658138 - PR_Poll does not call poll method when PR_POLL_EXCEPT is requested without PR_POLL_READ or PR_POLL_WRITE

Status: NEW

(NSPR :: NSPR, defect)

Description

[Patrick McManus [:mcmanus]]

a PR_poll of a ssl socket using in_flags of (PR_POLL_READ | PR_POLL_EXCEPT) will generate PR_POLL_EXCEPT (or maybe PR_POLL_ERR - I forget) if PK11LoggedOut or AlreadyShutDown is satisified..

but a PR_poll of the same socket using just PR_POLL_EXCEPT returns no conditions.

as PR_POLL_READ is just a test of whether there is data available to to be read, it shouldn't impact this. I am pretty certain that PR_POLL_WRITE could be substituted for PR_POLL_READ.

found during bug 654201 - which has inserted an extraneous PR_POLL_READ check into the code to workaround this.

Comment 1

[Patrick McManus [:mcmanus]]

35 ERROR TEST-UNEXPECTED-FAIL | /tests/security/ssl/stricttransportsecurity/test_sts_privatebrowsing.html | Test timed out.

in the absence of PR_POLL_READ in nsSocketTransport::IsAlive() this test fails often - more often on linux and os x (though not all the time).. it is in mochitest-5

Comment 2

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

This is due to the following code in the (platform-specific) implementations of PR_Poll:

            if (pd->in_flags & PR_POLL_READ)
            {
                in_flags_read = (pd->fd->methods->poll)(
                    pd->fd, (PRInt16)(pd->in_flags & ~PR_POLL_WRITE),
                    &out_flags_read);
            }
            if (pd->in_flags & PR_POLL_WRITE)
            {
                in_flags_write = (pd->fd->methods->poll)(
                    pd->fd, (PRInt16)(pd->in_flags & ~PR_POLL_READ),
                    &out_flags_write);
            }

If neither PR_POLL_READ or PR_POLL_WRITE is passed, then the poll method never gets called. Some poll methods (such as the one in PSM) return errors that are generated by non-network-related issues, and we (Mozilla) at one point tried to use PR_Poll to detect these errors.

Perhaps if neither PR_POLL_READ or PR_POLL_WRITE are passed in in_flags, but in_flags is nonzero, then we should call the poll method with in_flags.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee is inactive on Bugzilla, so the assignee is being reset.