[PATCH] [RFC] Add ip route {save,restore}

[PATCH] [RFC] Add ip route {save,restore}

[Dan Smith]

This patch adds save and restore commands to "ip route". Save dumps
the RTNL stream to stdout which can then be passed to restore later.
This may be helpful in some normal situations, and will allow C/R to
migrate the routing information in userspace.  Tweaking of the stream
can be done by userspace helpers to convert between versions and adjust
things like device indexes when restoring routes in a different
environment.

By factoring out some of the common bits of print_route() into
filter_nlmsg(), the "save" command can use the same selection logic
as "list," allowing the caller to save only specific routes as
necessary.

Signed-off-by: Dan Smith <danms@us.ibm.com>
---
 ip/iproute.c |  169 +++++++++++++++++++++++++++++++++++++++++++--------------
 1 files changed, 127 insertions(+), 42 deletions(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index 8252e18..3049975 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -23,6 +23,7 @@
 #include <netinet/ip.h>
 #include <arpa/inet.h>
 #include <linux/in_route.h>
+#include <errno.h>
 
 #include "rt_names.h"
 #include "utils.h"
@@ -32,7 +33,11 @@
 #define RTAX_RTTVAR RTAX_HOPS
 #endif
 
-
+enum list_action {
+	IPROUTE_LIST,
+	IPROUTE_FLUSH,
+	IPROUTE_SAVE,
+};
 static const char *mx_names[RTAX_MAX+1] = {
 	[RTAX_MTU]	= "mtu",
 	[RTAX_WINDOW]	= "window",
@@ -53,6 +58,8 @@ static void usage(void) __attribute__((noreturn));
 static void usage(void)
 {
 	fprintf(stderr, "Usage: ip route { list | flush } SELECTOR\n");
+	fprintf(stderr, "       ip route save SELECTOR\n");
+	fprintf(stderr, "       ip route restore\n");
 	fprintf(stderr, "       ip route get ADDRESS [ from ADDRESS iif STRING ]\n");
 	fprintf(stderr, "                            [ oif STRING ]  [ tos TOS ]\n");
 	fprintf(stderr, "       ip route { add | del | change | append | replace | monitor } ROUTE\n");
@@ -115,46 +122,16 @@ static int flush_update(void)
 	return 0;
 }
 
-int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
+int filter_nlmsg(struct nlmsghdr *n, struct rtattr **tb, int host_len)
 {
-	FILE *fp = (FILE*)arg;
 	struct rtmsg *r = NLMSG_DATA(n);
-	int len = n->nlmsg_len;
-	struct rtattr * tb[RTA_MAX+1];
-	char abuf[256];
 	inet_prefix dst;
 	inet_prefix src;
-	inet_prefix prefsrc;
 	inet_prefix via;
-	int host_len = -1;
-	static int ip6_multiple_tables;
+	inet_prefix prefsrc;
 	__u32 table;
-	SPRINT_BUF(b1);
-	static int hz;
-
-	if (n->nlmsg_type != RTM_NEWROUTE && n->nlmsg_type != RTM_DELROUTE) {
-		fprintf(stderr, "Not a route: %08x %08x %08x\n",
-			n->nlmsg_len, n->nlmsg_type, n->nlmsg_flags);
-		return 0;
-	}
-	if (filter.flushb && n->nlmsg_type != RTM_NEWROUTE)
-		return 0;
-	len -= NLMSG_LENGTH(sizeof(*r));
-	if (len < 0) {
-		fprintf(stderr, "BUG: wrong nlmsg len %d\n", len);
-		return -1;
-	}
-
-	if (r->rtm_family == AF_INET6)
-		host_len = 128;
-	else if (r->rtm_family == AF_INET)
-		host_len = 32;
-	else if (r->rtm_family == AF_DECnet)
-		host_len = 16;
-	else if (r->rtm_family == AF_IPX)
-		host_len = 80;
+	static int ip6_multiple_tables;
 
-	parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
 	table = rtm_get_table(r, tb);
 
 	if (r->rtm_family == AF_INET6 && table != RT_TABLE_MAIN)
@@ -281,6 +258,56 @@ int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
 	    *(int*)RTA_DATA(tb[RTA_PRIORITY]) == -1)
 		return 0;
 
