linux.git/include/net/netns/ipv4.h, branch v4.5

ipv4: Namespecify the tcp_keepalive_intvl sysctl knob

2016-01-10T22:32:09+00:00

This is the final part required to namespaceify the tcp
keep alive mechanism.

Signed-off-by: Nikolay Borisov 
Signed-off-by: David S. Miller

ipv4: Namespecify tcp_keepalive_probes sysctl knob

2016-01-10T22:32:09+00:00

This is required to have full tcp keepalive mechanism namespace
support.

Signed-off-by: Nikolay Borisov 
Signed-off-by: David S. Miller

ipv4: Namespaceify tcp_keepalive_time sysctl knob

2016-01-10T22:32:09+00:00

Different net namespaces might have different requirements as to
the keepalive time of tcp sockets. This might be required in cases
where different firewall rules are in place which require tcp
timeout sockets to be increased/decreased independently of the host.

Signed-off-by: Nikolay Borisov 
Signed-off-by: David S. Miller

net: Allow accepted sockets to be bound to l3mdev domain

2015-12-18T19:43:38+00:00

Allow accepted sockets to derive their sk_bound_dev_if setting from the
l3mdev domain in which the packets originated. A sysctl setting is added
to control the behavior which is similar to sk_mark and
sysctl_tcp_fwmark_accept.

This effectively allow a process to have a "VRF-global" listen socket,
with child sockets bound to the VRF device in which the packet originated.
A similar behavior can be achieved using sk_mark, but a solution using marks
is incomplete as it does not handle duplicate addresses in different L3
domains/VRFs. Allowing sockets to inherit the sk_bound_dev_if from l3mdev
domain provides a complete solution.

Signed-off-by: David Ahern 
Signed-off-by: David S. Miller

tcp/dccp: warn user for preferred ip_local_port_range

2015-05-27T18:35:36+00:00

After commit 07f4c90062f8f ("tcp/dccp: try to not exhaust
ip_local_port_range in connect()") it is advised to have an even number
of ports described in /proc/sys/net/ipv4/ip_local_port_range

This means start/end values should have a different parity.

Let's warn sysadmins of this, so that they can update their settings
if they want to.

Suggested-by: David S. Miller 
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: add rfc3168, section 6.1.1.1. fallback

2015-05-19T20:53:37+00:00

This work as a follow-up of commit f7b3bec6f516 ("net: allow setting ecn
via routing table") and adds RFC3168 section 6.1.1.1. fallback for outgoing
ECN connections. In other words, this work adds a retry with a non-ECN
setup SYN packet, as suggested from the RFC on the first timeout:

  [...] A host that receives no reply to an ECN-setup SYN within the
  normal SYN retransmission timeout interval MAY resend the SYN and
  any subsequent SYN retransmissions with CWR and ECE cleared. [...]

Schematic client-side view when assuming the server is in tcp_ecn=2 mode,
that is, Linux default since 2009 via commit 255cac91c3c9 ("tcp: extend
ECN sysctl to allow server-side only ECN"):

 1) Normal ECN-capable path:

    SYN ECE CWR ----->
                <----- SYN ACK ECE
            ACK ----->

 2) Path with broken middlebox, when client has fallback:

    SYN ECE CWR ----X crappy middlebox drops packet
                      (timeout, rtx)
            SYN ----->
                <----- SYN ACK
            ACK ----->

In case we would not have the fallback implemented, the middlebox drop
point would basically end up as:

    SYN ECE CWR ----X crappy middlebox drops packet
                      (timeout, rtx)
    SYN ECE CWR ----X crappy middlebox drops packet
                      (timeout, rtx)
    SYN ECE CWR ----X crappy middlebox drops packet
                      (timeout, rtx)

In any case, it's rather a smaller percentage of sites where there would
occur such additional setup latency: it was found in end of 2014 that ~56%
of IPv4 and 65% of IPv6 servers of Alexa 1 million list would negotiate
ECN (aka tcp_ecn=2 default), 0.42% of these webservers will fail to connect
when trying to negotiate with ECN (tcp_ecn=1) due to timeouts, which the
fallback would mitigate with a slight latency trade-off. Recent related
paper on this topic:

