src: add xt compat support

At compilation time, you have to pass this option.

  # ./configure --with-xtables

And libxtables needs to be installed in your system.

This patch allows to list a ruleset containing xt extensions loaded
through iptables-compat-restore tool.

Example:

$ iptables-save > ruleset

$ cat ruleset
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -p tcp -m multiport --dports 80,81 -j REJECT
COMMIT

$ sudo iptables-compat-restore ruleset

$ sudo nft list rulseset
table ip filter {
    chain INPUT {
        type filter hook input priority 0; policy accept;
        ip protocol tcp tcp dport { 80,81} counter packets 0 bytes 0 reject
    }

    chain FORWARD {
        type filter hook forward priority 0; policy drop;
    }

    chain OUTPUT {
        type filter hook output priority 0; policy accept;
    }
}

A translation of the extension is shown if this is available. In other
case, match or target definition is preceded by a hash. For example,
classify target has not translation:

$ sudo nft list chain mangle POSTROUTING
table ip mangle {
    chain POSTROUTING {
        type filter hook postrouting priority -150; policy accept;
        ip protocol tcp tcp dport 80 counter packets 0 bytes 0 # CLASSIFY set 20:10
                                                              ^^^
    }
}

If the whole ruleset is translatable, the users can (re)load it using
"nft -f" and get nft native support for all their rules.

This patch is joint work by the authors listed below.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo M. Bermudo Garay <pablombg@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 348 insertions, 0 deletions

