[PATCH 3/8] ch_monitor: Update virCHMonitorGet to handle accept a response

[Daniel P. Berrangé]

On Thu, Aug 26, 2021 at 02:59:17PM -0700, William Douglas wrote:
> The virCHMonitorGet function needed to be able to return data from the
> hypervisor. This functionality is needed in order for the driver to
> support PTY enablement and getting details about the VM state.
> 
> Signed-off-by: William Douglas <william.douglas at intel.com>
> ---
>  src/ch/ch_monitor.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 42 insertions(+), 2 deletions(-)
> 
> diff --git a/src/ch/ch_monitor.c b/src/ch/ch_monitor.c
> index b4bc10bfcf..ee7e4683e3 100644
> --- a/src/ch/ch_monitor.c
> +++ b/src/ch/ch_monitor.c
> @@ -611,12 +611,36 @@ virCHMonitorPutNoContent(virCHMonitor *mon, const char *endpoint)
>      return ret;
>  }
>  
> +struct curl_data {
> +    char *content;
> +    size_t size;
> +};
> +
> +static size_t
> +curl_callback(void *contents, size_t size, size_t nmemb, void *userp)
> +{
> +    size_t content_size = size * nmemb;
> +    struct curl_data *data = (struct curl_data *)userp;
> +
> +    if (content_size == 0)
> +        return content_size;
> +
> +    data->content = g_realloc(data->content, data->size + content_size);
> +
> +    memcpy(&(data->content[data->size]), contents, content_size);
> +    data->size += content_size;
> +
> +    return content_size;
> +}
> +
>  static int
> -virCHMonitorGet(virCHMonitor *mon, const char *endpoint)
> +virCHMonitorGet(virCHMonitor *mon, const char *endpoint, virJSONValue **response)
>  {
>      g_autofree char *url = NULL;
>      int responseCode = 0;
>      int ret = -1;
> +    struct curl_slist *headers = NULL;
> +    struct curl_data data = {0};
>  
>      url = g_strdup_printf("%s/%s", URL_ROOT, endpoint);
>  
> @@ -628,12 +652,28 @@ virCHMonitorGet(virCHMonitor *mon, const char *endpoint)
>      curl_easy_setopt(mon->handle, CURLOPT_UNIX_SOCKET_PATH, mon->socketpath);
>      curl_easy_setopt(mon->handle, CURLOPT_URL, url);
>  
> +    if (response) {
> +        headers = curl_slist_append(headers, "Accept: application/json");
> +        headers = curl_slist_append(headers, "Content-Type: application/json");
> +        curl_easy_setopt(mon->handle, CURLOPT_HTTPHEADER, headers);
> +        curl_easy_setopt(mon->handle, CURLOPT_WRITEFUNCTION, curl_callback);
> +        curl_easy_setopt(mon->handle, CURLOPT_WRITEDATA, (void *)&data);

This bit feels dodgy to me.   mon->handle has its lifetime tied to
the virCHMonitor object, but '&data' is allocated on the stack.
IOW, this pointer is persistent, but it goes out of scope.

I guess you're relying on the fact that calls to this method are
serialized, and we re-write the bad pointer on every call, but
if 'response' is NULL on the next call we're not going to do that
re-write.

Can all these options be set unconditionally when the mon->handle
is first created ?

> +    }
> +
>      responseCode = virCHMonitorCurlPerform(mon->handle);
>  
>      virObjectUnlock(mon);
>  
> -    if (responseCode == 200 || responseCode == 204)
> +    if (responseCode == 200 || responseCode == 204) {
>          ret = 0;
> +        if (response) {
> +            data.content = g_realloc(data.content, data.size + 1);
> +            data.content[data.size] = 0;
> +            *response = virJSONValueFromString(data.content);
> +        }
> +    }
> +
> +    g_free(data.content);
>  
>      return ret;
>  }

Regards,
Daniel
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