<feed xmlns='http://www.w3.org/2005/Atom'>
<title>kernel/linux.git/include/net/sctp/structs.h, branch v3.14.19</title>
<subtitle>Linux kernel stable tree (mirror)</subtitle>
<id>https://git.radix-linux.su/kernel/linux.git/atom?h=v3.14.19</id>
<link rel='self' href='https://git.radix-linux.su/kernel/linux.git/atom?h=v3.14.19'/>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/'/>
<updated>2014-05-31T20:20:34+00:00</updated>
<entry>
<title>net: sctp: cache auth_enable per endpoint</title>
<updated>2014-05-31T20:20:34+00:00</updated>
<author>
<name>Vlad Yasevich</name>
<email>vyasevic@redhat.com</email>
</author>
<published>2014-04-17T15:26:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=3938b0336a93fa5faa242dc9e5823ac69df9e066'/>
<id>urn:sha1:3938b0336a93fa5faa242dc9e5823ac69df9e066</id>
<content type='text'>
[ Upstream commit b14878ccb7fac0242db82720b784ab62c467c0dc ]

Currently, it is possible to create an SCTP socket, then switch
auth_enable via sysctl setting to 1 and crash the system on connect:

Oops[#1]:
CPU: 0 PID: 0 Comm: swapper Not tainted 3.14.1-mipsgit-20140415 #1
task: ffffffff8056ce80 ti: ffffffff8055c000 task.ti: ffffffff8055c000
[...]
Call Trace:
[&lt;ffffffff8043c4e8&gt;] sctp_auth_asoc_set_default_hmac+0x68/0x80
[&lt;ffffffff8042b300&gt;] sctp_process_init+0x5e0/0x8a4
[&lt;ffffffff8042188c&gt;] sctp_sf_do_5_1B_init+0x234/0x34c
[&lt;ffffffff804228c8&gt;] sctp_do_sm+0xb4/0x1e8
[&lt;ffffffff80425a08&gt;] sctp_endpoint_bh_rcv+0x1c4/0x214
[&lt;ffffffff8043af68&gt;] sctp_rcv+0x588/0x630
[&lt;ffffffff8043e8e8&gt;] sctp6_rcv+0x10/0x24
[&lt;ffffffff803acb50&gt;] ip6_input+0x2c0/0x440
[&lt;ffffffff8030fc00&gt;] __netif_receive_skb_core+0x4a8/0x564
[&lt;ffffffff80310650&gt;] process_backlog+0xb4/0x18c
[&lt;ffffffff80313cbc&gt;] net_rx_action+0x12c/0x210
[&lt;ffffffff80034254&gt;] __do_softirq+0x17c/0x2ac
[&lt;ffffffff800345e0&gt;] irq_exit+0x54/0xb0
[&lt;ffffffff800075a4&gt;] ret_from_irq+0x0/0x4
[&lt;ffffffff800090ec&gt;] rm7k_wait_irqoff+0x24/0x48
[&lt;ffffffff8005e388&gt;] cpu_startup_entry+0xc0/0x148
[&lt;ffffffff805a88b0&gt;] start_kernel+0x37c/0x398
Code: dd0900b8  000330f8  0126302d &lt;dcc60000&gt; 50c0fff1  0047182a  a48306a0
03e00008  00000000
---[ end trace b530b0551467f2fd ]---
Kernel panic - not syncing: Fatal exception in interrupt

What happens while auth_enable=0 in that case is, that
ep-&gt;auth_hmacs is initialized to NULL in sctp_auth_init_hmacs()
when endpoint is being created.

After that point, if an admin switches over to auth_enable=1,
the machine can crash due to NULL pointer dereference during
reception of an INIT chunk. When we enter sctp_process_init()
via sctp_sf_do_5_1B_init() in order to respond to an INIT chunk,
the INIT verification succeeds and while we walk and process
all INIT params via sctp_process_param() we find that
net-&gt;sctp.auth_enable is set, therefore do not fall through,
but invoke sctp_auth_asoc_set_default_hmac() instead, and thus,
dereference what we have set to NULL during endpoint
initialization phase.

The fix is to make auth_enable immutable by caching its value
during endpoint initialization, so that its original value is
being carried along until destruction. The bug seems to originate
from the very first days.

