luid: change last byte instead of first on luid_get() re-calls#12623
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miri64 wants to merge 1 commit into
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luid: change last byte instead of first on luid_get() re-calls#12623miri64 wants to merge 1 commit into
luid_get() re-calls#12623miri64 wants to merge 1 commit into
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For the first byte bit 2 and 3 are changed when used as EUI-64 to make it a valid unicast EUI-64. So changing only the first byte on re-calls of `luid_get()` reduces the potential pool of non-duplicates for nodes with multiple interfaces.
miri64
added
Type: bug
Contributor
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The problem is that (most)? drivers will use the first two bytes for the short address so this will now always be the same if there are multiple interfaces. |
Member
Author
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True. Then this needs to be fixed as well. I don't think using the second MSB arbitrarily is a good idea either. |
Member
Author
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Closing in favor of @benpicco's future PR ;-) (see #12592 (comment)) |
Contributor
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Well I haven not started yet 😉 |
Member
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The last byte is usually the most valuable in terms of uniqueness. Modifying it will yield a higher collision probability than modifying any other byte. |
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Contribution description
For the first byte bit 2 and 3 are changed when e.g. used as EUI-64 to make it a valid unicast EUI-64. So changing only the first byte on re-calls of
luid_get()reduces the potential pool of non-duplicates for nodes with multiple interfaces.The general doc btw already states as much:
RIOT/sys/include/luid.h
Lines 36 to 37 in 85a392e
Testing procedure
A node with two network devices using the same address length and using
luid_get()to generate the MAC address should differ in their last byte now, not the first.Issues/PRs references
Alternative to #12592