Hello, On Tue, 7 Jun 2011, Patrick McHardy wrote: > On 04.06.2011 16:02, Julian Anastasov wrote: > > > > Avoid double NAT and seq adjustment for loopback > > traffic because it causes silent repetition of TCP data. One > > example is passive FTP with DNAT rule and difference in the > > length of IP addresses. > > > > This patch adds checks if packet is sent and > > received via loopback device. As the same conntrack is used > > both for outgoing and incoming direction, we restrict NAT, > > seq adjustment and confirmation to happen only in > > outgoing direction (OUTPUT and POSTROUTING). > > > > Signed-off-by: Julian Anastasov <ja@xxxxxx> > > --- > > > > As the check is not so cheap, another alternative > > is to add new skb flag, eg. "loopback", that can be set in > > drivers/net/loopback.c, loopback_xmit(). May be there is space > > for it in flags2? > > I don't think we should be adding code specifically needed for netfilter > to the loopback driver if we can avoid it. I don't think we need to > actually avoid calling nf_nat_packet twice, that shouldn't do any harm, > just the sequence number adjustment. So we could add the loopback check Yes, may be calling nf_nat_packet is not fatal. > to the IPS_SEQ_ADJUST_BIT case to at least avoid it in some cases. > Would that work or am I missing something? Logically, the new check can be after test_bit(IPS_SEQ_ADJUST_BIT, &ct->status). But I suspect some modules adjust seqs in the helper->help call, for example, sip_help_tcp if I'm correctly reading the code. Regards -- Julian Anastasov <ja@xxxxxx> -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