+	return 1;
+}
+
+int calc_host_len(struct rtmsg *r)
+{
+	if (r->rtm_family == AF_INET6)
+		return 128;
+	else if (r->rtm_family == AF_INET)
+		return 32;
+	else if (r->rtm_family == AF_DECnet)
+		return 16;
+	else if (r->rtm_family == AF_IPX)
+		return 80;
+	else
+		return -1;
+}
+
+int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
+{
+	FILE *fp = (FILE*)arg;
+	struct rtmsg *r = NLMSG_DATA(n);
+	int len = n->nlmsg_len;
+	struct rtattr * tb[RTA_MAX+1];
+	char abuf[256];
+	int host_len = -1;
+	__u32 table;
+	SPRINT_BUF(b1);
+	static int hz;
+
+	if (n->nlmsg_type != RTM_NEWROUTE && n->nlmsg_type != RTM_DELROUTE) {
+		fprintf(stderr, "Not a route: %08x %08x %08x\n",
+			n->nlmsg_len, n->nlmsg_type, n->nlmsg_flags);
+		return 0;
+	}
+	if (filter.flushb && n->nlmsg_type != RTM_NEWROUTE)
+		return 0;
+	len -= NLMSG_LENGTH(sizeof(*r));
+	if (len < 0) {
+		fprintf(stderr, "BUG: wrong nlmsg len %d\n", len);
+		return -1;
+	}
+
+	host_len = calc_host_len(r);
+
+ 	parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
+	table = rtm_get_table(r, tb);
+
+	if (!filter_nlmsg(n, tb, host_len))
+		return 0;
+
 	if (filter.flushb) {
 		struct nlmsghdr *fn;
 		if (NLMSG_ALIGN(filter.flushp) + n->nlmsg_len > filter.flushe) {
@@ -1041,17 +1068,51 @@ static int iproute_flush_cache(void)
 	return 0;
 }
 
+int save_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
+{
+	int ret;
+	int len = n->nlmsg_len;
+	struct rtmsg *r = NLMSG_DATA(n);
+	struct rtattr *tb[RTA_MAX+1];
+	int host_len = -1;
+
+	if (isatty(STDOUT_FILENO)) {
+		fprintf(stderr, "Not sending binary stream to stdout\n");
+		return -1;
+	}
+
+	host_len = calc_host_len(r);
+	len -= NLMSG_LENGTH(sizeof(*r));
+ 	parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
+
+	if (!filter_nlmsg(n, tb, host_len))
+		return 0;
+
+	ret = write(STDOUT_FILENO, n, n->nlmsg_len);
+	if ((ret > 0) && (ret != n->nlmsg_len)) {
+		fprintf(stderr, "Short write while saving nlmsg\n");
+		ret = -EIO;
+	}
+
+	return ret == n->nlmsg_len ? 0 : ret;
+}
 
-static int iproute_list_or_flush(int argc, char **argv, int flush)
+static int iproute_list_flush_or_save(int argc, char **argv, int action)
 {
 	int do_ipv6 = preferred_family;
 	char *id = NULL;
 	char *od = NULL;
+	rtnl_filter_t filter_fn;
+
+	if (action == IPROUTE_SAVE)
+		filter_fn = save_route;
+	else
+		filter_fn = print_route;
 
 	iproute_reset_filter();
 	filter.tb = RT_TABLE_MAIN;
 
-	if (flush && argc <= 0) {
+	if ((action == IPROUTE_FLUSH) && argc <= 0) {
 		fprintf(stderr, "\"ip route flush\" requires arguments.\n");
 		return -1;
 	}
@@ -1201,7 +1262,7 @@ static int iproute_list_or_flush(int argc, char **argv, int flush)
 		}
 	}
 