Fix in joint work with Daniel Borkmann.

Reported-by: Joshua Kinard &lt;kumba@gentoo.org&gt;
Signed-off-by: Vlad Yasevich &lt;vyasevic@redhat.com&gt;
Signed-off-by: Daniel Borkmann &lt;dborkman@redhat.com&gt;
Acked-by: Neil Horman &lt;nhorman@tuxdriver.com&gt;
Tested-by: Joshua Kinard &lt;kumba@gentoo.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>Revert "net: sctp: Fix a_rwnd/rwnd management to reflect real state of the receiver's buffer"</title>
<updated>2014-05-31T20:20:33+00:00</updated>
<author>
<name>Daniel Borkmann</name>
<email>dborkman@redhat.com</email>
</author>
<published>2014-04-14T19:45:17+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=bde6d78b4a05212e6611c7c2fe104fa72512b6eb'/>
<id>urn:sha1:bde6d78b4a05212e6611c7c2fe104fa72512b6eb</id>
<content type='text'>
[ Upstream commit 362d52040c71f6e8d8158be48c812d7729cb8df1 ]

This reverts commit ef2820a735f7 ("net: sctp: Fix a_rwnd/rwnd management
to reflect real state of the receiver's buffer") as it introduced a
serious performance regression on SCTP over IPv4 and IPv6, though a not
as dramatic on the latter. Measurements are on 10Gbit/s with ixgbe NICs.

Current state:

[root@Lab200slot2 ~]# iperf3 --sctp -4 -c 192.168.241.3 -V -l 1452 -t 60
iperf version 3.0.1 (10 January 2014)
Linux Lab200slot2 3.14.0 #1 SMP Thu Apr 3 23:18:29 EDT 2014 x86_64
Time: Fri, 11 Apr 2014 17:56:21 GMT
Connecting to host 192.168.241.3, port 5201
      Cookie: Lab200slot2.1397238981.812898.548918
[  4] local 192.168.241.2 port 38616 connected to 192.168.241.3 port 5201
Starting Test: protocol: SCTP, 1 streams, 1452 byte blocks, omitting 0 seconds, 60 second test
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.09   sec  20.8 MBytes   161 Mbits/sec
[  4]   1.09-2.13   sec  10.8 MBytes  86.8 Mbits/sec
[  4]   2.13-3.15   sec  3.57 MBytes  29.5 Mbits/sec
[  4]   3.15-4.16   sec  4.33 MBytes  35.7 Mbits/sec
[  4]   4.16-6.21   sec  10.4 MBytes  42.7 Mbits/sec
[  4]   6.21-6.21   sec  0.00 Bytes    0.00 bits/sec
[  4]   6.21-7.35   sec  34.6 MBytes   253 Mbits/sec
[  4]   7.35-11.45  sec  22.0 MBytes  45.0 Mbits/sec
[  4]  11.45-11.45  sec  0.00 Bytes    0.00 bits/sec
[  4]  11.45-11.45  sec  0.00 Bytes    0.00 bits/sec
[  4]  11.45-11.45  sec  0.00 Bytes    0.00 bits/sec
[  4]  11.45-12.51  sec  16.0 MBytes   126 Mbits/sec
[  4]  12.51-13.59  sec  20.3 MBytes   158 Mbits/sec
[  4]  13.59-14.65  sec  13.4 MBytes   107 Mbits/sec
[  4]  14.65-16.79  sec  33.3 MBytes   130 Mbits/sec
[  4]  16.79-16.79  sec  0.00 Bytes    0.00 bits/sec
[  4]  16.79-17.82  sec  5.94 MBytes  48.7 Mbits/sec
(etc)

