ipv4: icmp: do not process ICMP_EXT_ECHOREPLY for broadcast/multicast…

… addresses

There is no point processing ICMP_EXT_ECHOREPLY for routes
which would drop ICMP_ECHOREPLY (RFC 1122 3.2.2.6, 3.2.2.8)

This seems an oversight of the initial implementation.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250226183437.1457318-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/icmp.c

@@ -1248,22 +1248,6 @@ int icmp_rcv(struct sk_buff *skb)
 		goto reason_check;
 	}
 
-	if (icmph->type == ICMP_EXT_ECHOREPLY) {
-		reason = ping_rcv(skb);
-		goto reason_check;
-	}
-
-	/*
-	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
-	 *
-	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
-	 *		  discarded.
-	 */
-	if (icmph->type > NR_ICMP_TYPES) {
-		reason = SKB_DROP_REASON_UNHANDLED_PROTO;
-		goto error;
-	}
-
 	/*
 	 *	Parse the ICMP message
 	 */
@@ -1290,6 +1274,22 @@ int icmp_rcv(struct sk_buff *skb)
 		}
 	}
 
+	if (icmph->type == ICMP_EXT_ECHOREPLY) {
+		reason = ping_rcv(skb);
+		goto reason_check;
+	}
+
+	/*
+	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
+	 *
+	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
+	 *		  discarded.
+	 */
+	if (icmph->type > NR_ICMP_TYPES) {
+		reason = SKB_DROP_REASON_UNHANDLED_PROTO;
+		goto error;
+	}
+
 	reason = icmp_pointers[icmph->type].handler(skb);
 reason_check:
 	if (!reason)  {