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| author | Johannes Berg <johannes.berg@intel.com> | 2012-05-07 15:39:06 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-05-07 19:21:29 -0400 |
| commit | 1c430a727fa512500a422ffe4712166c550ea06a (patch) | |
| tree | 5027e4edc9c66a9e49e0e73ba866f5bb326fadcd /include/linux/etherdevice.h | |
| parent | 6eddcb4c82883451aec3be1240f17793370fa62f (diff) | |
| download | lwn-1c430a727fa512500a422ffe4712166c550ea06a.tar.gz lwn-1c430a727fa512500a422ffe4712166c550ea06a.zip | |
net: compare_ether_addr[_64bits]() has no ordering
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>
Diffstat (limited to 'include/linux/etherdevice.h')
| -rw-r--r-- | include/linux/etherdevice.h | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h index 8a1835855faa..fe5136d81454 100644 --- a/include/linux/etherdevice.h +++ b/include/linux/etherdevice.h @@ -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. |