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Message-Id: <20120518.235409.1621981320285066566.davem@davemloft.net> Date: Fri, 18 May 2012 23:54:09 -0400 (EDT) From: David Miller <davem@...emloft.net> To: eric.dumazet@...il.com Cc: netdev@...r.kernel.org, tore@....no Subject: Re: [PATCH net-next] ipv6: ip6_fragment() should check CHECKSUM_PARTIAL From: Eric Dumazet <eric.dumazet@...il.com> Date: Fri, 18 May 2012 23:02:15 +0200 > From: Eric Dumazet <edumazet@...gle.com> > > Quoting Tore Anderson from : > > If the allfrag feature has been set on a host route (due to an ICMPv6 > Packet Too Big received indicating a MTU of less than 1280), > TCP SYN/ACK packets to that destination appears to get an incorrect > TCP checksum. This in turn means they are thrown away as invalid. > > In the case of an IPv4 client behind a link with a MTU of less than > 1260, accessing an IPv6 server through a stateless translator, > this means that the client can only download a single large file > from the server, because once it is in the server's routing cache > with the allfrag feature set, new TCP connections can no longer > be established. > > </endquote> > > It appears ip6_fragment() doesn't handle CHECKSUM_PARTIAL properly. > > As network drivers are not prepared to fetch correct transport header, a > safe fix is to call skb_checksum_help() before fragmenting packet. > > Reported-by: Tore Anderson <tore@....no> > Signed-off-by: Eric Dumazet <edumazet@...gle.com> > Tested-by: Tore Anderson <tore@....no> Applied, thanks. -- 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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