[PROTON-1837] [c] client generates invalid attach/detach sequence

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: proton-c-0.22.0
• Component/s: proton-c
• Assignee: Unassigned
• Reporter: Alan Conway
• Created: 26/Apr/18 14:25
• Updated: 05/Mar/19 21:38

Description

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:

open(l1); close(l1); open(l2)

generates this illegal protocol sequence:

attach("x"); attach("x"); detach(0) // 0 is the handle assigned to "x"

instead of the intended legal sequence:

attach("x"); detach(0); attach("x") // detach(0) detaches the first "x" so second "x" is allowed

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.

Issue Links

• is a clone of: PROTON-1832 [c] duplicate link names cause invalid read in pn_transport_unbind_handles