Merge branch 'net-improve-netns-handling-in-rtnetlink'

Xiao Liang says:

====================
net: Improve netns handling in rtnetlink

This patch series includes some netns-related improvements and fixes for
rtnetlink, to make link creation more intuitive:

 1) Creating link in another net namespace doesn't conflict with link
    names in current one.
 2) Refector rtnetlink link creation. Create link in target namespace
    directly.

So that

  # ip link add netns ns1 link-netns ns2 tun0 type gre ...

will create tun0 in ns1, rather than create it in ns2 and move to ns1.
And don't conflict with another interface named "tun0" in current netns.

Patch 01 avoids link name conflict in different netns.

To achieve 2), there're mainly 3 steps:

 - Patch 02 packs newlink() parameters into a struct, including
   the original "src_net" along with more netns context. No semantic
   changes are introduced.
 - Patch 03 ~ 09 converts device drivers to use the explicit netns
   extracted from params.
 - Patch 10 ~ 11 removes the old netns parameter, and converts
   rtnetlink to create device in target netns directly.

Patch 12 ~ 13 adds some tests for link name and link netns.

---

Please note there're some issues found in current code:

- In amt_newlink() drivers/net/amt.c:

    amt->net = net;
    ...
    amt->stream_dev = dev_get_by_index(net, ...

  Uses net, but amt_lookup_upper_dev() only searches in dev_net.
  So the AMT device may not be properly deleted if it's in a different
  netns from lower dev.

- In lowpan_newlink() in net/ieee802154/6lowpan/core.c:

    wdev = dev_get_by_index(dev_net(ldev), nla_get_u32(tb[IFLA_LINK]));

  Looks for IFLA_LINK in dev_net, but in theory the ifindex is defined
  in link netns.

And thanks to Kuniyuki for fixing related issues in gtp and pfcp:
https://lore.kernel.org/netdev/20250110014754.33847-1-kuniyu@amazon.com/

v9: https://lore.kernel.org/20250210133002.883422-1-shaw.leon@gmail.com
v8: https://lore.kernel.org/20250113143719.7948-1-shaw.leon@gmail.com
v7: https://lore.kernel.org/20250104125732.17335-1-shaw.leon@gmail.com
v6: https://lore.kernel.org/20241218130909.2173-1-shaw.leon@gmail.com
v5: https://lore.kernel.org/20241209140151.231257-1-shaw.leon@gmail.com
v4: https://lore.kernel.org/20241118143244.1773-1-shaw.leon@gmail.com
v3: https://lore.kernel.org/20241113125715.150201-1-shaw.leon@gmail.com
v2: https://lore.kernel.org/20241107133004.7469-1-shaw.leon@gmail.com
v1: https://lore.kernel.org/20241023023146.372653-1-shaw.leon@gmail.com
====================

Link: https://patch.msgid.link/20250219125039.18024-1-shaw.leon@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 30 insertions, 17 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index c9f11a046c26..26d15f907551 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;
@@ -1411,13 +1413,16 @@ static int ipgre_newlink(struct net *src_net, struct net_device *dev,
 	err = ipgre_netlink_parms(dev, data, tb, &p, &fwmark);
 	if (err < 0)
 		return err;
-	return ip_tunnel_newlink(dev, tb, &p, fwmark);
+	return ip_tunnel_newlink(params->link_net ? : dev_net(dev), 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;
@@ -1429,7 +1434,8 @@ static int erspan_newlink(struct net *src_net, struct net_device *dev,
 	err = erspan_netlink_parms(dev, data, tb, &p, &fwmark);
 	if (err)
 		return err;
-	return ip_tunnel_newlink(dev, tb, &p, fwmark);
+	return ip_tunnel_newlink(params->link_net ? : dev_net(dev), dev, tb, &p,
+				 fwmark);
 }
 
 static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
@@ -1697,6 +1703,7 @@ 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 = { .src_net = net };
 	struct nlattr *tb[IFLA_MAX + 1];
 	struct net_device *dev;
 	LIST_HEAD(list_kill);
@@ -1704,6 +1711,7 @@ 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 +1722,7 @@ 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_tunnel.c b/net/ipv4/ip_tunnel.c
index 09b73acf037a..011f2a5aab3b 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -1213,11 +1213,11 @@ void ip_tunnel_delete_nets(struct list_head *net_list, unsigned int id,
 }
 EXPORT_SYMBOL_GPL(ip_tunnel_delete_nets);
 
-int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
-		      struct ip_tunnel_parm_kern *p, __u32 fwmark)
+int ip_tunnel_newlink(struct net *net, struct net_device *dev,
+		      struct nlattr *tb[], struct ip_tunnel_parm_kern *p,
+		      __u32 fwmark)
 {
 	struct ip_tunnel *nt;
-	struct net *net = dev_net(dev);
 	struct ip_tunnel_net *itn;
 	int mtu;
 	int err;
@@ -1326,7 +1326,6 @@ int ip_tunnel_init(struct net_device *dev)
 	}
 
 	tunnel->dev = dev;
-	tunnel->net = dev_net(dev);
 	strscpy(tunnel->parms.name, dev->name);
 	iph->version		= 4;
 	iph->ihl		= 5;
diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index f0b4419cef34..159b4473290e 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -575,15 +575,18 @@ 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);
-	return ip_tunnel_newlink(dev, tb, &parms, fwmark);
+	return ip_tunnel_newlink(params->link_net ? : dev_net(dev), dev, tb,
+				 &parms, fwmark);
 }
 
 static int vti_changelink(struct net_device *dev, struct nlattr *tb[],
diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index dc0db5895e0e..bab0bf90c908 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;
@@ -453,7 +455,8 @@ static int ipip_newlink(struct net *src_net, struct net_device *dev,
 	}
 
 	ipip_netlink_parms(data, &p, &t->collect_md, &fwmark);
-	return ip_tunnel_newlink(dev, tb, &p, fwmark);
+	return ip_tunnel_newlink(params->link_net ? : dev_net(dev), dev, tb, &p,
+				 fwmark);
 }
 
 static int ipip_changelink(struct net_device *dev, struct nlattr *tb[],