netdev - Re: [PATCH net-next 13/13] ipv6: use xa_array iterator to implement inet6_netconf_dump

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Date: Mon, 26 Feb 2024 17:55:47 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
	eric.dumazet@...il.com
Subject: Re: [PATCH net-next 13/13] ipv6: use xa_array iterator to implement
 inet6_netconf_dump_devconf()

Mon, Feb 26, 2024 at 04:50:55PM CET, edumazet@...gle.com wrote:
>1) inet6_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 inet6_base_seq() anymore, for_each_netdev_dump()
>   has nice properties. Restarting a GETDEVCONF dump if a device has
>   been added/removed or if net->ipv6.dev_addr_genid has changed is moot.
>
>Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>---
> net/ipv6/addrconf.c | 103 +++++++++++++++++++-------------------------
> 1 file changed, 44 insertions(+), 59 deletions(-)
>
>diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>index 74c33b132073934290632a953bce8ee6a5124ca9..08b4728733e3ed16d139d2bd4b50328552b3c27f 100644
>--- a/net/ipv6/addrconf.c
>+++ b/net/ipv6/addrconf.c
>@@ -727,17 +727,18 @@ static u32 inet6_base_seq(const struct net *net)
> 	return res;
> }
> 
>-
> static int inet6_netconf_dump_devconf(struct sk_buff *skb,
> 				      struct netlink_callback *cb)
> {
> 	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;
> 	struct net_device *dev;
> 	struct inet6_dev *idev;
>-	struct hlist_head *head;
>+	int err = 0;
> 
> 	if (cb->strict_check) {
> 		struct netlink_ext_ack *extack = cb->extack;
>@@ -754,64 +755,47 @@ static int inet6_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 = inet6_base_seq(net);
>-		hlist_for_each_entry_rcu(dev, head, index_hlist) {
>-			if (idx < s_idx)
>-				goto cont;
>-			idev = __in6_dev_get(dev);
>-			if (!idev)
>-				goto cont;
>-
>-			if (inet6_netconf_fill_devconf(skb, dev->ifindex,
>-						       &idev->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) {
>+		idev = __in6_dev_get(dev);
>+		if (!idev)
>+			continue;
>+		err = inet6_netconf_fill_devconf(skb, dev->ifindex,
>+					         &idev->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 (inet6_netconf_fill_devconf(skb, NETCONFA_IFINDEX_ALL,
>-					       net->ipv6.devconf_all,
>-					       NETLINK_CB(cb->skb).portid,
>-					       nlh->nlmsg_seq,
>-					       RTM_NEWNETCONF, NLM_F_MULTI,
>-					       NETCONFA_ALL) < 0)
>+	if (ctx->all_default == 0) {
>+		err = inet6_netconf_fill_devconf(skb, NETCONFA_IFINDEX_ALL,
>+						 net->ipv6.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 (inet6_netconf_fill_devconf(skb, NETCONFA_IFINDEX_DEFAULT,
>-					       net->ipv6.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 = inet6_netconf_fill_devconf(skb, NETCONFA_IFINDEX_DEFAULT,
>+						 net->ipv6.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;
>+done:	if (err < 0 && likely(skb->len))

It is common to not mix label and other statement on the same line,
could you split?

Otherwise the patch and the set looks good to me. Thanks!


>+		err = skb->len;
>+	rcu_read_unlock();
>+	return err;
> }
> 
> #ifdef CONFIG_SYSCTL
>@@ -7503,7 +7487,8 @@ int __init addrconf_init(void)
> 	err = rtnl_register_module(THIS_MODULE, PF_INET6, RTM_GETNETCONF,
> 				   inet6_netconf_get_devconf,
> 				   inet6_netconf_dump_devconf,
>-				   RTNL_FLAG_DOIT_UNLOCKED);
>+				   RTNL_FLAG_DOIT_UNLOCKED |
>+				   RTNL_FLAG_DUMP_UNLOCKED);
> 	if (err < 0)
> 		goto errout;
> 	err = ipv6_addr_label_rtnl_register();
>-- 
>2.44.0.rc1.240.g4c46232300-goog
>
>