initial libmnl import

Make_global.am

@@ -0,0 +1,7 @@
+# This is _NOT_ the library release version, it's an API version.
+# Please read Chapter 6 "Library interface versions" of the libtool
+# documentation before making any modification
+# http://sources.redhat.com/autobook/autobook/autobook_91.html
+LIBVERSION=0:0:0
+
+INCLUDES=$(all_includes) -I$(top_srcdir)/include

Makefile.am

@@ -0,0 +1,14 @@
+include $(top_srcdir)/Make_global.am
+
+AUTOMAKE_OPTIONS = foreign dist-bzip2 1.6
+ACLOCAL_AMFLAGS = -I m4
+
+SUBDIRS = src include examples
+DIST_SUBDIRS = src include examples
+
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = libmnl.pc
+
+$(OBJECTS): libtool
+libtool: $(LIBTOOL_DEPS)
+	$(SHELL) ./config.status --recheck

README

@@ -0,0 +1,9 @@
+libmnl
+
+Features:
+- Minimalistic Netlink library
+- Low-level: you have to know how Netlink works.
+- Simplicity: as opposed to complexity.
+- Very low abstraction: try to leak as less Netlink details as possible.
+- Decoupling: the main bricks are decoupled to avoid inter-dependencies
+(eg. socket handling and callbacks are not attached).

autogen.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+
+include ()
+{
+    # If we keep a copy of the kernel header in the SVN tree, we'll have
+    # to worry about synchronization issues forever. Instead, we just copy 
+    # the headers that we need from the lastest kernel version at autogen
+    # stage.
+
+    INCLUDEDIR=${KERNEL_DIR:-/lib/modules/`uname -r`/build}/include/linux
+
+    if [ -f $INCLUDEDIR/netfilter/nfnetlink.h ]
+    then
+    	TARGET=include/libnfnetlink/linux_nfnetlink.h
+    	echo "Copying nfnetlink.h to linux_nfnetlink.h"
+    	cp $INCLUDEDIR/netfilter/nfnetlink.h $TARGET
+	TMP=`mktemp`
+	sed 's/__be16/u_int16_t/g' $TARGET > $TMP
+	cp $TMP $TARGET
+	sed 's/#include <linux\/netfilter\/nfnetlink_compat\.h>/#include <libnfnetlink\/linux_nfnetlink_compat\.h>/g' $TARGET > $TMP
+	cp $TMP $TARGET
+    else
+    	echo "can't find nfnetlink.h kernel file in $INCLUDEDIR"
+    	exit 1
+    fi
+
+    if [ -f $INCLUDEDIR/netfilter/nfnetlink_compat.h ]
+    then
+    	TARGET=include/libnfnetlink/linux_nfnetlink_compat.h
+    	echo "Copying nfnetlink_compat.h to linux_nfnetlink_compat.h"
+	cp $INCLUDEDIR/netfilter/nfnetlink_compat.h $TARGET
+    else
+    	echo "can't find nfnetlink.h kernel file in $INCLUDEDIR, ignoring"
+    fi
+}
+
+run ()
+{
+    echo "running: $*"
+    eval $*
+
+    if test $? != 0 ; then
+	echo "error: while running '$*'"
+	exit 1
+    fi
+}
+
+[ "x$1" = "xdistrib" ] && include
+run aclocal
+#run autoheader
+run libtoolize -f
+run automake -a
+run autoconf

configure.in

@@ -0,0 +1,18 @@
+dnl Process this file with autoconf to create configure.
+
+AC_INIT
+AC_CANONICAL_SYSTEM
+AC_CONFIG_MACRO_DIR([m4])
+AM_INIT_AUTOMAKE(libmnl, 1.0.0-beta0)
+
+AC_PROG_CC
+AC_EXEEXT
+AM_PROG_LIBTOOL
+AC_SUBST(LIBTOOL_DEPS)
+
+case $target in 
+*-*-linux*) ;;
+*) AC_MSG_ERROR([Linux only, dude!]);;
+esac
+
+AC_OUTPUT(Makefile src/Makefile include/Makefile include/libmnl/Makefile examples/Makefile libmnl.pc)

examples/Makefile.am

@@ -0,0 +1,24 @@
+include $(top_srcdir)/Make_global.am
+
+check_PROGRAMS = rtnl-link-dump rtnl-link-event rtnl-link-set \
+		 rtnl-route-dump genl-family-get
+
+rtnl_link_dump_SOURCES = rtnl-link-dump.c
+rtnl_link_dump_LDADD = ../src/libmnl.la
+rtnl_link_dump_LDFLAGS = -dynamic -ldl
+
+rtnl_link_event_SOURCES = rtnl-link-event.c
+rtnl_link_event_LDADD = ../src/libmnl.la
+rtnl_link_event_LDFLAGS = -dynamic -ldl
+
+rtnl_link_set_SOURCES = rtnl-link-set.c
+rtnl_link_set_LDADD = ../src/libmnl.la
+rtnl_link_set_LDFLAGS = -dynamic -ldl
+
+rtnl_route_dump_SOURCES = rtnl-route-dump.c
+rtnl_route_dump_LDADD = ../src/libmnl.la
+rtnl_route_dump_LDFLAGS = -dynamic -ldl
+
+genl_family_get_SOURCES = genl-family-get.c
+genl_family_get_LDADD = ../src/libmnl.la
+genl_family_get_LDFLAGS = -dynamic -ldl

