Changeset 2725 in MondoRescue for branches/2.2.9/mindi-busybox/networking/dnsd.c
- Timestamp:
- Feb 25, 2011, 9:26:54 PM (13 years ago)
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branches/2.2.9/mindi-busybox/networking/dnsd.c
r1765 r2725 7 7 * Copyright (C) 2003 Paul Sheer 8 8 * 9 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.9 * Licensed under GPLv2 or later, see file LICENSE in this source tree. 10 10 * 11 11 * Odd Arild Olsen started out with the sheerdns [1] of Paul Sheer and rewrote … … 18 18 */ 19 19 20 #include "libbb.h" 20 21 #include <syslog.h> 21 #include "libbb.h"22 22 23 23 //#define DEBUG 1 … … 25 25 26 26 enum { 27 MAX_HOST_LEN = 16, // longest host name allowed is 15 28 IP_STRING_LEN = 18, // .xxx.xxx.xxx.xxx\0 29 30 //must be strlen('.in-addr.arpa') larger than IP_STRING_LEN 31 MAX_NAME_LEN = (IP_STRING_LEN + 13), 32 33 /* Cannot get bigger packets than 512 per RFC1035 34 In practice this can be set considerably smaller: 35 Length of response packet is header (12B) + 2*type(4B) + 2*class(4B) + 36 ttl(4B) + rlen(2B) + r (MAX_NAME_LEN =21B) + 37 2*querystring (2 MAX_NAME_LEN= 42B), all together 90 Byte 38 */ 39 MAX_PACK_LEN = 512 + 1, 40 41 DEFAULT_TTL = 30, // increase this when not testing? 42 27 /* can tweak this */ 28 DEFAULT_TTL = 120, 29 30 /* cannot get bigger packets than 512 per RFC1035. */ 31 MAX_PACK_LEN = 512, 32 IP_STRING_LEN = sizeof(".xxx.xxx.xxx.xxx"), 33 MAX_NAME_LEN = IP_STRING_LEN - 1 + sizeof(".in-addr.arpa"), 43 34 REQ_A = 1, 44 REQ_PTR = 12 35 REQ_PTR = 12, 45 36 }; 46 37 47 struct dns_repl { // resource record, add 0 or 1 to accepted dns_msg in resp 48 uint16_t rlen; 49 uint8_t *r; // resource 50 uint16_t flags; 51 }; 52 53 struct dns_head { // the message from client and first part of response mag 38 /* the message from client and first part of response msg */ 39 struct dns_head { 54 40 uint16_t id; 55 41 uint16_t flags; 56 uint16_t nquer; // accepts 057 uint16_t nansw; // 1 in response58 uint16_t nauth; // 059 uint16_t nadd; // 042 uint16_t nquer; 43 uint16_t nansw; 44 uint16_t nauth; 45 uint16_t nadd; 60 46 }; 61 struct dns_prop { 62 uint16_t type; 63 uint16_t class; 47 /* Structure used to access type and class fields. 48 * They are totally unaligned, but gcc 4.3.4 thinks that pointer of type uint16_t* 49 * is 16-bit aligned and replaces 16-bit memcpy (in move_from_unaligned16 macro) 50 * with aligned halfword access on arm920t! 51 * Oh well. Slapping PACKED everywhere seems to help: */ 52 struct type_and_class { 53 uint16_t type PACKED; 54 uint16_t class PACKED; 55 } PACKED; 56 /* element of known name, ip address and reversed ip address */ 57 struct dns_entry { 58 struct dns_entry *next; 59 uint32_t ip; 60 char rip[IP_STRING_LEN]; /* length decimal reversed IP */ 61 char name[1]; 64 62 }; 65 struct dns_entry { // element of known name, ip address and reversed ip address 66 struct dns_entry *next; 67 char ip[IP_STRING_LEN]; // dotted decimal IP 68 char rip[IP_STRING_LEN]; // length decimal reversed IP 69 char name[MAX_HOST_LEN]; 70 }; 71 72 static struct dns_entry *dnsentry; 73 static uint32_t ttl = DEFAULT_TTL; 74 75 static const char *fileconf = "/etc/dnsd.conf"; 76 77 // Must match getopt32 call 78 #define OPT_daemon (option_mask32 & 0x10) 79 #define OPT_verbose (option_mask32 & 0x20) 80 81 82 /* 83 * Convert host name from C-string to dns length/string. 84 */ 85 static void convname(char *a, uint8_t *q) 86 { 87 int i = (q[0] == '.') ? 0 : 1; 88 for (; i < MAX_HOST_LEN-1 && *q; i++, q++) 89 a[i] = tolower(*q); 90 a[0] = i - 1; 91 a[i] = 0; 92 } 63 64 #define OPT_verbose (option_mask32 & 1) 65 #define OPT_silent (option_mask32 & 2) 66 93 67 94 68 /* 95 69 * Insert length of substrings instead of dots 96 70 */ 97 static void undot( uint8_t *rip)71 static void undot(char *rip) 98 72 { 99 int i = 0, s = 0; 73 int i = 0; 74 int s = 0; 75 100 76 while (rip[i]) 101 77 i++; … … 104 80 rip[i] = s; 105 81 s = 0; 106 } else s++; 107 } 108 } 109 110 /* 111 * Read one line of hostname/IP from file 112 * Returns 0 for each valid entry read, -1 at EOF 113 * Assumes all host names are lower case only 114 * Hostnames with more than one label are not handled correctly. 115 * Presently the dot is copied into name without 116 * converting to a length/string substring for that label. 