How do I force a specific MTU for only certain TCP ports?
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Dave S.
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Published on 2013-07-01T14:20:53Z
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2013/07/01
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Background
I have a set of embedded hardware deployed in the field. These remote machines connect back to my servers at AWS running Ubuntu and I use the iptables mangle chain to lower the MTU to 500 so these devices are happy. For reference, this is the iptables rule I am using:
-A POSTROUTING -p tcp --sport 12345 --tcp-flags SYN,RST SYN -o eth0 -j TCPMSS --set-mss 500
Current Problem
I'm trying to spin up some servers on the Joyent Cloud using SmartOS, but I can't find any information on selectively changing the MTU like I can on Linux (e.g. all info I've found is on changing it globally, which is not what I want).
How would I do it so that all connections on TCP port 12345 get the MTU I want?
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