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net: compare_ether_addr[_64bits]() has no ordering

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Neither compare_ether_addr() nor compare_ether_addr_64bits()
(as it can fall back to the former) have comparison semantics
like memcmp() where the sign of the return value indicates sort
order. We had a bug in the wireless code due to a blind memcmp
replacement because of this.

A cursory look suggests that the wireless bug was the only one
due to this semantic difference.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Johannes Berg 2012-05-07 15:39:06 +02:00 committed by David S. Miller
parent 6eddcb4c82
commit 1c430a727f
1 changed files with 6 additions and 5 deletions
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11
include/linux/etherdevice.h
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@ -159,7 +159,8 @@ static inline void eth_hw_addr_random(struct net_device *dev)
* @addr1: Pointer to a six-byte array containing the Ethernet address
* @addr2: Pointer other six-byte array containing the Ethernet address
*
* Compare two ethernet addresses, returns 0 if equal
* Compare two ethernet addresses, returns 0 if equal, non-zero otherwise.
* Unlike memcmp(), it doesn't return a value suitable for sorting.
*/
static inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2)
{
@ -184,10 +185,10 @@ static inline unsigned long zap_last_2bytes(unsigned long value)
* @addr1: Pointer to an array of 8 bytes
* @addr2: Pointer to an other array of 8 bytes
*
* Compare two ethernet addresses, returns 0 if equal.
* Same result than "memcmp(addr1, addr2, ETH_ALEN)" but without conditional
* branches, and possibly long word memory accesses on CPU allowing cheap
* unaligned memory reads.
* Compare two ethernet addresses, returns 0 if equal, non-zero otherwise.
* Unlike memcmp(), it doesn't return a value suitable for sorting.
* The function doesn't need any conditional branches and possibly uses
* word memory accesses on CPU allowing cheap unaligned memory reads.
* arrays = { byte1, byte2, byte3, byte4, byte6, byte7, pad1, pad2}
*
* Please note that alignment of addr1 & addr2 is only guaranted to be 16 bits.