[PATCH net-next 4/4] netns: enable to dump full nsid translation table

[Nicolas Dichtel]

Like the previous patch, the goal is to ease to convert nsids from one
netns to another netns.
A new attribute (NETNSA_CURRENT_NSID) is added to the kernel answer when
NETNSA_TARGET_NSID is provided, thus the user can easily convert nsids.

Signed-off-by: Nicolas Dichtel <nicolas.dich...@6wind.com>
---
 include/uapi/linux/net_namespace.h |  1 +
 net/core/net_namespace.c           | 30 ++++++++++++++++++++++++------
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/net_namespace.h 
b/include/uapi/linux/net_namespace.h
index 0ed9dd61d32a..9f9956809565 100644
--- a/include/uapi/linux/net_namespace.h
+++ b/include/uapi/linux/net_namespace.h
@@ -17,6 +17,7 @@ enum {
        NETNSA_PID,
        NETNSA_FD,
        NETNSA_TARGET_NSID,
+       NETNSA_CURRENT_NSID,
        __NETNSA_MAX,
 };
 
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 92730905886c..fc568cd0b560 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -740,7 +740,7 @@ static int rtnl_net_get_size(void)
 }
 
 static int rtnl_net_fill(struct sk_buff *skb, u32 portid, u32 seq, int flags,
-                        int cmd, int nsid)
+                        int cmd, int nsid, bool add_ref, int ref_nsid)
 {
        struct nlmsghdr *nlh;
        struct rtgenmsg *rth;
@@ -755,6 +755,9 @@ static int rtnl_net_fill(struct sk_buff *skb, u32 portid, 
u32 seq, int flags,
        if (nla_put_s32(skb, NETNSA_NSID, nsid))
                goto nla_put_failure;
 
+       if (add_ref && nla_put_s32(skb, NETNSA_CURRENT_NSID, ref_nsid))
+               goto nla_put_failure;
+
        nlmsg_end(skb, nlh);
        return 0;
 
@@ -769,9 +772,10 @@ static int rtnl_net_getid(struct sk_buff *skb, struct 
nlmsghdr *nlh,
        struct net *net = sock_net(skb->sk);
        struct nlattr *tb[NETNSA_MAX + 1];
        struct net *peer, *target = net;
+       bool add_ref = false;
        struct nlattr *nla;
        struct sk_buff *msg;
-       int err, id;
+       int err, id, ref_id;
 
        err = nlmsg_parse(nlh, sizeof(struct rtgenmsg), tb, NETNSA_MAX,
                          rtnl_net_policy, extack);
@@ -809,6 +813,8 @@ static int rtnl_net_getid(struct sk_buff *skb, struct 
nlmsghdr *nlh,
                        err = PTR_ERR(target);
                        goto put_peer;
                }
+               ref_id = peernet2id(net, peer);
+               add_ref = true;
        } else {
                get_net(target);
        }
@@ -821,7 +827,7 @@ static int rtnl_net_getid(struct sk_buff *skb, struct 
nlmsghdr *nlh,
 
        id = peernet2id(target, peer);
        err = rtnl_net_fill(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0,
-                           RTM_NEWNSID, id);
+                           RTM_NEWNSID, id, add_ref, ref_id);
        if (err < 0)
                goto free_nlmsg;
 
@@ -849,14 +855,17 @@ struct rtnl_net_dump_cb {
 static int rtnl_net_dumpid_one(int id, void *peer, void *data)
 {
        struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data;
-       int ret;
+       int ref_id = 0, ret;
 
        if (net_cb->idx < net_cb->s_idx)
                goto cont;
 
+       if (net_cb->ref_net)
+               ref_id = __peernet2id(net_cb->ref_net, peer);
+
        ret = rtnl_net_fill(net_cb->skb, NETLINK_CB(net_cb->cb->skb).portid,
                            net_cb->cb->nlh->nlmsg_seq, NLM_F_MULTI,
-                           RTM_NEWNSID, id);
+                           RTM_NEWNSID, id, net_cb->ref_net, ref_id);
        if (ret < 0)
                return ret;
 
@@ -923,7 +932,16 @@ static int rtnl_net_dumpid(struct sk_buff *skb, struct 
netlink_callback *cb)
        }
 
        spin_lock_bh(&net_cb.tgt_net->nsid_lock);
+       if (net_cb.ref_net &&
+           !net_eq(net_cb.ref_net, net_cb.tgt_net) &&
+           !spin_trylock_bh(&net_cb.ref_net->nsid_lock)) {
+               err = -EAGAIN;
+               goto end;
+       }
        idr_for_each(&net_cb.tgt_net->netns_ids, rtnl_net_dumpid_one, &net_cb);
+       if (net_cb.ref_net &&
+           !net_eq(net_cb.ref_net, net_cb.tgt_net))
+               spin_unlock_bh(&net_cb.ref_net->nsid_lock);
        spin_unlock_bh(&net_cb.tgt_net->nsid_lock);
 
        cb->args[0] = net_cb.idx;
@@ -942,7 +960,7 @@ static void rtnl_net_notifyid(struct net *net, int cmd, int 
id)
        if (!msg)
                goto out;
 
-       err = rtnl_net_fill(msg, 0, 0, 0, cmd, id);
+       err = rtnl_net_fill(msg, 0, 0, 0, cmd, id, false, 0);
        if (err < 0)
                goto err_out;
 
-- 
2.18.0