[PATCH RFC v3] ipvs: add genetlink cmd to dump all services and destinations

[Cezar Sa Espinola]

A common operation for userspace applications managing ipvs is to dump all
services and all destinations and then sort out what needs to be done.
Previously this could only be accomplished by issuing 1 netlink
IPVS_CMD_GET_SERVICE dump command followed by N IPVS_CMD_GET_DEST dump
commands. For a dynamic system with a very large number of services this
could be cause a performance impact.

This patch introduces a new way of dumping all services and destinations
with the new IPVS_CMD_GET_SERVICE_DEST command. A dump call for this
command will send the services as IPVS_CMD_NEW_SERVICE messages each
containing a nested array of destinations with the new IPVS_SVC_ATTR_DESTS
and IPVS_DESTS_ATTR_DEST attributes. Services may be repeated if their
destinations do not fit in a single packet, user space should be
responsible for merging the destinations from each repeated service.

It's also possible to dump a single service and its destinations by sending
a IPVS_CMD_ATTR_SERVICE argument to the dump command.

Signed-off-by: Cezar Sa Espinola <cezarsa@xxxxxxxxx>
---
Changes in v2:
- Send destinations nested in a service.
Changes in v3:
- Avoid tab lookups at EOF and other requested changes.

 include/uapi/linux/ip_vs.h     |  17 ++-
 net/netfilter/ipvs/ip_vs_ctl.c | 200 ++++++++++++++++++++++++++++++---
 2 files changed, 201 insertions(+), 16 deletions(-)

diff --git a/include/uapi/linux/ip_vs.h b/include/uapi/linux/ip_vs.h
index 4102ddcb4e14..ce9bfa03b61b 100644
--- a/include/uapi/linux/ip_vs.h
+++ b/include/uapi/linux/ip_vs.h
@@ -331,6 +331,8 @@ enum {
 	IPVS_CMD_ZERO,			/* zero all counters and stats */
 	IPVS_CMD_FLUSH,			/* flush services and dests */
 
+	IPVS_CMD_GET_SERVICE_DEST,	/* get service and destination info */
+
 	__IPVS_CMD_MAX,
 };
 
@@ -374,15 +376,28 @@ enum {
 
 	IPVS_SVC_ATTR_STATS64,		/* nested attribute for service stats */
 
+	IPVS_SVC_ATTR_DESTS,		/* nested destinations */
+
 	__IPVS_SVC_ATTR_MAX,
 };
 
 #define IPVS_SVC_ATTR_MAX (__IPVS_SVC_ATTR_MAX - 1)
 
+enum {
+	IPVS_DESTS_ATTR_UNSPEC = 0,
+
+	IPVS_DESTS_ATTR_DEST,	/* nested destination */
+
+	__IPVS_DESTS_ATTR_MAX,
+};
+
+#define IPVS_DESTS_ATTR_MAX (__IPVS_DESTS_ATTR_MAX - 1)
+
 /*
  * Attributes used to describe a destination (real server)
  *
- * Used inside nested attribute IPVS_CMD_ATTR_DEST
+ * Used inside nested attribute IPVS_CMD_ATTR_DEST and
+ * IPVS_DESTS_ATTR_DEST
  */
 enum {
 	IPVS_DEST_ATTR_UNSPEC = 0,
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index e279ded4e306..65456eaaf11f 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2981,6 +2981,7 @@ static const struct nla_policy ip_vs_svc_policy[IPVS_SVC_ATTR_MAX + 1] = {
 	[IPVS_SVC_ATTR_TIMEOUT]		= { .type = NLA_U32 },
 	[IPVS_SVC_ATTR_NETMASK]		= { .type = NLA_U32 },
 	[IPVS_SVC_ATTR_STATS]		= { .type = NLA_NESTED },
+	[IPVS_SVC_ATTR_DESTS]		= { .type = NLA_NESTED },
 };
 
 /* Policy used for attributes in nested attribute IPVS_CMD_ATTR_DEST */
@@ -3070,31 +3071,26 @@ static int ip_vs_genl_fill_stats64(struct sk_buff *skb, int container_type,
 	return -EMSGSIZE;
 }
 
-static int ip_vs_genl_fill_service(struct sk_buff *skb,
-				   struct ip_vs_service *svc)
+static int ip_vs_genl_put_service_attrs(struct sk_buff *skb,
+					struct ip_vs_service *svc)
 {
 	struct ip_vs_scheduler *sched;
 	struct ip_vs_pe *pe;
-	struct nlattr *nl_service;
 	struct ip_vs_flags flags = { .flags = svc->flags,
 				     .mask = ~0 };
 	struct ip_vs_kstats kstats;
 	char *sched_name;
 