examples/genl-family-get.c

@@ -0,0 +1,143 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/genetlink.h>
+
+static void parse_genl_mc_grps(struct nlattr *nested)
+{
+	struct nlattr *pos;
+	int len;
+
+	mnl_attr_for_each_nested(pos, nested, len) {
+		struct nlattr *tb[CTRL_ATTR_MCAST_GRP_MAX+1];
+
+		mnl_attr_parse_nested(pos, tb, CTRL_ATTR_MCAST_GRP_MAX);
+		if (tb[CTRL_ATTR_MCAST_GRP_ID]) {
+			printf("id-0x%x ",
+				mnl_attr_get_u32(tb[CTRL_ATTR_MCAST_GRP_ID]));
+		}
+		if (tb[CTRL_ATTR_MCAST_GRP_NAME]) {
+			printf("name: %s ",
+				mnl_attr_get_str(tb[CTRL_ATTR_MCAST_GRP_NAME]));
+		}
+		printf("\n");
+	}
+}
+
+static void parse_genl_family_ops(struct nlattr *nested)
+{
+	struct nlattr *pos;
+	int len;
+
+	mnl_attr_for_each_nested(pos, nested, len) {
+		struct nlattr *tb[CTRL_ATTR_OP_MAX+1];
+
+		mnl_attr_parse_nested(pos, tb, CTRL_ATTR_OP_MAX);
+		if (tb[CTRL_ATTR_OP_ID]) {
+			printf("id-0x%x ",
+				mnl_attr_get_u32(tb[CTRL_ATTR_OP_ID]));
+		}
+		if (tb[CTRL_ATTR_OP_MAX]) {
+			printf("flags ");
+		}
+		printf("\n");
+	}
+}
+
+static int data_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct nlattr *tb[CTRL_ATTR_MAX+1];
+	struct genlmsghdr *genl = mnl_nlmsg_get_data(nlh);
+
+	mnl_attr_parse_at_offset(nlh, sizeof(*genl), tb, CTRL_ATTR_MAX);
+	if (tb[CTRL_ATTR_FAMILY_NAME]) {
+		printf("name=%s\t",
+			mnl_attr_get_str(tb[CTRL_ATTR_FAMILY_NAME]));
+	}
+	if (tb[CTRL_ATTR_FAMILY_ID]) {
+		printf("id=%u\t",
+			mnl_attr_get_u16(tb[CTRL_ATTR_FAMILY_ID]));
+	}
+	if (tb[CTRL_ATTR_VERSION]) {
+		printf("version=%u\t",
+			mnl_attr_get_u32(tb[CTRL_ATTR_VERSION]));
+	}
+	if (tb[CTRL_ATTR_HDRSIZE]) {
+		printf("hdrsize=%u\t",
+			mnl_attr_get_u32(tb[CTRL_ATTR_HDRSIZE]));
+	}
+	if (tb[CTRL_ATTR_MAXATTR]) {
+		printf("maxattr=%u\t",
+			mnl_attr_get_u32(tb[CTRL_ATTR_MAXATTR]));
+	}
+	if (tb[CTRL_ATTR_OPS]) {
+		printf("\nops:\n");
+		parse_genl_family_ops(tb[CTRL_ATTR_OPS]);
+	}
+	if (tb[CTRL_ATTR_MCAST_GROUPS]) {
+		printf("\ngrps:\n");
+		parse_genl_mc_grps(tb[CTRL_ATTR_MCAST_GROUPS]);
+	}
+	return MNL_CB_OK;
+}
+
+int main(int argc, char *argv[])
+{
+	struct mnl_socket *nl;
+	char buf[getpagesize()];
+	struct nlmsghdr *nlh;
+	struct genlmsghdr *genl;
+	int ret;
+	unsigned int seq;
+
+	if (argc != 2) {
+		printf("%s [family name]\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	nlh = mnl_nlmsg_put_header(buf);
+	nlh->nlmsg_type	= GENL_ID_CTRL;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+	nlh->nlmsg_seq = seq = time(NULL);
+
+	genl = mnl_nlmsg_put_extra_header(nlh, sizeof(struct genlmsghdr));
+	genl->cmd = CTRL_CMD_GETFAMILY;
+	genl->version = 1;
+
+	mnl_attr_put_u32(nlh, CTRL_ATTR_FAMILY_ID, GENL_ID_CTRL);
+	mnl_attr_put_str_null(nlh, CTRL_ATTR_FAMILY_NAME, argv[1]);
+
+	nl = mnl_socket_open(NETLINK_GENERIC);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_sendto(nl, nlh, mnl_nlmsg_get_len(nlh)) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, seq, data_cb, NULL);
+		if (ret <= 0)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_socket_close(nl);
+
+	return 0;
+}

examples/rtnl-link-dump.c

@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/if.h>
+#include <linux/if_link.h>
+#include <linux/rtnetlink.h>
+
+static int data_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct nlattr *tb[IFLA_MAX+1];
+	struct ifinfomsg *ifm = mnl_nlmsg_get_data(nlh);
+	int len = mnl_nlmsg_get_len(nlh);
+	struct nlattr *attr;
+
+	printf("index=%d type=%d flags=%d family=%d ", 
+		ifm->ifi_index, ifm->ifi_type,
+		ifm->ifi_flags, ifm->ifi_family);
+
+	if (ifm->ifi_flags & IFF_RUNNING)
+		printf("[RUNNING] ");
+	else
+		printf("[NOT RUNNING] ");
+
+	mnl_attr_parse_at_offset(nlh, sizeof(*ifm), tb, IFLA_MAX);
+	if (tb[IFLA_MTU]) {
+		printf("mtu=%d ", mnl_attr_get_u32(tb[IFLA_MTU]));
+	}
+	if (tb[IFLA_IFNAME]) {
+		printf("name=%s", mnl_attr_get_str(tb[IFLA_IFNAME]));
+	}
+	printf("\n");
+	return MNL_CB_OK;
+}
+
+int main()
+{
+	struct mnl_socket *nl;
+	char buf[getpagesize()];
+	struct nlmsghdr *nlh;
+	struct rtgenmsg *rt;
+	int ret;
+	unsigned int seq;
+
+	nlh = mnl_nlmsg_put_header(buf);
+	nlh->nlmsg_type	= RTM_GETLINK;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
+	nlh->nlmsg_seq = seq = time(NULL);
+	rt = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtgenmsg));
+	rt->rtgen_family = AF_PACKET;
+
+	nl = mnl_socket_open(NETLINK_ROUTE);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_sendto(nl, nlh, mnl_nlmsg_get_len(nlh)) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, seq, data_cb, NULL);
+		if (ret <= MNL_CB_STOP)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_socket_close(nl);
+
+	return 0;
+}

examples/rtnl-link-event.c

@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/if.h>
+#include <linux/if_link.h>
+#include <linux/rtnetlink.h>
+
+static int data_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct nlattr *tb[IFLA_MAX+1];
+	struct ifinfomsg *ifm = mnl_nlmsg_get_data(nlh);
+	int len = mnl_nlmsg_get_len(nlh);
+	struct nlattr *attr;
+
+	printf("index=%d type=%d flags=%d family=%d ", 
+		ifm->ifi_index, ifm->ifi_type,
+		ifm->ifi_flags, ifm->ifi_family);
+
+	if (ifm->ifi_flags & IFF_RUNNING)
+		printf("[RUNNING] ");
+	else
+		printf("[NOT RUNNING] ");
+
+	mnl_attr_parse_at_offset(nlh, sizeof(*ifm), tb, IFLA_MAX);
+	if (tb[IFLA_MTU]) {
+		printf("mtu=%d ", mnl_attr_get_u32(tb[IFLA_MTU]));
+	}
+	if (tb[IFLA_IFNAME]) {
+		printf("name=%s", mnl_attr_get_str(tb[IFLA_IFNAME]));
+	}
+	printf("\n");
+	return MNL_CB_OK;
+}
+
+int main()
+{
+	struct mnl_socket *nl;
+	char buf[getpagesize()];
+	struct nlmsghdr *nlh = (struct nlmsghdr *) buf;
+	int ret;
+
+	nl = mnl_socket_open(NETLINK_ROUTE);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, RTMGRP_LINK, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, 0, data_cb, NULL);
+		if (ret <= 0)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_socket_close(nl);
+
+	return 0;
+}

