dhcpcd-discuss

Hi,

I've noticed some interesting behaviour in dhcpcd 9.0.2.

I was investigating a series of log messages like this:

  May 05 20:55:00 gateway dhcpcd[7402]: enp1s0: failed to renew DHCP, rebinding
  May 05 21:21:15 gateway dhcpcd[7402]: enp1s0: failed to renew DHCP, rebinding
  May 05 21:47:30 gateway dhcpcd[7402]: enp1s0: failed to renew DHCP, rebinding
  May 05 22:13:45 gateway dhcpcd[7402]: enp1s0: failed to renew DHCP, rebinding

A packet capture shows the reason for the renew failure. xx is the
dhcpcd client and yy is the server:

  Time           Source Port Destination Port Source                Destination           Protocol Length Info
  45.339308      39          67               xx.xxx.xxx.xxx        yy.yyy.yyy.y          DHCP     357    DHCP Request  - Transaction ID 0x0123456
  45.350879      67          68               yy.yyy.yyy.y          xx.xxx.xxx.xxx        DHCP     342    DHCP ACK      - Transaction ID 0x0123456
  87.300454      68          67               xx.xxx.xxx.xxx        255.255.255.255       DHCP     357    DHCP Request  - Transaction ID 0x0123456
  87.312131      67          68               yy.yyy.yyy.y          xx.xxx.xxx.xxx        DHCP     342    DHCP ACK      - Transaction ID 0x0123456

dhcpcd seems to be using a weird source port for the renew. The response
comes in to port 68, but it's getting dropped by the stateful firewall
so dhcpcd never sees it.
The rebind works because it uses the same source port that the response
comes in on, so the firewall lets it through.

Is this behaviour intentional?

-- 
Regards,
Scott Leggett.

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