inet: move inet_ehash_secret and udp_ehash_secret into net_hotdata

"struct net_protocol" has a 32bit hole in 32bit arches.

Use it to store the 32bit secret used by UDP and TCP,
to increase cache locality in rx path.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240306160031.874438-15-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/hotdata.h

@@ -36,6 +36,9 @@ struct net_hotdata {
 	int			dev_rx_weight;
 };
 
+#define inet_ehash_secret	net_hotdata.tcp_protocol.secret
+#define udp_ehash_secret	net_hotdata.udp_protocol.secret
+
 extern struct net_hotdata net_hotdata;
 
 #endif /* _NET_HOTDATA_H */

include/net/protocol.h

@@ -46,6 +46,7 @@ struct net_protocol {
 				 * socket lookup?
 				 */
 				icmp_strict_tag_validation:1;
+	u32			secret;
 };
 
 #if IS_ENABLED(CONFIG_IPV6)

net/ipv4/inet_hashtables.c

@@ -24,6 +24,7 @@
 #include <net/inet6_hashtables.h>
 #endif
 #include <net/secure_seq.h>
+#include <net/hotdata.h>
 #include <net/ip.h>
 #include <net/tcp.h>
 #include <net/sock_reuseport.h>
@@ -32,8 +33,6 @@ u32 inet_ehashfn(const 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,

net/ipv4/udp.c

@@ -411,8 +411,6 @@ INDIRECT_CALLABLE_SCOPE
 u32 udp_ehashfn(const 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,