Decode BGP Shutdown Communication messages (RFC 8203)

[Mikhail Grishin]

Hi,

1) You also implemented
enable bgp2 "enable message"
This message currently seen only at local side and doesn't seen at
remote peer.

Scenario: You made maintenance work with the shutdown message "Session
will be down from 13:00 till 14:00".
Later session was established again. Days after at remote peer side
still printed the same message. That's confusing.

Suggestion:
(May be) To show two different messages? Tx and Rx.
To clear Rx message every time when BGP session state  changed to
established.


2) Is it possible to log such messages and see via syslog?

P.S. For russian UTF8 text 128 bytes restriction (RFC) probably not
always enough.


Ondrej Zajicek пишет 19.09.2017 21:53:
> On Thu, Jul 27, 2017 at 05:55:40PM +0200, Job Snijders wrote:
>> Hi all,
>>
>> Here is a patch to decode received BGP shutdown communication messages
>> as specified in RFC 8203. In the following example scenario I'm sending
>> a shutdown communication with openbgpd:
>>
>> 	$ bgpctl neighbor 94.142.241.204 down "TICKET-2331 we are upgrading, back in 30 min"
>> 	request processed
> Hi
>
> Merged with some significant changes, with support for both RX and TX of
> shutdown communication:
>
> https://gitlab.labs.nic.cz/labs/bird/commit/cd1d99611e445c9fe2452d05627ccfc624f35c39
>
> I generalized it a bit, so the message is not specific to BGP, but can be
> attached to any protocol, so it makes sense that it can be changed by
> general commands like disable, restart. That means it also changed the
> output a bit:
>
> bird> show protocols all bgp2
> name     proto    table    state  since       info
> bgp2     BGP      master   down   19:39:00
>    Description:    My BGP session
>    Message:        Planned shutdown, back in 30 min
>    Preference:     100
>    Input filter:   ACCEPT
>    Output filter:  (unnamed)
>    BGP state:          Down
>      Neighbor address: 10.0.1.1
>      Neighbor AS:      10
>
> Conceptually, it is one-item mailbox, which can be set by either the core
> (using enable/disable/restart commands) or the protocol (received BGP
> Notification with the RFC 8203 message). I am not sure if it would not be
> better to have two separate mailboxes for both directions, but it
> probably does not matter.
>
> The message can be send from BIRD shell:
>
> birdc> disable bgp1 "hi, we will upgrade to bird 1.6.4"
>
> Unfortunately, that means that from Unix shell you have to do double qouting:
>
> birdc disable bgp1 '"hi, we will upgrade to bird 1.6.4"'
>
> Currently no support for message associated with 'disabled' in bird.conf
> or for message associated with BIRD global shutdown.
>
>
> Otherwise, there are some minor changes w.r.t. your patch:
>
> 1) Your patch requires that RFC 8203 message fills the entire space of
> BGP notification (i.e. msg_len + 1 == remaining_len). I do not see any
> such requirement in RFC 8203, so i accept if (msg_len + 1 <= remaining_len)
>
> 2) I reset the message not with any RX notification, but only with
> administrative shutdown/reset notification. That prevents message reset
> with subsequent errors unrelated to administrative notification.
>
> 3) Proper handling of zero-length messages (should be handled equally
> like no message at all according to RFC 8203).
>
> 4) Some basic sanitization of received strings to avoid escape-attacks
> and newlines in logs.
>
> Any comments, suggestions, opposition?
>