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1 .Linux SCTP is catching up and going above
Red Hat, Inc.
Marcelo Ricardo Leitner, Xin Long
Linux Plumber Conference in Vancouver, 2018
1 / 31
2 . What and Why is SCTP
Outline
1 What and Why is SCTP
Architecture
SCTP vs TCP
2 What We’ve Done on Linux
Projects
Improvements Made Recently
Features Implemented Lately
LINUX vs BSD
3 What’s the Next
Features Development
Code Refactor
Hardware Support
2 / 31
3 . What and Why is SCTP Architecture
Structures
overview
1 Endpoint
2 Association
3 Transport
4 Stream
5 Msg
6 Packet
7 Chunk
3 / 31
4 . What and Why is SCTP Architecture
SCTP Structures in Linux
4 / 31
5 . What and Why is SCTP Architecture
SCTP Procedures in Linux
5 / 31
6 . What and Why is SCTP SCTP vs TCP
SCTP vs TCP/UDP on Feature
6 / 31
7 . What and Why is SCTP SCTP vs TCP
SCTP vs TCP on Performance
Performance ?
7 / 31
8 . What We’ve Done on Linux
Outline
1 What and Why is SCTP
Architecture
SCTP vs TCP
2 What We’ve Done on Linux
Projects
Improvements Made Recently
Features Implemented Lately
LINUX vs BSD
3 What’s the Next
Features Development
Code Refactor
Hardware Support
8 / 31
9 . What We’ve Done on Linux Projects
lksctp-tools (lib and unit test)
MANIFEST ——– - sctp_darn, sctp_test
. - sctp_status, sctp_xconnect
|– bin - peel_client, peel_server
|– doc - bindx_test, myftp, nagle_rcv, nagle_snd
|– man
|– src
... |– apps
"""
... |– func_tests Unit Test: Look in src/func_tests and in lksctp-tests package for examples of
... |– include of tests. Please do not submit code that fails its own tests or any of the unit
tests. If it fails a functional test, please document that with the submission.
... |... ‘– netinet
... |– lib """
... |– testlib
... ‘– withsctp
- sctp_send, sctp_sendmsg, sctp_recvmsg
- sctp_connectx_orig, sctp_connectx2, sctp_connectx3
- sctp_bindx, sctp_opt_info
- sctp_peeloff, sctp_peeloff_flags
9 / 31
10 . What We’ve Done on Linux Projects
sctp-tests (regression test): 27 test cases so far
10 / 31
11 . What We’ve Done on Linux Projects
tahi-sctp (conformance test)
RFC4960: Association Initialization
RFC4960: Association Termination
RFC4960: Fault Management
RFC4960: Error Cause
RFC4960: Chunk Bundling
RFC4960: User Data Transfer
RFC4960: Retransmission Timer
RFC4960: Congestion Control
RFC4960: Path MTU Discovery
RFC4960: Multi-Homed Endpoints
RFC4960: Explicit Congestion Notification
RFC4960: Packet Format
RFC4960: Miscellaneous Test
RFC4895: Authentication Chunks
RFC5061: Dynamic Address Reconfiguration
RFC3758: Partial Reliability Extension
RFC3554: Internet Protocol Security
11 / 31
12 . What We’ve Done on Linux Projects
Others
Syzkaller (fuzz test)
Codenomicon (fuzz test)
Packetdrill (conformance test)
Scapy (packet generating)
More ?
