_skb.  In doing so,
the netfilter owner match lost its ability to block the SYNACK packet on
outbound listening sockets.  Revert the change, restoring the owner match
functionality.

This closes netfilter bugzilla #847.
Signed-off-by: NPhil Oester <kernel@linuxace.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

RTT cached in the TCP metrics are valuable for the initial timeout
because SYN RTT usually does not account for serialization delays
on low BW path.

However using it to seed the RTT estimator maybe disruptive because
other components (e.g., pacing) require the smooth RTT to be obtained
from actual connection.

The solution is to use the higher cached RTT to set the first RTO
conservatively like tcp_rtt_estimator(), but avoid seeding the other
RTT estimator variables such as srtt.  It is also a good idea to
keep RTO conservative to obtain the first RTT sample, and the
performance is insured by TCP loss probe if SYN RTT is available.

To keep the seeding formula consistent across SYN RTT and cached RTT,
the rttvar is twice the cached RTT instead of cached RTTVAR value. The
reason is because cached variation may be too small (near min RTO)
which defeats the purpose of being conservative on first RTO. However
the metrics still keep the RTT variations as they might be useful for
user applications (through ip).
Signed-off-by: NYuchung Cheng <ycheng@google.com>
Signed-off-by: NNeal Cardwell <ncardwell@google.com>
Signed-off-by: NEric Dumazet <edumazet@google.com>
Tested-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

ipv4: raw_sendmsg: don't use header's destination address

A sendto() regression was bisected and found to start with commit
f8126f1d (ipv4: Adjust semantics of rt->rt_gateway.)

The problem is that it tries to ARP-lookup the constructed packet's
destination address rather than the explicitly provided address.

Fix this using FLOWI_FLAG_KNOWN_NH so that given nexthop is used.

cf. commit 2ad5b9e4Reported-by: NChris Clark <chris.clark@alcatel-lucent.com>
Bisected-by: NChris Clark <chris.clark@alcatel-lucent.com>
Tested-by: NChris Clark <chris.clark@alcatel-lucent.com>
Suggested-by: NJulian Anastasov <ja@ssi.bg>
Signed-off-by: NChris Clark <chris.clark@alcatel-lucent.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

After hearing many people over past years complaining against TSO being
bursty or even buggy, we are proud to present automatic sizing of TSO
packets.

One part of the problem is that tcp_tso_should_defer() uses an heuristic
relying on upcoming ACKS instead of a timer, but more generally, having
big TSO packets makes little sense for low rates, as it tends to create
micro bursts on the network, and general consensus is to reduce the
buffering amount.

This patch introduces a per socket sk_pacing_rate, that approximates
the current sending rate, and allows us to size the TSO packets so
that we try to send one packet every ms.

This field could be set by other transports.

Patch has no impact for high speed flows, where having large TSO packets
makes sense to reach line rate.

For other flows, this helps better packet scheduling and ACK clocking.

This patch increases performance of TCP flows in lossy environments.

A new sysctl (tcp_min_tso_segs) is added, to specify the
minimal size of a TSO packet (default being 2).

A follow-up patch will provide a new packet scheduler (FQ), using
sk_pacing_rate as an input to perform optional per flow pacing.

This explains why we chose to set sk_pacing_rate to twice the current
rate, allowing 'slow start' ramp up.

sk_pacing_rate = 2 * cwnd * mss / srtt

v2: Neal Cardwell reported a suspect deferring of last two segments on
initial write of 10 MSS, I had to change tcp_tso_should_defer() to take
into account tp->xmit_size_goal_segs
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Van Jacobson <vanj@google.com>
Cc: Tom Herbert <therbert@google.com>
Acked-by: NYuchung Cheng <ycheng@google.com>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The zero value means that tsecr is not valid, so it's a special case.

tsoffset is used to customize tcp_time_stamp for one socket.
tsoffset is usually zero, it's used when a socket was moved from one
host to another host.

Currently this issue affects logic of tcp_rcv_rtt_measure_ts. Due to
incorrect value of rcv_tsecr, tcp_rcv_rtt_measure_ts sets rto to
TCP_RTO_MAX.

Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Reported-by: NCyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: NAndrey Vagin <avagin@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

u32 rcv_tstamp;     /* timestamp of last received ACK */

Its value used in tcp_retransmit_timer, which closes socket
if the last ack was received more then TCP_RTO_MAX ago.

Currently rcv_tstamp is initialized to zero and if tcp_retransmit_timer
is called before receiving a first ack, the connection is closed.

This patch initializes rcv_tstamp to a timestamp, when a socket was
restored.

Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Reported-by: NCyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: NAndrey Vagin <avagin@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add a SYNPROXY for netfilter. The code is split into two parts, the synproxy
core with common functions and an address family specific target.

The SYNPROXY receives the connection request from the client, responds with
a SYN/ACK containing a SYN cookie and announcing a zero window and checks
whether the final ACK from the client contains a valid cookie.

It then establishes a connection to the original destination and, if
successful, sends a window update to the client with the window size
announced by the server.

