tcp: Add tcp-close option to restore connected TCP sockets in closed state

New restore option 'tcp-close' was introduced. It restores all connected
TCP sockets in TCP_CLOSE state. Here we consider tcp sockets in
TCP_ESTABLISHED, TCP_FIN_WAIT2, TCP_FIN_WAIT1, TCP_CLOSE_WAIT,
TCP_LAST_ACK, TCP_CLOSING, TCP_SYN_SENT states as connected sockets.
This is consistent with current CRIU usage of these states. Thus this
option doesn't affect sockets with original states of TCP_LISTEN and
TCP_CLOSE.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Eugene Batalov <eabatalov89@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Documentation/criu.txt

@@ -264,6 +264,9 @@ For example, the command line for the above example should look like this:
     The TCP stack on the client side is expected to handle the
     re-connect gracefully.
 
+*--tcp-close*::
+    Restore connected TCP sockets in closed state.
+
 *--evasive-devices*::
     Use any path to a device file if the original one is inaccessible.
 

criu/crtools.c

@@ -290,6 +290,7 @@ int main(int argc, char *argv[], char *envp[])
 		BOOL_OPT("display-stats", &opts.display_stats),
 		BOOL_OPT("weak-sysctls", &opts.weak_sysctls),
 		{ "status-fd",			required_argument,	0, 1088 },
+		{ SK_CLOSE_PARAM, 		no_argument,		0, 1089 },
 		{ },
 	};
 
@@ -568,6 +569,9 @@ int main(int argc, char *argv[], char *envp[])
 				return 1;
 			}
 			break;
+		case 1089:
+			opts.tcp_close = true;
+			break;
 		case 'V':
 			pr_msg("Version: %s\n", CRIU_VERSION);
 			if (strcmp(CRIU_GITID, "0"))
@@ -826,6 +830,7 @@ usage:
 "* Special resources support:\n"
 "     --" SK_EST_PARAM "  checkpoint/restore established TCP connections\n"
 "     --" SK_INFLIGHT_PARAM "   skip (ignore) in-flight TCP connections\n"
+"     --" SK_CLOSE_PARAM "        restore connected TCP sockets in closed state\n"
 "  -r|--root PATH        change the root filesystem (when run in mount namespace)\n"
 "  --evasive-devices     use any path to a device file if the original one\n"
 "                        is inaccessible\n"

criu/include/cr_options.h

@@ -63,6 +63,7 @@ struct cr_options {
 	int			shell_job;
 	int			handle_file_locks;
 	int			tcp_established_ok;
+	bool			tcp_close;
 	int			evasive_devices;
 	int			link_remap_ok;
 	int			log_file_per_pid;

criu/include/sk-inet.h

@@ -75,6 +75,7 @@ extern int restore_one_tcp(int sk, struct inet_sk_info *si);
 
 #define SK_EST_PARAM	"tcp-established"
 #define SK_INFLIGHT_PARAM "skip-in-flight"
+#define SK_CLOSE_PARAM	"tcp-close"
 
 struct task_restore_args;
 int prepare_tcp_socks(struct task_restore_args *);

criu/sk-inet.c

@@ -648,7 +648,7 @@ static int open_inet_sk(struct file_desc *d, int *new_fd)
 		goto err;
 
 	if (tcp_connection(ie)) {
-		if (!opts.tcp_established_ok) {
+		if (!opts.tcp_established_ok && !opts.tcp_close) {
 			pr_err("Connected TCP socket in image\n");
 			goto err;
 		}

criu/sk-tcp.c

@@ -8,6 +8,7 @@
 
 #include "../soccr/soccr.h"
 
+#include "cr_options.h"
 #include "util.h"
 #include "common/list.h"
 #include "log.h"
@@ -407,6 +408,11 @@ int restore_one_tcp(int fd, struct inet_sk_info *ii)
 
 	pr_info("Restoring TCP connection\n");
 
+	if (opts.tcp_close &&
+		ii->ie->state != TCP_LISTEN && ii->ie->state != TCP_CLOSE) {
+		return 0;
+	}
+
 	sk = libsoccr_pause(fd);
 	if (!sk)
 		return -1;