[asterisk-bugs] [JIRA] (ASTERISK-26749) chan_dahdi.c: my_dahdi_write() returns zero even if it fails.

[Segii Cherkavskyi (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-26749?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Segii Cherkavskyi updated ASTERISK-26749:
-----------------------------------------

    Description: 
Although my asterisk version is not the newest, I checked chan_dahdi.c in the more recent asterisk version (13) and the code in question is remained untouched, so here is the problem: 
{code:title=chan_dahdi.c|borderStyle=solid}
static int my_dahdi_write(struct dahdi_pvt *p, unsigned char *buf, int len, int idx, int linear)
{
	int sent=0;
	int size;
	int res;
	int fd;
	fd = p->subs[idx].dfd;
	while (len) {
		size = len;
		if (size > (linear ? READ_SIZE * 2 : READ_SIZE))
			size = (linear ? READ_SIZE * 2 : READ_SIZE);
		res = write(fd, buf, size);
		if (res != size) {
			ast_debug(1, "Write returned %d (%s) on channel %d\n", res, strerror(errno), p->channel);
			return sent;
		}
		len -= size;
		buf += size;
	}
	return sent;
}
{code}
*apps/chan_dahdi.c* has a method *my_dahdi_write()*, which returns *0*, even if writing to a file descriptor fails. In case of failure *my_dahdi_write()* produces the following log output:
{noformat}
chan_dahdi.c: Write returned -1 (Resource temporarily unavailable) on channel 4
{noformat}

The return value of the method *my_dahdi_write()* is checked by the calling function *dahdi_write()* and returns with *-1*, in case if *my_dahdi_write()* fails, {color:red}which never happens{color}. 

While searching through the asterisk issue tracker, I found similar logs to the one I have, with discussions about echo cancellation etc. not directly discussing the return value of *my_dahdi_write()*.

  was:
Although my asterisk version is not the newest, I checked chan_dahdi.c in the more recent asterisk version (13) and the code in question is remained untouched, so here is the problem: 
apps/chan_dahdi.c has a method my_dahdi_write(), which returns zero, even if writing to a file descriptor fails. In case of failure my_dahdi_write() produces the following log output:
{noformat}
chan_dahdi.c: Write returned -1 (Resource temporarily unavailable) on channel 4
{noformat}

The return value of the method my_dahdi_write() is checked by the calling function dahdi_write() and this function returns with -1, in case if my_dahdi_write() fails, which never happens. 

While searching through the asterisk issue tracker, I found similar logs to the one I have, with discussions about echo cancellation etc. not directly discussing the return value of my_dahdi_write().


> chan_dahdi.c: my_dahdi_write() returns zero even if it fails. 
> --------------------------------------------------------------
>
>                 Key: ASTERISK-26749
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-26749
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_dahdi
>         Environment: Gentoo Linux, asterisk 1.8.31.1
>            Reporter: Segii Cherkavskyi
>            Assignee: Richard Mudgett
>         Attachments: asterisk-15-12-2017-10-02-55.log, jira_asterisk_26749_v13.patch
>
>
> Although my asterisk version is not the newest, I checked chan_dahdi.c in the more recent asterisk version (13) and the code in question is remained untouched, so here is the problem: 
> {code:title=chan_dahdi.c|borderStyle=solid}
> static int my_dahdi_write(struct dahdi_pvt *p, unsigned char *buf, int len, int idx, int linear)
> {
> 	int sent=0;
> 	int size;
> 	int res;
> 	int fd;
> 	fd = p->subs[idx].dfd;
> 	while (len) {
> 		size = len;
> 		if (size > (linear ? READ_SIZE * 2 : READ_SIZE))
> 			size = (linear ? READ_SIZE * 2 : READ_SIZE);
> 		res = write(fd, buf, size);
> 		if (res != size) {
> 			ast_debug(1, "Write returned %d (%s) on channel %d\n", res, strerror(errno), p->channel);
> 			return sent;
> 		}
> 		len -= size;
> 		buf += size;
> 	}
> 	return sent;
> }
> {code}
> *apps/chan_dahdi.c* has a method *my_dahdi_write()*, which returns *0*, even if writing to a file descriptor fails. In case of failure *my_dahdi_write()* produces the following log output:
> {noformat}
> chan_dahdi.c: Write returned -1 (Resource temporarily unavailable) on channel 4
> {noformat}
> The return value of the method *my_dahdi_write()* is checked by the calling function *dahdi_write()* and returns with *-1*, in case if *my_dahdi_write()* fails, {color:red}which never happens{color}. 
> While searching through the asterisk issue tracker, I found similar logs to the one I have, with discussions about echo cancellation etc. not directly discussing the return value of *my_dahdi_write()*.



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