[lvs-users] coloring LVS-NAT connections internally using TOS/DSCP - reliable?

Julian Anastasov ja at ssi.bg
Sun Nov 10 11:40:19 GMT 2013


On Thu, 7 Nov 2013, Patrick Schaaf wrote:

> Dear LVS users / gurus,
> I came across an idea today, which even appears to work, that could 
> potentially reduce the number of ipvs realserver entries in an LVS-NAT 
> scenario where multiple ports need to be passed through to the 
> realservers.
> Right now I have a separate (fwmark) virtualserver for port 80, and 
> several SSL ports that need different certificates on the realservers. The 
> usual mangle/PREROUTING marking selects which one to use.
> Now the idea is to reduce the LVS setup itself to the port 80 server entry, 
> always select the same fwmark for that, but use rules in 
> mangle/PREROUTING like -j TOS --set-tos 0x04/0xfc, with different TOS 
> values.
> All SSL connections then arrive at the realservers with dport 80, but 
> there I have nat/PREROUTING rules matching the TOS values, using -j 
> REDIRECT --to-port 44X to internally let the connection flow to the right 
> SSL port.
> This appears to work quite nicely in a prototype setup.
> My question would be: we run this on kernel 2.6.32 right now. That's a 
> little bit ancient, and will eventually be upgraded. Was there anything 
> changed in LVS kernel code since then that would make this TOS/DSCP 
> marking scheme fail?

	It should be safe to change TOS, IPVS does not
use it.


Julian Anastasov <ja at ssi.bg>

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