[RFC PATCH iproute2] ip: allow to monitor netconf messages

[Nicolas Dichtel <nicolas.dichtel@6wind.com>]

Example of the output:
$ ip monitor netconf&
[1] 24901
$ echo 0 > /proc/sys/net/ipv6/conf/all/forwarding
ipv6 dev lo forwarding off
ipv6 dev eth0 forwarding off
ipv6 all forwarding off
$ echo 1 > /proc/sys/net/ipv4/conf/eth0/forwarding
ipv4 dev eth0 forwarding on

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---
 include/libnetlink.h      |  1 +
 include/linux/netconf.h   | 22 ++++++++++++
 include/linux/rtnetlink.h |  7 ++++
 ip/Makefile               |  2 +-
 ip/ip_common.h            |  2 ++
 ip/ipmonitor.c            | 16 +++++++++
 ip/ipnetconf.c            | 92 +++++++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 141 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/netconf.h
 create mode 100644 ip/ipnetconf.c

diff --git a/include/libnetlink.h b/include/libnetlink.h
index 81649af..4a6b878 100644
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -8,6 +8,7 @@
 #include <linux/if_link.h>
 #include <linux/if_addr.h>
 #include <linux/neighbour.h>
+#include <linux/netconf.h>
 
 struct rtnl_handle
 {
diff --git a/include/linux/netconf.h b/include/linux/netconf.h
new file mode 100644
index 0000000..d051372
--- /dev/null
+++ b/include/linux/netconf.h
@@ -0,0 +1,22 @@
+#ifndef _UAPI_LINUX_NETCONF_H_
+#define _UAPI_LINUX_NETCONF_H_
+
+#include <linux/types.h>
+#include <linux/netlink.h>
+
+struct netconfmsg {
+	__u8	ncm_family;
+};
+
+enum {
+	NETCONFA_UNSPEC,
+	NETCONFA_IFINDEX,
+	NETCONFA_FORWARDING,
+	__NETCONFA_MAX
+};
+#define NETCONFA_MAX	(__NETCONFA_MAX - 1)
+
+#define NETCONFA_IFINDEX_ALL		-1
+#define NETCONFA_IFINDEX_DEFAULT	-2
+
+#endif /* _UAPI_LINUX_NETCONF_H_ */
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index d5b7fdd..f23d7ad 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -120,6 +120,9 @@ enum {
 	RTM_SETDCB,
 #define RTM_SETDCB RTM_SETDCB
 
+	RTM_NEWNETCONF = 80,
+#define RTM_NEWNETCONF RTM_NEWNETCONF
+
 	__RTM_MAX,
 #define RTM_MAX		(((__RTM_MAX + 3) & ~3) - 1)
 };
@@ -585,6 +588,10 @@ enum rtnetlink_groups {
 #define RTNLGRP_PHONET_ROUTE	RTNLGRP_PHONET_ROUTE
 	RTNLGRP_DCB,
 #define RTNLGRP_DCB		RTNLGRP_DCB
+	RTNLGRP_IPV4_NETCONF,
+#define RTNLGRP_IPV4_NETCONF	RTNLGRP_IPV4_NETCONF
+	RTNLGRP_IPV6_NETCONF,
+#define RTNLGRP_IPV6_NETCONF	RTNLGRP_IPV6_NETCONF
 	__RTNLGRP_MAX
 };
 #define RTNLGRP_MAX	(__RTNLGRP_MAX - 1)
diff --git a/ip/Makefile b/ip/Makefile
index dfe2e71..ccf9608 100644
--- a/ip/Makefile
+++ b/ip/Makefile
@@ -4,7 +4,7 @@ IPOBJ=ip.o ipaddress.o ipaddrlabel.o iproute.o iprule.o ipnetns.o \
     ipxfrm.o xfrm_state.o xfrm_policy.o xfrm_monitor.o \
     iplink_vlan.o link_veth.o link_gre.o iplink_can.o \
     iplink_macvlan.o iplink_macvtap.o ipl2tp.o link_vti.o \
-    iplink_vxlan.o tcp_metrics.o
+    iplink_vxlan.o tcp_metrics.o ipnetconf.o
 