examples/rtnl-link-set.c

@@ -0,0 +1,76 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/if.h>
+#include <linux/if_link.h>
+#include <linux/rtnetlink.h>
+
+int main(int argc, char *argv[])
+{
+	struct mnl_socket *nl;
+	char buf[getpagesize()];
+	struct nlmsghdr *nlh;
+	struct ifinfomsg *ifm;
+	int ret;
+	unsigned int seq, oper;
+
+	if (argc != 3) {
+		printf("Usage: %s [ifname] [up|down]\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	if (strncasecmp(argv[2], "up") == 0)
+		oper = IF_OPER_UP;
+	else if (strncasecmp(argv[2], "down") == 0)
+		oper = IF_OPER_DOWN;
+	else {
+		fprintf(stderr, "%s is not `up' nor `down'\n", argv[2]);
+		exit(EXIT_FAILURE);
+	}
+
+	nlh = mnl_nlmsg_put_header(buf);
+	nlh->nlmsg_type	= RTM_SETLINK;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+	nlh->nlmsg_seq = seq = time(NULL);
+	ifm = mnl_nlmsg_put_extra_header(nlh, sizeof(*ifm));
+	ifm->ifi_family = AF_PACKET;
+
+	mnl_attr_put_u8(nlh, IFLA_OPERSTATE, oper);
+	mnl_attr_put_str(nlh, IFLA_IFNAME, argv[1]);
+
+	nl = mnl_socket_open(NETLINK_ROUTE);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_nlmsg_print(nlh);
+
+	if (mnl_socket_sendto(nl, nlh, mnl_nlmsg_get_len(nlh)) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	if (ret == -1) {
+		perror("read");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_cb_run(buf, ret, seq, NULL, NULL);
+	if (ret == -1){
+		perror("callback");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_socket_close(nl);
+
+	return 0;
+}

examples/rtnl-route-dump.c

@@ -0,0 +1,192 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/if.h>
+#include <linux/if_link.h>
+#include <linux/rtnetlink.h>
+
+static void attributes_show_ipv4(struct nlattr *tb[])
+{
+	if (tb[RTA_TABLE]) {
+		printf("table=%u ", mnl_attr_get_u32(tb[RTA_TABLE]));
+	}
+	if (tb[RTA_DST]) {
+		printf("dst=%s ", inet_ntoa(mnl_attr_get_u32(tb[RTA_DST])));
+	}
+	if (tb[RTA_SRC]) {
+		printf("src=%s ", inet_ntoa(mnl_attr_get_u32(tb[RTA_SRC])));
+	}
+	if (tb[RTA_OIF]) {
+		printf("oif=%u ", mnl_attr_get_u32(tb[RTA_OIF]));
+	}
+	if (tb[RTA_FLOW]) {
+		printf("flow=%u ", mnl_attr_get_u32(tb[RTA_FLOW]));
+	}
+	if (tb[RTA_PREFSRC]) {
+		printf("prefsrc=%s ",
+			inet_ntoa(mnl_attr_get_u32(tb[RTA_PREFSRC])));
+	}
+	if (tb[RTA_GATEWAY]) {
+		printf("gw=%s ", inet_ntoa(mnl_attr_get_u32(tb[RTA_GATEWAY])));
+	}
+	if (tb[RTA_METRICS]) {
+		int i;
+		struct nlattr *tbx[RTAX_MAX+1] = {};
+
+		mnl_attr_parse_nested(tb[RTA_METRICS], tbx, RTAX_MAX);
+
+		for (i=0; i<RTAX_MAX; i++) {
+			if (tbx[i]) {
+				printf("metrics[%d]=%u ",
+					mnl_attr_get_u32(tbx[i]));
+			}
+		}
+	}
+	printf("\n");
+}
+
+static int data_cb(const struct nlmsghdr *nlh, void *data)
+{
+	/* parse() ya está inicializando este array, qué hacer ? */
+	struct nlattr *tb[RTA_MAX+1] = {};
+	struct rtmsg *rm = mnl_nlmsg_get_data(nlh);
+	int len = mnl_nlmsg_get_len(nlh);
+	struct nlattr *attr;
+
+	/* protocol family = AF_INET | AF_INET6 */
+	printf("family=%u ", rm->rtm_family);
+
+	/* destination CIDR, eg. 24 or 32 for IPv4 */
+	printf("dst_len=%u ", rm->rtm_dst_len);
+
+	/* source CIDR */
+	printf("src_len=%u ", rm->rtm_src_len);
+
+	/* type of service (TOS), eg. 0 */
+	printf("tos=%u ", rm->rtm_tos);
+
+	/* table id:
+	 *	RT_TABLE_UNSPEC		= 0
+	 *
+	 * 	... user defined values ...
+	 *
+	 *	RT_TABLE_COMPAT		= 252
+	 *	RT_TABLE_DEFAULT	= 253
+	 *	RT_TABLE_MAIN		= 254
+	 *	RT_TABLE_LOCAL		= 255
+	 *	RT_TABLE_MAX		= 0xFFFFFFFF
+	 *
+	 * Synonimous attribute: RTA_TABLE.
+	 */
+	printf("table=%u ", rm->rtm_table);
+
+	/* type:
+	 * 	RTN_UNSPEC	= 0
+	 * 	RTN_UNICAST	= 1
+	 * 	RTN_LOCAL	= 2
+	 * 	RTN_BROADCAST	= 3
+	 *	RTN_ANYCAST	= 4
+	 *	RTN_MULTICAST	= 5
+	 *	RTN_BLACKHOLE	= 6
+	 *	RTN_UNREACHABLE	= 7
+	 *	RTN_PROHIBIT	= 8
+	 *	RTN_THROW	= 9
+	 *	RTN_NAT		= 10
+	 *	RTN_XRESOLVE	= 11
+	 *	__RTN_MAX	= 12
+	 */
+	printf("type=%u ", rm->rtm_type);
+
+	/* scope:
+	 * 	RT_SCOPE_UNIVERSE	= 0   : everywhere in the universe
+	 *
+	 *      ... user defined values ...
+	 *
+	 * 	RT_SCOPE_SITE		= 200
+	 * 	RT_SCOPE_LINK		= 253 : destination attached to link
+	 * 	RT_SCOPE_HOST		= 254 : local address
+	 * 	RT_SCOPE_NOWHERE	= 255 : not existing destination
+	 */
+	printf("scope=%u ", rm->rtm_scope);
+
+	/* protocol:
+	 * 	RTPROT_UNSPEC	= 0
+	 * 	RTPROT_REDIRECT = 1
+	 * 	RTPROT_KERNEL	= 2 : route installed by kernel
+	 * 	RTPROT_BOOT	= 3 : route installed during boot
+	 * 	RTPROT_STATIC	= 4 : route installed by administrator
+	 *
+	 * Values >= RTPROT_STATIC are not interpreted by kernel, they are
+	 * just user-defined.
+	 */
+	printf("proto=%u ", rm->rtm_protocol);
+
+	/* flags:
+	 * 	RTM_F_NOTIFY	= 0x100: notify user of route change
+	 * 	RTM_F_CLONED	= 0x200: this route is cloned
+	 * 	RTM_F_EQUALIZE	= 0x400: Multipath equalizer: NI
+	 * 	RTM_F_PREFIX	= 0x800: Prefix addresses
+	 */
+	printf("flags=%x\n", rm->rtm_flags);
+
+	mnl_attr_parse_at_offset(nlh, sizeof(*rm), tb, RTA_MAX);
+
+	switch(rm->rtm_family) {
+	case AF_INET:
+		attributes_show_ipv4(tb);
+		break;
+	}
+
+	return MNL_CB_OK;
+}
+
+int main()
+{
+	struct mnl_socket *nl;
+	char buf[getpagesize()];
+	struct nlmsghdr *nlh;
+	struct rtmsg *rtm;
+	int ret;
+	unsigned int seq;
+
+	nlh = mnl_nlmsg_put_header(buf);
+	nlh->nlmsg_type = RTM_GETROUTE;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
+	nlh->nlmsg_seq = seq = time(NULL);
+	rtm = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtmsg));
+	rtm->rtm_family = AF_INET;
+
+	nl = mnl_socket_open(NETLINK_ROUTE);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_sendto(nl, nlh, mnl_nlmsg_get_len(nlh)) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, 0, data_cb, NULL);
+		if (ret <= MNL_CB_STOP)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_socket_close(nl);
+
+	return 0;
+}

