netns: Basic link dump, restore and show

Only support the lo device. This is not final yet (much more
stuff is to be handled for a link) but is rather a skeleton
showing how to do it and letting us check the LXC container
early.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

image.c

@@ -9,6 +9,7 @@
 #include "ipc_ns.h"
 #include "sk-inet.h"
 #include "mount.h"
+#include "net.h"
 #include "protobuf.h"
 #include "protobuf/inventory.pb-c.h"
 
@@ -117,6 +118,7 @@ struct cr_fd_desc_tmpl fdset_template[CR_FD_MAX] = {
 	FD_ENTRY(GHOST_FILE,	"ghost-file-%x", show_ghost_file),
 	FD_ENTRY(TCP_STREAM,	"tcp-stream-%x", show_tcp_stream),
 	FD_ENTRY(MOUNTPOINTS,	"mountpoints-%d", show_mountpoints),
+	FD_ENTRY(NETDEV,	"netdev-%d",	 show_netdevices),
 };
 
 static struct cr_fdset *alloc_cr_fdset(int nr)

include/crtools.h

@@ -46,6 +46,7 @@ enum {
 	CR_FD_IPCNS_MSG,
 	CR_FD_IPCNS_SEM,
 	CR_FD_MOUNTPOINTS,
+	CR_FD_NETDEV,
 	_CR_FD_NS_TO,
 
 	CR_FD_PSTREE,

include/image.h

@@ -56,6 +56,7 @@
 #define INOTIFY_MAGIC		0x48424431 /* Volgograd */
 #define INOTIFY_WD_MAGIC	0x54562009 /* Svetlogorsk (Rauschen) */
 #define MOUNTPOINTS_MAGIC	0x55563928 /* Petushki */
+#define NETDEV_MAGIC		0x57373951 /* Yaroslavl */
 
 #define PAGE_IMAGE_SIZE	4096
 #define PAGE_RSS	1

include/net.h

 #ifndef __CR_NET_H__
 #define __CR_NET_H__
+struct cr_options;
+void show_netdevices(int fd, struct cr_options *);
+
 struct cr_fdset;
 int dump_net_ns(int pid, struct cr_fdset *);
 int prepare_net_ns(int pid);