[root@Lab200slot2 ~]#  iperf3 --sctp -6 -c 2001:db8:0:f101::1 -V -l 1400 -t 60
iperf version 3.0.1 (10 January 2014)
Linux Lab200slot2 3.14.0 #1 SMP Thu Apr 3 23:18:29 EDT 2014 x86_64
Time: Fri, 11 Apr 2014 19:08:41 GMT
Connecting to host 2001:db8:0:f101::1, port 5201
      Cookie: Lab200slot2.1397243321.714295.2b3f7c
[  4] local 2001:db8:0:f101::2 port 55804 connected to 2001:db8:0:f101::1 port 5201
Starting Test: protocol: SCTP, 1 streams, 1400 byte blocks, omitting 0 seconds, 60 second test
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec   169 MBytes  1.42 Gbits/sec
[  4]   1.00-2.00   sec   201 MBytes  1.69 Gbits/sec
[  4]   2.00-3.00   sec   188 MBytes  1.58 Gbits/sec
[  4]   3.00-4.00   sec   174 MBytes  1.46 Gbits/sec
[  4]   4.00-5.00   sec   165 MBytes  1.39 Gbits/sec
[  4]   5.00-6.00   sec   199 MBytes  1.67 Gbits/sec
[  4]   6.00-7.00   sec   163 MBytes  1.36 Gbits/sec
[  4]   7.00-8.00   sec   174 MBytes  1.46 Gbits/sec
[  4]   8.00-9.00   sec   193 MBytes  1.62 Gbits/sec
[  4]   9.00-10.00  sec   196 MBytes  1.65 Gbits/sec
[  4]  10.00-11.00  sec   157 MBytes  1.31 Gbits/sec
[  4]  11.00-12.00  sec   175 MBytes  1.47 Gbits/sec
[  4]  12.00-13.00  sec   192 MBytes  1.61 Gbits/sec
[  4]  13.00-14.00  sec   199 MBytes  1.67 Gbits/sec
(etc)

After patch:

[root@Lab200slot2 ~]#  iperf3 --sctp -4 -c 192.168.240.3 -V -l 1452 -t 60
iperf version 3.0.1 (10 January 2014)
Linux Lab200slot2 3.14.0+ #1 SMP Mon Apr 14 12:06:40 EDT 2014 x86_64
Time: Mon, 14 Apr 2014 16:40:48 GMT
Connecting to host 192.168.240.3, port 5201
      Cookie: Lab200slot2.1397493648.413274.65e131
[  4] local 192.168.240.2 port 50548 connected to 192.168.240.3 port 5201
Starting Test: protocol: SCTP, 1 streams, 1452 byte blocks, omitting 0 seconds, 60 second test
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec   240 MBytes  2.02 Gbits/sec
[  4]   1.00-2.00   sec   239 MBytes  2.01 Gbits/sec
[  4]   2.00-3.00   sec   240 MBytes  2.01 Gbits/sec
[  4]   3.00-4.00   sec   239 MBytes  2.00 Gbits/sec
[  4]   4.00-5.00   sec   245 MBytes  2.05 Gbits/sec
[  4]   5.00-6.00   sec   240 MBytes  2.01 Gbits/sec
[  4]   6.00-7.00   sec   240 MBytes  2.02 Gbits/sec
[  4]   7.00-8.00   sec   239 MBytes  2.01 Gbits/sec

With the reverted patch applied, the SCTP/IPv4 performance is back
to normal on latest upstream for IPv4 and IPv6 and has same throughput
as 3.4.2 test kernel, steady and interval reports are smooth again.

Fixes: ef2820a735f7 ("net: sctp: Fix a_rwnd/rwnd management to reflect real state of the receiver's buffer")
Reported-by: Peter Butler &lt;pbutler@sonusnet.com&gt;
Reported-by: Dongsheng Song &lt;dongsheng.song@gmail.com&gt;
Reported-by: Fengguang Wu &lt;fengguang.wu@intel.com&gt;
Tested-by: Peter Butler &lt;pbutler@sonusnet.com&gt;
Signed-off-by: Daniel Borkmann &lt;dborkman@redhat.com&gt;
Cc: Matija Glavinic Pecotic &lt;matija.glavinic-pecotic.ext@nsn.com&gt;
Cc: Alexander Sverdlin &lt;alexander.sverdlin@nsn.com&gt;
Cc: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
Acked-by: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>net: sctp: Fix a_rwnd/rwnd management to reflect real state of the receiver's buffer</title>
<updated>2014-02-17T05:16:56+00:00</updated>
<author>
<name>Matija Glavinic Pecotic</name>
<email>matija.glavinic-pecotic.ext@nsn.com</email>
</author>
<published>2014-02-14T13:51:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=ef2820a735f74ea60335f8ba3801b844f0cb184d'/>
<id>urn:sha1:ef2820a735f74ea60335f8ba3801b844f0cb184d</id>
<content type='text'>
Implementation of (a)rwnd calculation might lead to severe performance issues
and associations completely stalling. These problems are described and solution
is proposed which improves lksctp's robustness in congestion state.