include/Makefile.am

@@ -0,0 +1 @@
+SUBDIRS = libmnl

include/libmnl/Makefile.am

@@ -0,0 +1 @@
+pkginclude_HEADERS = libmnl.h

include/libmnl/libmnl.h

@@ -0,0 +1,120 @@
+#ifndef _LIBMNL_H_
+#define _LIBMNL_H_
+
+#include <sys/socket.h> /* for sa_family_t */
+#include <linux/netlink.h>
+
+/*
+ * generic netlink socket API
+ */
+
+#define MNL_SOCKET_AUTOPID	0
+
+struct mnl_socket;
+
+extern struct mnl_socket *mnl_socket_open(int type);
+extern int mnl_socket_bind(struct mnl_socket *nl, int groups, int pid);
+extern int mnl_socket_close(struct mnl_socket *nl);
+extern int mnl_socket_get_fd(const struct mnl_socket *nl);
+extern unsigned int mnl_socket_get_portid(const struct mnl_socket *nl);
+extern int mnl_socket_sendto(struct mnl_socket *nl, const void *req, int siz);
+extern int mnl_socket_sendmsg(struct mnl_socket *nl, struct msghdr *msg, int flags);
+extern int mnl_socket_recvfrom(struct mnl_socket *nl, void *buf, int siz);
+extern int mnl_socket_recvmsg(const struct mnl_socket *nl, struct msghdr *msg, int flags);
+extern int mnl_socket_setsockopt(struct mnl_socket *nl, int type, void *buf, socklen_t len);
+extern int mnl_socket_getsockopt(struct mnl_socket *nl, int type, void *buf, socklen_t *len);
+
+/*
+ * generic netlink message API
+ */
+
+#define MNL_ALIGNTO	4
+#define MNL_NLMSG_HDRLEN	mnl_align(sizeof(struct nlmsghdr))
+
+extern int mnl_align(int len);
+extern size_t mnl_nlmsg_size(int len);
+extern size_t mnl_nlmsg_total_size(int len);
+extern size_t mnl_nlmsg_payload_size(const struct nlmsghdr *nlh);
+
+/* Netlink message header builder */
+extern struct nlmsghdr *mnl_nlmsg_put_header(void *buf);
+extern void *mnl_nlmsg_put_extra_header(struct nlmsghdr *nlh, int size);
+
+/* Netlink message iterators */
+extern int mnl_nlmsg_ok(const struct nlmsghdr *nlh, int len);
+extern struct nlmsghdr *mnl_nlmsg_next(const struct nlmsghdr *nlh, int *len);
+
+/* Netlink sequence tracking */
+extern int mnl_nlmsg_seq_ok(const struct nlmsghdr *nlh, unsigned int seq);
+
+/* Netlink header getters */
+extern u_int16_t mnl_nlmsg_get_len(const struct nlmsghdr *nlh);
+extern void *mnl_nlmsg_get_data(const struct nlmsghdr *nlh);
+extern void *mnl_nlmsg_get_data_offset(const struct nlmsghdr *nlh, int offset);
+extern void *mnl_nlmsg_get_tail(const struct nlmsghdr *nlh);
+
+/* Netlink dump message */
+extern void mnl_nlmsg_print(const struct nlmsghdr *nlh);
+
+/*
+ * generic netlink attributes API
+ */
+#define MNL_ATTR_HDRLEN	mnl_align(sizeof(struct nlattr))
+
+/* TLV attribute getters */
+extern u_int16_t mnl_attr_get_type(const struct nlattr *attr);
+extern u_int16_t mnl_attr_get_len(const struct nlattr *attr);
+extern u_int16_t mnl_attr_get_payload_len(const struct nlattr *attr);
+extern void *mnl_attr_get_data(const struct nlattr *attr);
+extern u_int8_t mnl_attr_get_u8(const struct nlattr *attr);
+extern u_int16_t mnl_attr_get_u16(const struct nlattr *attr);
+extern u_int32_t mnl_attr_get_u32(const struct nlattr *attr);
+extern u_int64_t mnl_attr_get_u64(const struct nlattr *attr);
+extern const char *mnl_attr_get_str(const struct nlattr *attr);
+
+/* TLV attribute putters */
+extern void mnl_attr_put(struct nlmsghdr *nlh, int type, size_t len, const void *data);
+extern void mnl_attr_put_u8(struct nlmsghdr *nlh, int type, u_int8_t data);
+extern void mnl_attr_put_u16(struct nlmsghdr *nlh, int type, u_int16_t data);
+extern void mnl_attr_put_u32(struct nlmsghdr *nlh, int type, u_int32_t data);
+extern void mnl_attr_put_u64(struct nlmsghdr *nlh, int type, u_int64_t data);
+extern void mnl_attr_put_str(struct nlmsghdr *nlh, int type, const void *data);
+extern void mnl_attr_put_str_null(struct nlmsghdr *nlh, int type, const void *data);
+
+/* TLV attribute parsers */
+extern int mnl_attr_parse(const struct nlmsghdr *nlh, struct nlattr *tb[], int max);
+extern int mnl_attr_parse_at_offset(const struct nlmsghdr *nlh, int offset, struct nlattr *tb[], int max);
+extern int mnl_attr_parse_nested(const struct nlattr *attr, struct nlattr *tb[], int max);
+extern int mnl_attr_ok(const struct nlattr *attr, int len);
+extern struct nlattr *mnl_attr_next(const struct nlattr *attr, int *len);
+
+#define mnl_attr_for_each_nested(pos, head, len)			    \
+	for (pos = mnl_attr_get_data(head), len = mnl_attr_get_len(head); \
+	     mnl_attr_ok(pos, len);					    \
+	     pos = mnl_attr_next(pos, &(len)))
+
+/*
+ * callback API
+ */
+#define MNL_CB_ERROR		-1
+#define MNL_CB_STOP		 0
+#define MNL_CB_OK		 1
+
+typedef int (*mnl_cb_t)(const struct nlmsghdr *nlh, void *data);
+
+extern int mnl_cb_run(const char *buf, int numbytes, unsigned int seq,
+		      mnl_cb_t cb_data, void *data);
+
+extern int mnl_cb_run2(const char *buf, int numbytes, unsigned int seq,
+		       mnl_cb_t cb_data, void *data,
+		       mnl_cb_t *cb_ctl_array, int cb_ctl_array_len);
+
+/*
+ * other declarations
+ */
+
+#ifndef SOL_NETLINK
+#define SOL_NETLINK	270
+#endif
+
+#endif

libmnl.pc.in

@@ -0,0 +1,15 @@
+# libmnl pkg-config file
+
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: libmnl
+Description: Minimalistic Netlink communication library
+URL: http://netfilter.org/projects/libmnl/
+Version: @VERSION@
+Requires:
+Conflicts:
+Libs: -L${libdir} -lmnl
+Cflags: -I${includedir}

