[CRIU] [PATCH 1/2] sysctl: Make CTL_READ nonfatal

[Cyrill Gorcunov]

Some entries might be missing and that should not cause
CRIU to stop dumping when we know the entries are safe
to unuse.

Thus introduce two fields in the request @flags and
@status which will carry the options and results.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 include/sysctl.h | 8 ++++++++
 net.c            | 2 ++
 sysctl.c         | 4 ++++
 3 files changed, 14 insertions(+)

diff --git a/include/sysctl.h b/include/sysctl.h
index 3d7b182e862f..249ff07a4e83 100644
--- a/include/sysctl.h
+++ b/include/sysctl.h
@@ -5,6 +5,8 @@ struct sysctl_req {
 	char	*name;
 	void	*arg;
 	int	type;
+	short	flags;
+	short	status;
 };
 
 extern int sysctl_op(struct sysctl_req *req, size_t nr_req, int op);
@@ -30,4 +32,10 @@ enum {
 #define CTL_LEN(t)	((t) >> CTL_SHIFT)
 #define CTL_TYPE(t)	((t) & ((1 << CTL_SHIFT) - 1))
 
+/*
+ * Some entries might be missing mark them as optional.
+ */
+#define CTL_FLAGS_OPTIONAL	1
+#define CTL_STATUS_ENOENT	1
+
 #endif /* __CR_SYSCTL_H__ */
diff --git a/net.c b/net.c
index 034793029eb2..4acb1e5bcdce 100644
--- a/net.c
+++ b/net.c
@@ -104,6 +104,8 @@ static int ipv4_conf_op(char *tgt, int *conf, int op, NetnsEntry **netns)
 		req[ri].name = path[i];
 		req[ri].arg = &conf[i];
 		req[ri].type = CTL_32;
+		req[ri].flags = 0;
+		req[ri].status = 0;
 		ri++;
 	}
 
diff --git a/sysctl.c b/sysctl.c
index 5c3a01f25ac8..f2320f0bf908 100644
--- a/sysctl.c
+++ b/sysctl.c
@@ -137,6 +137,10 @@ static int __sysctl_op(int dir, struct sysctl_req *req, int op)
 
 	fd = openat(dir, req->name, flags);
 	if (fd < 0) {
+		if (errno == ENOENT && (req->flags & CTL_FLAGS_OPTIONAL)) {
+			req->status |= CTL_STATUS_ENOENT;
+			return 0;
+		}
 		pr_perror("Can't open sysctl %s", req->name);
 		return -1;
 	}
-- 
2.1.0