1) Sudden drop of a_rwnd and incomplete window recovery afterwards

Data accounted in sctp_assoc_rwnd_decrease takes only payload size (sctp data),
but size of sk_buff, which is blamed against receiver buffer, is not accounted
in rwnd. Theoretically, this should not be the problem as actual size of buffer
is double the amount requested on the socket (SO_RECVBUF). Problem here is
that this will have bad scaling for data which is less then sizeof sk_buff.
E.g. in 4G (LTE) networks, link interfacing radio side will have a large portion
of traffic of this size (less then 100B).

An example of sudden drop and incomplete window recovery is given below. Node B
exhibits problematic behavior. Node A initiates association and B is configured
to advertise rwnd of 10000. A sends messages of size 43B (size of typical sctp
message in 4G (LTE) network). On B data is left in buffer by not reading socket
in userspace.

Lets examine when we will hit pressure state and declare rwnd to be 0 for
scenario with above stated parameters (rwnd == 10000, chunk size == 43, each
chunk is sent in separate sctp packet)

Logic is implemented in sctp_assoc_rwnd_decrease:

socket_buffer (see below) is maximum size which can be held in socket buffer
(sk_rcvbuf). current_alloced is amount of data currently allocated (rx_count)

A simple expression is given for which it will be examined after how many
packets for above stated parameters we enter pressure state:

We start by condition which has to be met in order to enter pressure state:

	socket_buffer &lt; currently_alloced;

currently_alloced is represented as size of sctp packets received so far and not
yet delivered to userspace. x is the number of chunks/packets (since there is no
bundling, and each chunk is delivered in separate packet, we can observe each
chunk also as sctp packet, and what is important here, having its own sk_buff):

	socket_buffer &lt; x*each_sctp_packet;

each_sctp_packet is sctp chunk size + sizeof(struct sk_buff). socket_buffer is
twice the amount of initially requested size of socket buffer, which is in case
of sctp, twice the a_rwnd requested:

	2*rwnd &lt; x*(payload+sizeof(struc sk_buff));

sizeof(struct sk_buff) is 190 (3.13.0-rc4+). Above is stated that rwnd is 10000
and each payload size is 43

	20000 &lt; x(43+190);

	x &gt; 20000/233;

	x ~&gt; 84;

After ~84 messages, pressure state is entered and 0 rwnd is advertised while
received 84*43B ~= 3612B sctp data. This is why external observer notices sudden
drop from 6474 to 0, as it will be now shown in example:

IP A.34340 &gt; B.12345: sctp (1) [INIT] [init tag: 1875509148] [rwnd: 81920] [OS: 10] [MIS: 65535] [init TSN: 1096057017]
IP B.12345 &gt; A.34340: sctp (1) [INIT ACK] [init tag: 3198966556] [rwnd: 10000] [OS: 10] [MIS: 10] [init TSN: 902132839]
IP A.34340 &gt; B.12345: sctp (1) [COOKIE ECHO]
IP B.12345 &gt; A.34340: sctp (1) [COOKIE ACK]
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057017] [SID: 0] [SSEQ 0] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057017] [a_rwnd 9957] [#gap acks 0] [#dup tsns 0]
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057018] [SID: 0] [SSEQ 1] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057018] [a_rwnd 9957] [#gap acks 0] [#dup tsns 0]
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057019] [SID: 0] [SSEQ 2] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057019] [a_rwnd 9914] [#gap acks 0] [#dup tsns 0]
&lt;...&gt;
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057098] [SID: 0] [SSEQ 81] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057098] [a_rwnd 6517] [#gap acks 0] [#dup tsns 0]
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057099] [SID: 0] [SSEQ 82] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057099] [a_rwnd 6474] [#gap acks 0] [#dup tsns 0]
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057100] [SID: 0] [SSEQ 83] [PPID 0x18]

--&gt; Sudden drop

IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057100] [a_rwnd 0] [#gap acks 0] [#dup tsns 0]