src/Makefile.am

@@ -0,0 +1,9 @@
+include $(top_srcdir)/Make_global.am
+
+AM_CFLAGS=-fPIC -Wall
+LIBS=
+
+lib_LTLIBRARIES = libmnl.la
+
+libmnl_la_LDFLAGS = -Wc,-nostartfiles -version-info $(LIBVERSION)
+libmnl_la_SOURCES = socket.c callback.c msg.c attr.c

src/attr.c

@@ -0,0 +1,212 @@
+/*
+ * (C) 2008-2010 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ */
+
+#include <libmnl/libmnl.h>
+#include <string.h>
+
+/**
+ * Netlink attribute:
+ *
+ *  |<-- 2 bytes -->|<-- 2 bytes -->|<-- variable -->|
+ *  -------------------------------------------------
+ *  |     length    |      type     |      value     |
+ *  -------------------------------------------------
+ */
+
+/**
+ * mnl_attr_get_type - get the attribute type of a netlink message
+ *
+ * This function returns the attribute type.
+ */
+u_int16_t mnl_attr_get_type(const struct nlattr *attr)
+{
+	return attr->nla_type & NLA_TYPE_MASK;
+}
+
+/**
+ * mnl_attr_get_len - get the attribute length
+ *
+ * This function returns the attribute length.
+ */
+u_int16_t mnl_attr_get_len(const struct nlattr *attr)
+{
+	return attr->nla_len;
+}
+
+/**
+ * mnl_attr_get_payload_len - get the attribute payload length
+ *
+ * This function returns the attribute payload length.
+ */
+u_int16_t mnl_attr_get_payload_len(const struct nlattr *attr)
+{
+	return attr->nla_len - MNL_ATTR_HDRLEN;
+}
+
+/**
+ * mnl_attr_get_data - get pointer to the attribute payload
+ *
+ * This function return a pointer to the attribute payload
+ */
+void *mnl_attr_get_data(const struct nlattr *attr)
+{
+	return (void *)attr + MNL_ATTR_HDRLEN;
+}
+
+/**
+ * mnl_attr_ok - check a there is room for an attribute
+ * @nlh: attribute that we want to check
+ * @len: remaining bytes in a buffer that contains the attribute
+ *
+ * This function is used to check that a buffer that contains an attribute
+ * has enough room for the attribute that it stores, ie. this function can
+ * be used to verify that an attribute is not malformed nor truncated.
+ */
+int mnl_attr_ok(const struct nlattr *attr, int len)
+{
+	return len >= sizeof(struct nlattr) &&
+	       attr->nla_len >= sizeof(struct nlattr) &&
+	       attr->nla_len <= len;
+}
+
+/**
+ * mnl_attr_next - get the next attribute in the payload of a netlink message
+ * @attr: pointer to the current attribute
+ * @len: pointer to the current remaining bytes in the buffer
+ *
+ * This function returns a pointer to the next attribute that is in the
+ * payload of a netlink message.
+ */
+struct nlattr *mnl_attr_next(const struct nlattr *attr, int *len)
+{
+	*len -= mnl_align(attr->nla_len);
+	return (struct nlattr *)((void *)attr + mnl_align(attr->nla_len));
+}
+
+/**
+ * mnl_attr_parse - returns an array with the attributes in a message
+ * @tb: array of pointers to the attribute found
+ * @tb_size: size of the attribute array
+ * @attr: first attribute in the stream
+ * @len: remaining bytes in the buffer that contain attributes
+ *
+ * This function returns a table of pointers to the attributes that has been
+ * found in a netlink payload. This function return 0 on sucess, and >0 to
+ * indicate the number of bytes the remaining bytes.
+ */
+int mnl_attr_parse_at_offset(const struct nlmsghdr *nlh, int offset,
+			      struct nlattr *tb[], int max)
+{
+	struct nlattr *attr = mnl_nlmsg_get_data_offset(nlh, offset);
+	int len = mnl_nlmsg_get_len(nlh);
+
+	memset(tb, 0, sizeof(struct nlattr *) * (max + 1));
+
+	while (mnl_attr_ok(attr, len)) {
+		if (mnl_attr_get_type(attr) <= max)
+			tb[mnl_attr_get_type(attr)] = attr;
+		attr = mnl_attr_next(attr, &len);
+	}
+	return len;
+}
+
+int mnl_attr_parse(const struct nlmsghdr *nlh, struct nlattr *tb[], int max)
+{
+	return mnl_attr_parse_at_offset(nlh, 0, tb, max);
+}
+
+int mnl_attr_parse_nested(const struct nlattr *nested,
+			   struct nlattr *tb[], int max)
+{
+	struct nlattr *attr = mnl_attr_get_data(nested);
+	int len = mnl_attr_get_payload_len(nested);
+
+	memset(tb, 0, sizeof(struct nlattr *) * (max + 1));
+
+	while (mnl_attr_ok(attr, len)) {
+		if (mnl_attr_get_type(attr) <= max)
+			tb[mnl_attr_get_type(attr)] = attr;
+		attr = mnl_attr_next(attr, &len);
+	}
+	return len;
+}
+
+u_int8_t mnl_attr_get_u8(const struct nlattr *attr)
+{
+	return *((u_int8_t *)mnl_attr_get_data(attr));
+}
+
+u_int16_t mnl_attr_get_u16(const struct nlattr *attr)
+{
+	return *((u_int16_t *)mnl_attr_get_data(attr));
+}
+
+u_int32_t mnl_attr_get_u32(const struct nlattr *attr)
+{
+	return *((u_int32_t *)mnl_attr_get_data(attr));
+}
+
+/**
+ * mnl_attr_get_u64 - returns an arra
+ * @attr: netlink attribute
+ *
+ * This function returns the payload of a 64-bits attribute. This function
+ * is align-safe since accessing 64-bits Netlink attributes is a common
+ * source of alignment issues.
+ */
+u_int64_t mnl_attr_get_u64(const struct nlattr *attr)
+{
+	u_int64_t tmp;
+	memcpy(&tmp, mnl_attr_get_data(attr), sizeof(tmp));
+	return tmp;
+}
+
+const char *mnl_attr_get_str(const struct nlattr *attr)
+{
+	return (const char *)mnl_attr_get_data(attr);
+}
+
+void mnl_attr_put(struct nlmsghdr *nlh, int type, size_t len, const void *data)
+{
+	struct nlattr *attr = mnl_nlmsg_get_tail(nlh);
+	int payload_len = mnl_align(sizeof(struct nlattr)) + len;
+
+	attr->nla_type = type;
+	attr->nla_len = payload_len;
+	memcpy(mnl_attr_get_data(attr), data, len);
+	nlh->nlmsg_len += mnl_align(payload_len);
+}
+
+void mnl_attr_put_u8(struct nlmsghdr *nlh, int type, u_int8_t data)
+{
+	mnl_attr_put(nlh, type, sizeof(u_int8_t), &data);
+}
+
+void mnl_attr_put_u16(struct nlmsghdr *nlh, int type, u_int16_t data)
+{
+	mnl_attr_put(nlh, type, sizeof(u_int16_t), &data);
+}
+
+void mnl_attr_put_u32(struct nlmsghdr *nlh, int type, u_int32_t data)
+{
+	mnl_attr_put(nlh, type, sizeof(u_int32_t), &data);
+}
+
+void mnl_attr_put_u64(struct nlmsghdr *nlh, int type, u_int64_t data)
+{
+	mnl_attr_put(nlh, type, sizeof(u_int64_t), &data);
+}
+
+void mnl_attr_put_str(struct nlmsghdr *nlh, int type, const void *data)
+{
+	mnl_attr_put(nlh, type, strlen(data), data);
+}
+
+void mnl_attr_put_str_null(struct nlmsghdr *nlh, int type, const void *data)
+{
+	mnl_attr_put(nlh, type, strlen(data)+1, data);
+}

