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Feature #3608

Support for SCTP multi-homing

Added by laforge 6 months ago. Updated 5 months ago.

Status:
New
Priority:
Normal
Assignee:
-
Target version:
-
Start date:
09/30/2018
Due date:
% Done:

0%


Description

My humble assumption here is that this is done entirely in the kernel. It will automatically learn about the peers' additional addresses and
use them as needed.

In OsmoSTP, the VTY would have to allow for manual specification of multiple IP addresses for each peer, so that during start up all of
those addresses are attempted (think of the case where the normal/primary address is unreachable at link-bringup time). After the association is up, SCTP exchanges information about the additional IPs dynamically.

The actual switch between using the addresses is entirely done in the kernel, we just get notifications (SCTP_PEER_ADDR_CHANGE) about this and
can log them.

History

#1 Updated by laforge 6 months ago

#2 Updated by mandersen 5 months ago

laforge wrote:

My humble assumption here is that this is done entirely in the kernel. It will automatically learn about the peers' additional addresses and
use them as needed.

In my experience the kernel will need a bit of help before the multi-homing works as we expect it to.

Consider a scenario where the STP runs on a server with 4 IPs (A, B, C and D). A and B are used for signaling, but C and D are firewalled and used for OAM/local SSH logins.

If we open a multi-homed SCTP connection to another host with kernel defaults, then the kernel (not knowing about our overall network design) will associate all 4 IPs (A, B, C and D) with this connection.

As a consequence, the peer will successfully communicate with our IPs A and B - but endless try (and fail) to communicate with our IPs C and D.

Therefore it can make sense to explicitly specify:
1. Which peer IPs this SCTP association connects to
2. Which IPs we bind on our end of the SCTP association

This explicit binding of IPs on our side can done by using sctp_bindx() on the fd before calling sctp_connectx().

#3 Updated by laforge 5 months ago

On Tue, Oct 16, 2018 at 07:51:04PM +0000, mandersen [REDMINE] wrote:

Issue #3608 has been updated by mandersen.

thanks a lot for your most valuable input.

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