src: add 'auto-merge' option to sets

After discussions with Karel here:

https://bugzilla.netfilter.org/show_bug.cgi?id=1184

And later on with Phil Sutter, we decided to disable the automatic merge
feature in sets with intervals. This feature is problematic because it
introduces an inconsistency between what we add and what we later on
get. This is going to get worse with the upcoming timeout support for
intervals. Therefore, we turned off this by default.

However, Jeff Kletsky and folks like this feature, so let's restore this
behaviour on demand with this new 'auto-merge' statement, that you can
place on the set definition, eg.

 # nft list ruleset
 table ip x {
	...
        set y {
                type ipv4_addr
                flags interval
                auto-merge
        }
 }
 # nft add element x z { 1.1.1.1-2.2.2.2, 1.1.1.2 }

Regarding implementation details: Given this feature only makes sense
from userspace, let's store this in the set user data area, so nft knows
it has to do automatic merge of adjacent/overlapping elements as per
user request.

 # nft add set x z { type ipv4_addr\; auto-merge\; }
 Error: auto-merge only works with interval sets
 add set x z { type ipv4_addr; auto-merge; }
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Fixes: https://bugzilla.netfilter.org/show_bug.cgi?id=1216
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

10 files changed, 36 insertions, 7 deletions

diff --git a/doc/nft.xml b/doc/nft.xml
index 9e979af3..6a95ea68 100644
--- a/doc/nft.xml
+++ b/doc/nft.xml
@@ -883,6 +883,7 @@ filter input iif $int_ifs accept
 				<arg choice="opt">elements = { <replaceable>element</replaceable>[,...] } ;</arg>
 				<arg choice="opt">size <replaceable>size</replaceable> ;</arg>
 				<arg choice="opt">policy <replaceable>policy</replaceable> ;</arg>
+				<arg choice="opt">auto-merge <replaceable>auto-merge</replaceable> ;</arg>
 				}
 			</cmdsynopsis>
 			<cmdsynopsis>
@@ -1013,6 +1014,11 @@ filter input iif $int_ifs accept
 						<entry>set policy</entry>
 						<entry>string: performance [default], memory</entry>
 					</row>
+					<row>
+						<entry>auto-merge</entry>
+						<entry>automatic merge of adjacent/overlapping set elements (only for interval sets)</entry>
+						<entry></entry>
+					</row>
 				</tbody>
 			</tgroup>
 		</table>
diff --git a/include/netlink.h b/include/netlink.h
index 0d71a6b9..66686e5a 100644
--- a/include/netlink.h
+++ b/include/netlink.h
@@ -42,7 +42,6 @@ extern const struct location netlink_location;
  * @octx:	output context
  * @debug_mask:	display debugging information
  * @cache:	cache context
- * @range_merge: merge adjacent/overlapping ranges in new set elements
  */
 struct netlink_ctx {
 	struct mnl_socket	*nf_sock;
@@ -56,7 +55,6 @@ struct netlink_ctx {
 	unsigned int		debug_mask;
 	struct output_ctx	*octx;
 	struct nft_cache	*cache;
-	bool			range_merge;
 };
 
