IP dynamic address hack-port v0.03

This stuff allows diald ONESHOT connections to get established by dynamically changing packet source address (and socket’s if local procs). It is implemented for TCP diald-box connections(1) and IP_MASQuerading(2).

If enabled[1] and forwarding interface has changed:

  1. Socket (and packet) source address is rewritten ON RETRANSMISSIONS while in SYN_SENT state (diald-box processes).
  2. Out-bounded MASQueraded source address changes ON OUTPUT (when internal host does retransmission) until a packet from outside is received by the tunnel.

This is specially helpful for auto dialup links (diald), where the actual outgoing address is unknown at the moment the link is going up. So, the same (local AND masqueraded) connections requests that bring the link up will be able to get established.


At boot, by default no address rewriting is attempted.

To enable:

# echo 1 > /proc/sys/net/ipv4/ip_dynaddr

To enable verbose mode:

# echo 2 > /proc/sys/net/ipv4/ip_dynaddr

To disable (default):

# echo 0 > /proc/sys/net/ipv4/ip_dynaddr


Juanjo <jjciarla@raiz.uncu.edu.ar>