[lwip-devel] [bug #59319] ICMPv6 neighbor solicitation fails if LWIP_IPV6_MLD is set

[H. Gregor Molter]

URL:
  <https://savannah.nongnu.org/bugs/?59319>

                 Summary: ICMPv6 neighbor solicitation fails if LWIP_IPV6_MLD
is set
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: cyberdeck
            Submitted on: Thu 22 Oct 2020 02:29:34 PM UTC
                Category: IPv6
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head

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Details:

In the IPv6 stack neighbor solicitation packages are dropped if LWIP_IPV6_MLD
is set. For me it seems that this is a logical bug included in the ip6.c
source. Please see the included patch.

Description of the bug:
If lwIP is compiled with LWIP_IPV6_MLD set, ICMPv6 neighbor solicitation
messages are dropped if they are targeted for the solicited-node multicast
address (e.g. "ff02::1:ff28:9c5a", cf. [1]).

That drop is by purpose because the logic for checking the received packets
against the solicited-node multicast address is excluded. In my opinion that
behavior is wrong. The attached patch will fix this behavior.

Effect of the bug:
Bring up an interface and try to ping it's global IPv6 address. As the
interface is not replying to neighbor solicitation it cannot be reached.

Effect after the patch:
Bring up an interface and try to ping it's global IPv6 address. Now the
interface is replying to neighbor solicitation and this, it can be reached
afterwards.

[1]: https://en.wikipedia.org/wiki/Solicited-node_multicast_address



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File Attachments:


-------------------------------------------------------
Date: Thu 22 Oct 2020 02:29:34 PM UTC  Name: ipv6.patch  Size: 658B   By:
cyberdeck

<http://savannah.nongnu.org/bugs/download.php?file_id=50049>

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