[Sessiond] Credits gets suspended and immediately un-suspended on CCA-U with FUA

[joary]

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Your Environment

• Version: 1.5
• Affected Component: AGW
• Affected Subcomponent: Sessiond
• Deployment Environment: Federeted FWA with Gx/Gy federation

Describe the Issue

When the subscriber quota ends the Gy will answer any CCR-U coming from magma with a CCA-U containing FUI and action configured to TERMINATE.

The behaviour seen is:

1. On the first CCA-U the rules are dropped as expected.
2. The next CCA-U the rules are dropped but are immediately reactivated
3. The subsequent CCA-U the rule is dropped again as expected.
4. The next CCA-U behavior on 2 reproduces

Follows the sessiond log for the suspention and imediatelly unsuspension seen in #2 and #4. (All IMSI values are the same)

Expected behavior

Magma should always drop the rules that are linked to the RG contained in the CCA-U with FUA TERMINATE

[joary]

The probable root cause is the fact that magma suspends a given session (drop the rule) when the FUI is received and later un-suspends if a CCR-U is received and there's a suspended session.

The first CCA-U + 4012 FUA-TERMINATE magma gets will suspend the session: as seen here

The second CCA-U + 4012 FUA-TERMINATE will also suspend the session but it will later un-suspend it since there's a suspended session already, as seen here

The proposed workaround is to avoid the credit suspension here by changing the conditional to not be executed on FUA, for example:

if (valid_credit && !credit_update_resp.credit().is_final() && session->is_credit_suspended(credit_key)) {

cc @uri200, @themarwhal

[themarwhal]

Does the second CCA-U include any credit? I wonder why we pass the valid_credi check if the second one has the 4012 code.

[joary]

Does the second CCA-U include any credit?

It does, my rationale:

valid_credit will only be false if the CCR-U has result PERMANENT_FAILURE. Though the CCR's that contains a FUI will also have a result code as TRANSIENT_FAILURE (4012) by Diameter definition.

[crbertoldo]

As per @joary's suggestion, adding && !credit_update_resp.credit().is_final() to this conditional, solves the issue:

Before:
if (valid_credit && session->is_credit_suspended(credit_key))

After:
if (valid_credit && !credit_update_resp.credit().is_final() && session->is_credit_suspended(credit_key))

[uri200]

that workaround will only work if the credit were final. If the credit was suspended for any other reason and it was not final the credit will never be unsuspended

[uri200]

The problem seems to be in fact this line

Being suspended and with no quota, should_activate should be fasle

[uri200]

this pr may fix this issue
#10671