Messages in this thread | | | Subject | RE: Cursed Checksums | From | Albert Cahalan <> | Date | 22 Aug 2004 16:14:00 -0400 |
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On Sun, 2004-08-22 at 18:38, Josan Kadett wrote: > In normal conditions, when NAT translates an IP header, it should do correct > checksumming. However; when the source IP address of a packet is > manipulated, Iptables still seems to use the "original" IP address and > calculate the checksum accordingly. This way even if I use 3 three boxes; > > Original Packet --> NAT 1 --> NAT 2 --> NAT3 --> Still incorrect checksum
Sure. That's why I think this is a job for ebtables. Note: EBtables, not IPtables. This is lower level, dealing with raw Ethernet packets. It should be able to mangle anything in the packet.
Just as iptables lets you change any 32-bit value in an IP packet, ebtables should let you change any 32-bit value in an Ethernet packet. Unlike iptables, it could operate prior to the IP checksum verification.
Sadly, it looks like u32 mangle rules are missing.
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