[RFC WIP 1/2] RDMA/Core: add RDMA_NLDEV_CMD_NEWLINK/DELLLINK support

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Add support for new LINK messages to allow adding and deleting rdma
interfaces.  This will be used initially for soft rdma drivers which
instantiate device instances dynamically by the admin specifying a netdev
device to use.  The rdma_rxe module will be the first user of these
messages.

The design is modeled after RTNL_NEWLINK/DELLINK:  rdma drivers
register with the rdma core if they provide link add/delete functions.
Each driver registers with a unique "type" string, that is used to
dispatch messages coming from user space.  A new RDMA_NLDEV_ATTR is
defined for the "type" string.  User mode will pass 3 attributes in a
NEWLINK message: RDMA_NLDEV_ATTR_IBDEV_NAME for the desired rdma device
name to be created, RDMA_NLDEV_ATTR_LINK_TYPE for the "type" of link
being added, and RDMA_NLDEV_ATTR_NDEV_NAME for the net_device interface
to use for this link. The DELLINK message will contain the IBDEV_NAME
and LINK_TYPE attributes.

Signed-off-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx>
---
 drivers/infiniband/core/nldev.c  | 113 +++++++++++++++++++++++++++++++++++++++
 include/rdma/rdma_netlink.h      |  11 ++++
 include/uapi/rdma/rdma_netlink.h |   9 ++++
 3 files changed, 133 insertions(+)

diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index 0385ab438320..d107b982c210 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c
@@ -33,6 +33,7 @@
 #include <linux/module.h>
 #include <linux/pid.h>
 #include <linux/pid_namespace.h>
+#include <linux/mutex.h>
 #include <net/netlink.h>
 #include <rdma/rdma_cm.h>
 #include <rdma/rdma_netlink.h>
@@ -107,6 +108,8 @@
 	[RDMA_NLDEV_ATTR_DRIVER_U32]		= { .type = NLA_U32 },
 	[RDMA_NLDEV_ATTR_DRIVER_S64]		= { .type = NLA_S64 },
 	[RDMA_NLDEV_ATTR_DRIVER_U64]		= { .type = NLA_U64 },
+	[RDMA_NLDEV_ATTR_LINK_TYPE]		= { .type = NLA_NUL_STRING,
+						    .len = IFNAMSIZ },
 };
 
 static int put_driver_name_print_type(struct sk_buff *msg, const char *name,
@@ -1072,6 +1075,110 @@ static int nldev_res_get_pd_dumpit(struct sk_buff *skb,
 	return res_get_common_dumpit(skb, cb, RDMA_RESTRACK_PD);
 }
 
