staging: update LMK from CAF 3.4 sources
Proportional Rate Reduction for TCP.

This patch implements Proportional Rate Reduction (PRR) for TCP.
PRR is an algorithm that determines TCP's sending rate in fast
recovery. PRR avoids excessive window reductions and aims for
the actual congestion window size at the end of recovery to be as
close as possible to the window determined by the congestion control
algorithm. PRR also improves accuracy of the amount of data sent
during loss recovery.

The patch implements the recommended flavor of PRR called PRR-SSRB
(Proportional rate reduction with slow start reduction bound) and
replaces the existing rate halving algorithm. PRR improves upon the
existing Linux fast recovery under a number of conditions including:
  1) burst losses where the losses implicitly reduce the amount of
outstanding data (pipe) below the ssthresh value selected by the
congestion control algorithm and,
  2) losses near the end of short flows where application runs out of
data to send.

As an example, with the existing rate halving implementation a single
loss event can cause a connection carrying short Web transactions to
go into the slow start mode after the recovery. This is because during
recovery Linux pulls the congestion window down to packets_in_flight+1
on every ACK. A short Web response often runs out of new data to send
and its pipe reduces to zero by the end of recovery when all its packets
are drained from the network. Subsequent HTTP responses using the same
connection will have to slow start to raise cwnd to ssthresh. PRR on
the other hand aims for the cwnd to be as close as possible to ssthresh
by the end of recovery.

A description of PRR and a discussion of its performance can be found at
the following links:
- IETF Draft:
    http://tools.ietf.org/html/draft-mathis-tcpm-proportional-rate-reduction-01
- IETF Slides:
    http://www.ietf.org/proceedings/80/slides/tcpm-6.pdf
    http://tools.ietf.org/agenda/81/slides/tcpm-2.pdf
- Paper to appear in Internet Measurements Conference (IMC) 2011:
    Improving TCP Loss Recovery
    Nandita Dukkipati, Matt Mathis, Yuchung Cheng

Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcp: fix validation of D-SACK

D-SACK is allowed to reside below snd_una. But the corresponding check
in tcp_is_sackblock_valid() is the exact opposite. It looks like a typo.

Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
TCP/IP tweaks
tcp: fix tcp_rcv_rtt_update() use of an unscaled RTT sample

[ Upstream commit 18a223e0b9ec8979320ba364b47c9772391d6d05 ]

Fix a code path in tcp_rcv_rtt_update() that was comparing scaled and
unscaled RTT samples.

The intent in the code was to only use the 'm' measurement if it was a
new minimum.  However, since 'm' had not yet been shifted left 3 bits
but 'new_sample' had, this comparison would nearly always succeed,
leading us to erroneously set our receive-side RTT estimate to the 'm'
sample when that sample could be nearly 8x too high to use.

The overall effect is to often cause the receive-side RTT estimate to
be significantly too large (up to 40% too large for brief periods in
my tests).

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tcp: fix tcp_grow_window() for large incoming frames

[ Upstream commit 4d846f02392a710f9604892ac3329e628e60a230 ]

tcp_grow_window() has to grow rcv_ssthresh up to window_clamp, allowing
sender to increase its window.

tcp_grow_window() still assumes a tcp frame is under MSS, but its no
longer true with LRO/GRO.

This patch fixes one of the performance issue we noticed with GRO on.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tcp: len check is unnecessarily devastating, change to WARN_ON

[ Upstream commit 2fceec13375e5d98ef033c6b0ee03943fc460950 ]

All callers are prepared for alloc failures anyway, so this error
can safely be boomeranged to the callers domain without super
bad consequences. ...At worst the connection might go into a state
where each RTO tries to (unsuccessfully) re-fragment with such
a mis-sized value and eventually dies.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
net: ip_expire() must revalidate route

commit 64f3b9e203bd06855072e295557dca1485a2ecba upstream.

Commit 4a94445c9a5c (net: Use ip_route_input_noref() in input path)
added a bug in IP defragmentation handling, in case timeout is fired.

When a frame is defragmented, we use last skb dst field when building
final skb. Its dst is valid, since we are in rcu read section.

But if a timeout occurs, we take first queued fragment to build one ICMP
TIME EXCEEDED message. Problem is all queued skb have weak dst pointers,
since we escaped RCU critical section after their queueing. icmp_send()
might dereference a now freed (and possibly reused) part of memory.

Calling skb_dst_drop() and ip_route_input_noref() to revalidate route is
the only possible choice.

Reported-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>