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From "Alan Conway (JIRA)" <j...@apache.org>
Subject [jira] [Created] (PROTON-1849) CLONE - [c] server behaves incorrectly on duplicate link attach
Date Fri, 18 May 2018 13:00:00 GMT
Alan Conway created PROTON-1849:
-----------------------------------

             Summary: CLONE - [c] server behaves incorrectly on duplicate link attach
                 Key: PROTON-1849
                 URL: https://issues.apache.org/jira/browse/PROTON-1849
             Project: Qpid Proton
          Issue Type: Bug
          Components: proton-c
    Affects Versions: proton-c-0.22.0
            Reporter: Alan Conway
            Assignee: Alan Conway


There is a disabled test to reproduce this problem, see test_duplicate_link_client() in

[https://github.com/alanconway/qpid-proton/blob/master/c/tests/connection_driver.c#L498]

pni_process does all pending link opens before all pending link closes, it does not respect
the order of individual open/close calls in the code. This doesn't cause a problem for distinct
links but if a link of the same name is opened/closed/reopened very quickly it can cause a
problem:

For example if l1 and l2 are both pn_links with name "x" then this sequence:
{code:java}
open(l1); close(l1); open(l2){code}
generates this illegal protocol sequence:
{code:java}
attach("x"); attach("x"); detach(0) // 0 is the handle assigned to "x"{code}
instead of the intended legal sequence:
{code:java}
attach("x"); detach(0); attach("x") // detach(0) detaches the first "x" so second "x" is allowed{code}
NOTE: This applies to all endpoints, not just links but since connections and sessions don't
have client-assignable names that can clash, the problem only shows up for links and only
if the detach/attach for the same name is processed in the same transport batch. This is unlikely
in practice and was discovered only because of investigation of PROTON-1832.



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