1/*
2 * em_nbyte.c		N-Byte Ematch
3 *
4 *		This program is free software; you can distribute it and/or
5 *		modify it under the terms of the GNU General Public License
6 *		as published by the Free Software Foundation; either version
7 *		2 of the License, or (at your option) any later version.
8 *
9 * Authors:	Thomas Graf <tgraf@suug.ch>
10 */
11
12#include <stdio.h>
13#include <stdlib.h>
14#include <unistd.h>
15#include <syslog.h>
16#include <fcntl.h>
17#include <sys/socket.h>
18#include <netinet/in.h>
19#include <arpa/inet.h>
20#include <string.h>
21#include <errno.h>
22
23#include "m_ematch.h"
24#include <linux/tc_ematch/tc_em_nbyte.h>
25
26extern struct ematch_util nbyte_ematch_util;
27
28static void nbyte_print_usage(FILE *fd)
29{
30	fprintf(fd,
31	    "Usage: nbyte(NEEDLE at OFFSET [layer LAYER])\n" \
32	    "where: NEEDLE := { string | \"c-escape-sequence\" }\n" \
33	    "       OFFSET := int\n" \
34	    "       LAYER  := { link | network | transport | 0..%d }\n" \
35	    "\n" \
36	    "Example: nbyte(\"ababa\" at 12 layer 1)\n",
37	    TCF_LAYER_MAX);
38}
39
40static int nbyte_parse_eopt(struct nlmsghdr *n, struct tcf_ematch_hdr *hdr,
41			    struct bstr *args)
42{
43	struct bstr *a;
44	struct bstr *needle = args;
45	unsigned long offset = 0, layer = TCF_LAYER_NETWORK;
46	int offset_present = 0;
47	struct tcf_em_nbyte nb;
48
49	memset(&nb, 0, sizeof(nb));
50
51#define PARSE_ERR(CARG, FMT, ARGS...) \
52	em_parse_error(EINVAL, args, CARG, &nbyte_ematch_util, FMT ,##ARGS)
53
54	if (args == NULL)
55		return PARSE_ERR(args, "nbyte: missing arguments");
56
57	if (needle->len <= 0)
58		return PARSE_ERR(args, "nbyte: needle length is 0");
59
60	for (a = bstr_next(args); a; a = bstr_next(a)) {
61		if (!bstrcmp(a, "at")) {
62			if (a->next == NULL)
63				return PARSE_ERR(a, "nbyte: missing argument");
64			a = bstr_next(a);
65
66			offset = bstrtoul(a);
67			if (offset == ULONG_MAX)
68				return PARSE_ERR(a, "nbyte: invalid offset, " \
69				    "must be numeric");
70
71			offset_present = 1;
72		} else if (!bstrcmp(a, "layer")) {
73			if (a->next == NULL)
74				return PARSE_ERR(a, "nbyte: missing argument");
75			a = bstr_next(a);
76
77			layer = parse_layer(a);
78			if (layer == INT_MAX) {
79				layer = bstrtoul(a);
80				if (layer == ULONG_MAX)
81					return PARSE_ERR(a, "nbyte: invalid " \
82					    "layer");
83			}
84
85			if (layer > TCF_LAYER_MAX)
86				return PARSE_ERR(a, "nbyte: illegal layer, " \
87				    "must be in 0..%d", TCF_LAYER_MAX);
88		} else
89			return PARSE_ERR(a, "nbyte: unknown parameter");
90	}
91
92	if (offset_present == 0)
93		return PARSE_ERR(a, "nbyte: offset required");
94
95	nb.len = needle->len;
96	nb.layer = (__u8) layer;
97	nb.off = (__u16) offset;
98
99	addraw_l(n, MAX_MSG, hdr, sizeof(*hdr));
100	addraw_l(n, MAX_MSG, &nb, sizeof(nb));
101	addraw_l(n, MAX_MSG, needle->data, needle->len);
102
103#undef PARSE_ERR
104	return 0;
105}
106
107static int nbyte_print_eopt(FILE *fd, struct tcf_ematch_hdr *hdr, void *data,
108			    int data_len)
109{
110	int i;
111	struct tcf_em_nbyte *nb = data;
112	__u8 *needle;
113
114	if (data_len < sizeof(*nb)) {
115		fprintf(stderr, "NByte header size mismatch\n");
116		return -1;
117	}
118
119	if (data_len < sizeof(*nb) + nb->len) {
120		fprintf(stderr, "NByte payload size mismatch\n");
121		return -1;
122	}
123
124	needle = data + sizeof(*nb);
125
126	for (i = 0; i < nb->len; i++)
127		fprintf(fd, "%02x ", needle[i]);
128
129	fprintf(fd, "\"");
130	for (i = 0; i < nb->len; i++)
131		fprintf(fd, "%c", isprint(needle[i]) ? needle[i] : '.');
132	fprintf(fd, "\" at %d layer %d", nb->off, nb->layer);
133
134	return 0;
135}
136
137struct ematch_util nbyte_ematch_util = {
138	.kind = "nbyte",
139	.kind_num = TCF_EM_NBYTE,
140	.parse_eopt = nbyte_parse_eopt,
141	.print_eopt = nbyte_print_eopt,
142	.print_usage = nbyte_print_usage
143};
144