icmp: move icmp_global.credit and icmp_global.stamp to per netns storage

Host wide ICMP ratelimiter should be per netns, to provide better isolation.

Following patch in this series makes the sysctl per netns.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20240829144641.3880376-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/ip.h

@@ -794,8 +794,8 @@ static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
 	ip_cmsg_recv_offset(msg, skb->sk, skb, 0, 0);
 }
 
-bool icmp_global_allow(void);
-void icmp_global_consume(void);
+bool icmp_global_allow(struct net *net);
+void icmp_global_consume(struct net *net);
 
 extern int sysctl_icmp_msgs_per_sec;
 extern int sysctl_icmp_msgs_burst;

include/net/netns/ipv4.h

@@ -122,7 +122,8 @@ struct netns_ipv4 {
 	u8 sysctl_icmp_errors_use_inbound_ifaddr;
 	int sysctl_icmp_ratelimit;
 	int sysctl_icmp_ratemask;
-
+	atomic_t icmp_global_credit;
+	u32 icmp_global_stamp;
 	u32 ip_rt_min_pmtu;
 	int ip_rt_mtu_expires;
 	int ip_rt_min_advmss;

net/ipv4/icmp.c

@@ -223,19 +223,15 @@ static inline void icmp_xmit_unlock(struct sock *sk)
 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
 int sysctl_icmp_msgs_burst __read_mostly = 50;
 
-static struct {
-	atomic_t	credit;
-	u32		stamp;
-} icmp_global;
-
 /**
  * icmp_global_allow - Are we allowed to send one more ICMP message ?
+ * @net: network namespace
  *
  * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
  * Returns false if we reached the limit and can not send another packet.
  * Works in tandem with icmp_global_consume().
  */
-bool icmp_global_allow(void)
+bool icmp_global_allow(struct net *net)
 {
 	u32 delta, now, oldstamp;
 	int incr, new, old;
@@ -244,11 +240,11 @@ bool icmp_global_allow(void)
 	 * Then later icmp_global_consume() could consume more credits,
 	 * this is an acceptable race.
 	 */
-	if (atomic_read(&icmp_global.credit) > 0)
+	if (atomic_read(&net->ipv4.icmp_global_credit) > 0)
 		return true;
 
 	now = jiffies;
-	oldstamp = READ_ONCE(icmp_global.stamp);
+	oldstamp = READ_ONCE(net->ipv4.icmp_global_stamp);
 	delta = min_t(u32, now - oldstamp, HZ);
 	if (delta < HZ / 50)
 		return false;
@@ -257,23 +253,23 @@ bool icmp_global_allow(void)
 	if (!incr)
 		return false;
 
-	if (cmpxchg(&icmp_global.stamp, oldstamp, now) == oldstamp) {
-		old = atomic_read(&icmp_global.credit);
+	if (cmpxchg(&net->ipv4.icmp_global_stamp, oldstamp, now) == oldstamp) {
+		old = atomic_read(&net->ipv4.icmp_global_credit);
 		do {
 			new = min(old + incr, READ_ONCE(sysctl_icmp_msgs_burst));
-		} while (!atomic_try_cmpxchg(&icmp_global.credit, &old, new));
+		} while (!atomic_try_cmpxchg(&net->ipv4.icmp_global_credit, &old, new));
 	}
 	return true;
 }
 EXPORT_SYMBOL(icmp_global_allow);
 
-void icmp_global_consume(void)
+void icmp_global_consume(struct net *net)
 {
 	int credits = get_random_u32_below(3);
 
 	/* Note: this might make icmp_global.credit negative. */
 	if (credits)
-		atomic_sub(credits, &icmp_global.credit);
+		atomic_sub(credits, &net->ipv4.icmp_global_credit);
 }
 EXPORT_SYMBOL(icmp_global_consume);
 
@@ -299,7 +295,7 @@ static bool icmpv4_global_allow(struct net *net, int type, int code,
 	if (icmpv4_mask_allow(net, type, code))
 		return true;
 
-	if (icmp_global_allow()) {
+	if (icmp_global_allow(net)) {
 		*apply_ratelimit = true;
 		return true;
 	}
@@ -337,7 +333,7 @@ static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
 	if (!rc)
 		__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
 	else
-		icmp_global_consume();
+		icmp_global_consume(net);
 	return rc;
 }
 

net/ipv6/icmp.c

@@ -181,7 +181,7 @@ static bool icmpv6_global_allow(struct net *net, int type,
 	if (icmpv6_mask_allow(net, type))
 		return true;
 
-	if (icmp_global_allow()) {
+	if (icmp_global_allow(net)) {
 		*apply_ratelimit = true;
 		return true;
 	}
@@ -231,7 +231,7 @@ static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
 		__ICMP6_INC_STATS(net, ip6_dst_idev(dst),
 				  ICMP6_MIB_RATELIMITHOST);
 	else
-		icmp_global_consume();
+		icmp_global_consume(net);
 	dst_release(dst);
 	return res;
 }