src/callback.c

@@ -0,0 +1,119 @@
+/*
+ * (C) 2008-2010 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ */
+
+#include <errno.h>
+#include <libmnl/libmnl.h>
+
+static int mnl_cb_noop(const struct nlmsghdr *nlh, void *data)
+{
+	return MNL_CB_OK;
+}
+
+static int mnl_cb_error(const struct nlmsghdr *nlh, void *data)
+{
+	const struct nlmsgerr *err = mnl_nlmsg_get_data(nlh);
+
+	if (nlh->nlmsg_len < mnl_nlmsg_size(sizeof(struct nlmsgerr))) {
+		errno = EBADMSG; 
+		return MNL_CB_ERROR;
+	}
+	/* Netlink subsystems returns the errno value with different signess */
+	if (err->error < 0)
+		errno = -err->error;
+	else
+		errno = err->error;
+
+	return err->error == 0 ? MNL_CB_STOP : MNL_CB_ERROR;
+}
+
+static int mnl_cb_stop(const struct nlmsghdr *nlh, void *data)
+{
+	return MNL_CB_STOP;
+}
+
+static mnl_cb_t default_cb_array[NLMSG_MIN_TYPE] = {
+	[NLMSG_NOOP]	= mnl_cb_noop,
+	[NLMSG_ERROR]	= mnl_cb_error,
+	[NLMSG_DONE]	= mnl_cb_stop,
+	[NLMSG_OVERRUN]	= mnl_cb_noop,
+};
+
+/**
+ * mnl_cb_run2 - callback runqueue for netlink messages
+ * @buf: buffer that contains the netlink messages
+ * @numbytes: number of bytes stored in the buffer
+ * @seq: sequence number that we expect to receive (use zero to skip)
+ * @cb_data: callback handler for data messages
+ * @data: pointer to data that will be passed to the data callback handler
+ * @cb_ctl_array: array of custom callback handlers from control messages
+ * @cb_ctl_array_len: length of the array of custom control callback handlers
+ *
+ * You can set the cb_ctl_array to NULL if you want to use the default control
+ * callback handlers, in that case, the parameter cb_ctl_array_len is not
+ * checked.
+ *
+ * This function returns -1 in case of error, 0 if we have received a
+ * NLMSG_DONE message or the callback has explicitly returned MNL_CB_STOP.
+ */
+int mnl_cb_run2(const char *buf, int numbytes, unsigned int seq,
+		mnl_cb_t cb_data, void *data,
+		mnl_cb_t *cb_ctl_array, int cb_ctl_array_len)
+{
+	int ret = MNL_CB_OK;
+	struct nlmsghdr *nlh = (struct nlmsghdr *)buf;
+
+	while (mnl_nlmsg_ok(nlh, numbytes)) {
+		/* perform sequence tracking */
+		if (!mnl_nlmsg_seq_ok(nlh, seq)) {
+			errno = EILSEQ;
+			return -1;
+		}
+
+		/* netlink data message handling */
+		if (nlh->nlmsg_type >= NLMSG_MIN_TYPE) { 
+			if (cb_data){
+				ret = cb_data(nlh, data);
+				if (ret <= MNL_CB_STOP)
+					goto out;
+			}
+		} else if (nlh->nlmsg_type < cb_ctl_array_len) {
+			if (cb_ctl_array && cb_ctl_array[nlh->nlmsg_type]) {
+				ret = cb_ctl_array[nlh->nlmsg_type](nlh, data);
+				if (ret <= MNL_CB_STOP)
+					goto out;
+			}
+		} else if (default_cb_array[nlh->nlmsg_type]) {
+			ret = default_cb_array[nlh->nlmsg_type](nlh, data);
+			if (ret <= MNL_CB_STOP)
+				goto out;
+		}
+		nlh = mnl_nlmsg_next(nlh, &numbytes);
+	}
+out:
+	return ret <= MNL_CB_ERROR ? -1 : 0;
+}
+
+/**
+ * mnl_cb_run - callback runqueue for netlink messages (simplified version)
+ * @buf: buffer that contains the netlink messages
+ * @numbytes: number of bytes stored in the buffer
+ * @seq: sequence number that we expect to receive (use zero to skip)
+ * @cb_data: callback handler for data messages
+ * @data: pointer to data that will be passed to the data callback handler
+ *
+ * This function is like mnl_cb_run2() but it does not allow you to set
+ * the control callback handlers.
+ *
+ * This function returns -1 in case of error, 0 if we have received a
+ * NLMSG_DONE message or the callback has explicitly returned MNL_CB_STOP.
+ */
+
+int mnl_cb_run(const char *buf, int numbytes, unsigned int seq,
+	       mnl_cb_t cb_data, void *data)
+{
+	return mnl_cb_run2(buf, numbytes, seq, cb_data, data, NULL, 0);
+}

