Re: iptables 'new but not syn' packets

From: Leonardo Rodrigues (coelhoat_private)
Date: Thu Dec 13 2001 - 06:20:42 PST

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        Problems with more than one iptables-router based are pretty
    obvious. This 'new but not syn' feature was apparently built exactly for
    these situations. Altough, I'm analising this in a specific situation:
    only 1 iptables based router.
    
        Dropping INVALID packets seems to not deal with these packets. As I
    stated, iptables recognizes them as NEW state. So a rule that drop
    INVALID ones wouldnt care about them.
    
        Sincerily,
        Leonardo Rodrigues
    
    ----- Original Message -----
    From: <sekureat_private>
    To: "Leonardo Rodrigues" <coelhoat_private>
    Sent: Tuesday, December 11, 2001 4:38 PM
    Subject: Re: iptables 'syn but not new' packets
    
    
    > Although this should be safe for single machines, such a setting
    > may cause problems for LANs which have multiple routers connecting
    them.
    >
    > Suppose the SYN and the SYN/ACK travel through one router, but the
    ACK,
    > or, perhaps some other packets travel through another router.
    > Packets seen by this second router are classified NEW or INVALID
    > by iptables.
    >
    > Since dropping INVALID-classified packets appears to be a common
    practice,
    > I may be overlooking something. Any ideeas?
    



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