1 files changed, 136 insertions, 0 deletions
diff --git a/tc/em_nbyte.c b/tc/em_nbyte.c
new file mode 100644
index 0000000..9f421fb
--- /dev/null
+++ b/tc/em_nbyte.c
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * em_nbyte.c		N-Byte Ematch
+ *
+ * Authors:	Thomas Graf <tgraf@suug.ch>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <string.h>
+#include <errno.h>
+
+#include "m_ematch.h"
+#include <linux/tc_ematch/tc_em_nbyte.h>
+
+extern struct ematch_util nbyte_ematch_util;
+
+static void nbyte_print_usage(FILE *fd)
+{
+	fprintf(fd,
+	    "Usage: nbyte(NEEDLE at OFFSET [layer LAYER])\n" \
+	    "where: NEEDLE := { string | \"c-escape-sequence\" }\n" \
+	    "       OFFSET := int\n" \
+	    "       LAYER  := { link | network | transport | 0..%d }\n" \
+	    "\n" \
+	    "Example: nbyte(\"ababa\" at 12 layer 1)\n",
+	    TCF_LAYER_MAX);
+}
+
+static int nbyte_parse_eopt(struct nlmsghdr *n, struct tcf_ematch_hdr *hdr,
+			    struct bstr *args)
+{
+	struct bstr *a;
+	struct bstr *needle = args;
+	unsigned long offset = 0, layer = TCF_LAYER_NETWORK;
+	int offset_present = 0;
+	struct tcf_em_nbyte nb = {};
+
+#define PARSE_ERR(CARG, FMT, ARGS...) \
+	em_parse_error(EINVAL, args, CARG, &nbyte_ematch_util, FMT, ##ARGS)
+
+	if (args == NULL)
+		return PARSE_ERR(args, "nbyte: missing arguments");
+
+	if (needle->len <= 0)
+		return PARSE_ERR(args, "nbyte: needle length is 0");
+
+	for (a = bstr_next(args); a; a = bstr_next(a)) {
+		if (!bstrcmp(a, "at")) {
+			if (a->next == NULL)
+				return PARSE_ERR(a, "nbyte: missing argument");
+			a = bstr_next(a);
+
+			offset = bstrtoul(a);
+			if (offset == ULONG_MAX)
+				return PARSE_ERR(a, "nbyte: invalid offset, " \
+				    "must be numeric");
+
+			offset_present = 1;
+		} else if (!bstrcmp(a, "layer")) {
+			if (a->next == NULL)
+				return PARSE_ERR(a, "nbyte: missing argument");
+			a = bstr_next(a);
+
+			layer = parse_layer(a);
+			if (layer == INT_MAX) {
+				layer = bstrtoul(a);
+				if (layer == ULONG_MAX)
+					return PARSE_ERR(a, "nbyte: invalid " \
+					    "layer");
+			}
+
+			if (layer > TCF_LAYER_MAX)
+				return PARSE_ERR(a, "nbyte: illegal layer, " \
+				    "must be in 0..%d", TCF_LAYER_MAX);
+		} else
+			return PARSE_ERR(a, "nbyte: unknown parameter");
+	}
+
+	if (offset_present == 0)
+		return PARSE_ERR(a, "nbyte: offset required");
+
+	nb.len = needle->len;
+	nb.layer = (__u8) layer;
+	nb.off = (__u16) offset;
+
+	addraw_l(n, MAX_MSG, hdr, sizeof(*hdr));
+	addraw_l(n, MAX_MSG, &nb, sizeof(nb));
+	addraw_l(n, MAX_MSG, needle->data, needle->len);
+
+#undef PARSE_ERR
+	return 0;
+}
+
+static int nbyte_print_eopt(FILE *fd, struct tcf_ematch_hdr *hdr, void *data,
+			    int data_len)
+{
+	int i;
+	struct tcf_em_nbyte *nb = data;
+	__u8 *needle;
+
+	if (data_len < sizeof(*nb)) {
+		fprintf(stderr, "NByte header size mismatch\n");
+		return -1;
+	}
+
+	if (data_len < sizeof(*nb) + nb->len) {
+		fprintf(stderr, "NByte payload size mismatch\n");
+		return -1;
+	}
+
+	needle = data + sizeof(*nb);
+
+	for (i = 0; i < nb->len; i++)
+		fprintf(fd, "%02x ", needle[i]);
+
+	fprintf(fd, "\"");
+	for (i = 0; i < nb->len; i++)
+		fprintf(fd, "%c", isprint(needle[i]) ? needle[i] : '.');
+	fprintf(fd, "\" at %d layer %d", nb->off, nb->layer);
+
+	return 0;
+}
+
+struct ematch_util nbyte_ematch_util = {
+	.kind = "nbyte",
+	.kind_num = TCF_EM_NBYTE,
+	.parse_eopt = nbyte_parse_eopt,
+	.print_eopt = nbyte_print_eopt,
+	.print_usage = nbyte_print_usage
+};