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

[Andrew Vagin]

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
* asynchronous operations and iterative 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