tap_user: fix DHCP lease renewal losing guest connectivity - #325
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DHCP was only handled locally when the client source address was zero and no UDP forwarding entry existed for its source port. Renewal requests use the leased address, so they fell through to ordinary UDP forwarding instead of reaching RVVM's DHCP server. Guests could acquire an address at boot but fail to renew it and lose connectivity when the lease expired. Intercept IPv4 DHCP client traffic from port 68 to port 67 at the gateway or broadcast address before looking up UDP forwarding entries. Send replies to the client address in ciaddr when it is set, keeping broadcast replies for initial address acquisition. Assisted-By: GPT-6 <noreply@openai.com> Signed-off-by: Jonathan Dieter <jdieter@resf.org>
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DHCP was only handled locally when the client source address was zero and no UDP forwarding entry existed for its source port. Renewal requests use the leased address, so they fell through to ordinary UDP forwarding instead of reaching RVVM's DHCP server. Guests could acquire an address at boot but fail to renew it and lose connectivity when the lease expired.
Intercept IPv4 DHCP client traffic from port 68 to port 67 at the gateway or broadcast address before looking up UDP forwarding entries. Send replies to the client address in ciaddr when it is set, keeping broadcast replies for initial address acquisition.