inet: use xa_array iterator to implement inet_netconf_dump_devconf()

1) inet_netconf_dump_devconf() can run under RCU protection
   instead of RTNL.

2) properly return 0 at the end of a dump, avoiding an
   an extra recvmsg() system call.

3) Do not use inet_base_seq() anymore, for_each_netdev_dump()
   has nice properties. Restarting a GETDEVCONF dump if a device has
   been added/removed or if net->ipv4.dev_addr_genid has changed is moot.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240227092411.2315725-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index f045a34..af741af 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2267,11 +2267,13 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 {
        const struct nlmsghdr *nlh = cb->nlh;
        struct net *net = sock_net(skb->sk);
-       int h, s_h;
-       int idx, s_idx;
+       struct {
+               unsigned long ifindex;
+               unsigned int all_default;
+       } *ctx = (void *)cb->ctx;
+       const struct in_device *in_dev;
        struct net_device *dev;
-       struct in_device *in_dev;
-       struct hlist_head *head;
+       int err = 0;
 
        if (cb->strict_check) {
                struct netlink_ext_ack *extack = cb->extack;
@@ -2288,64 +2290,47 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
                }
        }
 
-       s_h = cb->args[0];
-       s_idx = idx = cb->args[1];
-
-       for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
-               idx = 0;
-               head = &net->dev_index_head[h];
-               rcu_read_lock();
-               cb->seq = inet_base_seq(net);
-               hlist_for_each_entry_rcu(dev, head, index_hlist) {
-                       if (idx < s_idx)
-                               goto cont;
-                       in_dev = __in_dev_get_rcu(dev);
-                       if (!in_dev)
-                               goto cont;
-
-                       if (inet_netconf_fill_devconf(skb, dev->ifindex,
-                                                     &in_dev->cnf,
-                                                     NETLINK_CB(cb->skb).portid,
-                                                     nlh->nlmsg_seq,
-                                                     RTM_NEWNETCONF,
-                                                     NLM_F_MULTI,
-                                                     NETCONFA_ALL) < 0) {
-                               rcu_read_unlock();
-                               goto done;
-                       }
-                       nl_dump_check_consistent(cb, nlmsg_hdr(skb));
-cont:
-                       idx++;
-               }
-               rcu_read_unlock();
+       rcu_read_lock();
+       for_each_netdev_dump(net, dev, ctx->ifindex) {
+               in_dev = __in_dev_get_rcu(dev);
+               if (!in_dev)
+                       continue;
+               err = inet_netconf_fill_devconf(skb, dev->ifindex,
+                                               &in_dev->cnf,
+                                               NETLINK_CB(cb->skb).portid,
+                                               nlh->nlmsg_seq,
+                                               RTM_NEWNETCONF, NLM_F_MULTI,
+                                               NETCONFA_ALL);
+               if (err < 0)
+                       goto done;
        }
-       if (h == NETDEV_HASHENTRIES) {
-               if (inet_netconf_fill_devconf(skb, NETCONFA_IFINDEX_ALL,
-                                             net->ipv4.devconf_all,
-                                             NETLINK_CB(cb->skb).portid,
-                                             nlh->nlmsg_seq,
-                                             RTM_NEWNETCONF, NLM_F_MULTI,
-                                             NETCONFA_ALL) < 0)
+       if (ctx->all_default == 0) {
+               err = inet_netconf_fill_devconf(skb, NETCONFA_IFINDEX_ALL,
+                                               net->ipv4.devconf_all,
+                                               NETLINK_CB(cb->skb).portid,
+                                               nlh->nlmsg_seq,
+                                               RTM_NEWNETCONF, NLM_F_MULTI,
+                                               NETCONFA_ALL);
+               if (err < 0)
                        goto done;
-               else
-                       h++;
-       }
-       if (h == NETDEV_HASHENTRIES + 1) {
-               if (inet_netconf_fill_devconf(skb, NETCONFA_IFINDEX_DEFAULT,
-                                             net->ipv4.devconf_dflt,
-                                             NETLINK_CB(cb->skb).portid,
-                                             nlh->nlmsg_seq,
-                                             RTM_NEWNETCONF, NLM_F_MULTI,
-                                             NETCONFA_ALL) < 0)
+               ctx->all_default++;
+       }
+       if (ctx->all_default == 1) {
+               err = inet_netconf_fill_devconf(skb, NETCONFA_IFINDEX_DEFAULT,
+                                               net->ipv4.devconf_dflt,
+                                               NETLINK_CB(cb->skb).portid,
+                                               nlh->nlmsg_seq,
+                                               RTM_NEWNETCONF, NLM_F_MULTI,
+                                               NETCONFA_ALL);
+               if (err < 0)
                        goto done;
-               else
-                       h++;
+               ctx->all_default++;
        }
 done:
-       cb->args[0] = h;
-       cb->args[1] = idx;
-
-       return skb->len;
+       if (err < 0 && likely(skb->len))
+               err = skb->len;
+       rcu_read_unlock();
+       return err;
 }
 
 #ifdef CONFIG_SYSCTL
@@ -2829,5 +2814,5 @@ void __init devinet_init(void)
        rtnl_register(PF_INET, RTM_GETADDR, NULL, inet_dump_ifaddr, 0);
        rtnl_register(PF_INET, RTM_GETNETCONF, inet_netconf_get_devconf,
                      inet_netconf_dump_devconf,
-                     RTNL_FLAG_DOIT_UNLOCKED);
+                     RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED);
 }