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<base href="https://bugzilla.netfilter.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - With iPv6 masquerade, ICMPv6 time-exceeded pkts are forwarded with bad checksum"
href="https://bugzilla.netfilter.org/show_bug.cgi?id=1343">1343</a>
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<th>Summary</th>
<td>With iPv6 masquerade, ICMPv6 time-exceeded pkts are forwarded with bad checksum
</td>
</tr>
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<th>Product</th>
<td>netfilter/iptables
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>x86_64
</td>
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<th>OS</th>
<td>Debian GNU/Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P5
</td>
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<th>Component</th>
<td>NAT
</td>
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<th>Assignee</th>
<td>netfilter-buglog@lists.netfilter.org
</td>
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<th>Reporter</th>
<td>doron.shikmoni+netfilterorg@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>I have a system that does IPv6 MASQUERADE, a POSTROUTING rule in the NAT table.
For the most part it works fine, however ICMPv6 type 3 (TIME-EXCEED) seems to
have their ICMPv6 checksum botched, and hence are dropped at the next hop.
I see the packets entering the via the upstream interface just fine with good
cksum, but then on the forwarded-to interface (i.e. after translation) I get
bad checksum. The next hop does not see the packet at all.
I looked at nf_nat_proto_icmpv6.c for a bit but so far haven't found much.
Kernel 4.9.168.
e.g. on ingress:
IP6 (hlim 61, next-header ICMPv6 (58) payload length: 80) 2a01:4f9:0:c001::a015
<span class="quote">> 2a01:???:????:????::1: [icmp6 sum ok] ICMP6, time exceeded in-transit for</span >
fra16s12-in-x04.1e100.net
on egress:
IP6 (hlim 60, next-header ICMPv6 (58) payload length: 80) 2a01:4f9:0:c001::a015
<span class="quote">> fd01:???:????:????::2:1: [bad icmp6 cksum 0x735b -> 0x705b!] ICMP6, time</span >
exceeded in-transit for fra16s12-in-x04.1e100.net</pre>
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