[lwip-devel] [bug #53971] Lwip sends Router Solicitation on address changes

[Sylvain Chouleur]

URL:
  <http://savannah.nongnu.org/bugs/?53971>

                 Summary: Lwip sends Router Solicitation on address changes
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: schouleur
            Submitted on: Thu 24 May 2018 01:23:44 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:

An ipv6 address state change will lead to Router Solicitation sends when the
state switch from an invalid one (like TENTATIVE) to a valid one (like
PREFERRED).

This is due to the following callstack:
netif->rs_count = LWIP_ND6_MAX_MULTICAST_SOLICIT;
netif_issue_reports()
netif_ip6_addr_set_state()

The reset of rs_count will restart the send of Router Solicitation messages.

However the RFC2461 6.3.7. Sending Router Solicitations
does not include an address change in the list of events which causes the
sending of a Router Solicitation:

Router Solicitations may be sent after any of the following events:

      - The interface is initialized at system startup time.

      - The interface is reinitialized after a temporary interface
        failure or after being temporarily disabled by system
        management.

      - The system changes from being a router to being a host, by
        having its IP forwarding capability turned off by system
        management.

      - The host attaches to a link for the first time.

      - The host re-attaches to a link after being detached for some
        time.




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