 extern struct nftnl_table *alloc_nftnl_table(const struct handle *h);
diff --git a/include/nftables.h b/include/nftables.h
index f22df0d1..3bfa33e5 100644
--- a/include/nftables.h
+++ b/include/nftables.h
@@ -31,7 +31,6 @@ struct nft_ctx {
 	unsigned int		debug_mask;
 	struct output_ctx	output;
 	bool			check;
-	bool			range_merge;
 	struct nft_cache	cache;
 	uint32_t		flags;
 };
diff --git a/include/rule.h b/include/rule.h
index 4e5a349a..d9c172dd 100644
--- a/include/rule.h
+++ b/include/rule.h
@@ -220,6 +220,7 @@ extern struct rule *rule_lookup(const struct chain *chain, uint64_t handle);
  * @init:	initializer
  * @rg_cache:	cached range element (left)
  * @policy:	set mechanism policy
+ * @automerge:	merge adjacents and overlapping elements, if possible
  * @desc:	set mechanism desc
  */
 struct set {
@@ -237,6 +238,7 @@ struct set {
 	struct expr		*init;
 	struct expr		*rg_cache;
 	uint32_t		policy;
+	bool			automerge;
 	struct {
 		uint32_t	size;
 	} desc;
@@ -528,6 +530,7 @@ enum udata_type {
 enum udata_set_type {
 	UDATA_SET_KEYBYTEORDER,
 	UDATA_SET_DATABYTEORDER,
+	UDATA_SET_MERGE_ELEMENTS,
 	__UDATA_SET_MAX,
 };
 #define UDATA_SET_MAX (__UDATA_SET_MAX - 1)
diff --git a/src/evaluate.c b/src/evaluate.c
index 2da589c0..bcdd2dfd 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -2846,6 +2846,9 @@ static int set_evaluate(struct eval_ctx *ctx, struct set *set)
 		return cmd_error(ctx, "Could not process rule: Table '%s' does not exist",
 				 ctx->cmd->handle.table);
 
+	if (!(set->flags & NFT_SET_INTERVAL) && set->automerge)
+		return set_error(ctx, set, "auto-merge only works with interval sets");
+
 	type = set->flags & NFT_SET_MAP ? "map" : "set";
 
 	if (set->key == NULL)
diff --git a/src/libnftables.c b/src/libnftables.c
index 8a18bb78..c86d8947 100644
--- a/src/libnftables.c
+++ b/src/libnftables.c
@@ -43,7 +43,6 @@ static int nft_netlink(struct nft_ctx *nft,
 		ctx.nf_sock = nf_sock;
 		ctx.cache = &nft->cache;
 		ctx.debug_mask = nft->debug_mask;
-		ctx.range_merge = nft->range_merge;
 		init_list_head(&ctx.list);
 		ret = do_command(&ctx, cmd);
 		if (ret < 0)
diff --git a/src/netlink.c b/src/netlink.c
index 23f92443..488ae6f3 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -1052,6 +1052,7 @@ static int set_parse_udata_cb(const struct nftnl_udata *attr, void *data)
 	switch (type) {
 	case UDATA_SET_KEYBYTEORDER:
 	case UDATA_SET_DATABYTEORDER:
+	case UDATA_SET_MERGE_ELEMENTS:
 		if (len != sizeof(uint32_t))
 			return -1;
 		break;
@@ -1070,6 +1071,7 @@ static struct set *netlink_delinearize_set(struct netlink_ctx *ctx,
 	enum byteorder keybyteorder = BYTEORDER_INVALID;
 	enum byteorder databyteorder = BYTEORDER_INVALID;
 	const struct datatype *keytype, *datatype;
+	bool automerge = false;
 	const char *udata;
 	struct set *set;
 	uint32_t ulen;
@@ -1087,6 +1089,9 @@ static struct set *netlink_delinearize_set(struct netlink_ctx *ctx,
 		if (ud[UDATA_SET_DATABYTEORDER])
 			databyteorder =
 				nftnl_udata_get_u32(ud[UDATA_SET_DATABYTEORDER]);
+		if (ud[UDATA_SET_MERGE_ELEMENTS])
+			automerge =
+				nftnl_udata_get_u32(ud[UDATA_SET_MERGE_ELEMENTS]);
 	}
 
 	key = nftnl_set_get_u32(nls, NFTNL_SET_KEY_TYPE);
@@ -1119,6 +1124,7 @@ static struct set *netlink_delinearize_set(struct netlink_ctx *ctx,
 	set->handle.family = nftnl_set_get_u32(nls, NFTNL_SET_FAMILY);
 	set->handle.table  = xstrdup(nftnl_set_get_str(nls, NFTNL_SET_TABLE));
 	set->handle.set    = xstrdup(nftnl_set_get_str(nls, NFTNL_SET_NAME));
+	set->automerge	   = automerge;
 
 	set->key     = constant_expr_alloc(&netlink_location,
 					   set_datatype_alloc(keytype, keybyteorder),
@@ -1238,6 +1244,11 @@ static int netlink_add_set_batch(struct netlink_ctx *ctx,
 				 set->datatype->byteorder))
 		memory_allocation_error();
 