117 */ 118 static int getfileentry(FILE * fp, struct dns_entry *s) 119 { 120 unsigned int a,b,c,d; 121 char *line, *r, *name; 122 123 restart: 124 line = r = xmalloc_fgets(fp); 125 if (!r) 126 return -1; 127 while (*r == ' ' || *r == '\t') { 128 r++; 129 if (!*r || *r == '#' || *r == '\n') { 130 free(line); 131 goto restart; /* skipping empty/blank and commented lines */ 82 } else { 83 s++; 132 84 } 133 85 } 134 name = r;135 while (*r != ' ' && *r != '\t')136 r++;137 *r++ = '\0';138 if (sscanf(r, ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4) {139 free(line);140 goto restart; /* skipping wrong lines */141 }142 143 sprintf(s->ip, ".%u.%u.%u.%u"+1, a, b, c, d);144 sprintf(s->rip, ".%u.%u.%u.%u", d, c, b, a);145 undot((uint8_t*)s->rip);146 convname(s->name, (uint8_t*)name);147 148 if (OPT_verbose)149 fprintf(stderr, "\tname:%s, ip:%s\n", &(s->name[1]),s->ip);150 151 free(line);152 return 0;153 86 } 154 87 … … 156 89 * Read hostname/IP records from file 157 90 */ 158 static void dnsentryinit(void)91 static struct dns_entry *parse_conf_file(const char *fileconf) 159 92 { 160 FILE *fp; 161 struct dns_entry *m, *prev; 162 163 prev = dnsentry = NULL; 164 fp = xfopen(fileconf, "r"); 165 166 while (1) { 167 m = xzalloc(sizeof(*m)); 93 char *token[2]; 94 parser_t *parser; 95 struct dns_entry *m, *conf_data; 96 struct dns_entry **nextp; 97 98 conf_data = NULL; 99 nextp = &conf_data; 100 101 parser = config_open(fileconf); 102 while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) { 103 struct in_addr ip; 104 uint32_t v32; 105 106 if (inet_aton(token[1], &ip) == 0) { 107 bb_error_msg("error at line %u, skipping", parser->lineno); 108 continue; 109 } 110 111 if (OPT_verbose) 112 bb_error_msg("name:%s, ip:%s", token[0], token[1]); 113 114 /* sizeof(*m) includes 1 byte for m->name[0] */ 115 m = xzalloc(sizeof(*m) + strlen(token[0]) + 1); 168 116 /*m->next = NULL;*/ 169 if (getfileentry(fp, m)) 170 break; 171 172 if (prev == NULL) 173 dnsentry = m; 174 else 175 prev->next = m; 176 prev = m; 177 } 178 fclose(fp); 117 *nextp = m; 118 nextp = &m->next; 119 120 m->name[0] = '.'; 121 strcpy(m->name + 1, token[0]); 122 undot(m->name); 123 m->ip = ip.s_addr; /* in network order */ 124 v32 = ntohl(m->ip); 125 /* inverted order */ 126 sprintf(m->rip, ".%u.%u.%u.%u", 127 (uint8_t)(v32), 128 (uint8_t)(v32 >> 8), 129 (uint8_t)(v32 >> 16), 130 (v32 >> 24) 131 ); 132 undot(m->rip); 133 } 134 config_close(parser); 135 return conf_data; 179 136 } 180 137 181 138 /* 182 * Look query up in dns records and return answer if found 183 * qs is the query string, first byte the string length 184 */ 185 static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs) 139 * Look query up in dns records and return answer if found. 140 */ 141 static char *table_lookup(struct dns_entry *d, 142 uint16_t type, 143 char* query_string) 186 144 { 187 int i; 188 struct dns_entry *d = dnsentry; 189 190 do { 145 while (d) { 146 unsigned len = d->name[0]; 147 /* d->name[len] is the last (non NUL) char */ 191 148 #if DEBUG 192 char *p,*q; 193 q = (char *)&(qs[1]); 194 p = &(d->name[1]); 195 fprintf(stderr, "\n%s: %d/%d p:%s q:%s %d", 196 __FUNCTION__, (int)strlen(p), (int)(d->name[0]), 197 p, q, (int)strlen(q)); 149 char *p, *q; 150 q = query_string + 1; 151 p = d->name + 1; 152 fprintf(stderr, "%d/%d p:%s q:%s %d\n", 153 (int)strlen(p), len, 154 p, q, (int)strlen(q) 155 ); 198 156 #endif 199 if (type == REQ_A) { /* search by host name */ 200 for (i = 1; i <= (int)(d->name[0]); i++) 201 if (tolower(qs[i]) != d->name[i]) 202 break; 203 if (i > (int)(d->name[0])) { 204 strcpy((char *)as, d->ip); 157 if (type == htons(REQ_A)) { 158 /* search by host name */ 159 if (len != 1 || d->name[1] != '*') { 160 /* we are lax, hope no name component is ever >64 so that length 161 * (which will be represented as 'A','B'...) matches a lowercase letter. 162 * Actually, I think false matches are hard to construct. 163 * Example. 164 * [31] len is represented as '1', [65] as 'A', [65+32] as 'a'. 165 * [65] <65 same chars>[31]<31 same chars>NUL 166 * [65+32]<65 same chars>1 <31 same chars>NUL 167 * This example seems to be the minimal case when false match occurs. 