DF bit, fragmentace na TCP

[Dan Bar]

"Adam Pribyl" <covex na ahoj.fsik.cvut.cz> píse v diskusním príspevku
news:Pine.LNX.4.44.0212201945330.3136-100000 na ahoj.fsik.cvut.cz...
> Nevite nekdo jak nastavit (pravdepodobne kernel) v RH(7.0-8.0) aby
> neposilal pakety TCP spojeni s DF bitem?
>
> O co jde: mam problemy s tim, ze firewall (BSD) mi vraci TCP pakety
> na jakekoli ip:port, krom ip:22  s odpovedi TYPE=3 CODE=1 (=host
> unreachable).

Zkuste tento odkaz:
http://www.uwsg.iu.edu/hypermail/linux/kernel/9812.3/0240.html

Pokud by slo opravdu o problem s fragmentaci, pak:

z neho vyplyva to same co se rika v predchozim prispevku - MTU discovery.

"... The link with the low MTU is corrupting the packet header it sends
back. This problem is very common in routers based on BSD 4.2 and ..."

"... In some cases, the simplest option is for the sender to disable path
MTU discovery completely. This turns off the "do not fragment" bit in
the packet header. When a large packet hits the low MTU link, instead
of bouncing back to the sender, the packet is fragmented and forwarded
in pieces. However fragments can have their own problems, this option
does not always work... "

A jelikoz se zde pise i o bugu v BSD 4.2 mohl by to byt vas pripad.

Je mi sice divne proc Vam vraci code 1 (Host Unreachable) a ne code 4
(Fragmentation Needed and Don't Fragment was Set ), ale mozna to bude v tom
BSD bugu.

Pokud budete studovat proc se Win stroje dostanou skrz (zrejme mensi MTU)
tak se urcite ozvete (vubec jak jste dopadl), zajimalo by me to.

Dan



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