-	nl_service = nla_nest_start_noflag(skb, IPVS_CMD_ATTR_SERVICE);
-	if (!nl_service)
-		return -EMSGSIZE;
-
 	if (nla_put_u16(skb, IPVS_SVC_ATTR_AF, svc->af))
-		goto nla_put_failure;
+		return -EMSGSIZE;
 	if (svc->fwmark) {
 		if (nla_put_u32(skb, IPVS_SVC_ATTR_FWMARK, svc->fwmark))
-			goto nla_put_failure;
+			return -EMSGSIZE;
 	} else {
 		if (nla_put_u16(skb, IPVS_SVC_ATTR_PROTOCOL, svc->protocol) ||
 		    nla_put(skb, IPVS_SVC_ATTR_ADDR, sizeof(svc->addr), &svc->addr) ||
 		    nla_put_be16(skb, IPVS_SVC_ATTR_PORT, svc->port))
-			goto nla_put_failure;
+			return -EMSGSIZE;
 	}
 
 	sched = rcu_dereference_protected(svc->scheduler, 1);
@@ -3105,11 +3101,26 @@ static int ip_vs_genl_fill_service(struct sk_buff *skb,
 	    nla_put(skb, IPVS_SVC_ATTR_FLAGS, sizeof(flags), &flags) ||
 	    nla_put_u32(skb, IPVS_SVC_ATTR_TIMEOUT, svc->timeout / HZ) ||
 	    nla_put_be32(skb, IPVS_SVC_ATTR_NETMASK, svc->netmask))
-		goto nla_put_failure;
+		return -EMSGSIZE;
 	ip_vs_copy_stats(&kstats, &svc->stats);
 	if (ip_vs_genl_fill_stats(skb, IPVS_SVC_ATTR_STATS, &kstats))
-		goto nla_put_failure;
+		return -EMSGSIZE;
 	if (ip_vs_genl_fill_stats64(skb, IPVS_SVC_ATTR_STATS64, &kstats))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int ip_vs_genl_fill_service(struct sk_buff *skb,
+				   struct ip_vs_service *svc)
+{
+	struct nlattr *nl_service;
+
+	nl_service = nla_nest_start_noflag(skb, IPVS_CMD_ATTR_SERVICE);
+	if (!nl_service)
+		return -EMSGSIZE;
+
+	if (ip_vs_genl_put_service_attrs(skb, svc))
 		goto nla_put_failure;
 
 	nla_nest_end(skb, nl_service);
@@ -3286,12 +3297,13 @@ static struct ip_vs_service *ip_vs_genl_find_service(struct netns_ipvs *ipvs,
 	return ret ? ERR_PTR(ret) : svc;
 }
 
-static int ip_vs_genl_fill_dest(struct sk_buff *skb, struct ip_vs_dest *dest)
+static int ip_vs_genl_fill_dest(struct sk_buff *skb, int container_type,
+				struct ip_vs_dest *dest)
 {
 	struct nlattr *nl_dest;
 	struct ip_vs_kstats kstats;
 
-	nl_dest = nla_nest_start_noflag(skb, IPVS_CMD_ATTR_DEST);
+	nl_dest = nla_nest_start_noflag(skb, container_type);
 	if (!nl_dest)
 		return -EMSGSIZE;
 
@@ -3344,7 +3356,7 @@ static int ip_vs_genl_dump_dest(struct sk_buff *skb, struct ip_vs_dest *dest,
 	if (!hdr)
 		return -EMSGSIZE;
 
-	if (ip_vs_genl_fill_dest(skb, dest) < 0)
+	if (ip_vs_genl_fill_dest(skb, IPVS_CMD_ATTR_DEST, dest) < 0)
 		goto nla_put_failure;
 
 	genlmsg_end(skb, hdr);
@@ -3396,6 +3408,158 @@ static int ip_vs_genl_dump_dests(struct sk_buff *skb,
 	return skb->len;
 }
 
