Re: [Netconf] [netmod] draft-ietf-netconf-netconf-client-server – TCP keepalives

Mikael Abrahamsson <swmike@swm.pp.se> Tue, 12 June 2018 08:56 UTC

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Date: Tue, 12 Jun 2018 10:56:35 +0200 (CEST)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: Kent Watsen <kwatsen@juniper.net>
cc: NICK HANCOCK <nick.hancock@adtran.com>, "netconf@ietf.org" <netconf@ietf.org>
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Subject: Re: [Netconf] =?utf-8?q?=5Bnetmod=5D_draft-ietf-netconf-netconf-clie?= =?utf-8?q?nt-server_=E2=80=93_TCP_keepalives?=
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I support enabling possibility of TCP keepalives, and relevant 
configuration. I encourage this to be used everywhere. Operationally, I 
have seen lots of problems caused by not having keepalives enabled on 
sessions, and code not handling them stalling. TCP keepalives means the 
programmers do not really have to do anything, the TCP stack solves this 
for them.

On Tue, 12 Jun 2018, Kent Watsen wrote:

>
> Looking into this just a little more, I know that Heartbeat was supported by OpenSSL before (recall Heartbleed bug?), so I grepped the 1.1.0g source code (which has the Heartbleed fix) and found evidence that the support might still be in the code.  That said, I can't tell if the code is specific to DTLS or works on TLS as well…
>
> /kw
>
>
> ===== original message =====
>
> [+netconf, -netmod]
>
> The issue appears to be with current TLS libraries not implementing TLS keepalives, the HeartbeatRequest messages defined by [RFC6520].   I have not myself validated this yet, does anyone have any experience?
>
> If it is true that HeartbeatRequest messages is not supported today, do we:
>  a) encourage the TLS library maintainers to implement it
>  b) or introduce an ability to configure TCP-level keepalives
>  c) or both?
>
> Any other ideas?
>
> Thanks,
> Kent
>
>
>
> On 6/11/18, 12:32 PM, "netmod on behalf of NICK HANCOCK" <netmod-bounces@ietf.org on behalf of nick.hancock@adtran.com>; wrote:
>
> Hi All,
>
> A couple of companies are working on a solutions to implement devices, such as DPUs, based on the requirements of the Broadband Forum Technical Report TR-301 issue 2 “Architecture and Requirements for Fiber to the Distribution Point”, which requires TLS for the persistent NETCONF connection, for which the configuration of call home is to be by means of the ‘ietf-netconf-server’ module.
>
> TLS heartbeat cannot be supported to keep the call home connection alive, because TLS heartbeat is not or no longer supported by many TLS libraries, such as OpenSSL in the wake of the Heartbleed security bug. Although TCP keep-alives are not secure, we will nevertheless be required to support TCP keepalives to ensure that the connection remains persistent and these keepalives would also need to be configurable. Unfortunately, the keepalive configuration implemented in ‘ietf-netconf-server’, although not bound to the ‘transport’ choice, is bound to the secure layer textually in the description of the data nodes (references to “SSH/TLS client” and “SSH/TLS-level message”), which makes its use for configuring TCP keepalives for specific implementations possible, but obviously problematic. RFC 8071, Section 4.1, S7, also heavily implies that it is intended to be used for the designated transport layer (e.g., SSH, TLS).
>
> Since this issue affects the industry as a whole, we believe it would be better to provide support for the configuration of TCP keepalives within the ‘ietf-netconf-server’ module from the beginning, rather than wait for other SDOs or vendors to augment the module after publication as an RFC, which they will be practicably forced to do.
>
> Would supporting TCP keepalives in the IETF-defined module be something the WG would agree to discuss? A possible solution, shown below, could be to add a new container parallel to the existing ‘keep-alives’ container to explicitly support the configuration for TCP keepalives. In addition, a feature statement (e.g. "keep-alives") could be added to the existing ‘keep-alives’ container, as RFC 8071 S7 says SHOULD (not MUST).
>                   container tcp-keep-alives {
>                     if-feature tcp-keep-alives;
>                     description
>                       "Configures the keep-alive policy, to
>                        proactively test the aliveness of the TCP
>                        peer.  An unresponsive TCP peer will
>                        be dropped after approximately max-attempts *
>                        max-wait seconds.";
>                     reference
>                       "RFC 1122: Requirements for Internet Hosts --
>                        Communication Layers, section 4.2.3.6.";
>                     leaf max-wait {
>                       type uint16 {
>                         range "1..32767";
>                       }
>                       units seconds;
>                       default 30;
>                       description
>                        "Sets the amount of time in seconds after
>                         which if no data has been received from
>                         the TCP peer, a TCP-level message
>                         will be sent to test the aliveness of the
>                         TCP peer.";
>                     }
>                     leaf max-attempts {
>                       type uint8 {
>                         range "1..127";
>                       }
>                       default 3;
>                       description
>                        "Sets the maximum number of sequential keep-
>                        alive messages that can fail to obtain a
>                        response from the TCP peer before
>                        assuming the TCP peer is no longer
>                        alive.";
>                     }
>                     leaf interval-between-attempts {
>                       type uint16  {
>                         range "1..32767";
>                       }
>                       units seconds;
>                       default 30;
>                       description
>                        "Sets the amount of time in seconds after
>                         which, if no reply to a keep-alive message
>                         has been received from the TCP peer, the
>                         next keep-alive message will be sent.";
>                     }
>                   }
>                 }
>
>
> What is the opinion of the list? Would this solution work?
>
> Best regards
> Nick & Yves
>
>
>
>
>
>
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-- 
Mikael Abrahamsson    email: swmike@swm.pp.se