+	if (set->automerge &&
+	    !nftnl_udata_put_u32(udbuf, UDATA_SET_MERGE_ELEMENTS,
+				 set->automerge))
+		memory_allocation_error();
+
 	nftnl_set_set_data(nls, NFTNL_SET_USERDATA, nftnl_udata_buf_data(udbuf),
 			   nftnl_udata_buf_len(udbuf));
 	nftnl_udata_buf_free(udbuf);
diff --git a/src/parser_bison.y b/src/parser_bison.y
index 009b801f..2e79109f 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -234,6 +234,7 @@ int nft_lex(void *, void *, void *);
 
 %token CONSTANT			"constant"
 %token INTERVAL			"interval"
+%token AUTOMERGE		"auto-merge"
 %token TIMEOUT			"timeout"
 %token GC_INTERVAL		"gc-interval"
 %token ELEMENTS			"elements"
@@ -1407,6 +1408,11 @@ set_block		:	/* empty */	{ $$ = $<set>-1; }
 				$1->init = $4;
 				$$ = $1;
 			}
+			|	set_block	AUTOMERGE
+			{
+				$1->automerge = true;
+				$$ = $1;
+			}
 			|	set_block	set_mechanism	stmt_separator
 			;
 
diff --git a/src/rule.c b/src/rule.c
index f19197fe..c7b4b498 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -344,6 +344,9 @@ static void set_print_declaration(const struct set *set,
 		}
 		nft_print(octx, "%s", opts->stmt_separator);
 	}
+	if (set->automerge)
+		nft_print(octx, "%s%sauto-merge%s", opts->tab, opts->tab,
+			  opts->stmt_separator);
 
 	if (set->timeout) {
 		nft_print(octx, "%s%stimeout ", opts->tab, opts->tab);
@@ -998,7 +1001,7 @@ static int do_add_setelems(struct netlink_ctx *ctx, const struct handle *h,
 
 	if (set->flags & NFT_SET_INTERVAL &&
 	    set_to_intervals(ctx->msgs, set, init, true,
-			     ctx->debug_mask, ctx->range_merge) < 0)
+			     ctx->debug_mask, set->automerge) < 0)
 		return -1;
 
 	return __do_add_setelems(ctx, h, set, init, flags);
@@ -1010,7 +1013,7 @@ static int do_add_set(struct netlink_ctx *ctx, const struct handle *h,
 	if (set->init != NULL) {
 		if (set->flags & NFT_SET_INTERVAL &&
 		    set_to_intervals(ctx->msgs, set, set->init, true,
-				     ctx->debug_mask, ctx->range_merge) < 0)
+				     ctx->debug_mask, set->automerge) < 0)
 			return -1;
 	}
 	if (netlink_add_set(ctx, h, set, flags) < 0)
@@ -1110,7 +1113,7 @@ static int do_delete_setelems(struct netlink_ctx *ctx, const struct handle *h,
 
 	if (set->flags & NFT_SET_INTERVAL &&
 	    set_to_intervals(ctx->msgs, set, expr, false,
-			     ctx->debug_mask, ctx->range_merge) < 0)
+			     ctx->debug_mask, set->automerge) < 0)
 		return -1;
 
 	if (netlink_delete_setelems(ctx, h, expr) < 0)
diff --git a/src/scanner.l b/src/scanner.l
index 5402be1c..c3992a78 100644
--- a/src/scanner.l
+++ b/src/scanner.l
@@ -283,6 +283,7 @@ addrstring	({macaddr}|{ip4addr}|{ip6addr})
 
 "constant"		{ return CONSTANT; }
 "interval"		{ return INTERVAL; }
+"auto-merge"		{ return AUTOMERGE; }
 "timeout"		{ return TIMEOUT; }
 "gc-interval"		{ return GC_INTERVAL; }
 "elements"		{ return ELEMENTS; }