Allow carp(4) to be loaded as a kernel module. Follow precedent set by

bridge(4), lagg(4) etc. and make use of function pointers and
pf_proto_register() to hook carp into the network stack.

Currently, because of the uncertainty about whether the unload path is free
of race condition panics, unloads are disallowed by default.  Compiling with
CARPMOD_CAN_UNLOAD in CFLAGS removes this anti foot shooting measure.

This commit requires IP6PROTOSPACER, introduced in r211115.

Reviewed by:	bz, simon
Approved by:	ken (mentor)
MFC after:	2 weeks

2 files changed, 22 insertions, 0 deletions

diff --git a/sys/modules/Makefile b/sys/modules/Makefile
index d033a34..028c4cc 100644
--- a/sys/modules/Makefile
+++ b/sys/modules/Makefile
@@ -112,6 +112,7 @@ SUBDIR=	${_3dfx} \
 	${_ida} \
 	${_ie} \
 	if_bridge \
+	if_carp \
 	if_disc \
 	if_edsc \
 	if_ef \
diff --git a/sys/modules/if_carp/Makefile b/sys/modules/if_carp/Makefile
new file mode 100644
index 0000000..f315a80
--- /dev/null
+++ b/sys/modules/if_carp/Makefile
@@ -0,0 +1,21 @@
+# $FreeBSD$
+
+.PATH: ${.CURDIR}/../../netinet
+
+.include <bsd.own.mk>
+
+KMOD=	if_carp
+SRCS=	ip_carp.c
+SRCS+=	opt_carp.h opt_bpf.h opt_inet.h opt_inet6.h vnode_if.h
+
+.if !defined(KERNBUILDDIR)
+opt_inet.h:
+	@echo "#define INET 1" > ${.TARGET}
+
+.if ${MK_INET6_SUPPORT} != "no"
+opt_inet6.h:
+	@echo "#define INET6 1" > ${.TARGET}
+.endif
+.endif
+
+.include <bsd.kmod.mk>