[PATCH iproute2-next v2 1/2] iplink: add support for parent device

[Sergey Ryazanov <ryazanov.s.a@gmail.com>]

Add support for specifying a parent device (struct device) by its name
during the link creation and printing parent name in the links list.
This option will be used to create WWAN links and possibly by other
device classes that do not have a "natural parent netdev".

Add the parent device bus name printing for links list info
completeness. But do not add a corresponding command line argument, as
we do not have a use case for this attribute.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
---
Changes since v1:
* shorten the 'parentdevbus' parameter to 'parentbus', as Parav
  suggested and Loic recalled

Changes since RFC:
* add a parent device bus attribute support
* shorten the 'parentdev-name' parameter to just 'parentdev'

 ip/ipaddress.c | 14 ++++++++++++++
 ip/iplink.c    |  6 +++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 06ca7273..85534aaf 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -1242,6 +1242,20 @@ int print_linkinfo(struct nlmsghdr *n, void *arg)
 						   RTA_PAYLOAD(tb[IFLA_PHYS_SWITCH_ID]),
 						   b1, sizeof(b1)));
 		}
+
+		if (tb[IFLA_PARENT_DEV_BUS_NAME]) {
+			print_string(PRINT_ANY,
+				     "parentbus",
+				     "parentbus %s ",
+				     rta_getattr_str(tb[IFLA_PARENT_DEV_BUS_NAME]));
+		}
+
+		if (tb[IFLA_PARENT_DEV_NAME]) {
+			print_string(PRINT_ANY,
+				     "parentdev",
+				     "parentdev %s ",
+				     rta_getattr_str(tb[IFLA_PARENT_DEV_NAME]));
+		}
 	}
 
 	if ((do_link || show_details) && tb[IFLA_IFALIAS]) {
diff --git a/ip/iplink.c b/ip/iplink.c
index faafd7e8..33b7be30 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -63,7 +63,7 @@ void iplink_usage(void)
 {
 	if (iplink_have_newlink()) {
 		fprintf(stderr,
-			"Usage: ip link add [link DEV] [ name ] NAME\n"
+			"Usage: ip link add [link DEV | parentdev NAME] [ name ] NAME\n"
 			"		    [ txqueuelen PACKETS ]\n"
 			"		    [ address LLADDR ]\n"
 			"		    [ broadcast LLADDR ]\n"
@@ -938,6 +938,10 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 				       *argv);
 			addattr32(&req->n, sizeof(*req),
 				  IFLA_GSO_MAX_SEGS, max_segs);
+		} else if (strcmp(*argv, "parentdev") == 0) {
+			NEXT_ARG();
+			addattr_l(&req->n, sizeof(*req), IFLA_PARENT_DEV_NAME,
+				  *argv, strlen(*argv) + 1);
 		} else {
 			if (matches(*argv, "help") == 0)
 				usage();
-- 
2.26.3