[PATCH RFC iproute2-next] iplink: allow to change iplink value

[Ansuel Smith <ansuelsmth@gmail.com>]

Allow to change the interface to which a given interface is linked to.
This is useful in the case of multi-CPU port DSA, for changing the CPU
port of a given user port.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: David Ahern <dsahern@gmail.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
---
 ip/iplink.c           | 16 +++++-----------
 man/man8/ip-link.8.in |  7 +++++++
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/ip/iplink.c b/ip/iplink.c
index 212a0885..d52c0aaf 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -579,7 +579,6 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 {
 	char *name = NULL;
 	char *dev = NULL;
-	char *link = NULL;
 	int ret, len;
 	char abuf[32];
 	int qlen = -1;
@@ -590,6 +589,7 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 	int numrxqueues = -1;
 	int link_netnsid = -1;
 	int index = 0;
+	int link = -1;
 	int group = -1;
 	int addr_len = 0;
 
@@ -620,7 +620,10 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 				invarg("Invalid \"index\" value", *argv);
 		} else if (matches(*argv, "link") == 0) {
 			NEXT_ARG();
-			link = *argv;
+			link = ll_name_to_index(*argv);
+			if (!link)
+				return nodev(*argv);
+			addattr32(&req->n, sizeof(*req), IFLA_LINK, link);
 		} else if (matches(*argv, "address") == 0) {
 			NEXT_ARG();
 			addr_len = ll_addr_a2n(abuf, sizeof(abuf), *argv);
@@ -1004,15 +1007,6 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 			exit(-1);
 		}
 
-		if (link) {
-			int ifindex;
-
-			ifindex = ll_name_to_index(link);
-			if (!ifindex)
-				return nodev(link);
-			addattr32(&req->n, sizeof(*req), IFLA_LINK, ifindex);
-		}
-
 		req->i.ifi_index = index;
 	}
 
diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index a8ae72d2..800aed05 100644
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -149,6 +149,9 @@ ip-link \- network device configuration
 .br
 .RB "[ " nomaster " ]"
 .br
+.RB "[ " link
+.IR DEVICE " ]"
+.br
 .RB "[ " vrf
 .IR NAME " ]"
 .br
@@ -2131,6 +2134,10 @@ set master device of the device (enslave device).
 .BI nomaster
 unset master device of the device (release device).
 
+.TP
+.BI link " DEVICE"
+set device to which this device is linked to.
+
 .TP
 .BI addrgenmode " eui64|none|stable_secret|random"
 set the IPv6 address generation mode
-- 
2.21.0