diff --git a/src/xt.c b/src/xt.c
new file mode 100644
index 00000000..afcc8362
--- /dev/null
+++ b/src/xt.c
@@ -0,0 +1,348 @@
+/*
+ * Copyright (c) 2013-2015 Pablo Neira Ayuso <pablo@netfilter.org>
+ * Copyright (c) 2015 Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modifyi
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <stdlib.h>
+#include <time.h>
+#include <string.h>
+#include <xtables.h>
+#include <getopt.h>
+#include <ctype.h>	/* for isspace */
+#include <statement.h>
+#include <netlink.h>
+#include <xt.h>
+#include <erec.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/netfilter/nfnetlink.h>
+#include <linux/netfilter/nf_tables_compat.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#include <linux/netfilter_arp/arp_tables.h>
+#include <linux/netfilter_bridge/ebtables.h>
+
+void xt_stmt_xlate(const struct stmt *stmt)
+{
+	struct xt_xlate *xl = xt_xlate_alloc(10240);
+
+	switch (stmt->xt.type) {
+	case NFT_XT_MATCH:
+		if (stmt->xt.match == NULL && stmt->xt.opts) {
+			printf("%s", stmt->xt.opts);
+		} else if (stmt->xt.match->xlate) {
+			stmt->xt.match->xlate(stmt->xt.entry,
+					      stmt->xt.match->m, xl, 0);
+				printf("%s", xt_xlate_get(xl));
+		} else if (stmt->xt.match->print) {
+			printf("#");
+			stmt->xt.match->print(&stmt->xt.entry,
+					      stmt->xt.match->m, 0);
+		}
+		break;
+	case NFT_XT_WATCHER:
+	case NFT_XT_TARGET:
+		if (stmt->xt.target == NULL && stmt->xt.opts) {
+			printf("%s", stmt->xt.opts);
+		} else if (stmt->xt.target->xlate) {
+			stmt->xt.target->xlate(stmt->xt.entry,
+					       stmt->xt.target->t, xl, 0);
+			printf("%s", xt_xlate_get(xl));
+		} else if (stmt->xt.target->print) {
+			printf("#");
+			stmt->xt.target->print(NULL, stmt->xt.target->t, 0);
+		}
+		break;
+	default:
+		break;
+	}
+
+	xt_xlate_free(xl);
+}
+
+void xt_stmt_release(const struct stmt *stmt)
+{
+	switch (stmt->xt.type) {
+	case NFT_XT_MATCH:
+		if (!stmt->xt.match)
+			break;
+		if (stmt->xt.match->m)
+			xfree(stmt->xt.match->m);
+		xfree(stmt->xt.match);
+		break;
+	case NFT_XT_WATCHER:
+	case NFT_XT_TARGET:
+		if (!stmt->xt.target)
+			break;
+		if (stmt->xt.target->t)
+			xfree(stmt->xt.target->t);
+		xfree(stmt->xt.target);
+		break;
+	default:
+		break;
+	}
+	xfree(stmt->xt.entry);
+}
+
+static void *xt_entry_alloc(struct xt_stmt *xt, uint32_t af)
+{
+	union nft_entry {
+		struct ipt_entry ipt;
+		struct ip6t_entry ip6t;
+		struct arpt_entry arpt;
+		struct ebt_entry ebt;
+	} *entry;
+
+	entry = xmalloc(sizeof(union nft_entry));
+
+	switch (af) {
+	case NFPROTO_IPV4:
+		entry->ipt.ip.proto = xt->proto;
+		break;
+	case NFPROTO_IPV6:
+		entry->ip6t.ipv6.proto = xt->proto;
+		break;
+	case NFPROTO_BRIDGE:
+		entry->ebt.ethproto = xt->proto;
+		break;
+	case NFPROTO_ARP:
+		entry->arpt.arp.arhln_mask = 0xff;
+		entry->arpt.arp.arhln = 6;
+		break;
+	default:
+		break;
+	}
+
+	return entry;
+}
+
+static uint32_t xt_proto(const struct proto_ctx *pctx)
+{
+	const struct proto_desc *desc = NULL;
+
+	if (pctx->family == NFPROTO_BRIDGE) {
+		desc = pctx->protocol[PROTO_BASE_NETWORK_HDR].desc;
+		if (desc == NULL)
+			return 0;
+		if (strcmp(desc->name, "ip") == 0)
+			return __constant_htons(ETH_P_IP);
+		if (strcmp(desc->name, "ip6") == 0)
+			return __constant_htons(ETH_P_IPV6);
+		return 0;
+	}
+
+	desc = pctx->protocol[PROTO_BASE_TRANSPORT_HDR].desc;
+	if (desc == NULL)
+		return 0;
+	if (strcmp(desc->name, "tcp") == 0)
+		return IPPROTO_TCP;
+	else if (strcmp(desc->name, "udp") == 0)
+		return IPPROTO_UDP;
+	else if (strcmp(desc->name, "udplite") == 0)
+		return IPPROTO_UDPLITE;
+	else if (strcmp(desc->name, "sctp") == 0)
+		return IPPROTO_SCTP;
+	else if (strcmp(desc->name, "dccp") == 0)
+		return IPPROTO_DCCP;
+	else if (strcmp(desc->name, "esp") == 0)
+		return IPPROTO_ESP;
+	else if (strcmp(desc->name, "ah") == 0)
+		return IPPROTO_AH;
+
+	return 0;
+}
+
+static struct xtables_target *xt_target_clone(struct xtables_target *t)
+{
+	struct xtables_target *clone;
+
+	clone = xzalloc(sizeof(struct xtables_target));
+	memcpy(clone, t, sizeof(struct xtables_target));
+	return clone;
+}
+
+static struct xtables_match *xt_match_clone(struct xtables_match *m)
+{
+	struct xtables_match *clone;
+
+	clone = xzalloc(sizeof(struct xtables_match));
+	memcpy(clone, m, sizeof(struct xtables_match));
+	return clone;
+}
+
+/*
