net: defer net_secret[] initialization

Instead of feeding net_secret[] at boot time, defer the init
at the point first socket is created.

This permits some platforms to use better entropy sources than
the ones available at boot time.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/secure_seq.h

@@ -3,6 +3,7 @@
 
 #include <linux/types.h>
 
+extern void net_secret_init(void);
 extern __u32 secure_ip_id(__be32 daddr);
 extern __u32 secure_ipv6_id(const __be32 daddr[4]);
 extern u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);

net/core/secure_seq.c

@@ -12,12 +12,10 @@
 
 static u32 net_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
 
-static int __init net_secret_init(void)
+void net_secret_init(void)
 {
 	get_random_bytes(net_secret, sizeof(net_secret));
-	return 0;
 }
-late_initcall(net_secret_init);
 
 #ifdef CONFIG_INET
 static u32 seq_scale(u32 seq)

net/ipv4/af_inet.c

@@ -114,6 +114,7 @@
 #include <net/inet_common.h>
 #include <net/xfrm.h>
 #include <net/net_namespace.h>
+#include <net/secure_seq.h>
 #ifdef CONFIG_IP_MROUTE
 #include <linux/mroute.h>
 #endif
@@ -262,8 +263,10 @@ void build_ehash_secret(void)
 		get_random_bytes(&rnd, sizeof(rnd));
 	} while (rnd == 0);
 
-	if (cmpxchg(&inet_ehash_secret, 0, rnd) == 0)
+	if (cmpxchg(&inet_ehash_secret, 0, rnd) == 0) {
 		get_random_bytes(&ipv6_hash_secret, sizeof(ipv6_hash_secret));
+		net_secret_init();
+	}
 }
 EXPORT_SYMBOL(build_ehash_secret);