[asterisk-bugs] [JIRA] (ASTERISK-20414) Timeout antipattern using ast_waitfor_nandfds

[Digium Subversion (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-20414?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Digium Subversion closed ASTERISK-20414.
----------------------------------------

    Resolution: Fixed
    
> Timeout antipattern using ast_waitfor_nandfds
> ---------------------------------------------
>
>                 Key: ASTERISK-20414
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-20414
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/General
>    Affects Versions: 1.8.15.1
>            Reporter: David M. Lee
>
> While fixing ASTERISK-20375, I noticed a fairly subtle anti-pattern using {{ast_waitfor_nandfds}}.
> {code}
> int timeout_ms = 3000;
> while (timeout_ms) {
>   r = ast_waitfor_nandfds(chan, n, fds, nfds, NULL, &outfd, &timeout_ms);
>   /* whatever */
> }
> {code}
> If the {{waitfor}} function takes less than one millisecond to return, then it won't adjust {{timeout_ms}}. If that happens consistently, then this loop will never exit. A better approach would be:
> {code}
> int timeout_ms = 3000;
> struct timeval start = ast_tvnow();
> while (ast_tvdiff_ms(ast_tvnow(), start) < timeout_ms) {
>   int ms = timeout_ms - ast_tvdiff_ms(ast_tvnow(), start);
>   if (ms < 0) {
>     ms = 0;
>   }
>   r = ast_waitfor_nandfds(chan, n, fds, nfds, NULL, &outfd, &ms);
>   /* whatever */
> }
> {code}
> I've fixed the problem in question [for {{ast_waitfordigit_full}}|https://reviewboard.asterisk.org/r/2109], but we should look for other misuses of this pattern so we can avoid further lockups.

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