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Opened 5 years ago

Closed 2 years ago

#13460 closed defect (invalid)

IPv6 stack malfunction ?

Reported by: congelli501@… Owned by: developers
Priority: normal Milestone: Barrier Breaker 14.07
Component: kernel Version: Trunk
Keywords: ipv6 ping Cc:

Description

Hi,
I'm running OpenWRT 12.09 on a TL-WR740N. I built OpenWRT.

Build options

Image configuration :

⇒ Target System : Atheros AR7xxx/AR9xxx
⇒ Target Profile : TP-LINK TL-WR740N/ND
⇒ Target Images ⇒ Enlever jffs2

Installed packages (built in)

⇒ LuCI ⇒ Collections ⇒ luci
⇒ LuCI ⇒ Applications ⇒ luci-app-upnp
⇒ IPv6 ⇒ wide-dhcpv6 ⇒ wide-dhcpv6-client
⇒ IPv6 ⇒ radvd
⇒ Network ⇒ Firewall ⇒ miniupnpd
⇒ Network ⇒ Routing and Redirection ⇒ ip

Removed packages :

⇒ Network ⇒ ppp

Problem description

To begin, I have only link local IPs :

root@OpenWrt:~# ip -6 a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 fe80::fad1:11ff:fe32:6f35/64 scope link 
       valid_lft forever preferred_lft forever
5: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 
    inet6 fe80::fad1:11ff:fe32:6f33/64 scope link 
       valid_lft forever preferred_lft forever

My IPv6 routing table is empty :

root@OpenWrt:~# ip -6 r
fe80::/64 dev br-lan  proto kernel  metric 256 
fe80::/64 dev eth1  proto kernel  metric 256 

Then, I simply add an address :

root@OpenWrt:~# ip addr add 2001:910:1105:ff00::/48 dev eth1

And now I ping an IP that is *not* on the /48 subnet :

root@OpenWrt:~# ping6 2001:910:1105::

But the router answer its own ping while it's not the good address !

PING 2001:910:1105:: (2001:910:1105::): 56 data bytes
64 bytes from 2001:910:1105::: seq=0 ttl=64 time=0.348 ms
64 bytes from 2001:910:1105::: seq=1 ttl=64 time=0.371 ms
^C
--- 2001:910:1105:: ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.348/0.359/0.371 ms

And these packets go throw the loopback interface... why ?

root@OpenWrt:~# tcpdump icmp6 -i lo
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 65535 bytes
18:12:12.323998 IP6 2001:910:1105:ff00:: > 2001:910:1105::: ICMP6, echo request, seq 0, length 64
18:12:12.324098 IP6 2001:910:1105:ff00:: > 2001:910:1105:ff00::: ICMP6, echo reply, seq 0, length 64
18:12:13.326323 IP6 2001:910:1105:ff00:: > 2001:910:1105::: ICMP6, echo request, seq 1, length 64
18:12:13.326409 IP6 2001:910:1105:ff00:: > 2001:910:1105:ff00::: ICMP6, echo reply, seq 1, length 64
18:12:14.326664 IP6 2001:910:1105:ff00:: > 2001:910:1105::: ICMP6, echo request, seq 2, length 64
18:12:14.326748 IP6 2001:910:1105:ff00:: > 2001:910:1105:ff00::: ICMP6, echo reply, seq 2, length 64

I may have done a mistake, but there is something I don't understand here.

I can add more details, descriptions or logs if needed.

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Change History (3)

comment:1 Changed 4 years ago by jow

  • Milestone changed from Attitude Adjustment 12.09 to Barrier Breaker 14.07

Milestone Attitude Adjustment 12.09 deleted

comment:2 Changed 2 years ago by anonymous

What you're missing is broadcast addresses. Generally the all-zero and all-ones IP addresses are reserved and both can potentially handled as broadcast. So, when you ping 2001:910:1105::/48, this is being treated as a broadcast and all devices on the network may potentially respond; since the router's own IP address 2001:910:1105:ff00:: is on the subnet, it receives the broadcast and responds. If you had at least one more device you would see multiple responses for every ping packet sent out.

comment:3 Changed 2 years ago by jow

  • Resolution set to invalid
  • Status changed from new to closed

2001:910:1105:ff00::/48 ranges from 2001:0910:1105:: to 2001:0910:1105:ffff:ffff:ffff:ffff:ffff so the original report is invalid to begin with.

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