At this point, rwnd_press stores current rwnd value so it can be later restored
in sctp_assoc_rwnd_increase. This however doesn't happen as condition to start
slowly increasing rwnd until rwnd_press is returned to rwnd is never met. This
condition is not met since rwnd, after it hit 0, must first reach rwnd_press by
adding amount which is read from userspace. Let us observe values in above
example. Initial a_rwnd is 10000, pressure was hit when rwnd was ~6500 and the
amount of actual sctp data currently waiting to be delivered to userspace
is ~3500. When userspace starts to read, sctp_assoc_rwnd_increase will be blamed
only for sctp data, which is ~3500. Condition is never met, and when userspace
reads all data, rwnd stays on 3569.

IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057100] [a_rwnd 1505] [#gap acks 0] [#dup tsns 0]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057100] [a_rwnd 3010] [#gap acks 0] [#dup tsns 0]
IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057101] [SID: 0] [SSEQ 84] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057101] [a_rwnd 3569] [#gap acks 0] [#dup tsns 0]

--&gt; At this point userspace read everything, rwnd recovered only to 3569

IP A.34340 &gt; B.12345: sctp (1) [DATA] (B)(E) [TSN: 1096057102] [SID: 0] [SSEQ 85] [PPID 0x18]
IP B.12345 &gt; A.34340: sctp (1) [SACK] [cum ack 1096057102] [a_rwnd 3569] [#gap acks 0] [#dup tsns 0]

Reproduction is straight forward, it is enough for sender to send packets of
size less then sizeof(struct sk_buff) and receiver keeping them in its buffers.

2) Minute size window for associations sharing the same socket buffer

In case multiple associations share the same socket, and same socket buffer
(sctp.rcvbuf_policy == 0), different scenarios exist in which congestion on one
of the associations can permanently drop rwnd of other association(s).

Situation will be typically observed as one association suddenly having rwnd
dropped to size of last packet received and never recovering beyond that point.
Different scenarios will lead to it, but all have in common that one of the
associations (let it be association from 1)) nearly depleted socket buffer, and
the other association blames socket buffer just for the amount enough to start
the pressure. This association will enter pressure state, set rwnd_press and
announce 0 rwnd.
When data is read by userspace, similar situation as in 1) will occur, rwnd will
increase just for the size read by userspace but rwnd_press will be high enough
so that association doesn't have enough credit to reach rwnd_press and restore
to previous state. This case is special case of 1), being worse as there is, in
the worst case, only one packet in buffer for which size rwnd will be increased.
Consequence is association which has very low maximum rwnd ('minute size', in
our case down to 43B - size of packet which caused pressure) and as such
unusable.

Scenario happened in the field and labs frequently after congestion state (link
breaks, different probabilities of packet drop, packet reordering) and with
scenario 1) preceding. Here is given a deterministic scenario for reproduction:

&gt;From node A establish two associations on the same socket, with rcvbuf_policy
being set to share one common buffer (sctp.rcvbuf_policy == 0). On association 1
repeat scenario from 1), that is, bring it down to 0 and restore up. Observe
scenario 1). Use small payload size (here we use 43). Once rwnd is 'recovered',
bring it down close to 0, as in just one more packet would close it. This has as
a consequence that association number 2 is able to receive (at least) one more
packet which will bring it in pressure state. E.g. if association 2 had rwnd of
10000, packet received was 43, and we enter at this point into pressure,
rwnd_press will have 9957. Once payload is delivered to userspace, rwnd will
increase for 43, but conditions to restore rwnd to original state, just as in
1), will never be satisfied.

--&gt; Association 1, between A.y and B.12345

IP A.55915 &gt; B.12345: sctp (1) [INIT] [init tag: 836880897] [rwnd: 10000] [OS: 10] [MIS: 65535] [init TSN: 4032536569]
IP B.12345 &gt; A.55915: sctp (1) [INIT ACK] [init tag: 2873310749] [rwnd: 81920] [OS: 10] [MIS: 10] [init TSN: 3799315613]
IP A.55915 &gt; B.12345: sctp (1) [COOKIE ECHO]
IP B.12345 &gt; A.55915: sctp (1) [COOKIE ACK]

