From 6dde331da8e28e129010aee391e7ef3d757490cd Mon Sep 17 00:00:00 2001
From: "fu.lin" <fulin10@huawei.com>
Date: Tue, 26 Oct 2021 11:13:27 +0800
Subject: [PATCH 50/72] unix sk: improve dgram robustness

We should try out best to ensure the success of criu. As for unix dgram
socket, criu use re-connect instead of repair instead of unix stream
socket. Therefore, this patch does the following things:

- detect unix dgram unix sock file when criu dumps unix dgram socket
- add the fault tolerance of unix dgram socket connecting (focus on the
  condition of `/dev/log` disappearance when rsyslog restart)

Conflict:NA
Reference:https://gitee.com/src-openeuler/criu/pulls/21
Signed-off-by: fu.lin <fulin10@huawei.com>
---
 criu/sk-unix.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/criu/sk-unix.c b/criu/sk-unix.c
index 86bfa18..de75425 100644
--- a/criu/sk-unix.c
+++ b/criu/sk-unix.c
@@ -11,6 +11,7 @@
 #include <stdlib.h>
 #include <dlfcn.h>
 #include <libgen.h>
+#include <time.h>
 
 #include "libnetlink.h"
 #include "cr_options.h"
@@ -1435,6 +1436,33 @@ err:
 	return -1;
 }
 
+/*
+ * Sometimes, `/dev/log` will disappear because of the restart of rsyslog when
+ * rotating, criu try to connect `/dev/log` will report error at this time. We
+ * should try our best to ensure the success of criu restoration. Therefore,
+ * retry three times here.
+ */
+static int unix_dgram_reconnect(int fd, struct sockaddr_un *addr, int len)
+{
+	int retval = 0;
+	struct timespec tim = {
+		.tv_sec = 0,
+		.tv_nsec = 5e+8,
+	};
+
+	for (int i = 0; i < 3; i++) {
+		nanosleep(&tim, NULL);
+		pr_warn("Can't connect unix socket(%s), %d retry\n",
+					addr->sun_path, i);
+		retval = connect(fd, (struct sockaddr *)addr,
+					sizeof(addr->sun_family) + len);
+		if (retval == 0)
+			break;
+	}
+
+	return retval;
+}
+
 static int post_open_standalone(struct file_desc *d, int fd)
 {
 	int fdstore_fd = -1, procfs_self_dir = -1, len;
@@ -1521,8 +1549,11 @@ static int post_open_standalone(struct file_desc *d, int fd)
 			goto err_revert_and_exit;
 		}
 	} else if (connect(fd, (struct sockaddr *)&addr, sizeof(addr.sun_family) + len) < 0) {
-		pr_perror("Can't connect %d socket", ui->ue->ino);
-		goto err_revert_and_exit;
+		if (ui->ue->type != SOCK_DGRAM || errno != ENOENT
+				|| unix_dgram_reconnect(fd, &addr, len) != 0) {
+			pr_perror("Can't connect %d socket", ui->ue->ino);
+			goto err_revert_and_exit;
+		}
 	}
 	mutex_unlock(mutex_ghost);
 
-- 
2.34.1