[CRIU] [PATCH 1/5] tty: notify about orphan tty-s via rpc

Andrei Vagin avagin at virtuozzo.com
Wed Feb 8 10:38:39 PST 2017


On Wed, Feb 08, 2017 at 11:47:58AM +0300, Pavel Emelyanov wrote:
> On 02/07/2017 11:43 AM, Andrei Vagin wrote:
> > From: Andrei Vagin <avagin at virtuozzo.com>
> > 
> > Now Docker creates a pty pair from a container devpts to use is as console.
> > A slave tty is set as a control tty for the init process and bind-mounted
> > into /dev/console. The master tty is handled externelly.
> > 
> > Now CRIU can handle external resources, but here we have internal resources
> > which are used externaly.
> > 
> > https://github.com/opencontainers/runc/issues/1202
> > Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
> > ---
> >  criu/action-scripts.c         | 20 ++++++++++++++++++--
> >  criu/cr-restore.c             |  1 +
> >  criu/cr-service.c             | 27 +++++++++++++++++++++------
> >  criu/include/action-scripts.h |  6 +++++-
> >  criu/include/cr_options.h     |  1 +
> >  criu/include/servicefd.h      |  1 +
> >  criu/tty.c                    | 40 +++++++++++++++++++++++++++++++++++-----
> >  images/rpc.proto              |  1 +
> >  8 files changed, 83 insertions(+), 14 deletions(-)
> > 
> > diff --git a/criu/action-scripts.c b/criu/action-scripts.c
> > index 1a12311..4fa8e28 100644
> > --- a/criu/action-scripts.c
> > +++ b/criu/action-scripts.c
> > @@ -13,6 +13,9 @@
> >  #include "pstree.h"
> >  #include "common/bug.h"
> >  #include "util.h"
> > +#include <sys/un.h>
> > +#include <sys/socket.h>
> > +#include "common/scm.h"
> >  
> >  static const char *action_names[ACT_MAX] = {
> >  	[ ACT_PRE_DUMP ]	= "pre-dump",
> > @@ -25,6 +28,7 @@ static const char *action_names[ACT_MAX] = {
> >  	[ ACT_POST_SETUP_NS ]	= "post-setup-namespaces",
> >  	[ ACT_PRE_RESUME ]	= "pre-resume",
> >  	[ ACT_POST_RESUME ]	= "post-resume",
> > +	[ ACT_ORPHAN_PTS_MASTER ] = "orphan-pts-master",
> >  };
> >  
> >  struct script {
> > @@ -96,6 +100,17 @@ static int run_shell_scripts(const char *action)
> >  	return retval;
> >  }
> >  
> > +int rpc_send_fd(enum script_actions act, int fd)
> > +{
> > +	const char *action = action_names[act];
> > +
> > +	if (scripts_mode != SCRIPTS_RPC)
> > +		return -1;
> > +
> > +	pr_debug("\tRPC\n");
> > +	return send_criu_rpc_script(act, (char *)action, rpc_sk, fd);
> > +}
> > +
> >  int run_scripts(enum script_actions act)
> >  {
> >  	int ret = 0;
> > @@ -108,7 +123,7 @@ int run_scripts(enum script_actions act)
> >  
> >  	if (scripts_mode == SCRIPTS_RPC) {
> >  		pr_debug("\tRPC\n");
> > -		ret = send_criu_rpc_script(act, (char *)action, rpc_sk);
> > +		ret = send_criu_rpc_script(act, (char *)action, rpc_sk, -1);
> >  		goto out;
> >  	}
> >  
> > @@ -146,6 +161,7 @@ int add_rpc_notify(int sk)
> >  	BUG_ON(scripts_mode == SCRIPTS_SHELL);
> >  	scripts_mode = SCRIPTS_RPC;
> >  
> > -	rpc_sk = sk;
> > +	rpc_sk = install_service_fd(RPC_SK_OFF, sk);
> > +
> >  	return 0;
> >  }
> > diff --git a/criu/cr-restore.c b/criu/cr-restore.c
> > index ee6b848..9fa9bc3 100644
> > --- a/criu/cr-restore.c
> > +++ b/criu/cr-restore.c
> > @@ -3197,6 +3197,7 @@ static int sigreturn_restore(pid_t pid, struct task_restore_args *task_args, uns
> >  	close_proc();
> >  	close_service_fd(ROOT_FD_OFF);
> >  	close_service_fd(USERNSD_SK);
> > +	close_service_fd(RPC_SK_OFF);
> >  
> >  	__gcov_flush();
> >  
> > diff --git a/criu/cr-service.c b/criu/cr-service.c
> > index 4bac50d..130e2a7 100644
> > --- a/criu/cr-service.c
> > +++ b/criu/cr-service.c
> > @@ -36,6 +36,9 @@
> >  #include "irmap.h"
> >  #include "kerndat.h"
> >  #include "proc_parse.h"
> > +#include <sys/un.h>
> > +#include <sys/socket.h>
> > +#include "common/scm.h"
> >  
> >  #include "setproctitle.h"
> >  
> > @@ -84,10 +87,10 @@ err:
> >  	return -1;
> >  }
> >  
> > -static int send_criu_msg(int socket_fd, CriuResp *msg)
> > +static int send_criu_msg_with_fd(int socket_fd, CriuResp *msg, int fd)
> >  {
> >  	unsigned char *buf;
> > -	int len;
> > +	int len, ret;
> >  
> >  	len = criu_resp__get_packed_size(msg);
> >  
> > @@ -100,7 +103,11 @@ static int send_criu_msg(int socket_fd, CriuResp *msg)
> >  		goto err;
> >  	}
> >  
> > -	if (write(socket_fd, buf, len)  == -1) {
> > +	if (fd >= 0) {
> > +		ret = send_fds(socket_fd, NULL, 0, &fd, 1, buf, len);
> > +	} else
> > +		ret = write(socket_fd, buf, len);
> 
> I still don't get how the caller is supposed to use this.
> Caller sends criu_req(RESTORE) to criu, criu starts restoring and
> at some points notices the orphan tty. Then ...

