rtnetlink: Pack newlink() params into struct

There are 4 net namespaces involved when creating links:

 - source netns - where the netlink socket resides,
 - target netns - where to put the device being created,
 - link netns - netns associated with the device (backend),
 - peer netns - netns of peer device.

Currently, two nets are passed to newlink() callback - "src_net"
parameter and "dev_net" (implicitly in net_device). They are set as
follows, depending on netlink attributes in the request.

 +------------+-------------------+---------+---------+
 | peer netns | IFLA_LINK_NETNSID | src_net | dev_net |
 +------------+-------------------+---------+---------+
 |            | absent            | source  | target  |
 | absent     +-------------------+---------+---------+
 |            | present           | link    | link    |
 +------------+-------------------+---------+---------+
 |            | absent            | peer    | target  |
 | present    +-------------------+---------+---------+
 |            | present           | peer    | link    |
 +------------+-------------------+---------+---------+

When IFLA_LINK_NETNSID is present, the device is created in link netns
first and then moved to target netns. This has some side effects,
including extra ifindex allocation, ifname validation and link events.
These could be avoided if we create it in target netns from
the beginning.

On the other hand, the meaning of src_net parameter is ambiguous. It
varies depending on how parameters are passed. It is the effective
link (or peer netns) by design, but some drivers ignore it and use
dev_net instead.

To provide more netns context for drivers, this patch packs existing
newlink() parameters, along with the source netns, link netns and peer
netns, into a struct. The old "src_net" is renamed to "net" to avoid
confusion with real source netns, and will be deprecated later. The use
of src_net are converted to params->net trivially.

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250219125039.18024-3-shaw.leon@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 19 insertions, 9 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index c9f11a046c26..1fe9b13d351c 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1396,10 +1396,12 @@ ipgre_newlink_encap_setup(struct net_device *dev, struct nlattr *data[])
 	return 0;
 }
 
-static int ipgre_newlink(struct net *src_net, struct net_device *dev,
-			 struct nlattr *tb[], struct nlattr *data[],
+static int ipgre_newlink(struct net_device *dev,
+			 struct rtnl_newlink_params *params,
 			 struct netlink_ext_ack *extack)
 {
+	struct nlattr **data = params->data;
+	struct nlattr **tb = params->tb;
 	struct ip_tunnel_parm_kern p;
 	__u32 fwmark = 0;
 	int err;
@@ -1414,10 +1416,12 @@ static int ipgre_newlink(struct net *src_net, struct net_device *dev,
 	return ip_tunnel_newlink(dev, tb, &p, fwmark);
 }
 
-static int erspan_newlink(struct net *src_net, struct net_device *dev,
-			  struct nlattr *tb[], struct nlattr *data[],
+static int erspan_newlink(struct net_device *dev,
+			  struct rtnl_newlink_params *params,
 			  struct netlink_ext_ack *extack)
 {
+	struct nlattr **data = params->data;
+	struct nlattr **tb = params->tb;
 	struct ip_tunnel_parm_kern p;
 	__u32 fwmark = 0;
 	int err;
@@ -1697,6 +1701,7 @@ static struct rtnl_link_ops erspan_link_ops __read_mostly = {
 struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
 					u8 name_assign_type)
 {
+	struct rtnl_newlink_params params = { .net = net };
 	struct nlattr *tb[IFLA_MAX + 1];
 	struct net_device *dev;
 	LIST_HEAD(list_kill);
@@ -1704,6 +1709,7 @@ struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
 	int err;
 
 	memset(&tb, 0, sizeof(tb));
+	params.tb = tb;
 
 	dev = rtnl_create_link(net, name, name_assign_type,
 			       &ipgre_tap_ops, tb, NULL);
@@ -1714,7 +1720,7 @@ struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
 	t = netdev_priv(dev);
 	t->collect_md = true;
 
-	err = ipgre_newlink(net, dev, tb, NULL, NULL);
+	err = ipgre_newlink(dev, &params, NULL);
 	if (err < 0) {
 		free_netdev(dev);
 		return ERR_PTR(err);
diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index f0b4419cef34..b901bee03e6d 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -575,11 +575,13 @@ static void vti_netlink_parms(struct nlattr *data[],
 		*fwmark = nla_get_u32(data[IFLA_VTI_FWMARK]);
 }
 
-static int vti_newlink(struct net *src_net, struct net_device *dev,
-		       struct nlattr *tb[], struct nlattr *data[],
+static int vti_newlink(struct net_device *dev,
+		       struct rtnl_newlink_params *params,
 		       struct netlink_ext_ack *extack)
 {
+	struct nlattr **data = params->data;
 	struct ip_tunnel_parm_kern parms;
+	struct nlattr **tb = params->tb;
 	__u32 fwmark = 0;
 
 	vti_netlink_parms(data, &parms, &fwmark);
diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index dc0db5895e0e..a8b844bcfc64 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -436,11 +436,13 @@ static void ipip_netlink_parms(struct nlattr *data[],
 		*fwmark = nla_get_u32(data[IFLA_IPTUN_FWMARK]);
 }
 
-static int ipip_newlink(struct net *src_net, struct net_device *dev,
-			struct nlattr *tb[], struct nlattr *data[],
+static int ipip_newlink(struct net_device *dev,
+			struct rtnl_newlink_params *params,
 			struct netlink_ext_ack *extack)
 {
 	struct ip_tunnel *t = netdev_priv(dev);
+	struct nlattr **data = params->data;
+	struct nlattr **tb = params->tb;
 	struct ip_tunnel_encap ipencap;
 	struct ip_tunnel_parm_kern p;
 	__u32 fwmark = 0;