This patch corrects a few problems with the IP_ADD_MEMBERSHIP
socket option:
1) The existing code makes an attempt at reference counting joins when
using the ip_mreqn/imr_ifindex interface. Joining the same group
on the same socket is an error, whatever the API. This leads to
unexpected results when mixing ip_mreqn by index with ip_mreqn by
address, ip_mreq, or other API's. For example, ip_mreq followed by
ip_mreqn of the same group will "work" while the same two reversed
will not.
Fixed to always return EADDRINUSE on a duplicate join and
removed the (now unused) reference count in ip_mc_socklist.
2) The group-search list in ip_mc_join_group() is comparing a full
ip_mreqn structure and all of it must match for it to find the
group. This doesn't correctly match a group that was joined with
ip_mreq or ip_mreqn with an address (with or without an index). It
also doesn't match groups that are joined by different addresses on
the same interface. All of these are the same multicast group,
which is identified by group address and interface index.
Fixed the check to correctly match groups so we don't get
duplicate group entries on the ip_mc_socklist.
3) The old code allocates a multicast address before searching for
duplicates requiring it to free in various error cases. This
patch moves the allocate until after the search and
igmp_max_memberships check, so never a need to allocate, then free
an entry.
Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
ca9b907d14