--&gt; Association 2, between A.z and B.12346

IP A.55915 &gt; B.12346: sctp (1) [INIT] [init tag: 534798321] [rwnd: 10000] [OS: 10] [MIS: 65535] [init TSN: 2099285173]
IP B.12346 &gt; A.55915: sctp (1) [INIT ACK] [init tag: 516668823] [rwnd: 81920] [OS: 10] [MIS: 10] [init TSN: 3676403240]
IP A.55915 &gt; B.12346: sctp (1) [COOKIE ECHO]
IP B.12346 &gt; A.55915: sctp (1) [COOKIE ACK]

--&gt; Deplete socket buffer by sending messages of size 43B over association 1

IP B.12345 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3799315613] [SID: 0] [SSEQ 0] [PPID 0x18]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315613] [a_rwnd 9957] [#gap acks 0] [#dup tsns 0]

&lt;...&gt;

IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315696] [a_rwnd 6388] [#gap acks 0] [#dup tsns 0]
IP B.12345 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3799315697] [SID: 0] [SSEQ 84] [PPID 0x18]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315697] [a_rwnd 6345] [#gap acks 0] [#dup tsns 0]

--&gt; Sudden drop on 1

IP B.12345 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3799315698] [SID: 0] [SSEQ 85] [PPID 0x18]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315698] [a_rwnd 0] [#gap acks 0] [#dup tsns 0]

--&gt; Here userspace read, rwnd 'recovered' to 3698, now deplete again using
    association 1 so there is place in buffer for only one more packet

IP B.12345 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3799315799] [SID: 0] [SSEQ 186] [PPID 0x18]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315799] [a_rwnd 86] [#gap acks 0] [#dup tsns 0]
IP B.12345 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3799315800] [SID: 0] [SSEQ 187] [PPID 0x18]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315800] [a_rwnd 43] [#gap acks 0] [#dup tsns 0]

--&gt; Socket buffer is almost depleted, but there is space for one more packet,
    send them over association 2, size 43B

IP B.12346 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3676403240] [SID: 0] [SSEQ 0] [PPID 0x18]
IP A.55915 &gt; B.12346: sctp (1) [SACK] [cum ack 3676403240] [a_rwnd 0] [#gap acks 0] [#dup tsns 0]

--&gt; Immediate drop

IP A.60995 &gt; B.12346: sctp (1) [SACK] [cum ack 387491510] [a_rwnd 0] [#gap acks 0] [#dup tsns 0]

--&gt; Read everything from the socket, both association recover up to maximum rwnd
    they are capable of reaching, note that association 1 recovered up to 3698,
    and association 2 recovered only to 43

IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315800] [a_rwnd 1548] [#gap acks 0] [#dup tsns 0]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315800] [a_rwnd 3053] [#gap acks 0] [#dup tsns 0]
IP B.12345 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3799315801] [SID: 0] [SSEQ 188] [PPID 0x18]
IP A.55915 &gt; B.12345: sctp (1) [SACK] [cum ack 3799315801] [a_rwnd 3698] [#gap acks 0] [#dup tsns 0]
IP B.12346 &gt; A.55915: sctp (1) [DATA] (B)(E) [TSN: 3676403241] [SID: 0] [SSEQ 1] [PPID 0x18]
IP A.55915 &gt; B.12346: sctp (1) [SACK] [cum ack 3676403241] [a_rwnd 43] [#gap acks 0] [#dup tsns 0]

A careful reader might wonder why it is necessary to reproduce 1) prior
reproduction of 2). It is simply easier to observe when to send packet over
association 2 which will push association into the pressure state.

Proposed solution:

Both problems share the same root cause, and that is improper scaling of socket
buffer with rwnd. Solution in which sizeof(sk_buff) is taken into concern while
calculating rwnd is not possible due to fact that there is no linear
relationship between amount of data blamed in increase/decrease with IP packet
in which payload arrived. Even in case such solution would be followed,
complexity of the code would increase. Due to nature of current rwnd handling,
slow increase (in sctp_assoc_rwnd_increase) of rwnd after pressure state is
entered is rationale, but it gives false representation to the sender of current
buffer space. Furthermore, it implements additional congestion control mechanism
which is defined on implementation, and not on standard basis.