12 / 31
13 . What We’ve Done on Linux Improvements Made Recently
Transport Rhashtable 1
13 / 31
14 . What We’ve Done on Linux Improvements Made Recently
Transport Rhashtable 2
1 1-to-many(with "the same dport and different dip" lookup fast
2 1-step to find both transport and asoc
3 Rhashtable (rhlist) features: rcu_lock and resize memory
4 Why not use the key with hash(dport, lport, dip, lip) ?
5 Why not make rhashtable per endpoint/socket ?
14 / 31
15 . What We’ve Done on Linux Improvements Made Recently
SCTP Offload 1
15 / 31
16 . What We’ve Done on Linux Improvements Made Recently
SCTP Offload 2
16 / 31
17 . What We’ve Done on Linux Improvements Made Recently
SCTP Diag 1
[iproute2]# ss --sctp -n -l
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 172.16.254.254:8888 *:*
LISTEN 0 5 127.0.0.1:1234 *:*
LISTEN 0 5 127.0.0.1:1234 *:*
- ESTAB 0 0 127.0.0.1%lo:1234 127.0.0.1:4321
LISTEN 0 128 172.16.254.254:8888 *:*
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.253.253:8888
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.1.1:8888
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.1.2:8888
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.2.1:8888
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.2.2:8888
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.3.1:8888
- ESTAB 0 0 172.16.254.254%eth1:8888 172.16.3.2:8888
LISTEN 0 0 127.0.0.1:4321 *:*
- ESTAB 0 0 127.0.0.1%lo:4321 127.0.0.1:1234
[iproute2]# ss -Snai
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 1 127.0.0.1:27375 *:*
locals:127.0.0.1,192.168.42.2, v4mapped:1
ESTAB 0 0 127.0.0.1:37636 127.0.0.1:27375
locals:0.0.0.0, v4mapped:1
17 / 31
18 . What We’ve Done on Linux Improvements Made Recently
SCTP Diag 2
18 / 31
19 . What We’ve Done on Linux Improvements Made Recently
Others
Dst source addr selection
Rwnd improvements
Partial reliability fixes
MTU handling refactor
PMTU discovery (critical) fixes
CRC32c offloading on virtual interfaces
Some codes cleaning up
More ...
19 / 31
20 . What We’ve Done on Linux Features Implemented Lately
Overview
Stream Schedulers and User Message Interleaving for the
Stream Control Transmission Protocol [RFC8260]
Additional Policies for the Partially Reliable Stream Control
Transmission Protocol Extension [RFC7496]
Stream Control Transmission Protocol (SCTP) Stream
Reconfiguration [RFC6525]
Sockets API Extensions for the Stream Control Transmission
Protocol (SCTP) [RFC6458]
Full SELinux support
More ...
20 / 31
21 . What We’ve Done on Linux Features Implemented Lately
Stream Schedulers
21 / 31
22 . What We’ve Done on Linux Features Implemented Lately
Message Interleaving
22 / 31
23 . What We’ve Done on Linux Features Implemented Lately
PR_SCTP policies
1 Timed Reliability
SCTP_PR_SCTP_TTL
2 Limited Retransmissions Policy
SCTP_PR_SCTP_RTX
When dequeuing chunks from A
When dequeuing chunks from C
When moving chunks from B to C
After receiving a SACK, check B and C
3 Priority Policy
SCTP_PR_SCTP_PRIO
Before enqueuing chunk into A
And No Enough TX Buffer
Then try to drop C -> B -> A.
23 / 31
24 . What We’ve Done on Linux Features Implemented Lately
Stream Reconfig
1 Add Outgoing Streams:
No restrictions
2 Add Incoming Streams:
No restrictions
3 Reset Outgoing Streams:
Reset stream 1, b have to be empty
4 Reset Incoming Streams:
Peer will send Outgoing Stream request for which it has to follow the above rule
5 Reset SSN/TSN:
All queues have to be empty: A, B, C, a, b, c
24 / 31
25 . What We’ve Done on Linux Features Implemented Lately
Socket APIs
1 User APIs
sctp_sendv
sctp_recvv
2 Snd Info Flags
SENDALL
MSG_MORE
3 Cmsgs
PR_INFO
AUTH_INFO
DSTv4
DSTv6
25 / 31
26 . What We’ve Done on Linux LINUX vs BSD
Linux vs BSD on Features
Chunks Others
LINUX: LINUX:
ongoing sctp_do_sm()
transport rhashtable
BSD: offload
SCTP_NR_SELECTIVE_ACK (draft) diag
SCTP_PACKET_DROPPED (draft)
SCTP_PAD_CHUNK BSD:
sctp_cc_functions
26 / 31
27 . What’s the Next
Outline
1 What and Why is SCTP
Architecture
SCTP vs TCP
2 What We’ve Done on Linux
Projects
Improvements Made Recently
Features Implemented Lately
LINUX vs BSD
3 What’s the Next
Features Development
Code Refactor
Hardware Support
27 / 31
28 . What’s the Next Features Development
Features Development
Support more Chunks, Apis, Sockopts, Notifications.
Other features from Draft RFC, like SCTP NAT and CMT.
SCTP Performance Improvement (including sndbuf auto-tuning)
Add more test cases in sctp-tests.
28 / 31
29 . What’s the Next Code Refactor
Code Refactor
Some huge and messy functions.
Congestion framework.
Refactor lksctp-tools.
29 / 31
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