[CRIU] [PATCH 3/3] lib: add criu_check() to libcriu

[Pavel Emelyanov]

On 11/22/2013 01:24 PM, Andrew Vagin wrote:
> On Fri, Nov 22, 2013 at 12:50:58PM +0400, Pavel Emelyanov wrote:
>> On 11/22/2013 12:41 PM, Andrew Vagin wrote:
>>> On Fri, Nov 22, 2013 at 05:20:37AM +0400, Ruslan Kuprieiev wrote:
>>>>
>>>> Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
>>>> ---
>>>>  lib/criu.c | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 128 insertions(+)
>>>>
>>>> diff --git a/lib/criu.c b/lib/criu.c
>>>> index 2bd224e..f154a88 100644
>>>> --- a/lib/criu.c
>>>> +++ b/lib/criu.c
>>>> @@ -1,3 +1,131 @@
>>>>  #include "version.h"
>>>> +#include <sys/socket.h>
>>>> +#include <sys/un.h>
>>>> +#include <limits.h>
>>>> +#include <stdio.h>
>>>> +#include <unistd.h>
>>>> +#include <stdlib.h>
>>>> +
>>>> +#include "rpc.pb-c.h"
>>>> +
>>>> +#define MAX_MSG_SIZE 1024
>>>> +#define CR_DEFAULT_SERVICE_ADDRESS "/var/run/criu_service.socket"
>>>>  
>>>>  const char *criu_lib_version = CRIU_VERSION;
>>>> +
>>>> +static char *service_address = CR_DEFAULT_SERVICE_ADDRESS;
>>>> +
>>>> +void criu_set_service_address(char *path)
>>>> +{
>>>> +	if (path)
>>>> +		service_address = path;
>>>> +	else
>>>> +		service_address = CR_DEFAULT_SERVICE_ADDRESS;
>>>> +}
>>>> +
>>>> +static CriuResp *recv_resp(int socket_fd)
>>>> +{
>>>> +	unsigned char buf[MAX_MSG_SIZE];
>>>> +	int len;
>>>> +	CriuResp *msg = 0;
>>>> +
>>>> +	len = read(socket_fd, buf, MAX_MSG_SIZE);
>>>> +	if (len == -1) {
>>>> +		perror("Can't read response");
>>>> +		return NULL;
>>>> +	}
>>>> +
>>>> +	msg = criu_resp__unpack(NULL, len, buf);
>>>> +	if (!msg) {
>>>> +		perror("Failed unpacking response");
>>>> +		return NULL;
>>>> +	}
>>>> +
>>>> +	return msg;
>>>> +}
>>>> +
>>>> +static int send_req(int socket_fd, CriuReq *req)
>>>> +{
>>>> +	unsigned char buf[MAX_MSG_SIZE];
>>>> +	int len;
>>>> +
>>>> +	len = criu_req__get_packed_size(req);
>>>> +
>>>> +	if (criu_req__pack(req, buf) != len) {
>>>> +		perror("Failed packing request");
>>>> +		return -1;
>>>> +	}
>>>> +
>>>> +	if (write(socket_fd, buf, len)  == -1) {
>>>> +		perror("Can't send request");
>>>> +		return -1;
>>>> +	}
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int criu_connect(void)
>>>> +{
>>>> +	int fd, ret;
>>>> +	struct sockaddr_un addr;
>>>> +	socklen_t addr_len;
>>>> +
>>>> +	fd = socket(AF_LOCAL, SOCK_SEQPACKET, 0);
>>>> +	if (fd < 0) {
>>>> +		perror("Can't create socket");
>>>> +		return -1;
>>>> +	}
>>>> +
>>>> +	memset(&addr, 0, sizeof(addr));
>>>> +	addr.sun_family = AF_LOCAL;
>>>> +
>>>> +	strcpy(addr.sun_path, service_address);
>>>> +
>>>> +	addr_len = strlen(addr.sun_path) + sizeof(addr.sun_family);
>>>> +
>>>> +	ret = connect(fd, (struct sockaddr *) &addr, addr_len);
>>>> +	if (ret < 0) {
>>>> +		perror("Can't connect to socket");
>>>> +		close(fd);
>>>> +	}
>>>> +
>>>> +	return fd;
>>>> +}
>>>> +
>>>> +int criu_check(void)
>>>
>>> I'm not sure that a stateless approach is good here. First of all you
>>> will need to connect and disconnect each time.
>>
>> Why is it bad?
> 
> I don't know yet.
> 
>>
>>> Can we create interface similar with dynamic linking loader (man
>>> dlopen).
>>>
>>> struct criu_handle *h;
>>>
>>> h = criu_open()
>>> criu_check(h);
>>> ...
>>> criu_smth(h);
>>> ...
>>> criu_close(h);
>>
>> We can. What are the benefits of state-full approach?
> 
> * don't need to connect/disconnect each time

Why is it good?

> * asynchronous operations and iterative operations

We don't have async operations.

> And one more example when state-less approach doesn't work
> 
> * criu_check(h) returns true
> * yum update criu; service criu restart
> * criu_dump() returns a error
> .

If updated criu fails it's a bug ;)