-	if (flush) {
+	if (action == IPROUTE_FLUSH) {
 		int round = 0;
 		char flushb[4096-512];
 		time_t start = time(0);
@@ -1226,7 +1287,7 @@ static int iproute_list_or_flush(int argc, char **argv, int flush)
 				exit(1);
 			}
 			filter.flushed = 0;
-			if (rtnl_dump_filter(&rth, print_route, stdout, NULL, NULL) < 0) {
+			if (rtnl_dump_filter(&rth, filter_fn, stdout, NULL, NULL) < 0) {
 				fprintf(stderr, "Flush terminated\n");
 				exit(1);
 			}
@@ -1269,7 +1330,7 @@ static int iproute_list_or_flush(int argc, char **argv, int flush)
 		}
 	}
 
-	if (rtnl_dump_filter(&rth, print_route, stdout, NULL, NULL) < 0) {
+	if (rtnl_dump_filter(&rth, filter_fn, stdout, NULL, NULL) < 0) {
 		fprintf(stderr, "Dump terminated\n");
 		exit(1);
 	}
@@ -1436,6 +1497,26 @@ int iproute_get(int argc, char **argv)
 	exit(0);
 }
 
+int restore_handler(struct sockaddr_nl *nl, struct nlmsghdr *n, void *arg)
+{
+	int ret;
+
+	n->nlmsg_flags |= NLM_F_REQUEST | NLM_F_CREATE | NLM_F_ACK;
+
+	ll_init_map(&rth);
+
+	ret = rtnl_talk(&rth, n, 0, 0, n, NULL, NULL);
+	if ((ret < 0) && (errno == EEXIST))
+		ret = 0;
+
+	return ret;
+}
+
+int iproute_restore(void)
+{
+	exit(rtnl_from_file(stdin, &restore_handler, NULL));
+}
+
 void iproute_reset_filter()
 {
 	memset(&filter, 0, sizeof(filter));
@@ -1446,7 +1527,7 @@ void iproute_reset_filter()
 int do_iproute(int argc, char **argv)
 {
 	if (argc < 1)
-		return iproute_list_or_flush(0, NULL, 0);
+		return iproute_list_flush_or_save(0, NULL, IPROUTE_LIST);
 
 	if (matches(*argv, "add") == 0)
 		return iproute_modify(RTM_NEWROUTE, NLM_F_CREATE|NLM_F_EXCL,
@@ -1471,11 +1552,15 @@ int do_iproute(int argc, char **argv)
 				      argc-1, argv+1);
 	if (matches(*argv, "list") == 0 || matches(*argv, "show") == 0
 	    || matches(*argv, "lst") == 0)
-		return iproute_list_or_flush(argc-1, argv+1, 0);
+		return iproute_list_flush_or_save(argc-1, argv+1, IPROUTE_LIST);
 	if (matches(*argv, "get") == 0)
 		return iproute_get(argc-1, argv+1);
 	if (matches(*argv, "flush") == 0)
-		return iproute_list_or_flush(argc-1, argv+1, 1);
+		return iproute_list_flush_or_save(argc-1, argv+1, IPROUTE_FLUSH);
+	if (matches(*argv, "save") == 0)
+		return iproute_list_flush_or_save(argc-1, argv+1, IPROUTE_SAVE);
+	if (matches(*argv, "restore") == 0)
+		return iproute_restore();
 	if (matches(*argv, "help") == 0)
 		usage();
 	fprintf(stderr, "Command \"%s\" is unknown, try \"ip route help\".\n", *argv);
-- 
1.7.0.4

Re: [PATCH] [RFC] Add ip route {save,restore}

[Stephen Hemminger]

On Fri, 21 May 2010 08:14:23 -0700
Dan Smith <danms@us.ibm.com> wrote:

> This patch adds save and restore commands to "ip route". Save dumps
> the RTNL stream to stdout which can then be passed to restore later.
> This may be helpful in some normal situations, and will allow C/R to
> migrate the routing information in userspace.  Tweaking of the stream
> can be done by userspace helpers to convert between versions and adjust
> things like device indexes when restoring routes in a different
> environment.
> 
> By factoring out some of the common bits of print_route() into
> filter_nlmsg(), the "save" command can use the same selection logic
> as "list," allowing the caller to save only specific routes as
> necessary.
> 
> Signed-off-by: Dan Smith <danms@us.ibm.com>

Looks good, please add man page and doc entry for this in final
version.