[Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC

[Adam Litke <agl@us.ibm.com>]

On Fri, 2010-12-03 at 12:03 -0600, Michael Roth wrote:
> Add RPC to retrieve a guest file. This interface is intended
> for smaller reads like peeking at logs and /proc and such.
> 
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  virtagent-server.c |   59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 59 insertions(+), 0 deletions(-)
> 
> diff --git a/virtagent-server.c b/virtagent-server.c
> index 36fbae2..a430b58 100644
> --- a/virtagent-server.c
> +++ b/virtagent-server.c
> @@ -26,12 +26,71 @@ static bool va_enable_syslog = false; /* enable syslog'ing of RPCs */
>      syslog(LOG_INFO, "virtagent, %s", msg_buf); \
>  } while(0)
> 
> +/* RPC functions common to guest/host daemons */
> +
> +/* va_getfile(): return file contents
> + * rpc return values:
> + *   - base64-encoded file contents
> + */
> +static xmlrpc_value *va_getfile(xmlrpc_env *env,
> +                                xmlrpc_value *param,
> +                                void *user_data)
> +{
> +    const char *path;
> +    char *file_contents = NULL;
> +    char buf[VA_FILEBUF_LEN];
> +    int fd, ret, count = 0;
> +    xmlrpc_value *result = NULL;
> +
> +    /* parse argument array */
> +    xmlrpc_decompose_value(env, param, "(s)", &path);
> +    if (env->fault_occurred) {
> +        return NULL;
> +    }
> +
> +    SLOG("va_getfile(), path:%s", path);

I would log all calls (even those that would fail
xmlrpc_decompose_value(). You might catch someone trying to do something
tricky.

> +
> +    fd = open(path, O_RDONLY);
> +    if (fd == -1) {
> +        LOG("open failed: %s", strerror(errno));
> +        xmlrpc_faultf(env, "open failed: %s", strerror(errno));
> +        return NULL;
> +    }
> +
> +    while ((ret = read(fd, buf, VA_FILEBUF_LEN)) > 0) {
> +        file_contents = qemu_realloc(file_contents, count + VA_FILEBUF_LEN);
> +        memcpy(file_contents + count, buf, ret);
> +        count += ret;
> +        if (count > VA_GETFILE_MAX) {
> +            xmlrpc_faultf(env, "max file size (%d bytes) exceeded",
> +                          VA_GETFILE_MAX);
> +            goto EXIT_CLOSE_BAD;
> +        }
> +    }
> +    if (ret == -1) {
> +        LOG("read failed: %s", strerror(errno));
> +        xmlrpc_faultf(env, "read failed: %s", strerror(errno));
> +        goto EXIT_CLOSE_BAD;
> +    }
> +
> +    result = xmlrpc_build_value(env, "6", file_contents, count);
> +
> +EXIT_CLOSE_BAD:
> +    if (file_contents) {
> +        qemu_free(file_contents);
> +    }
> +    close(fd);
> +    return result;
> +}
> +
>  typedef struct RPCFunction {
>      xmlrpc_value *(*func)(xmlrpc_env *env, xmlrpc_value *param, void *unused);
>      const char *func_name;
>  } RPCFunction;
> 
>  static RPCFunction guest_functions[] = {
> +    { .func = va_getfile,
> +      .func_name = "va.getfile" },
>      { NULL, NULL }
>  };
>  static RPCFunction host_functions[] = {

-- 
Thanks,
Adam