iproute2: add support for IFLA_NET_NS_PID in ip link

Hi Stephen,

I resend you this patch once more. This time I updated the documentation
too (may be that was the reason why you didn't take it before?).

Please tell me if there are other things missing in this patch
It applies on iproute2 git tree.

Regards,
Benjamin

Description:
------------

This patch adds support for the IFLA_NET_NS_PID type. It is used to
move network devices between network namespaces.

The syntax is:
ip link set DEVICE netns PID

PID is the pid of a process in the target network namespace.

(Daniel Lezcano is the original author).
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
Signed-off-by: Stephen Hemminger <stephen.hemminger@vyatta.com>

doc/ip-cref.tex

@@ -294,6 +294,10 @@ broadcast address will break networking.
 Do not use it, if you do not understand what this operation really does.
 \end{NB}
 
+\item \verb|netns PID|
+
+--- move the device to the network namespace associated with the process PID.
+
 \end{itemize}
 
 \vskip 1mm

ip/iplink.c

@@ -49,6 +49,7 @@ void iplink_usage(void)
 	fprintf(stderr, "	                     name NEWNAME |\n");
 	fprintf(stderr, "	                     address LLADDR | broadcast LLADDR |\n");
 	fprintf(stderr, "	                     mtu MTU }\n");
+	fprintf(stderr, "	                     netns PID }\n");
 	fprintf(stderr, "       ip link show [ DEVICE ]\n");
 	exit(-1);
 }
@@ -156,6 +157,7 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req,
 	char abuf[32];
 	int qlen = -1;
 	int mtu = -1;
+	int netns = -1;
 
 	ret = argc;
 
@@ -197,6 +199,13 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req,
 			if (get_integer(&mtu, *argv, 0))
 				invarg("Invalid \"mtu\" value\n", *argv);
 			addattr_l(&req->n, sizeof(*req), IFLA_MTU, &mtu, 4);
+                } else if (strcmp(*argv, "netns") == 0) {
+                        NEXT_ARG();
+                        if (netns != -1)
+                                duparg("netns", *argv);
+                        if (get_integer(&netns, *argv, 0))
+                                invarg("Invalid \"netns\" value\n", *argv);
+                        addattr_l(&req->n, sizeof(*req), IFLA_NET_NS_PID, &netns, 4);
 		} else if (strcmp(*argv, "multicast") == 0) {
 			NEXT_ARG();
 			req->i.ifi_change |= IFF_MULTICAST;

man/man8/ip.8

@@ -50,7 +50,10 @@ ip \- show / manipulate routing, devices, policy routing and tunnels
 .IR LLADDR " |"
 .br
 .B  mtu
-.IR MTU " }"
+.IR MTU " |"
+.br
+.B  netns
+.IR PID " }"
 
 .ti -8
 .B ip link show
@@ -873,6 +876,11 @@ change the link layer broadcast address or the peer address when
 the interface is
 .IR "POINTOPOINT" .
 
+.TP
+.BI netns " PID"
+move the device to the network namespace associated with the process
+.IR "PID" .
+
 .PP
 .B Warning:
 If multiple parameter changes are requested,