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

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On 12/06/2010 04:06 PM, Adam Litke wrote:
> 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.
>

Agreed, I'll fix this up for the next round

>> +
>> +    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[] = {
>