Sources for building netlink sockets on FreeBSD,
derived from routing sockets in FreeBSD and modified by
Daniele Di Proietto and Luigi Rizzo, Universita` di Pisa - 2014

This project implements netlink and generic netlink sockets,
enough to build the in-kernel openvswitch datapath.

Documentation on netlink sockets is at

http://1984.lsi.us.es/~pablo/docs/spae.pdf
http://tools.ietf.org/html/rfc3549

Code is organised as follows:
- main source files in sys/netlink/
- the BSDmakefile to be copied to sys/modules/netlink/Makefile
- headers part of the API in sys/netlink/net and sys/netlink/linux
  to be copied into /usr/include/net and /usr/include/linux
  (or /usr/include/netlink/net and /usr/include/netlink/linux/ )

--- NETLINK sockets and functions ---

netlink sockets natively operate on mbufs in FreeBSD,
on sk_buff on linux. To build the native linux code in FreeBSD, use
#define __COMPAT_MBUF_TYPE sk_buff
in the forced include so the netlink prototypes use the correct type.

netlink build routines expect a linear buffer, which is not what
mbufs provide. To help that, we may allocate a linear buffer during
the construction, which is then freed at the end before sending
the mbuf to the kernel clients.

------

NOTE ON THE HEADERS
In the new-world linux kernel:

According to linux convention sources:
include/uapi/linux/netlink.h
    API shared by user and kernel, guarded by _UAPI__LINUX_NETLINK_H
    and then installed to userspace as
    include/linux/*netlink.h guarded by __LINUX_NETLINK_H

include/linux/netlink.h
    main kernel API, starts with #include <uapi/linux/netlink.h>
    not used by userspace

include/net/netlink.h
    extended kernel API, starts with #include <linux/netlink.h>
    (i.e. knows everything)

(same goes for genetlink.h nfnetlink.h and other subfamilies).
In FreeBSD we rename uapi/linux/netlink.h to linux/uapi_netlink.h
so we do not need to modify it when installing.

For installation of the header we need to change
etc/mtree/BSD.include.dist

Case 1: files in /usr/include/linux and /usr/include/net

Index: /home/luigi/FreeBSD/head/etc/mtree/BSD.include.dist
===================================================================
--- /home/luigi/FreeBSD/head/etc/mtree/BSD.include.dist	(revision 273452)
+++ /home/luigi/FreeBSD/head/etc/mtree/BSD.include.dist	(working copy)
@@ -249,6 +249,8 @@
     ..
     libmilter
     ..
+    linux
+    ..
     lzma
     ..
     machine
Index: /home/luigi/FreeBSD/head/share/mk/src.opts.mk
===================================================================
--- /home/luigi/FreeBSD/head/share/mk/src.opts.mk	(revision 273452)
+++ /home/luigi/FreeBSD/head/share/mk/src.opts.mk	(working copy)
@@ -116,6 +116,7 @@
     NDIS \
     NETCAT \
     NETGRAPH \
+    NETLINK \
     NLS_CATALOGS \
     NS_CACHING \
     NTP \
Index: /home/luigi/FreeBSD/head/include/Makefile
===================================================================
--- /home/luigi/FreeBSD/head/include/Makefile	(revision 273452)
+++ /home/luigi/FreeBSD/head/include/Makefile	(working copy)
@@ -186,6 +186,14 @@
 	${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 *.h \
 	    ${DESTDIR}${INCLUDEDIR}/netinet
 .endif
+.if ${MK_NETLINK} != "no"
+	cd ${.CURDIR}/../sys/netlink/linux; \
+	${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 *.h \
+	    ${DESTDIR}${INCLUDEDIR}/linux
+	cd ${.CURDIR}/../sys/netlink/net; \
+	${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 *.h \
+	    ${DESTDIR}${INCLUDEDIR}/net
+.endif
 .if ${MK_PF} != "no"
 	cd ${.CURDIR}/../sys/netpfil/pf; \
 	${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 *.h \
@@ -287,6 +295,18 @@
 		    ${DESTDIR}${INCLUDEDIR}/netinet; \
 	done
 .endif
+.if ${MK_NETLINK} != "no"
+	cd ${.CURDIR}/../sys/netlink/linux; \
+	for h in *.h; do \
+		ln -fs ../../../sys/netlink/linux/$$h \
+		    ${DESTDIR}${INCLUDEDIR}/linux; \
+	done
+	cd ${.CURDIR}/../sys/netlink/net; \
+	for h in *.h; do \
+		ln -fs ../../../sys/netlink/net/$$h \
+		    ${DESTDIR}${INCLUDEDIR}/net; \
+	done
+.endif
 .if ${MK_PF} != "no"
 	cd ${.CURDIR}/../sys/netpfil/pf; \
 	for h in *.h; do \

--- case 2: files in /usr/include/netlink/{net|linux}


Index: /home/luigi/FreeBSD/head/etc/mtree/BSD.include.dist
===================================================================
--- /home/luigi/FreeBSD/head/etc/mtree/BSD.include.dist	(revision 273452)
+++ /home/luigi/FreeBSD/head/etc/mtree/BSD.include.dist	(working copy)
@@ -275,6 +275,12 @@
     ..
     netipsec
     ..
+    netlink
+        linux
+        ..
+        net
+        ..
+    ..
     netnatm
         api
         ..
Index: /home/luigi/FreeBSD/head/include/Makefile
===================================================================
--- /home/luigi/FreeBSD/head/include/Makefile	(revision 273452)
+++ /home/luigi/FreeBSD/head/include/Makefile	(working copy)
@@ -52,6 +52,7 @@
 	geom/mirror geom/mountver geom/multipath geom/nop \
 	geom/raid geom/raid3 geom/shsec geom/stripe geom/virstor \
 	netgraph/atm netgraph/netflow \
+	netlink/linux netlink/net \
 	security/audit \
 	security/mac_biba security/mac_bsdextended security/mac_lomac \
 	security/mac_mls security/mac_partition \