rdma: use resp.len after validation in qemu_rdma_registration_stop

resp.len is given from remote host. So should be validated before use.
Otherwise memcpy can access beyond the buffer.

Cc: Michael R. Hines <mrhines@us.ibm.com>
Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Isaku Yamahata <yamahata@private.email.ne.jp>
rdma: validate RDMAControlHeader::len

RMDAControlHeader::len is provided from remote, so validate it.

Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Isaku Yamahata <yamahata@private.email.ne.jp>
rdma: check if RDMAControlHeader::len match transferred byte

RDMAControlHeader::len is provided from remote, so check if the value
match the actual transferred byte_len.

Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Isaku Yamahata <yamahata@private.email.ne.jp>
rdma: proper getaddrinfo() handling

getaddrinfo() already knows what it's doing,
wqand can potentially return multiple addresses.
ipv6 over RoCE is broken - warn the user if we can