ipv6: move inet6_ehash_secret and udp6_ehash_secret into net_hotdata

"struct inet6_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/20240306160031.874438-16-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/hotdata.h

@@ -38,6 +38,8 @@ struct net_hotdata {
 
 #define inet_ehash_secret	net_hotdata.tcp_protocol.secret
 #define udp_ehash_secret	net_hotdata.udp_protocol.secret
+#define inet6_ehash_secret	net_hotdata.tcpv6_protocol.secret
+#define udp6_ehash_secret	net_hotdata.udpv6_protocol.secret
 
 extern struct net_hotdata net_hotdata;
 

include/net/protocol.h

@@ -60,6 +60,7 @@ struct inet6_protocol {
 			       __be32 info);
 
 	unsigned int	flags;	/* INET6_PROTO_xxx */
+	u32		secret;
 };
 
 #define INET6_PROTO_NOPOLICY	0x1

net/ipv6/inet6_hashtables.c

@@ -14,6 +14,7 @@
 #include <linux/random.h>
 
 #include <net/addrconf.h>
+#include <net/hotdata.h>
 #include <net/inet_connection_sock.h>
 #include <net/inet_hashtables.h>
 #include <net/inet6_hashtables.h>
@@ -25,7 +26,6 @@ u32 inet6_ehashfn(const struct net *net,
 		  const struct in6_addr *laddr, const u16 lport,
 		  const struct in6_addr *faddr, const __be16 fport)
 {
-	static u32 inet6_ehash_secret __read_mostly;
 	static u32 ipv6_hash_secret __read_mostly;
 
 	u32 lhash, fhash;

net/ipv6/udp.c

@@ -79,7 +79,6 @@ u32 udp6_ehashfn(const struct net *net,
 		 const struct in6_addr *faddr,
 		 const __be16 fport)
 {
-	static u32 udp6_ehash_secret __read_mostly;
 	static u32 udp_ipv6_hash_secret __read_mostly;
 
 	u32 lhash, fhash;