Message-Id: <F02013B3-C485-4998-B68A-26118D8ACF9C@fh-muenster.de>
Date:   Tue, 29 Sep 2020 18:39:59 +0200
From:   Michael Tuexen <tuexen@...muenster.de>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Tom Herbert <therbert@...gle.com>, davem@...emloft.net
Subject: Re: [PATCH net-next 00/15] sctp: Implement RFC6951: UDP Encapsulation
 of SCTP

> On 29. Sep 2020, at 15:48, Xin Long <lucien.xin@...il.com> wrote:
> 
> Description From the RFC:
> 
>   The Main Reasons:
> 
>   o  To allow SCTP traffic to pass through legacy NATs, which do not
>      provide native SCTP support as specified in [BEHAVE] and
>      [NATSUPP].
> 
>   o  To allow SCTP to be implemented on hosts that do not provide
>      direct access to the IP layer.  In particular, applications can
>      use their own SCTP implementation if the operating system does not
>      provide one.
> 
>   Implementation Notes:
> 
>   UDP-encapsulated SCTP is normally communicated between SCTP stacks
>   using the IANA-assigned UDP port number 9899 (sctp-tunneling) on both
>   ends.  There are circumstances where other ports may be used on
>   either end, and it might be required to use ports other than the
>   registered port.
> 
>   Each SCTP stack uses a single local UDP encapsulation port number as
>   the destination port for all its incoming SCTP packets, this greatly
>   simplifies implementation design.
> 
>   An SCTP implementation supporting UDP encapsulation MUST maintain a
>   remote UDP encapsulation port number per destination address for each
>   SCTP association.  Again, because the remote stack may be using ports
>   other than the well-known port, each port may be different from each
>   stack.  However, because of remapping of ports by NATs, the remote
>   ports associated with different remote IP addresses may not be
>   identical, even if they are associated with the same stack.
> 
>   Because the well-known port might not be used, implementations need
>   to allow other port numbers to be specified as a local or remote UDP
>   encapsulation port number through APIs.
Hi Xin Long,

I really appreciate that UDP encapsulation gets implemented in Linux.

The FreeBSD implementation initially had a bug due to missing text in
RFC6951. Please make sure the implementation also follows
https://www.ietf.org/id/draft-tuexen-tsvwg-sctp-udp-encaps-cons-03.html

The plan is to revise RFC6951 and let RFC6951bis include the contents of
the above Internet Draft. But this most likely will happen after the
NAT document is ready and RFC4960bis finished...

If you want to do some interop testing, a web server supporting SCTP/UDP
is running at interop.fh-muenster.de. You can find a client (phttpget) at
https://github.com/NEAT-project/HTTPOverSCTP.

Best regards
Michael

> 
> Patches:
> 
>   This patchset is using the udp4/6 tunnel APIs to implement the UDP
>   Encapsulation of SCTP with not much change in SCTP protocol stack
>   and with all current SCTP features keeped in Linux Kernel.
> 
>   1 - 4: Fix some UDP issues that may be triggered by SCTP over UDP.
>   5 - 7: Process incoming UDP encapsulated packets and ICMP packets.
>   8 -10: Remote encap port's update by sysctl, sockopt and packets.
>   11-14: Process outgoing pakects with UDP encapsulated and its GSO.
>      15: Enable this feature.
> 
> Tests:
> 
>  - lksctp-tools/src/func_tests with UDP Encapsulation enabled/disabled:
> 
>      Both make v4test and v6test passed.
> 
>  - sctp-tests with UDP Encapsulation enabled/disabled:
> 
>      repeatability/procdumps/sctpdiag/gsomtuchange/extoverflow/
>      sctphashtable passed. Others failed as expected due to those
>      "iptables -p sctp" rules.
> 
>  - netperf on lo/netns/virtio_net, with gso enabled/disabled and
>    with ip_checksum enabled/disabled, with UDP Encapsulation
>    enabled/disabled:
> 
>      No clear performance dropped.
> 
> Xin Long (15):
>  udp: check udp sock encap_type in __udp_lib_err
>  udp6: move the mss check after udp gso tunnel processing
>  udp: do checksum properly in skb_udp_tunnel_segment
>  udp: support sctp over udp in skb_udp_tunnel_segment
>  sctp: create udp4 sock and add its encap_rcv
>  sctp: create udp6 sock and set its encap_rcv
>  sctp: add encap_err_lookup for udp encap socks
>  sctp: add encap_port for netns sock asoc and transport
>  sctp: add SCTP_REMOTE_UDP_ENCAPS_PORT sockopt
>  sctp: allow changing transport encap_port by peer packets
>  sctp: add udphdr to overhead when udp_port is set
>  sctp: call sk_setup_caps in sctp_packet_transmit instead
>  sctp: support for sending packet over udp4 sock
>  sctp: support for sending packet over udp6 sock
>  sctp: enable udp tunneling socks
> 
> include/net/netns/sctp.h     |   8 +++
> include/net/sctp/constants.h |   2 +
> include/net/sctp/sctp.h      |   9 ++-
> include/net/sctp/sm.h        |   1 +
> include/net/sctp/structs.h   |  13 ++--
> include/uapi/linux/sctp.h    |   7 ++
> net/ipv4/udp.c               |   2 +-
> net/ipv4/udp_offload.c       |  16 +++--
> net/ipv6/udp.c               |   2 +-
> net/ipv6/udp_offload.c       | 154 +++++++++++++++++++++----------------------
> net/sctp/associola.c         |   4 ++
> net/sctp/ipv6.c              |  48 ++++++++++----
> net/sctp/output.c            |  22 +++----
> net/sctp/protocol.c          | 145 ++++++++++++++++++++++++++++++++++++----
> net/sctp/sm_make_chunk.c     |   1 +
> net/sctp/sm_statefuns.c      |   2 +
> net/sctp/socket.c            | 111 +++++++++++++++++++++++++++++++
> net/sctp/sysctl.c            |  53 +++++++++++++++
> 18 files changed, 471 insertions(+), 129 deletions(-)
> 
> -- 
> 2.1.0
> 


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