inet: convert inet_ehash_secret and ipv6_hash_secret to net_get_random_once

Initialize the ehash and ipv6_hash_secrets with net_get_random_once.

Each compilation unit gets its own secret now:
  ipv4/inet_hashtables.o
  ipv4/udp.o
  ipv6/inet6_hashtables.o
  ipv6/udp.o
  rds/connection.o

The functions still get inlined into the hashing functions. In the fast
path we have at most two (needed in ipv6) if (unlikely(...)).

Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 9 insertions, 28 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 4049906..9433a61 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -245,29 +245,6 @@ out:
 }
 EXPORT_SYMBOL(inet_listen);
 
-u32 inet_ehash_secret __read_mostly;
-EXPORT_SYMBOL(inet_ehash_secret);
-
-u32 ipv6_hash_secret __read_mostly;
-EXPORT_SYMBOL(ipv6_hash_secret);
-
-/*
- * inet_ehash_secret must be set exactly once, and to a non nul value
- * ipv6_hash_secret must be set exactly once.
- */
-void build_ehash_secret(void)
-{
-	u32 rnd;
-
-	do {
-		get_random_bytes(&rnd, sizeof(rnd));
-	} while (rnd == 0);
-
-	if (cmpxchg(&inet_ehash_secret, 0, rnd) == 0)
-		get_random_bytes(&ipv6_hash_secret, sizeof(ipv6_hash_secret));
-}
-EXPORT_SYMBOL(build_ehash_secret);
-
 /*
  *	Create an inet socket.
  */
@@ -284,10 +261,6 @@ static int inet_create(struct net *net, struct socket *sock, int protocol,
 	int try_loading_module = 0;
 	int err;
 
-	if (unlikely(!inet_ehash_secret))
-		if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
-			build_ehash_secret();
-
 	sock->state = SS_UNCONNECTED;
 
 	/* Look for the requested type/protocol pair. */
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 18aa668..8b9cf27 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -28,6 +28,10 @@ static unsigned int inet_ehashfn(struct net *net, const __be32 laddr,
 				 const __u16 lport, const __be32 faddr,
 				 const __be16 fport)
 {
+	static u32 inet_ehash_secret __read_mostly;
+
+	net_get_random_once(&inet_ehash_secret, sizeof(inet_ehash_secret));
+
 	return __inet_ehashfn(laddr, lport, faddr, fport,
 			      inet_ehash_secret + net_hash_mix(net));
 }
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index b4437c7..89909dd 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -411,8 +411,12 @@ static unsigned int udp_ehashfn(struct net *net, const __be32 laddr,
 				 const __u16 lport, const __be32 faddr,
 				 const __be16 fport)
 {
+	static u32 udp_ehash_secret __read_mostly;
+
+	net_get_random_once(&udp_ehash_secret, sizeof(udp_ehash_secret));
+
 	return __inet_ehashfn(laddr, lport, faddr, fport,
-			      inet_ehash_secret + net_hash_mix(net));
+			      udp_ehash_secret + net_hash_mix(net));
 }