src/msg.c

@@ -0,0 +1,213 @@
+/*
+ * (C) 2008-2010 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ */
+
+#include <stdio.h>
+#include <ctype.h>
+#include <errno.h>
+#include <string.h>
+#include <libmnl/libmnl.h>
+
+/**
+ * mnl_align - align a value to four bytes
+ * @value: the value that we want to get aligned
+ *
+ * This function returns the value passed aligned to four bytes. Netlink
+ * message headers and its attributes are always aligned to four bytes.
+ */
+int mnl_align(int value)
+{
+	return (value + MNL_ALIGNTO - 1) & ~(MNL_ALIGNTO - 1);
+}
+
+/**
+ * mnl_nlmsg_size - get size of the netlink messages (without alignment)
+ * @len: length of the netlink message
+ *
+ * This function returns the size of a netlink message (header plus payload)
+ * without alignment.
+ */
+size_t mnl_nlmsg_size(int len)
+{
+	return len + mnl_align(MNL_NLMSG_HDRLEN);
+}
+
+/**
+ * mnl_nlmsg_aligned_size - get size of the netlink messages (with alignment)
+ * @len: length of the netlink message
+ *
+ * This function returns the size of a netlink message (header plus payload)
+ * with alignment.
+ */
+size_t mnl_nlmsg_aligned_size(int len)
+{
+	return mnl_align(mnl_nlmsg_size(len));
+}
+
+/**
+ * mnl_nlmsg_payload_size - get the size of the payload
+ * @nlh: pointer to the header of the netlink message
+ *
+ * This function returns the size of the netlink payload
+ */
+size_t mnl_nlmsg_payload_size(const struct nlmsghdr *nlh)
+{
+	return nlh->nlmsg_len - MNL_NLMSG_HDRLEN;
+}
+
+/**
+ * mnl_nlmsg_put_header - prepare room for Netlink header
+ * @buf: memory already allocated to store the Netlink message
+ *
+ * This function sets to zero the room that is required to put a Netlink
+ * header in the memory buffer passed as parameter. This function also
+ * initializes the nlmsg_len field. This function returns a pointer to the
+ * Netlink header structure.
+ */
+struct nlmsghdr *mnl_nlmsg_put_header(void *buf)
+{
+	int len = mnl_align(sizeof(struct nlmsghdr));
+	struct nlmsghdr *nlh = buf;
+
+	memset(buf, 0, len);
+	nlh->nlmsg_len = len;
+	return nlh;
+}
+
+/**
+ * mnl_nlmsg_put_extra_header - prepare room for an extra header
+ * @nlh: pointer to Netlink header
+ * @size: size of the extra header that we want to put
+ *
+ * This function sets to zero the room that is required to put the extra
+ * header after the initial Netlink header. This function also increases
+ * the nlmsg_len field. This function returns a pointer to the extra
+ * header.
+ */
+void *mnl_nlmsg_put_extra_header(struct nlmsghdr *nlh, int size)
+{
+	char *ptr = (char *)nlh + nlh->nlmsg_len;
+	nlh->nlmsg_len += mnl_align(size);
+	memset(ptr, 0, size);
+	return ptr;
+}
+
+/**
+ * mnl_nlmsg_get_len - get the length field from the netlink message
+ * @nlh: pointer to a netlink header
+ *
+ * This function returns the length of the netlink message by return the field
+ * nlmsg_len of the message.
+ */
+u_int16_t mnl_nlmsg_get_len(const struct nlmsghdr *nlh)
+{
+	return nlh->nlmsg_len;
+}
+
+/**
+ * mnl_nlmsg_get_data - get a pointer to the payload of the netlink message
+ * @nlh: pointer to a netlink header
+ *
+ * This function returns a pointer to the payload of the netlink message.
+ */
+void *mnl_nlmsg_get_data(const struct nlmsghdr *nlh)
+{
+	return (void *)nlh + MNL_NLMSG_HDRLEN;
+}
+
+/**
+ * mnl_nlmsg_get_data_offset - get a pointer to the payload of the message
+ * @nlh: pointer to a netlink header
+ * @offset: offset to the payload of the attributes TLV set
+ *
+ * This function returns a pointer to the payload of the netlink message plus
+ * a given offset.
+ */
+void *mnl_nlmsg_get_data_offset(const struct nlmsghdr *nlh, int offset)
+{
+	return (void *)nlh + MNL_NLMSG_HDRLEN + mnl_align(offset);
+}
+
+/**
+ * mnl_nlmsg_ok - check a there is room for netlink message
+ * @nlh: netlink message that we want to check
+ * @len: remaining bytes in a buffer that contains the netlink message
+ *
+ * This function is used to check that a buffer that contains a netlink
+ * message has enough room for the netlink message that it stores, ie. this
+ * function can be used to verify that a netlink message is not malformed nor
+ * truncated.
+ */
+int mnl_nlmsg_ok(const struct nlmsghdr *nlh, int len)
+{
+	return len >= sizeof(struct nlmsghdr) &&
+	       nlh->nlmsg_len >= sizeof(struct nlmsghdr) &&
+	       nlh->nlmsg_len <= len;
+}
+
+/**
+ * mnl_nlmsg_next - get the next netlink message in a multipart message
+ * @nlh: current netlink message that we are handling
+ * @len: pointer to the current remaining bytes in the buffer
+ *
+ * This function returns a pointer to the next netlink message that is part
+ * of a multi-part netlink message. Netlink can batches messages into a buffer
+ * so that the receiver has to iterate over the whole set of netlink
+ * messages.
+ */
+struct nlmsghdr *mnl_nlmsg_next(const struct nlmsghdr *nlh, int *len)
+{
+	*len -= mnl_align(nlh->nlmsg_len);
+	return (struct nlmsghdr *)((void *)nlh + mnl_align(nlh->nlmsg_len));
+}
+
+void *mnl_nlmsg_get_tail(const struct nlmsghdr *nlh)
+{
+	return (struct nlmsghdr *)((void *)nlh + mnl_align(nlh->nlmsg_len));
+}
+
+/**
+ * mnl_nlmsg_seq_ok - perform sequence tracking
+ * @nlh: current netlink message that we are handling
+ * @seq: last sequence number used to send a message
+ *
+ * This functions returns 1 if the sequence tracking is fulfilled, otherwise
+ * 0 is returned. If seq is 0, then the sequence tracking is skipped. This
+ * value is generally used by the kernel for asynchronous notifications,
+ * for that reason, this library consider that it is reserved.
+ */
+int mnl_nlmsg_seq_ok(const struct nlmsghdr *nlh, unsigned int seq)
+{
+	return seq ? nlh->nlmsg_seq == seq : 1;
+}
+
+/* XXX: rework this, please */
+void mnl_nlmsg_print(const struct nlmsghdr *nlh)
+{
+	int i;
+
+	printf("========= netlink header ==========\n");
+	printf("length(32 bits)=%.08u\n", nlh->nlmsg_len);
+	printf("type(16 bits)=%.04u flags(16 bits)=%.04x\n",
+		nlh->nlmsg_type, nlh->nlmsg_flags);
+	printf("sequence number(32 bits)=%.08x\n", nlh->nlmsg_seq);
+	printf("port ID(32 bits)=%.08u\n", nlh->nlmsg_pid);
+	printf("===================================\n");
+
+	for (i=sizeof(struct nlmsghdr); i<mnl_nlmsg_get_len(nlh); i+=4) {
+		char *b = (char *) nlh;
+
+		printf("(%.3d) %.2x %.2x %.2x %.2x | ", i,
+			0xff & b[i],	0xff & b[i+1],
+			0xff & b[i+2],	0xff & b[i+3]);
+
+		printf("%c %c %c %c\n",
+			isalnum(b[i]) ? b[i] : 0,
+			isalnum(b[i+1]) ? b[i+1] : 0,
+			isalnum(b[i+2]) ? b[i+2] : 0,
+			isalnum(b[i+3]) ? b[i+3] : 0);
+	}
+}