Proposed solution simplifies whole algorithm having on mind definition from rfc:

o  Receiver Window (rwnd): This gives the sender an indication of the space
   available in the receiver's inbound buffer.

Core of the proposed solution is given with these lines:

sctp_assoc_rwnd_update:
	if ((asoc-&gt;base.sk-&gt;sk_rcvbuf - rx_count) &gt; 0)
		asoc-&gt;rwnd = (asoc-&gt;base.sk-&gt;sk_rcvbuf - rx_count) &gt;&gt; 1;
	else
		asoc-&gt;rwnd = 0;

We advertise to sender (half of) actual space we have. Half is in the braces
depending whether you would like to observe size of socket buffer as SO_RECVBUF
or twice the amount, i.e. size is the one visible from userspace, that is,
from kernelspace.
In this way sender is given with good approximation of our buffer space,
regardless of the buffer policy - we always advertise what we have. Proposed
solution fixes described problems and removes necessity for rwnd restoration
algorithm. Finally, as proposed solution is simplification, some lines of code,
along with some bytes in struct sctp_association are saved.

Version 2 of the patch addressed comments from Vlad. Name of the function is set
to be more descriptive, and two parts of code are changed, in one removing the
superfluous call to sctp_assoc_rwnd_update since call would not result in update
of rwnd, and the other being reordering of the code in a way that call to
sctp_assoc_rwnd_update updates rwnd. Version 3 corrected change introduced in v2
in a way that existing function is not reordered/copied in line, but it is
correctly called. Thanks Vlad for suggesting.

Signed-off-by: Matija Glavinic Pecotic &lt;matija.glavinic-pecotic.ext@nsn.com&gt;
Reviewed-by: Alexander Sverdlin &lt;alexander.sverdlin@nsn.com&gt;
Acked-by: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>sctp: make sctp_addto_chunk_fixed local</title>
<updated>2014-01-13T22:42:30+00:00</updated>
<author>
<name>stephen hemminger</name>
<email>stephen@networkplumber.org</email>
</author>
<published>2014-01-10T06:31:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=6daaf0de2f3170206f57e7881adfbd8682cdd7fb'/>
<id>urn:sha1:6daaf0de2f3170206f57e7881adfbd8682cdd7fb</id>
<content type='text'>
Signed-off-by: Stephen Hemminger &lt;stephen@networkplumber.org&gt;
Acked-by: Neil Horman &lt;nhorman@tuxdriver.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/davem/net</title>
<updated>2014-01-06T22:37:45+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2014-01-06T22:37:45+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=56a4342dfe3145cd66f766adccb28fd9b571606d'/>
<id>urn:sha1:56a4342dfe3145cd66f766adccb28fd9b571606d</id>
<content type='text'>
Conflicts:
	drivers/net/ethernet/qlogic/qlcnic/qlcnic_sriov_pf.c
	net/ipv6/ip6_tunnel.c
	net/ipv6/ip6_vti.c

ipv6 tunnel statistic bug fixes conflicting with consolidation into
generic sw per-cpu net stats.

qlogic conflict between queue counting bug fix and the addition
of multiple MAC address support.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>sctp: Remove outqueue empty state</title>
<updated>2014-01-02T22:22:48+00:00</updated>
<author>
<name>Vlad Yasevich</name>
<email>vyasevich@gmail.com</email>
</author>
<published>2014-01-02T19:39:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=619a60ee04be33238721a15c1f9704a2a515a33e'/>
<id>urn:sha1:619a60ee04be33238721a15c1f9704a2a515a33e</id>
<content type='text'>
The SCTP outqueue structure maintains a data chunks
that are pending transmission, the list of chunks that
are pending a retransmission and a length of data in
flight.  It also tries to keep the emtpy state so that
it can performe shutdown sequence or notify user.

The problem is that the empy state is inconsistently
tracked.  It is possible to completely drain the queue
without sending anything when using PR-SCTP.  In this
case, the empty state will not be correctly state as
report by Jamal Hadi Salim &lt;jhs@mojatatu.com&gt;.  This
can cause an association to be perminantly stuck in the
SHUTDOWN_PENDING state.

Additionally, SCTP is incredibly inefficient when setting
the empty state.  Even though all the data is availaible
in the outqueue structure, we ignore it and walk a list
of trasnports.