 RTMONOBJ=rtmon.o
 
diff --git a/ip/ip_common.h b/ip/ip_common.h
index 2fd66b7..d50f763 100644
--- a/ip/ip_common.h
+++ b/ip/ip_common.h
@@ -25,6 +25,8 @@ extern int print_prefix(const struct sockaddr_nl *who,
 			struct nlmsghdr *n, void *arg);
 extern int print_rule(const struct sockaddr_nl *who,
 		      struct nlmsghdr *n, void *arg);
+extern int print_netconf(const struct sockaddr_nl *who,
+			 struct nlmsghdr *n, void *arg);
 extern int do_ipaddr(int argc, char **argv);
 extern int do_ipaddrlabel(int argc, char **argv);
 extern int do_iproute(int argc, char **argv);
diff --git a/ip/ipmonitor.c b/ip/ipmonitor.c
index 4b1d469..d87e58f 100644
--- a/ip/ipmonitor.c
+++ b/ip/ipmonitor.c
@@ -85,6 +85,12 @@ int accept_msg(const struct sockaddr_nl *who,
 		print_rule(who, n, arg);
 		return 0;
 	}
+	if (n->nlmsg_type == RTM_NEWNETCONF) {
+		if (prefix_banner)
+			fprintf(fp, "[NETCONF]");
+		print_netconf(who, n, arg);
+		return 0;
+	}
 	if (n->nlmsg_type == 15) {
 		char *tstr;
 		time_t secs = ((__u32*)NLMSG_DATA(n))[0];
@@ -118,6 +124,7 @@ int do_ipmonitor(int argc, char **argv)
 	int lroute=0;
 	int lprefix=0;
 	int lneigh=0;
+	int lnetconf=0;
 
 	rtnl_close(&rth);
 	ipaddr_reset_filter(1);
@@ -143,6 +150,9 @@ int do_ipmonitor(int argc, char **argv)
 		} else if (matches(*argv, "neigh") == 0) {
 			lneigh = 1;
 			groups = 0;
+		} else if (matches(*argv, "netconf") == 0) {
+			lnetconf = 1;
+			groups = 0;
 		} else if (strcmp(*argv, "all") == 0) {
 			groups = ~RTMGRP_TC;
 			prefix_banner=1;
@@ -176,6 +186,12 @@ int do_ipmonitor(int argc, char **argv)
 	if (lneigh) {
 		groups |= nl_mgrp(RTNLGRP_NEIGH);
 	}
+	if (lnetconf) {
+		if (!preferred_family || preferred_family == AF_INET)
+			groups |= nl_mgrp(RTNLGRP_IPV4_NETCONF);
+		if (!preferred_family || preferred_family == AF_INET6)
+			groups |= nl_mgrp(RTNLGRP_IPV6_NETCONF);
+	}
 	if (file) {
 		FILE *fp;
 		fp = fopen(file, "r");
diff --git a/ip/ipnetconf.c b/ip/ipnetconf.c
new file mode 100644
index 0000000..f92eabf
--- /dev/null
+++ b/ip/ipnetconf.c
@@ -0,0 +1,92 @@
+/*
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ * Authors:	Nicolas Dichtel, <nicolas.dichtel@6wind.com>
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <syslog.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+#include "rt_names.h"
+#include "utils.h"
+#include "ip_common.h"
+
+static struct
+{
+	int family;
+} filter;
+
+#define NETCONF_RTA(r)	((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct netconfmsg))))
+
+int print_netconf(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
+{
+	FILE *fp = (FILE*)arg;
+	struct netconfmsg *ncm = NLMSG_DATA(n);
+	int len = n->nlmsg_len;
+	struct rtattr *tb[NETCONFA_MAX+1];
+
+	if (n->nlmsg_type != RTM_NEWNETCONF) {
+		fprintf(stderr, "Not RTM_NEWNETCONF: %08x %08x %08x\n",
+			n->nlmsg_len, n->nlmsg_type, n->nlmsg_flags);
+
+		return 0;
+	}
+	len -= NLMSG_SPACE(sizeof(*ncm));
+	if (len < 0) {
+		fprintf(stderr, "BUG: wrong nlmsg len %d\n", len);
+		return -1;
+	}
+
+	if (filter.family && filter.family != ncm->ncm_family)
+		return 0;
+
+	parse_rtattr(tb, NETCONFA_MAX, NETCONF_RTA(ncm),
+		     NLMSG_PAYLOAD(n, sizeof(*ncm)));
+
+	switch (ncm->ncm_family) {
+	case AF_INET:
+		fprintf(fp, "ipv4 ");
+		break;
+	case AF_INET6:
+		fprintf(fp, "ipv6 ");
+		break;
+	default:
+		fprintf(fp, "unknown ");
+		break;
+	}
+
+	if (tb[NETCONFA_IFINDEX]) {
+		int *ifindex = (int *)RTA_DATA(tb[NETCONFA_IFINDEX]);
+
+		switch (*ifindex) {
+		case NETCONFA_IFINDEX_ALL:
+			fprintf(fp, "all ");
+			break;
+		case NETCONFA_IFINDEX_DEFAULT:
+			fprintf(fp, "default ");
+			break;
+		default:
+			fprintf(fp, "dev %s ", ll_index_to_name(*ifindex));
+			break;
+		}
+	}
+
+	if (tb[NETCONFA_FORWARDING])
+		fprintf(fp, "forwarding %s ",
+			*(int *)RTA_DATA(tb[NETCONFA_FORWARDING])?"on":"off");
+
+	fprintf(fp, "\n");
+	fflush(fp);
+	return 0;
+}
-- 
1.7.12