net: Introduce netdev index to name resolver

It will be required to support socket bound to devices.

When restoring w/o net namespaces -- collect existing devices.
When restoring with them -- collect what is received from image.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -764,6 +764,9 @@ static int restore_task_with_children(void *_arg)
 		if (collect_mount_info())
 			exit(-1);
 
+		if (collect_net_devs(ca->clone_flags))
+			exit(-1);
+
 		if (prepare_namespace(current->pid.virt, ca->clone_flags))
 			exit(-1);
 

include/net.h

@@ -19,4 +19,7 @@ struct veth_pair {
 
 extern int network_lock(void);
 extern void network_unlock(void);
+
+char *resolve_dev_name(int index);
+int collect_net_devs(unsigned long flags);
 #endif

net.c

@@ -6,6 +6,8 @@
 #include <net/if_arp.h>
 #include <sys/wait.h>
 #include <sched.h>
+#include <linux/if.h>
+
 #include "syscall-types.h"
 #include "namespaces.h"
 #include "net.h"
@@ -18,6 +20,8 @@
 
 static int ns_fd = -1;
 
+static int collect_one_netdev(int idx, char *name);
+
 void show_netdevices(int fd, struct cr_options *opt)
 {
 	pb_show_plain_pretty(fd, PB_NETDEV, "2:%d");
@@ -270,6 +274,9 @@ static int restore_links(int pid)
 			break;
 
 		ret = restore_link(nde, nlsk);
+		if (!ret)
+			ret = collect_one_netdev(nde->ifindex, nde->name);
+
 		net_device_entry__free_unpacked(nde, NULL);
 		if (ret)
 			break;
@@ -401,3 +408,70 @@ void network_unlock(void)
 	run_scripts("network-unlock");
 }
 
+struct net_dev {
+	int idx;
+	char name[IFNAMSIZ];
+	struct net_dev *next;
+};
+
+static struct net_dev *net_devs;
+
+static int collect_one_netdev(int idx, char *name)
+{
+	struct net_dev *nd;
+
+	nd = xmalloc(sizeof(*nd));
+	if (!nd)
+		return -1;
+
+	nd->idx = idx;
+	strncpy(nd->name, name, IFNAMSIZ);
+	nd->next = net_devs;
+	net_devs = nd;
+
+	pr_debug("\tCollected %d:%s netdev\n", idx, name);
+
+	return 0;
+}
+
+static int collect_netdev(struct nlmsghdr *hdr, void *arg)
+{
+	struct ifinfomsg *ifi;
+	int len = hdr->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
+	struct rtattr *tb[IFLA_MAX + 1];
+
+	ifi = NLMSG_DATA(hdr);
+	if (len < 0) {
+		pr_err("No iflas for link %d\n", ifi->ifi_index);
+		return -1;
+	}
+
+	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
+	if (!tb[IFLA_IFNAME]) {
+		pr_err("No name for device %d\n", ifi->ifi_index);
+		return -1;
+	}
+
+	return collect_one_netdev(ifi->ifi_index, RTA_DATA(tb[IFLA_IFNAME]));
+}
+
+int collect_net_devs(unsigned long flags)
+{
+	if (flags & CLONE_NEWNET)
+		/* restore_links() will collect them */
+		return 0;
+
+	pr_info("Collecting net devices\n");
+	return do_dump_links(collect_netdev, NULL);
+}
+
+char *resolve_dev_name(int index)
+{
+	struct net_dev *nd;
+
+	for (nd = net_devs; nd; nd = nd->next)
+		if (nd->idx == index)
+			return nd->name;
+
+	return NULL;
+}