On Thu, Oct 10, 2019 at 8:40 PM Neil Horman [off-list ref] wrote:

On Thu, Oct 10, 2019 at 05:28:34PM +0800, Xin Long wrote:

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On Thu, Oct 10, 2019 at 12:18 AM Neil Horman [off-list ref] wrote:

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On Tue, Oct 08, 2019 at 11:28:32PM +0800, Xin Long wrote:

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On Tue, Oct 8, 2019 at 9:02 PM David Laight [off-list ref] wrote:

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From: Xin Long

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Sent: 08 October 2019 12:25

This is a sockopt defined in section 7.3 of rfc7829: "Exposing
the Potentially Failed Path State", by which users can change
pf_expose per sock and asoc.

If I read these patches correctly the default for this sockopt in 'enabled'.
Doesn't this mean that old application binaries will receive notifications
that they aren't expecting?

I'd have thought that applications would be required to enable it.

If we do that, sctp_getsockopt_peer_addr_info() in patch 2/5 breaks.

I don't think we can safely do either of these things.  Older
applications still need to behave as they did prior to the introduction
of this notification, and we shouldn't allow unexpected notifications to
be sent.

What if you added a check in get_peer_addr_info to only return -EACCESS
if pf_expose is 0 and the application isn't subscribed to the PF event?

We can't subscribe to PF event only, but all the SCTP_PEER_ADDR_CHANGE
events.

Now I'm thinking both PF event and "return -EACCES" in get_peer_addr_info
are new, we should give 'expose' a default value that would disable both.
How do think if we set 'pf_expose = -1' by default. We send the pf event
only if (asoc->pf_expose > 0) in sctp_assoc_control_transport().

And if pf_expose = 0, we send the event, and return -EACCESS if we call
the socket option and find a PF assoc?  If so, yes, I think that makes
sense.

pf_expose:
-1: compatible with old application (by default)
0: not expose PF to user
1: expose PF to user

So it should be:
if pf_expose == -1:  not send event, not return -EACCESS
if pf_expose == 0: not send event, return -EACCESS
if pf_expose > 0: sent event, not return -EACCESS

makes sense?

Neil

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Neil

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        David

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