On Mon, Aug 18, 2014 at 10:04:58AM -0600, Stephen Warren wrote: > On 08/15/2014 03:39 PM, Thierry Reding wrote: > >On Fri, Aug 15, 2014 at 10:02:40AM -0600, Stephen Warren wrote: > ... > >>Re-transmitting a DHCP request shouldn't prevent a response to the previous > >>request from being processed - AFAIK each request is idempotent. Can you > >>debug what is causing the 8s delay? Are earlier responses received and > >>rejected for some reason, or is your DHCP server getting confused by the > >>multiple requests and not responding, or ...? > > > >I haven't really tested this, but by looking at the code in net/bootp.c > >(function BootpCheckPkt()) the U-Boot implementation will reject all > >packets that don't match the BootpID (which is composed of the lower 4 > >bytes of the ethernet address plus the time in milliseconds when the > >discover packet was sent, see BootpRequest()). > > > >So indeed earlier responses will be rejected, which would also explain > >the 8 second delay since that's about the time it takes for the backoff > >to reach the timeout that the server requires to reply before the next > >retransmission. > > Ah, that's a problem then, especially given that Thierry mentioned > that (some) DHCP servers send out an ARP address and wait for any > responses, to avoid address conflicts. > > I suppose we have two options here: > > a) Make each of U-Boot's DHCP requests identical, so that responses > to an earlier request are accepted even if a later request has been > sent. I don't know what the implications are here; perhaps some dumb > DHCP server might give out different results for the different > responses, so we actively don't want to accept the stale data? > > b) Revert my patch. Perhaps think about tweaking the initial retry > time-out later. > > (b) seems simplest. Tom, it's f59be6e850b3 "net: BOOTP retry timeout > improvements". It looks like nothing has touched the same files > since it was applied, so it should be a simple revert.
I'm leaning this way as well for now and I see some "funny" behavior sometimes in my setup, but not consistent (but I bet it's this same thing) and I haven't had time to tcpdump it. -- Tom
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