[PATCH 1/2] ip: add support for changing the netns of a device.

[Nicholas Niro]

This patch adds 2 things.

First the supported 'ip link' commands are added to the 'ip --help'
output. Previously, only the 'set' command was shown. This adds the
other commands that we support, namely :  'add', 'del' and 'show'.

Second, support was added to change the netns by PID of a device. Do
note that this patch adds support for only 1 of the 2 netns methods that
iproute2 supports. It supports a netns by PID or by path and this patch
only adds support for the PID version (which is a lot lighter to
implement).

In effect, changing the network namespace of a device 'moves' it to that
namespace so it can be used in that namespace only. This is crucial for
setting up virtual ethernet (veth) devices when setting up network accessible
namespaces.

Signed-off-by: Nicholas Niro <blowfist at xroutine.net>

---
 networking/ip.c                |  4 ++--
 networking/libiproute/iplink.c | 35 ++++++++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/networking/ip.c b/networking/ip.c
index 034ee4fc8..b5638c1d9 100644
--- a/networking/ip.c
+++ b/networking/ip.c
@@ -155,9 +155,9 @@
 //usage:
 //--------------123456789.123456789.123456789.123456789.123456789.123456789.123456789.123....79
 //usage:#define iplink_trivial_usage
-//usage:       /*Usage:iplink*/"set IFACE [up|down] [arp on|off] [multicast on|off]\n"
+//usage:       /*Usage:iplink*/"set|add|del|show IFACE [up|down] [arp on|off] [multicast on|off]\n"
 //usage:       "	[promisc on|off] [mtu NUM] [name NAME] [qlen NUM] [address MAC]\n"
-//usage:       "	[master IFACE | nomaster]"
+//usage:       "	[master IFACE | nomaster] [netns PID]"
 // * short help shows only "set" command, long help continues (with just one "\n")
 // * and shows all other commands:
 //usage:#define iplink_full_usage "\n"
diff --git a/networking/libiproute/iplink.c b/networking/libiproute/iplink.c
index 1a1064bdc..68d199044 100644
--- a/networking/libiproute/iplink.c
+++ b/networking/libiproute/iplink.c
@@ -152,6 +152,30 @@ static void set_master(char *dev, int master)
 		xfunc_die();
 }
 
+/* Exits on error */
+static void set_netns(char *dev, int netns)
+{
+	struct rtnl_handle rth;
+	struct {
+		struct nlmsghdr  n;
+		struct ifinfomsg i;
+		char             buf[1024];
+	} req;
+
+	memset(&req, 0, sizeof(req));
+	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+	req.n.nlmsg_flags = NLM_F_REQUEST;
+	req.n.nlmsg_type = RTM_NEWLINK;
+	req.i.ifi_family = preferred_family;
+
+	xrtnl_open(&rth);
+	req.i.ifi_index = xll_name_to_index(dev);
+	//printf("netns %i for %i\n", netns, req.i.ifi_index);
+	addattr_l(&req.n, sizeof(req), IFLA_NET_NS_PID, &netns, 4);
+	if (rtnl_talk(&rth, &req.n, 0, 0, NULL, NULL, NULL) < 0)
+		xfunc_die();
+}
+
 /* Exits on error */
 static int get_address(char *dev, int *htype)
 {
@@ -226,6 +250,7 @@ static int do_set(char **argv)
 	int qlen = -1;
 	int mtu = -1;
 	int master = -1;
+	int netns = -1;
 	char *newaddr = NULL;
 	char *newbrd = NULL;
 	struct ifreq ifr0, ifr1;
@@ -234,11 +259,11 @@ static int do_set(char **argv)
 	/* If you add stuff here, update iplink_full_usage */
 	static const char keywords[] ALIGN1 =
 		"up\0""down\0""name\0""mtu\0""qlen\0""multicast\0"
-		"arp\0""promisc\0""address\0"
+		"arp\0""promisc\0""address\0""netns\0"
 		"master\0""nomaster\0"
 		"dev\0" /* must be last */;
 	enum { ARG_up = 0, ARG_down, ARG_name, ARG_mtu, ARG_qlen, ARG_multicast,
-		ARG_arp, ARG_promisc, ARG_addr,
+		ARG_arp, ARG_promisc, ARG_addr, ARG_netns,
 		ARG_master, ARG_nomaster,
 		ARG_dev };
 	enum { PARM_on = 0, PARM_off };
@@ -276,6 +301,9 @@ static int do_set(char **argv)
 			master = xll_name_to_index(*argv);
 		} else if (key == ARG_nomaster) {
 			master = 0;
+		} else if (key == ARG_netns) {
+			NEXT_ARG();
+			netns = get_unsigned(*argv, "netns");
 		} else if (key >= ARG_dev) {
 			/* ^^^^^^ ">=" here results in "dev IFACE" treated as default */
 			if (key == ARG_dev) {
@@ -463,6 +491,9 @@ static int do_set(char **argv)
 	if (master != -1) {
 		set_master(dev, master);
 	}
+	if (netns != -1) {
+		set_netns(dev, netns);
+	}
 	if (mask)
 		do_chflags(dev, flags, mask);
 	return 0;
-- 
2.24.1.485.gad05a3d8e5.dirty