1) In the full-state API when imsf_numsrc == 0
   errno should be "0", but returns EADDRNOTAVAIL

2) An illegal filter mode change
   errno should be EINVAL, but returns EADDRNOTAVAIL

3) Trying to do an any-source option without IP_ADD_MEMBERSHIP
   errno should be EINVAL, but returns EADDRNOTAVAIL

4) Adds comments for the less obvious error return values
Signed-off-by: NDavid L Stevens <dlstevens@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

1) Changes IP_ADD_SOURCE_MEMBERSHIP and MCAST_JOIN_SOURCE_GROUP to ignore
   EADDRINUSE errors on a "courtesy join" -- prior membership or not
   is ok for these.

2) Adds "leave group" equivalence of (INCLUDE, empty) filters in the 
   delta-based API. Without this, mixing delta-based API calls that
   end in an (INCLUDE, empty) filter would not allow a subsequent
   regular IP_ADD_MEMBERSHIP. It also frees socket buffer memory that
   isn't needed for both the multicast group record and source filter.
Signed-off-by: NDavid L Stevens <dlstevens@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

        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: NDavid L Stevens <dlstevens@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!