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Message-ID: <20101203230250.GA3612@electric-eye.fr.zoreil.com> Date: Sat, 4 Dec 2010 00:02:50 +0100 From: Francois Romieu <romieu@...zoreil.com> To: Jan Engelhardt <jengelh@...ozas.de> Cc: David Miller <davem@...emloft.net>, cooldavid@...ldavid.org, netdev@...r.kernel.org Subject: Re: jme: UDP checksum error, and lots of them Jan Engelhardt <jengelh@...ozas.de> : > On Friday 2010-12-03 00:15, Francois Romieu wrote: > >David Miller <davem@...emloft.net> : > >[...] > >> Something isn't right here. The only thing that makes sense is if > >> the tcpdump checksum validation is wrong for some reason. Because > >> only then could we give a reason for the UDP frames to not be > >> dropped before vpnc can see them. > > > >Wild guess : 192.168... is the local address and tcpdump chokes on > >an outgoing, yet-not-checksummed packet. > > Then the checksums of all other packets I am emitting would also be 0000 > or wrong, which isn't the case. No. :o) net/ipv4/udp.c::udp4_hwcsum_outgoing provides a packet data length dependent partial checksum and it checksums fragments. -- Ueimor -- 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
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