[LARTC] masquerading with dhcp

[LARTC] masquerading with dhcp

[christopher cuse]

hi all, 

i have a curious problem -- 

a user has dialup connectivity to isp via pppd on-demand. 

tcp syn request to an ip address 
.or. 
dns lookup for a host name (bind cfg forwards to isp dns) 

.and. 

default route is ppp0 

.so. 

udp dns request to isp dns ip address 
.or. 
tcp syn packet to ip address 


the issue becsome the source ip address for these packets -- they are
sent by the last ip address that the ppp interface had. of course, once
the connection is established, then ip address has changed, so all those
neat little packets have an invalid source ip address. 

so, the end goal is to keep retrying the tcp syn packets until the ppp
interface is happy with its new ip address and the routing table updated
with the new default route.

tcp syn packets are sent at time 0, 3, 9, 21, seconds respectively.
there seems to be some tcp parameter with a geometric component to it,
that tries syn packets later and later.

could anyone direct me to what sysctl parameter i might change to in
order shorter times between the syn packets?

anyone else run across this? 

all comments welcome!

cheers 

christopher cuse

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