Support for timestamps, SACK, window scaling and MSS options can be
statically configured as target parameters if the features of the server
are known. If timestamps are used, the timestamp value sent back to
the client in the SYN/ACK will be different from the real timestamp of
the server. In order to now break PAWS, the timestamps are translated in
the direction server->client.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Tested-by: NMartin Topholm <mph@one.com>
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

Extract the local TCP stack independant parts of tcp_v4_init_sequence()
and cookie_v4_check() and export them for use by the upcoming SYNPROXY
target.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Tested-by: NMartin Topholm <mph@one.com>
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

Split out sequence number adjustments from NAT and move them to the conntrack
core to make them usable for SYN proxying. The sequence number adjustment
information is moved to a seperate extend. The extend is added to new
conntracks when a NAT mapping is set up for a connection using a helper.

As a side effect, this saves 24 bytes per connection with NAT in the common
case that a connection does not have a helper assigned.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Tested-by: NMartin Topholm <mph@one.com>
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

As reported by Casper Gripenberg, in a bridged setup, using ip[6]t_REJECT
with the tcp-reset option sends out reset packets with the src MAC address
of the local bridge interface, instead of the MAC address of the intended
destination.  This causes some routers/firewalls to drop the reset packet
as it appears to be spoofed.  Fix this by bypassing ip[6]_local_out and
setting the MAC of the sender in the tcp reset packet.

This closes netfilter bugzilla #531.
Signed-off-by: NPhil Oester <kernel@linuxace.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

Currently, the tcp_probe snooper can either filter packets by a given
port (handed to the module via module parameter e.g. port=80) or lets
all TCP traffic pass (port=0, default). When a port is specified, the
port number is tested against the sk's source/destination port. Thus,
if one of them matches, the information will be further processed for
the log.

As this is quite limited, allow for more advanced filtering possibilities
which can facilitate debugging/analysis with the help of the tcp_probe
snooper. Therefore, similarly as added to BPF machine in commit 7e75f93e
("pkt_sched: ingress socket filter by mark"), add the possibility to
use skb->mark as a filter.

If the mark is not being used otherwise, this allows ingress filtering
by flow (e.g. in order to track updates from only a single flow, or a
subset of all flows for a given port) and other things such as dynamic
logging and reconfiguration without removing/re-inserting the tcp_probe
module, etc. Simple example:

  insmod net/ipv4/tcp_probe.ko fwmark=8888 full=1
  ...
  iptables -A INPUT -i eth4 -t mangle -p tcp --dport 22 \
           --sport 60952 -j MARK --set-mark 8888
  [... sampling interval ...]
  iptables -D INPUT -i eth4 -t mangle -p tcp --dport 22 \
           --sport 60952 -j MARK --set-mark 8888

The current option to filter by a given port is still being preserved. A
similar approach could be done for the sctp_probe module as a follow-up.
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In commit 0ea9d5e3 ("xfrm: introduce
helper for safe determination of mtu") I switched the determination of
ipv4 mtus from dst_mtu to ip_skb_dst_mtu. This was an error because in
case of IP_PMTUDISC_PROBE we fall back to the interface mtu, which is
never correct for ipv4 ipsec.

This patch partly reverts 0ea9d5e3
("xfrm: introduce helper for safe determination of mtu").

Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>

Eric Dumazet says that my previous fix for an ERR_PTR dereference
(ea857f28 'ipip: dereferencing an ERR_PTR in ip_tunnel_init_net()')
could be racy and suggests the following fix instead.
Reported-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The tcp_probe currently only supports analysis of IPv4 connections.
Therefore, it would be nice to have IPv6 supported as well. Since we
have the recently added %pISpc specifier that is IPv4/IPv6 generic,
build related sockaddress structures from the flow information and
pass this to our format string. Tested with SSH and HTTP sessions
on IPv4 and IPv6.
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patches fixes a rather unproblematic function signature mismatch
as the const specifier was missing for the th variable; and next to
that it adds a build-time assertion so that future function signature
mismatches for kprobes will not end badly, similarly as commit 22222997
("net: sctp: add build check for sctp_sf_eat_sack_6_2/jsctp_sf_eat_sack")
did it for SCTP.
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

It is helpful to sometimes know the TCP window sizes of an established
socket e.g. to confirm that window scaling is working or to tweak the
window size to improve high-latency connections, etc etc. Currently the
TCP snooper only exports the send window size, but not the receive window
size. Therefore, also add the receive window size to the end of the
output line.
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The stack currently detects reordering and avoid spurious
retransmission very well. However the throughput is sub-optimal under
high reordering because cwnd is increased only if the data is deliverd
in order. I.e., FLAG_DATA_ACKED check in tcp_ack().  The more packet
are reordered the worse the throughput is.

Therefore when reordering is proven high, cwnd should advance whenever
the data is delivered regardless of its ordering. If reordering is low,
conservatively advance cwnd only on ordered deliveries in Open state,
and retain cwnd in Disordered state (RFC5681).

Using netperf on a qdisc setup of 20Mbps BW and random RTT from 45ms
to 55ms (for reordering effect). This change increases TCP throughput
by 20 - 25% to near bottleneck BW.

A special case is the stretched ACK with new SACK and/or ECE mark.
For example, a receiver may receive an out of order or ECN packet with
unacked data buffered because of LRO or delayed ACK. The principle on
such an ACK is to advance cwnd on the cummulative acked part first,
then reduce cwnd in tcp_fastretrans_alert().
Signed-off-by: NYuchung Cheng <ycheng@google.com>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We need to move the derefernce after the IS_ERR() check.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>