[Dnsmasq-discuss] DNS request timeout problem on dial-in account with dynamic ip

Jean Wolter jw5-dns at os.inf.tu-dresden.de
Wed Feb 8 17:43:49 GMT 2006


I use dnsmasq on a small Linux router, which uses pppd to dial in to
my provider and netfilter to provide NAT and stateful packet filtering.

When a DNS request triggers a dial-in the request usually times out
due to one of the following reasons:

    - the DNS request sent to the server has still the old IP - the IP
      the interface had before pppd finished the IPCP protocol and got
      a new IP. Therefore the DNS server replies to the wrong IP and
      dnsmasq never gets a reply
    - if the pppd rewrites the IP address of the packet netfilter
      generates a connection tracking entry with the old IP and
      refuses the reply of the DNS server since the packet doesn't
      belong to any known "connection"

So dnsmasq doesn't get a reply for the first request and the client
runs into a timeout and sends a new request for this name. Under some
operating systems this leads to a failed name resolution and the user
has to repeat whatever lead to the DNS request.

Is there any chance to automatically re-send all un-replied DNS requests
after a dial-in happened? I tried to browse through the source but I
did not find the right spot to add such a resend operation.


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