Then criu sends a master via rpc to a caller and he will handle it.

For example, runc creates a pty pair and mounts a slave end to
/dev/console and handles a master from an external process.

So when we dump a runc contaner, we will meet a slave with an external
master. On restore, runc gets a master from criu and handles it as it
handles a console master.

https://github.com/avagin/runc/blob/cr-console/libcontainer/container_linux.go#L1126

>             
> > @@ -956,6 +957,32 @@ static int pty_open_unpaired_slave(struct file_desc *d, struct tty_info *slave)
> >  	 */
> >  
> >  	if (likely(slave->inherit)) {
> > +		if (opts.orphan_pts_master) {
> > +			fake = pty_alloc_fake_master(slave);
> > +			if (!fake)
> > +				goto err;
> > +			master = pty_open_ptmx_index(&fake->d, slave, O_RDWR);
> > +			if (master < 0) {
> > +				pr_err("Can't open master pty %x (index %d)\n",
> > +					  slave->tfe->id, slave->tie->pty->index);
> > +				goto err;
> > +			}
> > +
> > +			unlock_pty(master);
> > +
> > +			if (opts.orphan_pts_master &&
> > +			    rpc_send_fd(ACT_ORPHAN_PTS_MASTER, master) == 0) {
> 
> It just sends the fd to the caller. Caller's recvmsg wakes up and ... sees no
> message in the queue, only the new file descriptor. How is he supposed to tell
> action-script notification (which he expects with recvmsg) from the orphan tty
> fd received?

The caller gets a file descriptor with a message! and it is a regular
notification message.
> 
> > +
> > +				fd = open_tty_reg(slave->reg_d, slave->tfe->flags);
> > +				if (fd < 0) {
> > +					pr_err("Can't open slave pty %s\n", path_from_reg(slave->reg_d));
> > +					goto err;
> > +				}
> > +
> > +				goto out;
> > +			}
> > +		}
> > +
> >  		if (!stdin_isatty) {
> >  			pr_err("Don't have tty to inherit session from, aborting\n");
> >  			return -1;
> > @@ -990,6 +1017,7 @@ static int pty_open_unpaired_slave(struct file_desc *d, struct tty_info *slave)
> >  
> >  	}
> >  
> > +out:
> >  	if (restore_tty_params(fd, slave))
> >  		goto err;
> >  
> > @@ -1002,7 +1030,7 @@ static int pty_open_unpaired_slave(struct file_desc *d, struct tty_info *slave)
> >  	 * be already restored properly thus we can simply
> >  	 * use syscalls instead of lookup via process tree.
> >  	 */
> > -	if (likely(slave->inherit)) {
> > +	if (slave->inherit && opts.shell_job) {
> >  		/*
> >  		 * The restoration procedure only works if we're
> >  		 * migrating not a session leader, otherwise it's
> > @@ -1241,8 +1269,10 @@ static int tty_find_restoring_task(struct tty_info *info)
> >  		if (!tty_is_master(info)) {
> >  			if (tty_has_active_pair(info))
> >  				return 0;
> > -			else
> > +			else if (!opts.orphan_pts_master)
> >  				goto shell_job;
> > +			else
> > +				info->inherit = true;
> >  		}
> >  
> >  		/*
> > @@ -1366,7 +1396,7 @@ static int tty_setup_slavery(void * unused)
> >  		    info->driver->type == TTY_TYPE__CTTY)
> >  			continue;
> >  
> > -		if (!tty_is_master(info))
> > +		if (!tty_is_master(info) && info->link)
> >  			continue;
> >  
> >  		info->ctl_tty = info;
> > diff --git a/images/rpc.proto b/images/rpc.proto
> > index 4811738..ddc28db 100644
> > --- a/images/rpc.proto
> > +++ b/images/rpc.proto
> > @@ -109,6 +109,7 @@ message criu_opts {
> >  	optional bool			tcp_skip_in_flight	= 46;
> >  	optional bool			weak_sysctls		= 47;
> >  	optional bool			lazy_pages		= 48;
> > +	optional bool			orphan_pts_master	= 49;
> >  }
> >  
> >  message criu_dump_resp {
> > 
> 


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