Re: [PATCH net-next 4/4] inetpeer: do not get a refcount in inet_getpeer()

[Ido Schimmel <idosch@idosch.org>]

On Fri, Dec 13, 2024 at 01:02:12PM +0000, Eric Dumazet wrote:
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index 5eeb9f569a706cf2766d74bcf1a667c8930804f2..7a1b1af2edcae0b0648ef3c3411b4ef36e6d9b14 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -322,11 +322,11 @@ static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
>  		goto out;
>  
>  	vif = l3mdev_master_ifindex(dst->dev);
> +	rcu_read_lock();
>  	peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif);
>  	rc = inet_peer_xrlim_allow(peer,
>  				   READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
> -	if (peer)
> -		inet_putpeer(peer);
> +	rcu_read_unlock();
>  out:
>  	if (!rc)
>  		__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);

Maybe convert l3mdev_master_ifindex() to l3mdev_master_ifindex_rcu() and
move it into the RCU critical section?

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 7a1b1af2edca..094084b61bff 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -312,7 +312,6 @@ static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
        struct dst_entry *dst = &rt->dst;
        struct inet_peer *peer;
        bool rc = true;
-       int vif;
 
        if (!apply_ratelimit)
                return true;
@@ -321,9 +320,9 @@ static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
        if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
                goto out;
 
-       vif = l3mdev_master_ifindex(dst->dev);
        rcu_read_lock();
-       peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif);
+       peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr,
+                              l3mdev_master_ifindex_rcu(dst->dev));
        rc = inet_peer_xrlim_allow(peer,
                                   READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
        rcu_read_unlock();

[...]

> @@ -975,9 +975,9 @@ static int ip_error(struct sk_buff *skb)
>  		break;
>  	}
>  
> +	rcu_read_lock();
>  	peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr,
>  			       l3mdev_master_ifindex(skb->dev));
> -
>  	send = true;
>  	if (peer) {
>  		now = jiffies;

And here?

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d2086648dcf1..9f9d4e6ea1b9 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -977,7 +977,7 @@ static int ip_error(struct sk_buff *skb)
 
        rcu_read_lock();
        peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr,
-                              l3mdev_master_ifindex(skb->dev));
+                              l3mdev_master_ifindex_rcu(skb->dev));
        send = true;
        if (peer) {
                now = jiffies;