In the end, we can completely remove the extra empty
state and figure out if the queue is empty by looking
at 3 things:  length of pending data, length of in-flight
data, and exisiting of retransmit data.  All of these
are already in the strucutre.

Reported-by: Jamal Hadi Salim &lt;jhs@mojatatu.com&gt;
Signed-off-by: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
Acked-by: Neil Horman &lt;nhorman@tuxdriver.com&gt;
Tested-by: Jamal Hadi Salim &lt;jhs@mojatatu.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net</title>
<updated>2013-12-18T21:42:06+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2013-12-18T21:42:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=143c9054949436cb05e468439dc5e46231f33d09'/>
<id>urn:sha1:143c9054949436cb05e468439dc5e46231f33d09</id>
<content type='text'>
Conflicts:
	drivers/net/ethernet/intel/i40e/i40e_main.c
	drivers/net/macvtap.c

Both minor merge hassles, simple overlapping changes.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>sctp: Reorder 'struc association' members to reduce its size</title>
<updated>2013-12-17T19:32:43+00:00</updated>
<author>
<name>wangweidong</name>
<email>wangweidong1@huawei.com</email>
</author>
<published>2013-12-13T05:51:04+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=be78cfcb25fd163ad7c415cdc0ff343fbc8d22ec'/>
<id>urn:sha1:be78cfcb25fd163ad7c415cdc0ff343fbc8d22ec</id>
<content type='text'>
Members of 'struct association' are not in appropriate order to
reuse compiler added padding on 64bit architectures. In this patch
we reorder those struct members and help reduce the size of the
structure from 2776 bytes to 2720 bytes on 64 bit architectures.

Signed-off-by: Wang Weidong &lt;wangweidong1@huawei.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>sctp: properly latch and use autoclose value from sock to association</title>
<updated>2013-12-11T03:41:26+00:00</updated>
<author>
<name>Neil Horman</name>
<email>nhorman@tuxdriver.com</email>
</author>
<published>2013-12-10T11:48:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=9f70f46bd4c7267d48ef461a1d613ec9ec0d520c'/>
<id>urn:sha1:9f70f46bd4c7267d48ef461a1d613ec9ec0d520c</id>
<content type='text'>
Currently, sctp associations latch a sockets autoclose value to an association
at association init time, subject to capping constraints from the max_autoclose
sysctl value.  This leads to an odd situation where an application may set a
socket level autoclose timeout, but sliently sctp will limit the autoclose
timeout to something less than that.

Fix this by modifying the autoclose setsockopt function to check the limit, cap
it and warn the user via syslog that the timeout is capped.  This will allow
getsockopt to return valid autoclose timeout values that reflect what subsequent
associations actually use.

While were at it, also elimintate the assoc-&gt;autoclose variable, it duplicates
whats in the timeout array, which leads to multiple sources for the same
information, that may differ (as the former isn't subject to any capping).  This
gives us the timeout information in a canonical place and saves some space in
the association structure as well.

Signed-off-by: Neil Horman &lt;nhorman@tuxdriver.com&gt;
Acked-by: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
CC: Wang Weidong &lt;wangweidong1@huawei.com&gt;
CC: David Miller &lt;davem@davemloft.net&gt;
CC: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
CC: netdev@vger.kernel.org
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>sctp: Fix FSF address in file headers</title>
<updated>2013-12-06T17:37:56+00:00</updated>
<author>
<name>Jeff Kirsher</name>
<email>jeffrey.t.kirsher@intel.com</email>
</author>
<published>2013-12-06T14:28:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=4b2f13a25133b115eb56771bd4a8e71a82aea968'/>
<id>urn:sha1:4b2f13a25133b115eb56771bd4a8e71a82aea968</id>
<content type='text'>
Several files refer to an old address for the Free Software Foundation
in the file header comment.  Resolve by replacing the address with
the URL &lt;http://www.gnu.org/licenses/&gt; so that we do not have to keep
updating the header comments anytime the address changes.

CC: Vlad Yasevich &lt;vyasevich@gmail.com&gt;
CC: Neil Horman &lt;nhorman@tuxdriver.com&gt;
Signed-off-by: Jeff Kirsher &lt;jeffrey.t.kirsher@intel.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
</feed>
