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 <dlfcn.h>
22#include <errno.h>
23
24#include "m_ematch.h"
25#include <linux/tc_ematch/tc_em_nbyte.h>
26
27extern struct ematch_util nbyte_ematch_util;
28
29static void nbyte_print_usage(FILE *fd)
30{
31	fprintf(fd,
32	    "Usage: nbyte(NEEDLE at OFFSET [layer LAYER])\n" \
33	    "where: NEEDLE := { string | \"c-escape-sequence\" }\n" \
34	    "       OFFSET := int\n" \
35	    "       LAYER  := { link | header | next-header | 0..%d }\n" \
36	    "\n" \
37	    "Example: nbyte(\"ababa\" at 12 layer 1)\n",
38	    TCF_LAYER_MAX);
39}
40
41static int nbyte_parse_eopt(struct nlmsghdr *n, struct tcf_ematch_hdr *hdr,
42			    struct bstr *args)
43{
44	struct bstr *a;
45	struct bstr *needle = args;
46	unsigned long offset = 0, layer = TCF_LAYER_NETWORK;
47	int offset_present = 0;
48	struct tcf_em_nbyte nb;
49
50	memset(&nb, 0, sizeof(nb));
51
52#define PARSE_ERR(CARG, FMT, ARGS...) \
53	em_parse_error(EINVAL, args, CARG, &nbyte_ematch_util, FMT ,##ARGS)
54
55	if (args == NULL)
56		return PARSE_ERR(args, "nbyte: missing arguments");
57
58	if (needle->len <= 0)
59		return PARSE_ERR(args, "nbyte: needle length is 0");
60
61	for (a = bstr_next(args); a; a = bstr_next(a)) {
62		if (!bstrcmp(a, "at")) {
63			if (a->next == NULL)
64				return PARSE_ERR(a, "nbyte: missing argument");
65			a = bstr_next(a);
66
67			offset = bstrtoul(a);
68			if (offset == ULONG_MAX)
69				return PARSE_ERR(a, "nbyte: invalid offset, " \
70				    "must be numeric");
71
72			offset_present = 1;
73		} else if (!bstrcmp(a, "layer")) {
74			if (a->next == NULL)
75				return PARSE_ERR(a, "nbyte: missing argument");
76			a = bstr_next(a);
77
78			layer = parse_layer(a);
79			if (layer == INT_MAX) {
80				layer = bstrtoul(a);
81				if (layer == ULONG_MAX)
82					return PARSE_ERR(a, "nbyte: invalid " \
83					    "layer");
84			}
85
86			if (layer > TCF_LAYER_MAX)
87				return PARSE_ERR(a, "nbyte: illegal layer, " \
88				    "must be in 0..%d", TCF_LAYER_MAX);
89		} else
90			return PARSE_ERR(a, "nbyte: unknown parameter");
91	}
92
93	if (offset_present == 0)
94		return PARSE_ERR(a, "nbyte: offset required");
95
96	nb.len = needle->len;
97	nb.layer = (__u8) layer;
98	nb.off = (__u16) offset;
99
100	addraw_l(n, MAX_MSG, hdr, sizeof(*hdr));
101	addraw_l(n, MAX_MSG, &nb, sizeof(nb));
102	addraw_l(n, MAX_MSG, needle->data, needle->len);
103
104#undef PARSE_ERR
105	return 0;
106}
107
108static int nbyte_print_eopt(FILE *fd, struct tcf_ematch_hdr *hdr, void *data,
109			    int data_len)
110{
111	int i;
112	struct tcf_em_nbyte *nb = data;
113	__u8 *needle;
114
115	if (data_len < sizeof(*nb)) {
116		fprintf(stderr, "NByte header size mismatch\n");
117		return -1;
118	}
119
120	if (data_len < sizeof(*nb) + nb->len) {
121		fprintf(stderr, "NByte payload size mismatch\n");
122		return -1;
123	}
124
125	needle = data + sizeof(*nb);
126
127	for (i = 0; i < nb->len; i++)
128		fprintf(fd, "%02x ", needle[i]);
129
130	fprintf(fd, "\"");
131	for (i = 0; i < nb->len; i++)
132		fprintf(fd, "%c", isprint(needle[i]) ? needle[i] : '.');
133	fprintf(fd, "\" at %d layer %d", nb->off, nb->layer);
134
135	return 0;
136}
137
138struct ematch_util nbyte_ematch_util = {
139	.kind = "nbyte",
140	.kind_num = TCF_EM_NBYTE,
141	.parse_eopt = nbyte_parse_eopt,
142	.print_eopt = nbyte_print_eopt,
143	.print_usage = nbyte_print_usage
144};
145