Description of problem:
On, RHEL4 IPv6 sendto to a multicast fails with EADDRNOTAVAIL when there are bind()'ed sockets to the same multicast address.

This works in RHEL5  kernel-2.6.18-92.1.13.el5 and Fedora 9 kernel.
IPv4 also appears to work.

Version-Release number of selected component (if applicable):
kernel-2.6.9-78.0.5.EL

How reproducible:

Download ttcp from http://netcore.fi/pekkas/linux/ipv6/ttcp.c, compile it.
The prerequisites are that there is some ipv6 connectivity (at least ff00::/8 route exists) and that ip6tables is disabled (or at least packets to ff00::/8 are accepted).

Steps to Reproduce:
1. start two ipv6 multicast receivers: 'ttcp -r ff05::1 -u -p 1234 -I eth0 &' and 'ttcp -r ff05::2 -u -p 1234 -I eth0 &'
2. try to send to the group: 'ttcp -t ff05::2 -u -p 1234 -I eth0', type in something and hit enter (here tested 'aaa').

Actual results:
ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=1234  udp  -> ff05::1234
ttcp-t: socket
aaa
ttcp-t: IO: Cannot assign requested address
errno=99

Expected results:
No error printed.  'aaa' is echoed by the ttcp process set to receive the multicast group.

Additional info:
The expected state of bound sockets after reproduce step 1 is:

$ netstat -an | grep 1234
udp        0      0 ff05::2:1234                :::*
udp        0      0 ff05::1:1234                :::*
$ netstat -gn | grep ff05
eth0            1      ff05::2
eth0            1      ff05::1

sendto failure looks like:

sendto(3, "aaa\n", 4, 0, {sa_family=AF_INET6, sin6_port=htons(1234), inet_pton(AF_INET6, "ff05::1", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0}, 28) = -1 EADDRNOTAVAIL (Cannot assign requested address)

See comment #46 in bug number #231899 for some background.