Andy McCammont <firstname.lastname@example.org> writes:
>I understand that the default for SunOS 4.1.x fo udp checksumming is off
>I've found from the sun-managers archives that I can turn this on using adb
(And reboot, thjis changing only /vmunix, not the in kernel value.
or also do adb -k -w /vmunix /dev/mem and udp_cksum/W1)
>but - what does this give me? Will UDP packets that don't meet the checksum be
>ignored? What happens if that occurs half way through an NFS file operation -
>will NFS handle this correctly, and resend - if so how does it know, if UDP
>doesn't ACK packets?
Yes. The bug in SunOS 4 is that with udp_cksum not set, incoming checksums
are ignored. It is up to the protocol implemented on top of RPC
to do the retransmissions (NFS, DNS, ONC RPC will all retransmit after a time
It buys you that bad udp packets (no silent NFS file corruption, DNS corruption)
will be ignored.
>Also, any indication of what sort of performance hit this will incur per
-- Casper Dik - Network Security Engineer - Sun Microsystems This article is posted from my guest account at the University of Amsterdam. My real-life e-mail address is: Casper.Dik@Holland.Sun.COM Opinions expressed here are mine (but you're welcome to share them with me)
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