[libvirt] [PATCH 3/5] virStorageBackendIQNFound: Rework iscsiadm output parsing

[Peter Krempa]

On Fri, Jun 29, 2018 at 17:01:49 +0200, Michal Privoznik wrote:
> Firstly, we can utilize virCommandSetOutputBuffer() API which
> will collect the command output for us. Secondly, sscanf()-ing
> through each line is easier to understand (and more robust) than
> jumping over a string with strchr().
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  src/util/viriscsi.c | 85 +++++++++++++++++++++--------------------------------
>  1 file changed, 34 insertions(+), 51 deletions(-)
> 
> diff --git a/src/util/viriscsi.c b/src/util/viriscsi.c
> index 2e55b3c10b..44788056fd 100644
> --- a/src/util/viriscsi.c
> +++ b/src/util/viriscsi.c

[...]

> @@ -117,71 +116,56 @@ static int
>  virStorageBackendIQNFound(const char *initiatoriqn,
>                            char **ifacename)
>  {
> -    int ret = IQN_ERROR, fd = -1;
> -    char ebuf[64];
> -    FILE *fp = NULL;
> -    char *line = NULL, *newline = NULL, *iqn = NULL, *token = NULL;
> +    int ret = IQN_ERROR;
> +    char *outbuf = NULL;
> +    char *line = NULL;
> +    char *iface = NULL;
> +    char *iqn = NULL;
>      virCommandPtr cmd = virCommandNewArgList(ISCSIADM,
>                                               "--mode", "iface", NULL);
>  
>      *ifacename = NULL;
>  
> -    if (VIR_ALLOC_N(line, LINE_SIZE) != 0) {
> -        virReportError(VIR_ERR_INTERNAL_ERROR,
> -                       _("Could not allocate memory for output of '%s'"),
> -                       ISCSIADM);
> +    virCommandSetOutputBuffer(cmd, &outbuf);
> +    if (virCommandRun(cmd, NULL) < 0)
>          goto cleanup;
> -    }
>  
> -    memset(line, 0, LINE_SIZE);
> +    /* Example of data we are dealing with:
> +     * default tcp,<empty>,<empty>,<empty>,<empty>
> +     * iser iser,<empty>,<empty>,<empty>,<empty>
> +     * libvirt-iface-253db048 tcp,<empty>,<empty>,<empty>,iqn.2017-03.com.user:client
> +     */
>  
> -    virCommandSetOutputFD(cmd, &fd);
> -    if (virCommandRunAsync(cmd, NULL) < 0)
> -        goto cleanup;
> +    line = outbuf;
> +    while (line) {

This is severely misleading and makes this loop technically infinite. Or
just checks that output buffer was not null. Both operations should be
made explicit. Or you meant *line or line[0]

> +        char *newline;
> +        int num;
>  
> -    if ((fp = VIR_FDOPEN(fd, "r")) == NULL) {
> -        virReportError(VIR_ERR_INTERNAL_ERROR,
> -                       _("Failed to open stream for file descriptor "
> -                         "when reading output from '%s': '%s'"),
> -                       ISCSIADM, virStrerror(errno, ebuf, sizeof(ebuf)));
> -        goto cleanup;
> -    }
> +        if (!(newline = strchr(line, '\n')))
> +            break;

This is ther reason why it's working at this point.

>  
> -    while (fgets(line, LINE_SIZE, fp) != NULL) {
> -        newline = strrchr(line, '\n');
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