netns: notify netns id events

With this patch, netns ids that are created and deleted are advertised into the
group RTNLGRP_NSID.

Because callers of rtnl_net_notifyid() already know the id of the peer, there is
no need to call __peernet2id() in rtnl_net_fill().

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 48 insertions, 8 deletions

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index bea910f924dd..974db03f7b1a 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -134,6 +134,8 @@ enum {
 
         RTM_NEWNSID = 88,
 #define RTM_NEWNSID RTM_NEWNSID
+        RTM_DELNSID = 89,
+#define RTM_DELNSID RTM_DELNSID
         RTM_GETNSID = 90,
 #define RTM_GETNSID RTM_GETNSID
 
@@ -635,6 +637,8 @@ enum rtnetlink_groups {
 #define RTNLGRP_MDB             RTNLGRP_MDB
         RTNLGRP_MPLS_ROUTE,
 #define RTNLGRP_MPLS_ROUTE      RTNLGRP_MPLS_ROUTE
+        RTNLGRP_NSID,
+#define RTNLGRP_NSID            RTNLGRP_NSID
         __RTNLGRP_MAX
 };
 #define RTNLGRP_MAX     (__RTNLGRP_MAX - 1)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index be28afccfbbb..b3b5f22f0e90 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -148,9 +148,11 @@ static void ops_free_list(const struct pernet_operations *ops,
         }
 }
 
+static void rtnl_net_notifyid(struct net *net, struct net *peer, int cmd,
+                              int id);
 static int alloc_netid(struct net *net, struct net *peer, int reqid)
 {
-        int min = 0, max = 0;
+        int min = 0, max = 0, id;
 
         ASSERT_RTNL();
 
@@ -159,7 +161,11 @@ static int alloc_netid(struct net *net, struct net *peer, int reqid)
                 max = reqid + 1;
         }
 
-        return idr_alloc(&net->netns_ids, peer, min, max, GFP_KERNEL);
+        id = idr_alloc(&net->netns_ids, peer, min, max, GFP_KERNEL);
+        if (id >= 0)
+                rtnl_net_notifyid(net, peer, RTM_NEWNSID, id);
+
+        return id;
 }
 
 /* This function is used by idr_for_each(). If net is equal to peer, the
@@ -359,8 +365,10 @@ static void cleanup_net(struct work_struct *work)
                 for_each_net(tmp) {
                         int id = __peernet2id(tmp, net, false);
 
-                        if (id >= 0)
+                        if (id >= 0) {
+                                rtnl_net_notifyid(tmp, net, RTM_DELNSID, id);
                                 idr_remove(&tmp->netns_ids, id);
+                        }
                 }
                 idr_destroy(&net->netns_ids);
 
@@ -531,7 +539,8 @@ static int rtnl_net_get_size(void)
 }
 
 static int rtnl_net_fill(struct sk_buff *skb, u32 portid, u32 seq, int flags,
-                         int cmd, struct net *net, struct net *peer)
+                         int cmd, struct net *net, struct net *peer,
+                         int nsid)
 {
         struct nlmsghdr *nlh;
         struct rtgenmsg *rth;
@@ -546,9 +555,13 @@ static int rtnl_net_fill(struct sk_buff *skb, u32 portid, u32 seq, int flags,
         rth = nlmsg_data(nlh);
         rth->rtgen_family = AF_UNSPEC;
 
-        id = __peernet2id(net, peer, false);
-        if  (id < 0)
-                id = NETNSA_NSID_NOT_ASSIGNED;
+        if (nsid >= 0) {
+                id = nsid;
+        } else {
+                id = __peernet2id(net, peer, false);
+                if  (id < 0)
+                        id = NETNSA_NSID_NOT_ASSIGNED;
+        }
         if (nla_put_s32(skb, NETNSA_NSID, id))
                 goto nla_put_failure;
 
@@ -589,7 +602,7 @@ static int rtnl_net_getid(struct sk_buff *skb, struct nlmsghdr *nlh)
         }
 
         err = rtnl_net_fill(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0,
-                            RTM_GETNSID, net, peer);
+                            RTM_GETNSID, net, peer, -1);
         if (err < 0)
                 goto err_out;
 
@@ -603,6 +616,29 @@ out:
         return err;
 }
 
+static void rtnl_net_notifyid(struct net *net, struct net *peer, int cmd,
+                              int id)
+{
+        struct sk_buff *msg;
+        int err = -ENOMEM;
+
+        msg = nlmsg_new(rtnl_net_get_size(), GFP_KERNEL);
+        if (!msg)
+                goto out;
+
+        err = rtnl_net_fill(msg, 0, 0, 0, cmd, net, peer, id);
+        if (err < 0)
+                goto err_out;
+
+        rtnl_notify(msg, net, 0, RTNLGRP_NSID, NULL, 0);
+        return;
+
+err_out:
+        nlmsg_free(msg);
+out:
+        rtnl_set_sk_err(net, RTNLGRP_NSID, err);
+}
+
 static int __init net_ns_init(void)
 {
         struct net_generic *ng;