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 (at) 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 26 extern struct ematch_util nbyte_ematch_util; 27 28 static 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 40 static 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 #define PARSE_ERR(CARG, FMT, ARGS...) \ 50 em_parse_error(EINVAL, args, CARG, &nbyte_ematch_util, FMT, ##ARGS) 51 52 if (args == NULL) 53 return PARSE_ERR(args, "nbyte: missing arguments"); 54 55 if (needle->len <= 0) 56 return PARSE_ERR(args, "nbyte: needle length is 0"); 57 58 for (a = bstr_next(args); a; a = bstr_next(a)) { 59 if (!bstrcmp(a, "at")) { 60 if (a->next == NULL) 61 return PARSE_ERR(a, "nbyte: missing argument"); 62 a = bstr_next(a); 63 64 offset = bstrtoul(a); 65 if (offset == ULONG_MAX) 66 return PARSE_ERR(a, "nbyte: invalid offset, " \ 67 "must be numeric"); 68 69 offset_present = 1; 70 } else if (!bstrcmp(a, "layer")) { 71 if (a->next == NULL) 72 return PARSE_ERR(a, "nbyte: missing argument"); 73 a = bstr_next(a); 74 75 layer = parse_layer(a); 76 if (layer == INT_MAX) { 77 layer = bstrtoul(a); 78 if (layer == ULONG_MAX) 79 return PARSE_ERR(a, "nbyte: invalid " \ 80 "layer"); 81 } 82 83 if (layer > TCF_LAYER_MAX) 84 return PARSE_ERR(a, "nbyte: illegal layer, " \ 85 "must be in 0..%d", TCF_LAYER_MAX); 86 } else 87 return PARSE_ERR(a, "nbyte: unknown parameter"); 88 } 89 90 if (offset_present == 0) 91 return PARSE_ERR(a, "nbyte: offset required"); 92 93 nb.len = needle->len; 94 nb.layer = (__u8) layer; 95 nb.off = (__u16) offset; 96 97 addraw_l(n, MAX_MSG, hdr, sizeof(*hdr)); 98 addraw_l(n, MAX_MSG, &nb, sizeof(nb)); 99 addraw_l(n, MAX_MSG, needle->data, needle->len); 100 101 #undef PARSE_ERR 102 return 0; 103 } 104 105 static int nbyte_print_eopt(FILE *fd, struct tcf_ematch_hdr *hdr, void *data, 106 int data_len) 107 { 108 int i; 109 struct tcf_em_nbyte *nb = data; 110 __u8 *needle; 111 112 if (data_len < sizeof(*nb)) { 113 fprintf(stderr, "NByte header size mismatch\n"); 114 return -1; 115 } 116 117 if (data_len < sizeof(*nb) + nb->len) { 118 fprintf(stderr, "NByte payload size mismatch\n"); 119 return -1; 120 } 121 122 needle = data + sizeof(*nb); 123 124 for (i = 0; i < nb->len; i++) 125 fprintf(fd, "%02x ", needle[i]); 126 127 fprintf(fd, "\""); 128 for (i = 0; i < nb->len; i++) 129 fprintf(fd, "%c", isprint(needle[i]) ? needle[i] : '.'); 130 fprintf(fd, "\" at %d layer %d", nb->off, nb->layer); 131 132 return 0; 133 } 134 135 struct ematch_util nbyte_ematch_util = { 136 .kind = "nbyte", 137 .kind_num = TCF_EM_NBYTE, 138 .parse_eopt = nbyte_parse_eopt, 139 .print_eopt = nbyte_print_eopt, 140 .print_usage = nbyte_print_usage 141 }; 142
