netdev - Re: Bad TCP timestamps on non-PC platforms

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <117536.54377.qm@web37607.mail.mud.yahoo.com>
Date:	Thu, 6 Jan 2011 17:55:34 -0800 (PST)
From:	Alex Dubov <oakad@...oo.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: Bad TCP timestamps on non-PC platforms

Sorry for the awful synopsis of my problem. I never cease to amaze myself
at how bad those usually turn up. :-)

What I really meant to write is:

I have a dev board running 2.6.37-rc7. Normal kernel config, nothing fancy.
Remote machines are just usual linux boxes in constant operation (I tried
several of those).

UDP/DHCP works correctly all the time, so ethernet side is probably ok.

When tcp_timestamps are enabled, SYN packets from dev board just get
ignored by the remote side. I see them arrive in wireshark, but nothing
else happens.

When I disable tcp_timestamps on the dev board everything works.

The problem is reproducible every single time.

The only difference is the "Options" block of the SYN packets.
If timestamps are not really to blame, then it probably window scale
parameters. That's what I see on a usual dropped packet:

Options: (20 bytes)
        Maximum segment size: 1460 bytes
        SACK permitted
        Timestamps: TSval 4294893842, TSecr 0
        NOP
        Window scale: 5 (multiply by 32)

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html