[PATCH v3 3/5] mac80211_hwsim: add generation count for netlink dump operation

[Benjamin Beichler]

Make the dump operation aware of changes on radio list and corresponding
inconsistent dumps. Change the dump iteration to be independent from
increasing radio indices on radio list.

Signed-off-by: Benjamin Beichler <benjamin.beich...@uni-rostock.de>
---
 drivers/net/wireless/mac80211_hwsim.c | 43 ++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c 
b/drivers/net/wireless/mac80211_hwsim.c
index 55d25e3fbbcc..2d4e97b6dc8f 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -493,6 +493,7 @@ static LIST_HEAD(hwsim_radios);
 static struct workqueue_struct *hwsim_wq;
 static struct rhashtable hwsim_radios_rht;
 static int hwsim_radio_idx;
+static int hwsim_radios_generation = 1;
 
 static struct platform_driver mac80211_hwsim_driver = {
        .driver = {
@@ -2758,6 +2759,7 @@ static int mac80211_hwsim_new_radio(struct genl_info 
*info,
        }
 
        list_add_tail(&data->list, &hwsim_radios);
+       hwsim_radios_generation++;
        spin_unlock_bh(&hwsim_radio_lock);
 
        if (idx > 0)
@@ -3209,6 +3211,7 @@ static int hwsim_del_radio_nl(struct sk_buff *msg, struct 
genl_info *info)
                list_del(&data->list);
                rhashtable_remove_fast(&hwsim_radios_rht, &data->rht,
                                       hwsim_rht_params);
+               hwsim_radios_generation++;
                spin_unlock_bh(&hwsim_radio_lock);
                mac80211_hwsim_del_radio(data, wiphy_name(data->hw->wiphy),
                                         info);
@@ -3265,19 +3268,34 @@ static int hwsim_get_radio_nl(struct sk_buff *msg, 
struct genl_info *info)
 static int hwsim_dump_radio_nl(struct sk_buff *skb,
                               struct netlink_callback *cb)
 {
-       int idx = cb->args[0];
-       struct mac80211_hwsim_data *data = NULL;
-       int res;
+       struct mac80211_hwsim_data *data =
+                       (struct mac80211_hwsim_data *)cb->args[0];
+       int res = 0;
+       void *hdr;
 
        spin_lock_bh(&hwsim_radio_lock);
+       cb->seq = hwsim_radios_generation;
+
+       /* list changed, send msg with dump interrupted header*/
+       if (cb->prev_seq && cb->seq != cb->prev_seq) {
+               hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
+                                 cb->nlh->nlmsg_seq, &hwsim_genl_family,
+                                 NLM_F_MULTI, HWSIM_CMD_GET_RADIO);
+               if (!hdr)
+                       res = -EMSGSIZE;
+               genl_dump_check_consistent(cb, hdr);
+               genlmsg_end(skb, hdr);
+               goto cleanup;
+       }
 
-       if (idx == hwsim_radio_idx)
-               goto done;
+       /* iterator is at head again, finish*/
+       if (data && &data->list == &hwsim_radios)
+               goto cleanup;
 
-       list_for_each_entry(data, &hwsim_radios, list) {
-               if (data->idx < idx)
-                       continue;
+       /* data will NULL or valid since we quit, if list changed */
+       data = list_prepare_entry(data, &hwsim_radios, list);
 
+       list_for_each_entry_continue(data, &hwsim_radios, list) {
                if (!net_eq(wiphy_net(data->hw->wiphy), sock_net(skb->sk)))
                        continue;
 
@@ -3287,15 +3305,13 @@ static int hwsim_dump_radio_nl(struct sk_buff *skb,
                                               NLM_F_MULTI);
                if (res < 0)
                        break;
-
-               idx = data->idx + 1;
        }
 
-       cb->args[0] = idx;
+       cb->args[0] = (long)data;
 
-done:
+cleanup:
        spin_unlock_bh(&hwsim_radio_lock);
-       return skb->len;
+       return (res)? res : skb->len;
 }
 
 /* Generic Netlink operations array */
@@ -3353,6 +3369,7 @@ static void destroy_radio(struct work_struct *work)
        struct mac80211_hwsim_data *data =
                container_of(work, struct mac80211_hwsim_data, destroy_work);
 
+       hwsim_radios_generation++;
        mac80211_hwsim_del_radio(data, wiphy_name(data->hw->wiphy), NULL);
 }
 
-- 
2.15.1