+ * Delinearization
+ */
+
+void netlink_parse_match(struct netlink_parse_ctx *ctx,
+			 const struct location *loc,
+			 const struct nftnl_expr *nle)
+{
+	struct stmt *stmt;
+	const char *name;
+	struct xtables_match *mt;
+	const char *mtinfo;
+	struct xt_entry_match *m;
+	uint32_t mt_len;
+
+	xtables_set_nfproto(ctx->table->handle.family);
+
+	name = nftnl_expr_get_str(nle, NFT_EXPR_MT_NAME);
+
+	mt = xtables_find_match(name, XTF_TRY_LOAD, NULL);
+	if (!mt)
+		BUG("XT match %s not found\n", name);
+
+	mtinfo = nftnl_expr_get(nle, NFT_EXPR_MT_INFO, &mt_len);
+
+	m = xzalloc(sizeof(struct xt_entry_match) + mt_len);
+	memcpy(&m->data, mtinfo, mt_len);
+
+	m->u.match_size = mt_len + XT_ALIGN(sizeof(struct xt_entry_match));
+	m->u.user.revision = nftnl_expr_get_u32(nle, NFT_EXPR_MT_REV);
+
+	stmt = xt_stmt_alloc(loc);
+	stmt->xt.name = strdup(name);
+	stmt->xt.type = NFT_XT_MATCH;
+	stmt->xt.match = xt_match_clone(mt);
+	stmt->xt.match->m = m;
+
+	list_add_tail(&stmt->list, &ctx->rule->stmts);
+}
+
+void netlink_parse_target(struct netlink_parse_ctx *ctx,
+			  const struct location *loc,
+			  const struct nftnl_expr *nle)
+{
+	struct stmt *stmt;
+	const char *name;
+	struct xtables_target *tg;
+	const void *tginfo;
+	struct xt_entry_target *t;
+	size_t size;
+	uint32_t tg_len;
+
+	xtables_set_nfproto(ctx->table->handle.family);
+
+	name = nftnl_expr_get_str(nle, NFT_EXPR_TG_NAME);
+	tg = xtables_find_target(name, XTF_TRY_LOAD);
+	if (!tg)
+		BUG("XT target %s not found\n", name);
+
+	tginfo = nftnl_expr_get(nle, NFT_EXPR_TG_INFO, &tg_len);
+
+	size = XT_ALIGN(sizeof(struct xt_entry_target)) + tg_len;
+	t = xzalloc(size);
+	memcpy(&t->data, tginfo, tg_len);
+	t->u.target_size = size;
+	t->u.user.revision = nftnl_expr_get_u32(nle, NFT_EXPR_TG_REV);
+	strcpy(t->u.user.name, tg->name);
+
+	stmt = xt_stmt_alloc(loc);
+	stmt->xt.name = strdup(name);
+	stmt->xt.type = NFT_XT_TARGET;
+	stmt->xt.target = xt_target_clone(tg);
+	stmt->xt.target->t = t;
+
+	list_add_tail(&stmt->list, &ctx->rule->stmts);
+}
+
+static bool is_watcher(uint32_t family, struct stmt *stmt)
+{
+	if (family != NFPROTO_BRIDGE ||
+	    stmt->xt.type != NFT_XT_TARGET)
+		return false;
+
+	/* this has to be hardcoded :-( */
+	if (strcmp(stmt->xt.name, "log") == 0)
+		return true;
+	else if (strcmp(stmt->xt.name, "nflog") == 0)
+		return true;
+
+	return false;
+}
+
+void stmt_xt_postprocess(struct rule_pp_ctx *rctx, struct stmt *stmt,
+			 struct rule *rule)
+{
+	if (is_watcher(rctx->pctx.family, stmt))
+		stmt->xt.type = NFT_XT_WATCHER;
+
+	stmt->xt.proto = xt_proto(&rctx->pctx);
+	stmt->xt.entry = xt_entry_alloc(&stmt->xt, rctx->pctx.family);
+}
+
+static int nft_xt_compatible_revision(const char *name, uint8_t rev, int opt)
+{
+	struct mnl_socket *nl;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
+	uint32_t portid, seq, type;
+	struct nfgenmsg *nfg;
+	int ret = 0;
+
+	if (opt == IPT_SO_GET_REVISION_MATCH)
+		type = 0;
+	else
+		type = 1;
+
+	nlh = mnl_nlmsg_put_header(buf);
+	nlh->nlmsg_type = (NFNL_SUBSYS_NFT_COMPAT << 8) | NFNL_MSG_COMPAT_GET;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+	nlh->nlmsg_seq = seq = time(NULL);
+
+	nfg = mnl_nlmsg_put_extra_header(nlh, sizeof(*nfg));
+	nfg->nfgen_family = AF_INET;
+	nfg->version = NFNETLINK_V0;
+	nfg->res_id = 0;
+
+	mnl_attr_put_strz(nlh, NFTA_COMPAT_NAME, name);
+	mnl_attr_put_u32(nlh, NFTA_COMPAT_REV, htonl(rev));
+	mnl_attr_put_u32(nlh, NFTA_COMPAT_TYPE, htonl(type));
+
+	nl = mnl_socket_open(NETLINK_NETFILTER);
+	if (nl == NULL)
+		return 0;
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0)
+		goto err;
+
+	portid = mnl_socket_get_portid(nl);
+
+	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
+		goto err;
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	if (ret == -1)
+		goto err;
+
+	ret = mnl_cb_run(buf, ret, seq, portid, NULL, NULL);
+	if (ret == -1)
+		goto err;
+
+err:
+	mnl_socket_close(nl);
+
+	return ret < 0 ? 0 : 1;
+}
+
+static struct option original_opts[] = {
+	{ NULL },
+};
+
+static struct xtables_globals xt_nft_globals = {
+	.program_name		= "nft",
+	.program_version	= PACKAGE_VERSION,
+	.orig_opts		= original_opts,
+	.compat_rev		= nft_xt_compatible_revision,
+};
+
+static void __init xt_init(void)
+{
+	/* Default to IPv4, but this changes in runtime */
+	xtables_init_all(&xt_nft_globals, NFPROTO_IPV4);
+}