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FS#2555 - kmod-nat46 incorrect src-address for icmp packet too big #8469

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openwrt-bot opened this issue Oct 16, 2019 · 1 comment
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christf:

On a x86 openwrt with kernel
Linux kd-qemu 4.14.137 #0 SMP Sun Jun 23 13:10:01 2019 x86_64 GNU/Linux

with loaded nat46 module

[ 8.118800] nat46: adding device (clat) [ 8.165298] nat46: netdevice nat46 'clat' created successfully. [ 8.168445] nat46: configure device (clat) with 'local.style RFC6052 local.v4 10.139.0.0/17 local.v6 fdff:ffff:ffff:5254:ee:43::/96 local.ea-len 0 local.psid-offset 0 remote.style RFC6052 remote.v4 0.0.0.0/0 remote.v6 64:ff9b::/96 remote.ea-len 0 remote.psid-offset 0'

I am observing ICMP packet too big messages that are sent from the router to the client that have an incorrect src-address: Instead of the router-IPv4 IP, the clients IPv4-IP is placed in the src-address field in the ipv4 packet.

In this particular case, I have a client connected to the openwrt router. The client has IP address 10.139.41.200 and the router has 10.139.0.1

tcpdump shows:

21:07:12.910199 IP 10.139.41.200 > 10.139.41.200: ICMP 140.82.118.4 unreachable - need to frag (mtu 1354), length 1220

The client discards these packets instead of processing them which results in broken network connectivity.

Instead the packet should look like this:

21:07:12.910199 IP 10.139.0.1 > 10.139.41.200: ICMP 140.82.118.4 unreachable - need to frag (mtu 1354), length 1220
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christf:

sorry for this, I only saw the version field after posting. This is not for trunk but for r7835+24-89808e211c according to /etc/openwrt-version

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