I am running kernel 2.4.31 on my dsl modem.

When some packet is received on the wan interface of modem, it forwards the packet to PC connected but here on the PC, I receive "TCP Acked Segment lost". This is due to the Ack number sent in the IP packet.

The Ack number received on the WAN interface ( of modem was suppose 516 bytes wherein the size of IP address was 14 bytes. This packet when reaches the LAN interface ( has the ack number as 516 bytes wherein it should be 514 bytes as IP address contributing here is 12 bytes.

Does anyone have idea about the code in kernel where the ack number gets changed and the issue in this scenario ??