netdev - [patch iproute2-next 3/3] devlink: get devlink port for ifname using RTNL get link command

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Message-Id: <20221104102327.770260-4-jiri@resnulli.us>
Date:   Fri,  4 Nov 2022 11:23:27 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     netdev@...r.kernel.org
Cc:     sthemmin@...rosoft.com, dsahern@...il.com, kuba@...nel.org,
        moshe@...dia.com, aeedm@...dia.com
Subject: [patch iproute2-next 3/3] devlink: get devlink port for ifname using RTNL get link command

From: Jiri Pirko <jiri@...dia.com>

Currently, when user specifies ifname as a handle on command line of
devlink, the related devlink port is looked-up in previously taken dump
of all devlink ports on the system. There are 3 problems with that:
1) The dump iterates over all devlink instances in kernel and takes a
   devlink instance lock for each.
2) Dumping all devlink ports would not scale.
3) Alternative ifnames are not exposed by devlink netlink interface.

Instead, benefit from RTNL get link command extension and get the
devlink port handle info from IFLA_DEVLINK_PORT attribute, if supported.

Signed-off-by: Jiri Pirko <jiri@...dia.com>
---
 devlink/devlink.c | 88 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 86 insertions(+), 2 deletions(-)

diff --git a/devlink/devlink.c b/devlink/devlink.c
index 6e8e03aa14b7..f656d0a7c514 100644
--- a/devlink/devlink.c
+++ b/devlink/devlink.c
@@ -43,6 +43,8 @@
 #include "json_print.h"
 #include "utils.h"
 #include "namespace.h"
+#include "libnetlink.h"
+#include "../ip/ip_common.h"
 
 #define ESWITCH_MODE_LEGACY "legacy"
 #define ESWITCH_MODE_SWITCHDEV "switchdev"
@@ -793,6 +795,81 @@ static void ifname_map_del(struct ifname_map *ifname_map)
 	ifname_map_free(ifname_map);
 }
 
+static int ifname_map_rtnl_port_parse(struct dl *dl, const char *ifname,
+				      struct rtattr *nest)
+{
+	struct rtattr *tb[DEVLINK_ATTR_MAX + 1];
+	const char *bus_name;
+	const char *dev_name;
+	uint32_t port_index;
+
+	parse_rtattr_nested(tb, DEVLINK_ATTR_MAX, nest);
+	if (!tb[DEVLINK_ATTR_BUS_NAME] || !tb[DEVLINK_ATTR_DEV_NAME] ||
+	    !tb[DEVLINK_ATTR_PORT_INDEX])
+		return -ENOENT;
+
+	bus_name = rta_getattr_str(tb[DEVLINK_ATTR_BUS_NAME]);
+	dev_name = rta_getattr_str(tb[DEVLINK_ATTR_DEV_NAME]);
+	port_index = rta_getattr_u32(tb[DEVLINK_ATTR_PORT_INDEX]);
+	return ifname_map_add(dl, ifname, bus_name, dev_name, port_index);
+}
+
+static int ifname_map_rtnl_init(struct dl *dl, const char *ifname)
+{
+	struct iplink_req req = {
+		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+		.n.nlmsg_flags = NLM_F_REQUEST,
+		.n.nlmsg_type = RTM_GETLINK,
+		.i.ifi_family = AF_UNSPEC,
+	};
+	struct rtattr *tb[IFLA_MAX + 1];
+	struct rtnl_handle rth;
+	struct ifinfomsg *ifi;
+	struct nlmsghdr *n;
+	int len;
+	int err;
+
+	if (rtnl_open(&rth, 0) < 0) {
+		pr_err("Cannot open rtnetlink\n");
+		return -EINVAL;
+	}
+
+	addattr_l(&req.n, sizeof(req),
+		  !check_ifname(ifname) ? IFLA_IFNAME : IFLA_ALT_IFNAME,
+		  ifname, strlen(ifname) + 1);
+
+	if (rtnl_talk(&rth, &req.n, &n) < 0) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (n->nlmsg_type != RTM_NEWLINK) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	ifi = NLMSG_DATA(n);
+	len = n->nlmsg_len;
+
+	len -= NLMSG_LENGTH(sizeof(*ifi));
+	if (len < 0) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	parse_rtattr_flags(tb, IFLA_MAX, IFLA_RTA(ifi), len, NLA_F_NESTED);
+	if (!tb[IFLA_DEVLINK_PORT]) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
+	err = ifname_map_rtnl_port_parse(dl, ifname, tb[IFLA_DEVLINK_PORT]);
+
+out:
+	rtnl_close(&rth);
+	return err;
+}
+
 static int ifname_map_cb(const struct nlmsghdr *nlh, void *data)
 {
 	struct nlattr *tb[DEVLINK_ATTR_MAX + 1] = {};
@@ -838,11 +915,18 @@ static void ifname_map_init(struct dl *dl)
 	INIT_LIST_HEAD(&dl->ifname_map_list);
 }
 
-static int ifname_map_load(struct dl *dl)
+static int ifname_map_load(struct dl *dl, const char *ifname)
 {
 	struct nlmsghdr *nlh;
 	int err;
 
+	err = ifname_map_rtnl_init(dl, ifname);
+	if (!err)
+		return 0;
+	/* In case kernel does not support devlink port info passed over
+	 * RT netlink, fall-back to ports dump.
+	 */
+
 	nlh = mnlu_gen_socket_cmd_prepare(&dl->nlg, DEVLINK_CMD_PORT_GET,
 			       NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);
 
@@ -862,7 +946,7 @@ static int ifname_map_lookup(struct dl *dl, const char *ifname,
 	int err;
 
 	if (!dl->map_loaded) {
-		err = ifname_map_load(dl);
+		err = ifname_map_load(dl, ifname);
 		if (err) {
 			pr_err("Failed to create index map\n");
 			return err;
-- 
2.37.3