src/socket.c

@@ -0,0 +1,255 @@
+/*
+ * (C) 2008-2010 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ */
+
+#include <libmnl/libmnl.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+#include <errno.h>
+
+struct mnl_socket {
+	int 			fd;
+	struct sockaddr_nl	addr;
+};
+
+/**
+ * mnl_socket_get_fd - obtain file descriptor from netlink socket
+ * @nl: netlink socket obtained via mnl_socket_open()
+ *
+ * This function returns the file descriptor of a given netlink socket.
+ */
+int mnl_socket_get_fd(const struct mnl_socket *nl)
+{
+	return nl->fd;
+}
+
+/**
+ * mnl_socket_get_portid - obtain Netlink PortID from netlink socket
+ * @nl: netlink socket obtained via mnl_socket_open()
+ *
+ * This function returns the Netlink PortID of a given netlink socket.
+ * It's a common mistake to assume that this PortID equals the process ID
+ * which is not always true. This is the case if you open more than one
+ * socket that is binded to the same Netlink subsystem.
+ */
+unsigned int mnl_socket_get_portid(const struct mnl_socket *nl)
+{
+	return nl->addr.nl_pid;
+}
+
+/**
+ * mnl_socket_open - open a netlink socket
+ * @unit: the netlink socket unit (see NETLINK_* constants)
+ *
+ * On error, it returns -1 and errno is appropriately set. Otherwise, it
+ * returns a valid pointer to the mnl_socket structure.
+ */
+struct mnl_socket *mnl_socket_open(int unit)
+{
+	struct mnl_socket *nl;
+
+	nl = calloc(sizeof(struct mnl_socket), 1);
+	if (nl == NULL)
+		return NULL;
+
+	nl->fd = socket(AF_NETLINK, SOCK_RAW, unit);
+	if (nl->fd == -1)
+		return NULL;
+
+	return nl;
+}
+
+/**
+ * mnl_socket_bind - bind netlink socket
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @groups: the group of message you're interested in
+ * @pid: the port ID you want to use (use zero for automatic selection)
+ *
+ * On error, this function returns -1 and errno is appropriately set. On
+ * success, 0 is returned.
+ */
+int mnl_socket_bind(struct mnl_socket *nl, int groups, int pid)
+{
+	int ret;
+	socklen_t addr_len;
+
+	nl->addr.nl_family = AF_NETLINK;
+	nl->addr.nl_groups = groups;
+
+	ret = bind(nl->fd, (struct sockaddr *) &nl->addr, sizeof (nl->addr));
+	if (ret < 0)
+		return ret;
+
+	addr_len = sizeof(nl->addr);
+	ret = getsockname(nl->fd, (struct sockaddr *) &nl->addr, &addr_len);
+	if (ret < 0)	
+		return ret;
+
+	if (addr_len != sizeof(nl->addr)) {
+		errno = EINVAL;
+		return -1;
+	}
+	if (nl->addr.nl_family != AF_NETLINK) {
+		errno = EINVAL;
+		return -1;
+	}
+	return 0;
+}
+
+/**
+ * mnl_socket_sendto - send a netlink message of a certain size
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @buf: buffer containing the netlink message to be sent
+ * @bufsiz: number of bytes in the buffer that you want to send
+ *
+ * On error, it returns -1 and errno is appropriately set. Otherwise, it 
+ * returns the number of bytes sent.
+ */
+int mnl_socket_sendto(struct mnl_socket *nl, const void *buf, int len)
+{
+	struct sockaddr_nl snl = {
+		.nl_family = AF_NETLINK
+	};
+	return sendto(nl->fd, buf, len, 0, 
+		      (struct sockaddr *) &snl, sizeof(snl));
+}
+
+/**
+ * mnl_socket_sendmsg - send a netlink message of a certain size
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @msg: pointer to struct msghdr (must be initialized appropriately)
+ * @flags: flags passed to sendmsg()
+ *
+ * On error, it returns -1 and errno is appropriately set. Otherwise, it 
+ * returns the number of bytes sent.
+ */
+int
+mnl_socket_sendmsg(struct mnl_socket *nl, struct msghdr *msg, int flags)
+{
+	return sendmsg(nl->fd, msg, flags);
+}
+
+/**
+ * mnl_socket_recvfrom - receive a netlink message
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @buf: buffer that you want to use to store the netlink message
+ * @bufsiz: size of the buffer passed to store the netlink message
+ *
+ * On error, it returns -1 and errno is appropriately set. If errno is set
+ * to ENOSPC, it means that the buffer that you have passed to store the
+ * netlink message is small so you have received a truncated message. Make
+ * sure your program set a buffer big enough to store the netlink message.
+ */
+int mnl_socket_recvfrom(struct mnl_socket *nl, void *buf, int bufsiz)
+{
+	int ret;
+	struct sockaddr_nl addr;
+	struct iovec iov = {
+		.iov_base	= buf,
+		.iov_len	= bufsiz,
+	};
+	struct msghdr msg = {
+		.msg_name	= (void *)&addr,
+		.msg_namelen	= sizeof(struct sockaddr_nl),
+		.msg_iov	= &iov,
+		.msg_iovlen	= 1,
+		.msg_control	= NULL,
+		.msg_controllen	= 0,
+		.msg_flags	= 0,
+	};
+	ret = recvmsg(nl->fd, &msg, 0);
+	if (ret == -1)
+		return ret;
+
+	if (msg.msg_flags & MSG_TRUNC) {
+		errno = ENOSPC;
+		return -1;
+	}
+	if (msg.msg_namelen != sizeof(struct sockaddr_nl)) {
+		errno = EINVAL;
+		return -1;
+	}
+	return ret;
+}
+
+/**
+ * mnl_socket_recvmsg- receive a netlink message
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @msg: pointer to struct msghdr (must be initialized appropriately)
+ * @flags: flags passed to recvmsg()
+ *
+ * On error, this function returns -1 and errno is appropriately set.
+ * On sucess, this function returns the number of bytes received.
+ */
+int
+mnl_socket_recvmsg(const struct mnl_socket *nl, struct msghdr *msg, int flags)
+{
+	return recvmsg(nl->fd, msg, flags);
+}
+
+/**
+ * mnl_socket_close - close a given netlink socket
+ * @nl: netlink socket obtained via mnl_socket_open()
+ *
+ * On error, this function returns -1 and errno is appropriately set.
+ * On success, it returns 0.
+ */
+int mnl_socket_close(struct mnl_socket *nl)
+{
+	int ret = close(nl->fd);
+	free(nl);
+	nl = NULL;
+	return ret;
+}
+
+/**
+ * mnl_socket_setsockopt - set Netlink socket option
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @type: type of Netlink socket options
+ * @buf: the buffer that contains the data about this option
+ * @len: the size of the buffer passed
+ *
+ * This function allows you to set some Netlink socket option. As of writing
+ * this, the existing options are:
+ *
+ * #define NETLINK_ADD_MEMBERSHIP  1
+ * #define NETLINK_DROP_MEMBERSHIP 2
+ * #define NETLINK_PKTINFO         3
+ * #define NETLINK_BROADCAST_ERROR 4
+ * #define NETLINK_NO_ENOBUFS      5
+ *
+ * In the early days, Netlink only supported 32 groups expressed in a
+ * 32-bits mask. However, since 2.6.14, Netlink may have up to 2^32 multicast
+ * groups but you have to use setsockopt() with NETLINK_ADD_MEMBERSHIP to
+ * join a given multicast group. This function internally calls setsockopt()
+ * to join a given netlink multicast group. You can still use mnl_bind()
+ * and the 32-bit mask to join a set of Netlink multicast groups.
+ *
+ * On error, this function returns -1 and errno is appropriately set.
+ */
+int mnl_socket_setsockopt(struct mnl_socket *nl, int type,
+			  void *buf, socklen_t len)
+{
+	return setsockopt(nl->fd, SOL_NETLINK, type, buf, len);
+}
+
+/**
+ * mnl_socket_getsockopt - get a Netlink socket option
+ * @nl: netlink socket obtained via mnl_socket_open()
+ * @type: type of Netlink socket options
+ * @buf: pointer to the buffer to store the value of this option
+ * @len: size of the information written in the buffer
+ *
+ * On error, this function returns -1 and errno is appropriately set.
+ */
+int mnl_socket_getsockopt(struct mnl_socket *nl, int type,
+			  void *buf, socklen_t *len)
+{
+	return getsockopt(nl->fd, SOL_NETLINK, type, buf, len);
+}