net.c

 #include <unistd.h>
+#include <sys/socket.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <string.h>
+#include <net/if_arp.h>
+#include <sys/wait.h>
 #include "syscall-types.h"
 #include "namespaces.h"
 #include "net.h"
+#include "libnetlink.h"
+
+#include "protobuf.h"
+#include "protobuf/netdev.pb-c.h"
+
+void show_netdevices(int fd, struct cr_options *opt)
+{
+	pb_show_plain(fd, net_device_entry);
+}
+
+static int dump_one_netdev(int type, struct nlmsghdr *h, struct ifinfomsg *ifi, struct cr_fdset *fds)
+{
+	int len = h->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
+	struct rtattr * tb[IFLA_MAX+1];
+	NetDeviceEntry netdev = NET_DEVICE_ENTRY__INIT;
+
+	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 link %d\n", ifi->ifi_index);
+		return -1;
+	}
+
+	netdev.type = type;
+	netdev.ifindex = ifi->ifi_index;
+	netdev.mtu = *(int *)RTA_DATA(tb[IFLA_MTU]);
+	netdev.flags = ifi->ifi_flags;
+	netdev.name = RTA_DATA(tb[IFLA_IFNAME]);
+
+	return pb_write(fdset_fd(fds, CR_FD_NETDEV), &netdev, net_device_entry);
+}
+
+static int dump_one_link(struct nlmsghdr *hdr, void *arg)
+{
+	struct cr_fdset *fds = arg;
+	struct ifinfomsg *ifi;
+	int ret = 0;
+
+	ifi = NLMSG_DATA(hdr);
+	pr_info("\tLD: Got link %d, type %d\n", ifi->ifi_index, ifi->ifi_type);
+
+	switch (ifi->ifi_type) {
+	case ARPHRD_LOOPBACK:
+		ret = dump_one_netdev(ND_TYPE__LOOPBACK, hdr, ifi, fds);
+		break;
+	default:
+		pr_err("Unsupported link type %d\n", ifi->ifi_type);
+		ret = 0; /* just skip for now */
+		break;
+	}
+
+	return ret;
+}
+
+static int dump_links(struct cr_fdset *fds)
+{
+	int sk, ret;
+	struct {
+		struct nlmsghdr nlh;
+		struct rtgenmsg g;
+	} req;
+
+	pr_info("Dumping netns links\n");
+
+	ret = sk = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+	if (sk < 0) {
+		pr_perror("Can't open rtnl sock for net dump");
+		goto out;
+	}
+
+	memset(&req, 0, sizeof(req));
+	req.nlh.nlmsg_len = sizeof(req);
+	req.nlh.nlmsg_type = RTM_GETLINK;
+	req.nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
+	req.nlh.nlmsg_pid = 0;
+	req.nlh.nlmsg_seq = CR_NLMSG_SEQ;
+	req.g.rtgen_family = AF_PACKET;
+
+	ret = do_rtnl_req(sk, &req, sizeof(req), dump_one_link, fds);
+	close(sk);
+out:
+	return ret;
+}
+
+static int restore_link_cb(struct nlmsghdr *hdr, void *arg)
+{
+	pr_info("Got responce on SETLINK =)\n");
+	return 0;
+}
+
+static int restore_one_link(NetDeviceEntry *nde, int nlsk)
+{
+	struct {
+		struct nlmsghdr h;
+		struct ifinfomsg i;
+	} req;
+
+	memset(&req, 0, sizeof(req));
+
+	req.h.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+	req.h.nlmsg_flags = NLM_F_REQUEST|NLM_F_ACK;
+	req.h.nlmsg_type = RTM_NEWLINK;
+	req.h.nlmsg_seq = CR_NLMSG_SEQ;
+	req.i.ifi_family = AF_PACKET;
+	req.i.ifi_index = nde->ifindex;
+	req.i.ifi_flags = nde->flags;
+
+	/* FIXME -- restore mtu as well */
+
+	pr_info("Restoring netdev idx %d\n", nde->ifindex);
+	return do_rtnl_req(nlsk, &req, sizeof(req), restore_link_cb, NULL);
+}
+
+static int restore_link(NetDeviceEntry *nde, int nlsk)
+{
+	pr_info("Restoring link type %d\n", nde->type);
+
+	switch (nde->type) {
+	case ND_TYPE__LOOPBACK:
+		return restore_one_link(nde, nlsk);
+	}
+
+	BUG_ON(1);
+	return -1;
+}
+
+static int restore_links(int pid)
+{
+	int fd, nlsk, ret;
+	NetDeviceEntry *nde;
+
+	fd = open_image_ro(CR_FD_NETDEV, pid);
+	if (fd < 0)
+		return -1;
+
+	nlsk = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+	if (nlsk < 0) {
+		pr_perror("Can't create nlk socket");
+		return -1;
+	}
+
+	while (1) {
+		ret = pb_read_eof(fd, &nde, net_device_entry);
+		if (ret <= 0)
+			break;
+
+		ret = restore_link(nde, nlsk);
+		net_device_entry__free_unpacked(nde, NULL);
+		if (ret)
+			break;
+	}
+
+	close(nlsk);
+	close(fd);
+	return ret;
+}
 
 int dump_net_ns(int pid, struct cr_fdset *fds)
 {
 	int ret;
 
 	ret = switch_ns(pid, CLONE_NEWNET, "net", NULL);
+	if (!ret)
+		ret = dump_links(fds);
 
 	return ret;
 }
 
 int prepare_net_ns(int pid)
 {
-	return -1;
+	int ret;
+
+	ret = restore_links(pid);
+
+	return ret;
 }

protobuf/Makefile

@@ -52,6 +52,7 @@ PROTO_FILES	+= utsns.proto
 PROTO_FILES	+= creds.proto
 PROTO_FILES	+= vma.proto
 PROTO_FILES	+= core.proto
+PROTO_FILES	+= netdev.proto
 
 HDRS	:= $(patsubst %.proto,%.pb-c.h,$(PROTO_FILES))
 SRCS	:= $(patsubst %.proto,%.pb-c.c,$(PROTO_FILES))

protobuf/netdev.proto

+enum nd_type {
+	LOOPBACK	= 1;
+}
+
+message net_device_entry {
+	required nd_type type		= 1;
+	required uint32  ifindex	= 2;
+	required uint32  mtu		= 3;
+	required uint32  flags		= 4;
+	required string  name		= 5;
+}