cmsg->cmsg_len is 'size_t' not 'socklen_t' - so it is 8 bytes on 64bit
platforms instead of 4. There is also never padding after the header.
Redo linux sendmsg() so that it stands a chance of getting it right.
Redo linux recvmsg() so that it process control data directly from the mbuf
list. Allowing it to hack the data without using the stackgap.
* translate MSG_* flags
* rewrite CMSG level/type to appropriate NetBSD value on input, and to Linux
value on output
* handle different CMSG_DATA alignment for some archs
This fixes SCM_RIGHTS passing. Other SCM_* types are not supported -
the set is different on NetBSD and Linux. SCM_TIMESTAMP doesn't seem
to be actually implemented in Linux 2.5.15, so it's not supported
for Linux binaries either (for now).
PR: 21577 by Todd Vierling