  Brian Trammell, Mirja Kühlewind, Damiano Boppart, Iain Learmonth,
  Gorry Fairhurst, and Richard Scheffenegger:
    "Enabling Internet-Wide Deployment of Explicit Congestion Notification."
    Proc. PAM 2015, New York.
  http://ecn.ethz.ch/ecn-pam15.pdf

Thus, when net.ipv4.tcp_ecn=1 is being set, the patch will perform RFC3168,
section 6.1.1.1. fallback on timeout. For users explicitly not wanting this
which can be in DC use case, we add a net.ipv4.tcp_ecn_fallback knob that
allows for disabling the fallback.

tp->ecn_flags are not being cleared in tcp_ecn_clear_syn() on output, but
rather we let tcp_ecn_rcv_synack() take that over on input path in case a
SYN ACK ECE was delayed. Thus a spurious SYN retransmission will not prevent
ECN being negotiated eventually in that case.

Reference: https://www.ietf.org/proceedings/92/slides/slides-92-iccrg-1.pdf
Reference: https://www.ietf.org/proceedings/89/slides/slides-89-tsvarea-1.pdf
Signed-off-by: Daniel Borkmann 
Signed-off-by: Florian Westphal 
Signed-off-by: Mirja Kühlewind 
Signed-off-by: Brian Trammell 
Cc: Eric Dumazet 
Cc: Dave That 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp_metrics: Use a single hash table for all network namespaces.

2015-03-13T05:57:07+00:00

Now that all of the operations are safe on a single hash table
accross network namespaces, allocate a single global hash table
and update the code to use it.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: David S. Miller

ipv4: Create probe timer for tcp PMTU as per RFC4821

2015-03-06T19:57:42+00:00

As per RFC4821 7.3.  Selecting Probe Size, a probe timer should
be armed once probing has converged. Once this timer expired,
probing again to take advantage of any path PMTU change. The
recommended probing interval is 10 minutes per RFC1981. Probing
interval could be sysctled by sysctl_tcp_probe_interval.

Eric Dumazet suggested to implement pseudo timer based on 32bits
jiffies tcp_time_stamp instead of using classic timer for such
rare event.

Signed-off-by: Fan Du 
Signed-off-by: David S. Miller

ipv4: Use binary search to choose tcp PMTU probe_size

2015-03-06T19:57:41+00:00

Current probe_size is chosen by doubling mss_cache,
the probing process will end shortly with a sub-optimal
mss size, and the link mtu will not be taken full
advantage of, in return, this will make user to tweak
tcp_base_mss with care.

Use binary search to choose probe_size in a fine
granularity manner, an optimal mss will be found
to boost performance as its maxmium.

In addition, introduce a sysctl_tcp_probe_threshold
to control when probing will stop in respect to
the width of search range.

Test env:
Docker instance with vxlan encapuslation(82599EB)
iperf -c 10.0.0.24  -t 60

before this patch:
1.26 Gbits/sec

After this patch: increase 26%
1.59 Gbits/sec

Signed-off-by: Fan Du 
Acked-by: John Heffner 
Signed-off-by: David S. Miller

ipv4: add net bool fib_offload_disabled

2015-03-06T05:24:58+00:00

If something goes wrong with IPv4 FIB offload, mark entire net offload
disabled.  This is brute force policy to basically shut down IPv4 FIB offload
permanently if there is a problem offloading any route to an external device.
We can refine the policy in the future, to handle failures on a per-device or
per-route basis, but for now, this policy is per-net.

What we're trying to avoid is an inconsistent split between the kernel's FIB
and the offload device's FIB.  We don't want the device to fwd a pkt
inconsitent with what the kernel would do.  An example of a split is if device
has 10.0.0.0/16 and kernel has 10.0.0.0/16 and 10.0.0.0/24, the device wouldn't
see the longest prefix 10.0.0.0/24 and potentially forward pkts incorrectly.

Limited capacity or limited capability are two ways a route may fail to install
to the offload device.  We'll not differentiate between failures at this time,
and treat any failure as fatal and mark the net as fib_offload_disabled.

Signed-off-by: Scott Feldman 
Signed-off-by: David S. Miller