netdev - [PATCH net-next 12/13] rtnetlink: make rtnl_fill_link

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Message-ID: <20240221105915.829140-13-edumazet@google.com>
Date: Wed, 21 Feb 2024 10:59:14 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 12/13] rtnetlink: make rtnl_fill_link_ifmap() RCU ready

Use READ_ONCE() to read the following device fields:

	dev->mem_start
	dev->mem_end
	dev->base_addr
	dev->irq
	dev->dma
	dev->if_port

Provide IFLA_MAP attribute only if at least one of these fields
is not zero. This saves some space in the output skb for most devices.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/rtnetlink.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1b26dfa5668d22fb2e30ceefbf143e98df13ae29..b91ec216c593aaebf97ea69aa0d2d265ab61c098 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1455,19 +1455,21 @@ static noinline_for_stack int rtnl_fill_vf(struct sk_buff *skb,
 	return 0;
 }
 
-static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
+static int rtnl_fill_link_ifmap(struct sk_buff *skb,
+				const struct net_device *dev)
 {
 	struct rtnl_link_ifmap map;
 
 	memset(&map, 0, sizeof(map));
-	map.mem_start   = dev->mem_start;
-	map.mem_end     = dev->mem_end;
-	map.base_addr   = dev->base_addr;
-	map.irq         = dev->irq;
-	map.dma         = dev->dma;
-	map.port        = dev->if_port;
-
-	if (nla_put_64bit(skb, IFLA_MAP, sizeof(map), &map, IFLA_PAD))
+	map.mem_start = READ_ONCE(dev->mem_start);
+	map.mem_end   = READ_ONCE(dev->mem_end);
+	map.base_addr = READ_ONCE(dev->base_addr);
+	map.irq       = READ_ONCE(dev->irq);
+	map.dma       = READ_ONCE(dev->dma);
+	map.port      = READ_ONCE(dev->if_port);
+	/* Only report non zero information. */
+	if (memchr_inv(&map, 0, sizeof(map)) &&
+	    nla_put_64bit(skb, IFLA_MAP, sizeof(map), &map, IFLA_PAD))
 		return -EMSGSIZE;
 
 	return 0;
@@ -1875,9 +1877,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 			goto nla_put_failure;
 	}
 
-	if (rtnl_fill_link_ifmap(skb, dev))
-		goto nla_put_failure;
-
 	if (dev->addr_len) {
 		if (nla_put(skb, IFLA_ADDRESS, dev->addr_len, dev->dev_addr) ||
 		    nla_put(skb, IFLA_BROADCAST, dev->addr_len, dev->broadcast))
@@ -1927,6 +1926,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 	rcu_read_lock();
 	if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
 		goto nla_put_failure_rcu;
+	if (rtnl_fill_link_ifmap(skb, dev))
+		goto nla_put_failure_rcu;
+
 	rcu_read_unlock();
 
 	if (rtnl_fill_prop_list(skb, dev))
-- 
2.44.0.rc0.258.g7320e95886-goog