ip: nexthop: add print_cache_nexthop which prints and manages the nh cache

Add a new helper print_cache_nexthop replacing print_nexthop which can
update the nexthop cache if the process_cache argument is true. It is
used when monitoring netlink messages to keep the nexthop cache up to
date with nexthop changes happening. For the old callers and anyone
who's just dumping nexthops its _nocache version is used which is a
wrapper for print_cache_nexthop.

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David Ahern <dsahern@kernel.org>

ip/ip_common.h

@@ -53,7 +53,6 @@ int print_prefix(struct nlmsghdr *n, void *arg);
 int print_rule(struct nlmsghdr *n, void *arg);
 int print_netconf(struct rtnl_ctrl_data *ctrl,
 		  struct nlmsghdr *n, void *arg);
-int print_nexthop(struct nlmsghdr *n, void *arg);
 int print_nexthop_bucket(struct nlmsghdr *n, void *arg);
 void netns_map_init(void);
 void netns_nsid_socket_init(void);

ip/ipmonitor.c

@@ -22,6 +22,7 @@
 
 #include "utils.h"
 #include "ip_common.h"
+#include "nh_common.h"
 
 static void usage(void) __attribute__((noreturn));
 static int prefix_banner;
@@ -88,7 +89,7 @@ static int accept_msg(struct rtnl_ctrl_data *ctrl,
 	case RTM_NEWNEXTHOP:
 	case RTM_DELNEXTHOP:
 		print_headers(fp, "[NEXTHOP]", ctrl);
-		print_nexthop(n, arg);
+		print_cache_nexthop(n, arg, true);
 		return 0;
 
 	case RTM_NEWNEXTHOPBUCKET:

ip/ipnexthop.c

@@ -602,6 +602,42 @@ static void ipnh_cache_del(struct nh_entry *nhe)
 	free(nhe);
 }
 
+/* update, add or delete a nexthop entry based on nlmsghdr */
+static int ipnh_cache_process_nlmsg(const struct nlmsghdr *n,
+				    struct nh_entry *new_nhe)
+{
+	struct nh_entry *nhe;
+
+	nhe = ipnh_cache_get(new_nhe->nh_id);
+	switch (n->nlmsg_type) {
+	case RTM_DELNEXTHOP:
+		if (nhe)
+			ipnh_cache_del(nhe);
+		ipnh_destroy_entry(new_nhe);
+		break;
+	case RTM_NEWNEXTHOP:
+		if (!nhe) {
+			nhe = malloc(sizeof(*nhe));
+			if (!nhe) {
+				ipnh_destroy_entry(new_nhe);
+				return -1;
+			}
+		} else {
+			/* this allows us to save 1 allocation on updates by
+			 * reusing the old nh entry, but we need to cleanup its
+			 * internal storage
+			 */
+			ipnh_cache_unlink_entry(nhe);
+			ipnh_destroy_entry(nhe);
+		}
+		memcpy(nhe, new_nhe, sizeof(*nhe));
+		ipnh_cache_link_entry(nhe);
+		break;
+	}
+
+	return 0;
+}
+
 void print_cache_nexthop_id(FILE *fp, const char *fp_prefix, const char *jsobj,
 			    __u32 nh_id)
 {
@@ -618,7 +654,7 @@ void print_cache_nexthop_id(FILE *fp, const char *fp_prefix, const char *jsobj,
 	__print_nexthop_entry(fp, jsobj, nhe, false);
 }
 
-int print_nexthop(struct nlmsghdr *n, void *arg)
+int print_cache_nexthop(struct nlmsghdr *n, void *arg, bool process_cache)
 {
 	struct nhmsg *nhm = NLMSG_DATA(n);
 	FILE *fp = (FILE *)arg;
@@ -651,11 +687,20 @@ int print_nexthop(struct nlmsghdr *n, void *arg)
 	__print_nexthop_entry(fp, NULL, &nhe, n->nlmsg_type == RTM_DELNEXTHOP);
 	print_string(PRINT_FP, NULL, "%s", "\n");
 	fflush(fp);
-	ipnh_destroy_entry(&nhe);
+
+	if (process_cache)
+		ipnh_cache_process_nlmsg(n, &nhe);
+	else
+		ipnh_destroy_entry(&nhe);
 
 	return 0;
 }
 
+static int print_nexthop_nocache(struct nlmsghdr *n, void *arg)
+{
+	return print_cache_nexthop(n, arg, false);
+}
+
 int print_nexthop_bucket(struct nlmsghdr *n, void *arg)
 {
 	struct nhmsg *nhm = NLMSG_DATA(n);
@@ -967,7 +1012,7 @@ static int ipnh_get_id(__u32 id)
 
 	new_json_obj(json);
 
-	if (print_nexthop(answer, (void *)stdout) < 0) {
+	if (print_nexthop_nocache(answer, (void *)stdout) < 0) {
 		free(answer);
 		return -1;
 	}
@@ -1052,7 +1097,7 @@ static int ipnh_list_flush(int argc, char **argv, int action)
 
 	new_json_obj(json);
 
-	if (rtnl_dump_filter(&rth, print_nexthop, stdout) < 0) {
+	if (rtnl_dump_filter(&rth, print_nexthop_nocache, stdout) < 0) {
 		fprintf(stderr, "Dump terminated\n");
 		return -2;
 	}

ip/nh_common.h

@@ -48,5 +48,6 @@ struct nh_entry {
 
 void print_cache_nexthop_id(FILE *fp, const char *fp_prefix, const char *jsobj,
 			    __u32 nh_id);
+int print_cache_nexthop(struct nlmsghdr *n, void *arg, bool process_cache);
 
 #endif /* __NH_COMMON_H__ */