Hi,
On 28-07-16 05:13, Chen-Yu Tsai wrote:
Hi,
On Thu, Jul 28, 2016 at 3:14 AM, Siarhei Siamashka
<siarhei.siamas...@gmail.com> wrote:
Hello Hans,
On Wed, 27 Jul 2016 18:10:34 +0200
Hans de Goede <hdego...@redhat.com> wrote:
It seems that bytes 13-14 of the SID / bytes 1-2 from word 3 of the SID
are always 0 on H3 making it a poor candidate to use as source for the
serialnr / mac-address, switch to word1 which seems to be more random.
Cc: Chen-Yu Tsai <w...@csie.org>
Cc: Corentin LABBE <clabbe.montj...@gmail.com>
Cc: Amit Singh Tomar <amittome...@gmail.com>
Signed-off-by: Hans de Goede <hdego...@redhat.com>
---
board/sunxi/board.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/board/sunxi/board.c b/board/sunxi/board.c
index ef3fe26..bbe5340 100644
--- a/board/sunxi/board.c
+++ b/board/sunxi/board.c
@@ -620,12 +620,17 @@ static void setup_environment(const void *fdt)
uint8_t mac_addr[6];
char ethaddr[16];
int i, ret;
+#ifdef CONFIG_MACH_SUN8I_H3
+ const int idx0 = 0, idx1 = 1;
+#else
+ const int idx0 = 0, idx1 = 3;
+#endif
ret = sunxi_get_sid(sid);
- if (ret == 0 && sid[0] != 0 && sid[3] != 0) {
+ if (ret == 0 && sid[idx0] != 0 && sid[idx1] != 0) {
/* Ensure the NIC specific bytes of the mac are not all 0 */
- if ((sid[3] & 0xffffff) == 0)
- sid[3] |= 0x800000;
+ if ((sid[idx1] & 0xffffff) == 0)
+ sid[idx1] |= 0x800000;
for (i = 0; i < 4; i++) {
sprintf(ethaddr, "ethernet%d", i);
@@ -642,18 +647,18 @@ static void setup_environment(const void *fdt)
/* Non OUI / registered MAC address */
mac_addr[0] = (i << 4) | 0x02;
- mac_addr[1] = (sid[0] >> 0) & 0xff;
- mac_addr[2] = (sid[3] >> 24) & 0xff;
- mac_addr[3] = (sid[3] >> 16) & 0xff;
- mac_addr[4] = (sid[3] >> 8) & 0xff;
- mac_addr[5] = (sid[3] >> 0) & 0xff;
+ mac_addr[1] = (sid[idx0] >> 0) & 0xff;
+ mac_addr[2] = (sid[idx1] >> 24) & 0xff;
+ mac_addr[3] = (sid[idx1] >> 16) & 0xff;
+ mac_addr[4] = (sid[idx1] >> 8) & 0xff;
+ mac_addr[5] = (sid[idx1] >> 0) & 0xff;
eth_setenv_enetaddr(ethaddr, mac_addr);
}
if (!getenv("serial#")) {
snprintf(serial_string, sizeof(serial_string),
- "%08x%08x", sid[0], sid[3]);
+ "%08x%08x", sid[idx0], sid[idx1]);
setenv("serial#", serial_string);
}
Is it really a good idea trying to guess which parts of the SID are
sufficiently unique, depending on the SoC generation?
Probably not, but that is what we've been doing so far.
We can calculate some kind of hash (CRC32? SHA256?) over the whole
SID. This will ensure that all the SID bits are accounted for.
That seems like a good idea.
I'm thinking about doing the following (for H3 at least, and probably
also for other new SoCs):
sid[3] ^= sid[1] ^ sid[2];
No need to use a crpytho graphically secure hash, and AFAIK we
don't have enough data for that anyways (without using some seed).
Before using sid[3] to get the low 4 bytes of the mac / serial.
I believe that using sid[0] as the first 4 bytes of the serial
is still a good idea, as it gives us info on which SoC is being used.
Also changing the MAC address generation algorithm is an invasive
change, which is affecting the end users. So IMHO it's best to have
it implemented properly right from the start, rather than evolving
via a trial and error method. What if it turns out that word1
from the SID is actually not sufficiently random on H3? How large
was your sample set?
I've added the SID values from whatever H3 boards I have to:
http://linux-sunxi.org/SID_Register_Guide#Currently_known_SID.27s
I had done the same for my boards yesterday, but apparently never saved
the preview :|
I've just done this a second time.
And it seems word1 is more like a batch number. Note the last 3 boards,
which have identical word1's. These were given to me by Steven at the
same time. word2 seems to follow the pattern 5xxxxxxe.
In short there are quite a few bits that are the same.
Ack, so nack to my own patch as using word1 is worse then using word3,
I suggest we simply ex-or word1-3 together and use that, any comments
on that ?
Regards,
Hans
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