kerndat: check the SIOCGSKNS ioctl

This ioctl is called for a socket and returns a file descriptor
for network namespace where a socket has been created.
Acked-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/cr-check.c

@@ -1062,6 +1062,17 @@ static int check_can_map_vdso(void)
 	return -1;
 }
 
+static int check_sk_netns(void)
+{
+	if (kerndat_socket_netns() < 0)
+		return -1;
+
+	if (!kdat.sk_ns)
+		return -1;
+
+	return 0;
+}
+
 static int (*chk_feature)(void);
 
 /*
@@ -1168,6 +1179,7 @@ int cr_check(void)
 		ret |= check_can_map_vdso();
 		ret |= check_uffd();
 		ret |= check_uffd_noncoop();
+		ret |= check_sk_netns();
 	}
 
 	/*
@@ -1220,6 +1232,7 @@ static struct feature_list feature_list[] = {
 	{ "uffd", check_uffd },
 	{ "uffd-noncoop", check_uffd_noncoop },
 	{ "can_map_vdso", check_can_map_vdso},
+	{ "sk_ns", check_sk_netns },
 	{ NULL, NULL },
 };
 

criu/include/kerndat.h

@@ -46,6 +46,7 @@ struct kerndat_s {
 	bool ipv6;
 	enum loginuid_func luid;
 	bool compat_cr;
+	bool sk_ns;
 	enum pagemap_func pmap;
 	unsigned int has_xtlocks;
 	unsigned long mmap_min_addr;

criu/include/sockets.h

@@ -87,4 +87,10 @@ static inline int sk_decode_shutdown(int val)
 
 extern int set_netns(uint32_t ns_id);
 
+#ifndef SIOCGSKNS
+#define SIOCGSKNS      0x894C          /* get socket network namespace */
+#endif
+
+extern int kerndat_socket_netns(void);
+
 #endif /* __CR_SOCKETS_H__ */

criu/kerndat.c

@@ -27,6 +27,7 @@
 #include "lsm.h"
 #include "proc_parse.h"
 #include "sk-inet.h"
+#include "sockets.h"
 #include <compel/plugins/std/syscall-codes.h>
 #include <compel/compel.h>
 #include "netfilter.h"
@@ -873,6 +874,8 @@ int kerndat_init(void)
 	/* Depends on kerndat_vdso_fill_symtable() */
 	if (!ret)
 		ret = kerndat_vdso_preserves_hint();
+	if (!ret)
+		ret = kerndat_socket_netns();
 
 	kerndat_lsm();
 	kerndat_mmap_min_addr();

criu/net.c

@@ -2297,6 +2297,30 @@ struct ns_id *get_socket_ns(int lfd)
 	return NULL;
 }
 
+int kerndat_socket_netns(void)
+{
+	int sk, ns_fd;
+
+	sk = socket(AF_UNIX, SOCK_DGRAM, 0);
+	if (sk < 0) {
+		pr_perror("Unable to create socket");
+		return -1;
+	}
+	ns_fd = ioctl(sk, SIOCGSKNS);
+	if (ns_fd < 0) {
+		pr_warn("Unable to get a socket network namespace\n");
+		kdat.sk_ns = false;
+		close(sk);
+		return 0;
+	}
+	close(sk);
+	close(ns_fd);
+
+	kdat.sk_ns = true;
+
+	return 0;
+}
+
 static int move_to_bridge(struct external *ext, void *arg)
 {
 	int s = *(int *)arg;