+struct dump_services_dests_ctx {
+	int	idx_svc;
+	int	idx_dest;
+	int	start_svc;
+	int	start_dest;
+};
+
+static int ip_vs_genl_dump_service_dests(struct sk_buff *skb,
+					 struct netlink_callback *cb,
+					 struct netns_ipvs *ipvs,
+					 struct ip_vs_service *svc,
+					 struct dump_services_dests_ctx *ctx)
+{
+	void *hdr;
+	struct nlattr *nl_service;
+	struct nlattr *nl_dests;
+	struct ip_vs_dest *dest;
+	int ret = 0;
+
+	if (svc->ipvs != ipvs)
+		return 0;
+
+	if (++ctx->idx_svc <= ctx->start_svc)
+		return 0;
+
+	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
+			  cb->nlh->nlmsg_seq, &ip_vs_genl_family,
+			  NLM_F_MULTI, IPVS_CMD_NEW_SERVICE);
+	if (!hdr)
+		goto out_err;
+
+	nl_service = nla_nest_start_noflag(skb, IPVS_CMD_ATTR_SERVICE);
+	if (!nl_service)
+		goto nla_put_failure;
+
+	if (ip_vs_genl_put_service_attrs(skb, svc))
+		goto nla_nested_failure;
+
+	nl_dests = nla_nest_start_noflag(skb, IPVS_SVC_ATTR_DESTS);
+	if (!nl_dests)
+		goto nla_nested_failure;
+
+	list_for_each_entry(dest, &svc->destinations, n_list) {
+		if (++ctx->idx_dest <= ctx->start_dest)
+			continue;
+		if (ip_vs_genl_fill_dest(skb, IPVS_DESTS_ATTR_DEST, dest) < 0) {
+			ctx->idx_svc--;
+			ctx->idx_dest--;
+			ret = -EMSGSIZE;
+			goto nla_nested_end;
+		}
+	}
+	ctx->idx_dest = 0;
+	ctx->start_dest = 0;
+
+nla_nested_end:
+	nla_nest_end(skb, nl_dests);
+	nla_nest_end(skb, nl_service);
+	genlmsg_end(skb, hdr);
+	return ret;
+
+nla_nested_failure:
+	nla_nest_cancel(skb, nl_service);
+
+nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+
+out_err:
+	ctx->idx_svc--;
+	return -EMSGSIZE;
+}
+
+static int ip_vs_genl_dump_services_destinations(struct sk_buff *skb,
+						 struct netlink_callback *cb)
+{
+	struct dump_services_dests_ctx ctx = {
+		.idx_svc = 0,
+		.start_svc = cb->args[0],
+		.idx_dest = 0,
+		.start_dest = cb->args[1],
+	};
+	struct net *net = sock_net(skb->sk);
+	struct netns_ipvs *ipvs = net_ipvs(net);
+	struct ip_vs_service *svc;
+	struct nlattr *attrs[IPVS_CMD_ATTR_MAX + 1];
+	int tab = cb->args[2];
+	int row = cb->args[3];
+
+	mutex_lock(&__ip_vs_mutex);
+
+	if (nlmsg_parse_deprecated(cb->nlh, GENL_HDRLEN, attrs,
+				   IPVS_CMD_ATTR_MAX, ip_vs_cmd_policy,
+				   cb->extack) == 0) {
+		if (attrs[IPVS_CMD_ATTR_SERVICE]) {
+			svc = ip_vs_genl_find_service(ipvs,
+						      attrs[IPVS_CMD_ATTR_SERVICE]);
+			if (IS_ERR_OR_NULL(svc))
+				goto out_err;
+			ip_vs_genl_dump_service_dests(skb, cb, ipvs, svc, &ctx);
+			goto nla_put_failure;
+		}
+	}
+
+	if (tab >= 2)
+		goto nla_put_failure;
+
+	if (tab >= 1)
+		goto tab_1;
+
+	for (; row < IP_VS_SVC_TAB_SIZE; row++) {
+		hlist_for_each_entry(svc, &ip_vs_svc_table[row], s_list) {
+			if (ip_vs_genl_dump_service_dests(skb, cb, ipvs,
+							  svc, &ctx))
+				goto nla_put_failure;
+		}
+		ctx.idx_svc = 0;
+		ctx.start_svc = 0;
+		ctx.idx_dest = 0;
+		ctx.start_dest = 0;
+	}
+
+	row = 0;
+	tab++;
+
+tab_1:
+	for (; row < IP_VS_SVC_TAB_SIZE; row++) {
+		hlist_for_each_entry(svc, &ip_vs_svc_fwm_table[row], f_list) {
+			if (ip_vs_genl_dump_service_dests(skb, cb, ipvs,
+							  svc, &ctx))
+				goto nla_put_failure;
+		}
+		ctx.idx_svc = 0;
+		ctx.start_svc = 0;
+		ctx.idx_dest = 0;
+		ctx.start_dest = 0;
+	}
+
+	row = 0;
+	tab++;
+
+nla_put_failure:
+	cb->args[0] = ctx.idx_svc;
+	cb->args[1] = ctx.idx_dest;
+	cb->args[2] = tab;
+	cb->args[3] = row;
+
+out_err:
+	mutex_unlock(&__ip_vs_mutex);
+
+	return skb->len;
+}
+
 static int ip_vs_genl_parse_dest(struct ip_vs_dest_user_kern *udest,
 				 struct nlattr *nla, bool full_entry)
 {
@@ -3991,6 +4155,12 @@ static const struct genl_small_ops ip_vs_genl_ops[] = {
 		.flags	= GENL_ADMIN_PERM,
 		.doit	= ip_vs_genl_set_cmd,
 	},
+	{
+		.cmd	= IPVS_CMD_GET_SERVICE_DEST,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.flags	= GENL_ADMIN_PERM,
+		.dumpit	= ip_vs_genl_dump_services_destinations,
+	},
 };
 
 static struct genl_family ip_vs_genl_family __ro_after_init = {
-- 
2.25.1