The Babel seqno request code keeps track of which seqno requests are
outstanding for a neighbour by putting them onto a per-neighbour list. When
reusing a seqno request, it will try to remove this node, but if the seqno
request in question was a multicast request with no neighbour attached this
will result in a crash because it tries to remove a list node that wasn't
added to any list.
Fix this by making the list remove conditional. Also add a check so that
seqno requests are only reused if the neighbour also matches, allowing
multiple outstanding requests for the same router ID.
Fixes: ebd5751cde ("Babel: Seqno requests are properly decoupled from neighbors when the underlying interface disappears")
Reported-by: Stefan Haller <stefan.haller@stha.de>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
8f9a091d30