Fix flaky DHCP in non-Thunder builds in rpi3 #563
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If your DHCP server is dnsmasq-based, you're not building Thunder and you're using a rpi3, there is a good chance half the time the rpi boots without an IP address. This is because: * udhcp sends 3 DISCOVER, waiting 3 seconds for a response in each case. * The NIC of the rpi3 usually takes slightly above 6 seconds from `ifconfig eth0 up` to being functional enough to send packets, so the first two DISCOVER packets never reach the network. * dnsmasq will do a 3 second long ping of an IP address before assigning it to a lease, unless its has done this recently and has it cached. If this happens on the last DISCOVER, by the time the rpi3 gets the OFFER packet, udhcp has already given up. Once identified the problem, a simple fix is trivial: patch udhcp to send more DISCOVER packets.
magomez
approved these changes
Sep 1, 2025
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If your DHCP server is dnsmasq-based, you're not building Thunder and you're using a rpi3, there is a good chance half the time the rpi boots without an IP address.
This is because:
ifconfig eth0 upto being functional enough to send packets, so the first two DISCOVER packets never reach the network.Once identified the problem, a simple fix is trivial: patch udhcp to send more DISCOVER packets.