+static LIST_HEAD(link_ops);
+static DEFINE_MUTEX(link_ops_mutex);
+
+void rdma_link_register(struct rdma_link_ops *ops)
+{
+	mutex_lock(&link_ops_mutex);
+	list_add(&ops->list, &link_ops);
+	mutex_unlock(&link_ops_mutex);
+}
+EXPORT_SYMBOL(rdma_link_register);
+
+void rdma_link_unregister(struct rdma_link_ops *ops)
+{
+	mutex_lock(&link_ops_mutex);
+	list_del_init(&ops->list);
+	mutex_unlock(&link_ops_mutex);
+}
+EXPORT_SYMBOL(rdma_link_unregister);
+
+static const struct rdma_link_ops *link_ops_get(const char *type)
+{
+	const struct rdma_link_ops *ops;
+
+	mutex_lock(&link_ops_mutex);
+	list_for_each_entry(ops, &link_ops, list) {
+		if (!strncmp(ops->type, type, IFNAMSIZ))
+			goto out;
+	}
+	ops = NULL;
+out:
+	mutex_unlock(&link_ops_mutex);
+	return ops;
+}
+
+static int nldev_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
+	char ibdev_name[IB_DEVICE_NAME_MAX];
+	const struct rdma_link_ops *ops;
+	char ndev_name[IFNAMSIZ];
+	char type[IFNAMSIZ];
+	int err;
+
+	err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1,
+			  nldev_policy, extack);
+	if (err || !tb[RDMA_NLDEV_ATTR_DEV_NAME] ||
+	    !tb[RDMA_NLDEV_ATTR_LINK_TYPE] || !tb[RDMA_NLDEV_ATTR_NDEV_NAME]) {
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	nla_strlcpy(ibdev_name, tb[RDMA_NLDEV_ATTR_DEV_NAME],
+		    sizeof(ibdev_name));
+	nla_strlcpy(type, tb[RDMA_NLDEV_ATTR_LINK_TYPE], sizeof(type));
+	nla_strlcpy(ndev_name, tb[RDMA_NLDEV_ATTR_NDEV_NAME],
+		    sizeof(ndev_name));
+	pr_debug("ibdev_name |%s| type |%s| ndev_name |%s|\n", ibdev_name,
+		 type, ndev_name);
+
+	ops = link_ops_get(type);
+	if (!ops) {
+		err = -ENODEV;
+		goto err_out;
+	}
+	
+	err = ops->newlink(ibdev_name, ndev_name);
+err_out:
+	return err;
+}
+
+static int nldev_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
+	char ibdev_name[IB_DEVICE_NAME_MAX];
+	const struct rdma_link_ops *ops;
+	char type[IFNAMSIZ];
+	int err;
+
+	err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1,
+			  nldev_policy, extack);
+	if (err || !tb[RDMA_NLDEV_ATTR_DEV_NAME] ||
+	    !tb[RDMA_NLDEV_ATTR_LINK_TYPE]) {
+		err = !err ? -EINVAL : err;
+		goto err_out;
+	}
+
+	nla_strlcpy(ibdev_name, tb[RDMA_NLDEV_ATTR_DEV_NAME],
+		    sizeof(ibdev_name));
+	nla_strlcpy(type, tb[RDMA_NLDEV_ATTR_LINK_TYPE], sizeof(type));
+	pr_debug("ibdev_name |%s| type |%s|\n", ibdev_name, type);
+
+	ops = link_ops_get(type);
+	if (!ops) {
+		err = -ENODEV;
+		goto err_out;
+	}
+	
+	err = ops->dellink(ibdev_name);
+err_out:
+	return err;
+}
+
 static const struct rdma_nl_cbs nldev_cb_table[RDMA_NLDEV_NUM_OPS] = {
 	[RDMA_NLDEV_CMD_GET] = {
 		.doit = nldev_get_doit,
@@ -1110,6 +1217,12 @@ static int nldev_res_get_pd_dumpit(struct sk_buff *skb,
 	[RDMA_NLDEV_CMD_RES_PD_GET] = {
 		.dump = nldev_res_get_pd_dumpit,
 	},
+	[RDMA_NLDEV_CMD_NEWLINK] = {
+		.doit = nldev_newlink,
+	},
+	[RDMA_NLDEV_CMD_DELLINK] = {
+		.doit = nldev_dellink,
+	},
 };
 
 void __init nldev_init(void)
diff --git a/include/rdma/rdma_netlink.h b/include/rdma/rdma_netlink.h
index c369703fcd69..b5a5a1a7cddc 100644
--- a/include/rdma/rdma_netlink.h
+++ b/include/rdma/rdma_netlink.h
@@ -99,4 +99,15 @@ int ibnl_put_attr(struct sk_buff *skb, struct nlmsghdr *nlh,
  * Returns 0 on success or a negative for no listeners.
  */
 int rdma_nl_chk_listeners(unsigned int group);
+
+struct rdma_link_ops {
+	struct list_head list;
+	const char *type;
+	int (*newlink)(char *ibdev_name, char *ndev_name);
+	int (*dellink)(char *ibdev_name);
+};
+
+void rdma_link_register(struct rdma_link_ops *ops);
+void rdma_link_unregister(struct rdma_link_ops *ops);
+
 #endif /* _RDMA_NETLINK_H */
diff --git a/include/uapi/rdma/rdma_netlink.h b/include/uapi/rdma/rdma_netlink.h
index edba6351ac13..025172d41fa7 100644
--- a/include/uapi/rdma/rdma_netlink.h
+++ b/include/uapi/rdma/rdma_netlink.h
@@ -246,6 +246,10 @@ enum rdma_nldev_command {
 
 	RDMA_NLDEV_CMD_RES_PD_GET, /* can dump */
 
+	RDMA_NLDEV_CMD_NEWLINK,
+
+	RDMA_NLDEV_CMD_DELLINK,
+
 	RDMA_NLDEV_NUM_OPS
 };
 
@@ -427,6 +431,11 @@ enum rdma_nldev_attr {
 	RDMA_NLDEV_ATTR_DRIVER_U64,		/* u64 */
 
 	/*
+	 * Identifies the rdma driver. eg: "rxe" or "siw"
+	 */
+	RDMA_NLDEV_ATTR_LINK_TYPE,		/* string */
+
+	/*
 	 * Always the end
 	 */
 	RDMA_NLDEV_ATTR_MAX
-- 
1.8.3.1




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