[INET]: Move the TCP ehash functions to include/net/inet_hashtables.h

To be shared with DCCP (and others), this is the start of a series of patches
that will expose the already generic TCP hash table routines.

The few changes noticed when calling gcc -S before/after on a pentium4 were of
this type:

        movl    40(%esp), %edx
        cmpl    %esi, 472(%edx)
        je      .L168
-       pushl   $291
+       pushl   $272
        pushl   $.LC0
        pushl   $.LC1
        pushl   $.LC2

[acme@toy net-2.6.14]$ size net/ipv4/tcp_ipv4.before.o net/ipv4/tcp_ipv4.after.o
   text    data     bss     dec     hex filename
  17804     516     140   18460    481c net/ipv4/tcp_ipv4.before.o
  17804     516     140   18460    481c net/ipv4/tcp_ipv4.after.o

Holler if some weird architecture has issues with things like this 8)

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 40 insertions, 0 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
new file mode 100644
index 00000000000..c4c9e39f450
--- /dev/null
+++ b/include/net/inet_hashtables.h
@@ -0,0 +1,40 @@
+/*
+ * INET         An implementation of the TCP/IP protocol suite for the LINUX
+ *              operating system.  INET is implemented using the BSD Socket
+ *              interface as the means of communication with the user level.
+ *
+ * Authors:     Lotsa people, from code originally in tcp
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _INET_HASHTABLES_H
+#define _INET_HASHTABLES_H
+
+#include <linux/types.h>
+
+static inline int inet_ehashfn(const __u32 laddr, const __u16 lport,
+                               const __u32 faddr, const __u16 fport,
+                               const int ehash_size)
+{
+        int h = (laddr ^ lport) ^ (faddr ^ fport);
+        h ^= h >> 16;
+        h ^= h >> 8;
+        return h & (ehash_size - 1);
+}
+
+static inline int inet_sk_ehashfn(const struct sock *sk, const int ehash_size)
+{
+        const struct inet_sock *inet = inet_sk(sk);
+        const __u32 laddr = inet->rcv_saddr;
+        const __u16 lport = inet->num;
+        const __u32 faddr = inet->daddr;
+        const __u16 fport = inet->dport;
+
+        return inet_ehashfn(laddr, lport, faddr, fport, ehash_size);
+}
+
+#endif /* _INET_HASHTABLES_H */