src: add ipsec (xfrm) expression

This allows matching on ipsec tunnel/beet addresses in xfrm state
associated with a packet, ipsec request id and the SPI.

Examples:

 ipsec in ip saddr 192.168.1.0/24
 ipsec out ip6 daddr @endpoints
 ipsec in spi 1-65536

Joint work with Florian Westphal.

Cc: Máté Eckl <ecklm94@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 120 insertions, 0 deletions

diff --git a/src/xfrm.c b/src/xfrm.c
new file mode 100644
index 00000000..0f5818c5
--- /dev/null
+++ b/src/xfrm.c
@@ -0,0 +1,120 @@
+/*
+ * XFRM (ipsec) expression
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <nftables.h>
+#include <erec.h>
+#include <expression.h>
+#include <xfrm.h>
+#include <datatype.h>
+#include <gmputil.h>
+#include <utils.h>
+#include <string.h>
+
+#include <netinet/ip.h>
+#include <linux/netfilter.h>
+#include <linux/xfrm.h>
+
+#define XFRM_TEMPLATE_BE(__token, __dtype, __len) {	\
+	.token		= (__token),			\
+	.dtype		= (__dtype),			\
+	.len		= (__len),			\
+	.byteorder	= BYTEORDER_BIG_ENDIAN,		\
+}
+
+#define XFRM_TEMPLATE_HE(__token, __dtype, __len) {	\
+	.token		= (__token),			\
+	.dtype		= (__dtype),			\
+	.len		= (__len),			\
+	.byteorder	= BYTEORDER_HOST_ENDIAN,	\
+}
+
+const struct xfrm_template xfrm_templates[] = {
+	[NFT_XFRM_KEY_DADDR_IP4]	= XFRM_TEMPLATE_BE("daddr", &ipaddr_type, 4 * BITS_PER_BYTE),
+	[NFT_XFRM_KEY_SADDR_IP4]	= XFRM_TEMPLATE_BE("saddr", &ipaddr_type, 4 * BITS_PER_BYTE),
+	[NFT_XFRM_KEY_DADDR_IP6]	= XFRM_TEMPLATE_BE("daddr", &ip6addr_type, 16 * BITS_PER_BYTE),
+	[NFT_XFRM_KEY_SADDR_IP6]	= XFRM_TEMPLATE_BE("saddr", &ip6addr_type, 16 * BITS_PER_BYTE),
+	[NFT_XFRM_KEY_REQID]		= XFRM_TEMPLATE_HE("reqid", &integer_type, 4 * BITS_PER_BYTE),
+	[NFT_XFRM_KEY_SPI]		= XFRM_TEMPLATE_HE("spi", &integer_type, 4 * BITS_PER_BYTE),
+};
+
+static void xfrm_expr_print(const struct expr *expr, struct output_ctx *octx)
+{
+	switch (expr->xfrm.direction) {
+	case XFRM_POLICY_IN:
+		nft_print(octx, "ipsec in");
+		break;
+	case XFRM_POLICY_OUT:
+		nft_print(octx, "ipsec out");
+		break;
+	default:
+		nft_print(octx, "ipsec (unknown dir %d)", expr->xfrm.direction);
+		break;
+	}
+
+	if (expr->xfrm.spnum)
+		nft_print(octx, " spnum %u", expr->xfrm.spnum);
+
+	switch (expr->xfrm.key) {
+	case NFT_XFRM_KEY_DADDR_IP4:
+	case NFT_XFRM_KEY_SADDR_IP4:
+		 nft_print(octx, " ip");
+		 break;
+	case NFT_XFRM_KEY_DADDR_IP6:
+	case NFT_XFRM_KEY_SADDR_IP6:
+		 nft_print(octx, " ip6");
+		 break;
+	case NFT_XFRM_KEY_REQID:
+	case NFT_XFRM_KEY_SPI:
+		 break;
+	default:
+		 nft_print(octx, " (unknown key 0x%x)", expr->xfrm.key);
+		 return;
+	}
+
+	nft_print(octx, " %s", xfrm_templates[expr->xfrm.key].token);
+}
+
+static bool xfrm_expr_cmp(const struct expr *e1, const struct expr *e2)
+{
+	return e1->xfrm.key == e2->xfrm.key &&
+	       e1->xfrm.direction == e2->xfrm.direction &&
+	       e1->xfrm.spnum == e2->xfrm.spnum;
+}
+
+static void xfrm_expr_clone(struct expr *new, const struct expr *expr)
+{
+	memcpy(&new->xfrm, &expr->xfrm, sizeof(new->xfrm));
+}
+
+static const struct expr_ops xfrm_expr_ops = {
+	.type		= EXPR_XFRM,
+	.name		= "xfrm",
+	.print		= xfrm_expr_print,
+	.json		= xfrm_expr_json,
+	.cmp		= xfrm_expr_cmp,
+	.clone		= xfrm_expr_clone,
+};
+
+struct expr *xfrm_expr_alloc(const struct location *loc,
+			     uint8_t direction,
+			     uint8_t spnum,
+			     enum nft_xfrm_keys key)
+{
+	struct expr *expr;
+
+	expr = expr_alloc(loc, &xfrm_expr_ops,
+			  xfrm_templates[key].dtype,
+			  xfrm_templates[key].byteorder,
+			  xfrm_templates[key].len);
+
+	expr->xfrm.direction = direction;
+	expr->xfrm.spnum = spnum;
+	expr->xfrm.key = key;
+
+	return expr;
+}