[net-next 2/3] tipc: make node number calculation reproducible

[jmaloy@redhat.com]

From: Jon Maloy <jmaloy@redhat.com>

The 32-bit node number, aka node hash or node address, is calculated
based on the 128-bit node identity when it is not set explicitly by
the user. In future commits we will need to perform this hash operation
on peer nodes while feeling safe that we obtain the same result.

We do this by interpreting the initial hash as a network byte order
number. Whenever we need to use the number locally on a node
we must therefore translate it to host byte order to obtain an
architecure independent result.

Furthermore, given the context where we use this number, we must not
allow it to be zero unless the node identity also is zero. Hence, in
the rare cases when the xor-ed hash value may end up as zero we replace
it with a fix number, knowing that the code anyway is capable of
handling hash collisions.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 net/tipc/addr.c |  7 +++----
 net/tipc/addr.h |  1 +
 net/tipc/core.h | 12 ++++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/net/tipc/addr.c b/net/tipc/addr.c
index 0f1eaed1bd1b..abe29d1aa23a 100644
--- a/net/tipc/addr.c
+++ b/net/tipc/addr.c
@@ -55,12 +55,11 @@ bool tipc_in_scope(bool legacy_format, u32 domain, u32 addr)
 void tipc_set_node_id(struct net *net, u8 *id)
 {
 	struct tipc_net *tn = tipc_net(net);
-	u32 *tmp = (u32 *)id;
 
 	memcpy(tn->node_id, id, NODE_ID_LEN);
 	tipc_nodeid2string(tn->node_id_string, id);
-	tn->trial_addr = tmp[0] ^ tmp[1] ^ tmp[2] ^ tmp[3];
-	pr_info("Own node identity %s, cluster identity %u\n",
+	tn->trial_addr = hash128to32(id);
+	pr_info("Node identity %s, cluster identity %u\n",
 		tipc_own_id_string(net), tn->net_id);
 }
 
@@ -76,7 +75,7 @@ void tipc_set_node_addr(struct net *net, u32 addr)
 	}
 	tn->trial_addr = addr;
 	tn->addr_trial_end = jiffies;
-	pr_info("32-bit node address hash set to %x\n", addr);
+	pr_info("Node number set to %u\n", addr);
 }
 
 char *tipc_nodeid2string(char *str, u8 *id)
diff --git a/net/tipc/addr.h b/net/tipc/addr.h
index 31bee0ea7b3e..1a11831bef62 100644
--- a/net/tipc/addr.h
+++ b/net/tipc/addr.h
@@ -3,6 +3,7 @@
  *
  * Copyright (c) 2000-2006, 2018, Ericsson AB
  * Copyright (c) 2004-2005, Wind River Systems
+ * Copyright (c) 2020, Red Hat Inc
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/net/tipc/core.h b/net/tipc/core.h
index df34dcdd0607..e6657cf97000 100644
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -3,6 +3,7 @@
  *
  * Copyright (c) 2005-2006, 2013-2018 Ericsson AB
  * Copyright (c) 2005-2007, 2010-2013, Wind River Systems
+ * Copyright (c) 2020, Red Hat Inc
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -210,6 +211,17 @@ static inline u32 tipc_net_hash_mixes(struct net *net, int tn_rand)
 	return net_hash_mix(&init_net) ^ net_hash_mix(net) ^ tn_rand;
 }
 
+static inline u32 hash128to32(char *bytes)
+{
+	u32 res, *tmp = (u32 *)bytes;
+
+	res = ntohl(tmp[0] ^ tmp[1] ^ tmp[2] ^ tmp[3]);
+	if (likely(res))
+		return res;
+	res = tmp[0] | tmp[1] | tmp[2] | tmp[3];
+	return !res ? 0 : ntohl(18140715);
+}
+
 #ifdef CONFIG_SYSCTL
 int tipc_register_sysctl(void);
 void tipc_unregister_sysctl(void);
-- 
2.25.4