168 */ 169 if (strcasecmp(d->name, query_string) != 0) 170 goto next; 171 } 172 return (char *)&d->ip; 205 173 #if DEBUG 206 fprintf(stderr, " OK as:%s\n", as);174 fprintf(stderr, "Found IP:%x\n", (int)d->ip); 207 175 #endif 208 return 0; 209 } 210 } else if (type == REQ_PTR) { /* search by IP-address */ 211 if (!strncmp((char*)&d->rip[1], (char*)&qs[1], strlen(d->rip)-1)) { 212 strcpy((char *)as, d->name); 213 return 0; 214 } 176 return 0; 215 177 } 178 /* search by IP-address */ 179 if ((len != 1 || d->name[1] != '*') 180 /* we assume (do not check) that query_string 181 * ends in ".in-addr.arpa" */ 182 && strncmp(d->rip, query_string, strlen(d->rip)) == 0 183 ) { 184 #if DEBUG 185 fprintf(stderr, "Found name:%s\n", d->name); 186 #endif 187 return d->name; 188 } 189 next: 216 190 d = d->next; 217 } while (d); 218 return -1; 191 } 192 193 return NULL; 219 194 } 220 221 195 222 196 /* 223 197 * Decode message and generate answer 224 198 */ 225 static int process_packet(uint8_t * buf) 199 /* RFC 1035 200 ... 201 Whenever an octet represents a numeric quantity, the left most bit 202 in the diagram is the high order or most significant bit. 203 That is, the bit labeled 0 is the most significant bit. 204 ... 205 206 4.1.1. Header section format 207 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 208 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 209 | ID | 210 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 211 |QR| OPCODE |AA|TC|RD|RA| 0 0 0| RCODE | 212 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 213 | QDCOUNT | 214 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 215 | ANCOUNT | 216 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 217 | NSCOUNT | 218 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 219 | ARCOUNT | 220 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 221 ID 16 bit random identifier assigned by querying peer. 222 Used to match query/response. 223 QR message is a query (0), or a response (1). 224 OPCODE 0 standard query (QUERY) 225 1 inverse query (IQUERY) 226 2 server status request (STATUS) 227 AA Authoritative Answer - this bit is valid in responses. 228 Responding name server is an authority for the domain name 229 in question section. Answer section may have multiple owner names 230 because of aliases. The AA bit corresponds to the name which matches 231 the query name, or the first owner name in the answer section. 232 TC TrunCation - this message was truncated. 233 RD Recursion Desired - this bit may be set in a query and 234 is copied into the response. If RD is set, it directs 235 the name server to pursue the query recursively. 236 Recursive query support is optional. 237 RA Recursion Available - this be is set or cleared in a 238 response, and denotes whether recursive query support is 239 available in the name server. 240 RCODE Response code. 241 0 No error condition 242 1 Format error 243 2 Server failure - server was unable to process the query 244 due to a problem with the name server. 245 3 Name Error - meaningful only for responses from 246 an authoritative name server. The referenced domain name 247 does not exist. 248 4 Not Implemented. 249 5 Refused. 250 QDCOUNT number of entries in the question section. 251 ANCOUNT number of records in the answer section. 252 NSCOUNT number of records in the authority records section. 253 ARCOUNT number of records in the additional records section. 254 255 4.1.2. Question section format 256 257 The section contains QDCOUNT (usually 1) entries, each of this format: 258 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 259 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 260 / QNAME / 261 / / 262 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 263 | QTYPE | 264 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 265 | QCLASS | 266 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 267 QNAME a domain name represented as a sequence of labels, where 268 each label consists of a length octet followed by that 269 number of octets. The domain name terminates with the 270 zero length octet for the null label of the root. Note 271 that this field may be an odd number of octets; no 272 padding is used. 273 QTYPE a two octet type of the query. 274 1 a host address [REQ_A const] 275 2 an authoritative name server 276 3 a mail destination (Obsolete - use MX) 277 4 a mail forwarder (Obsolete - use MX) 278 5 the canonical name for an alias 279 6 marks the start of a zone of authority 280 7 a mailbox domain name (EXPERIMENTAL) 281 8 a mail group member (EXPERIMENTAL) 282 9 a mail rename domain name (EXPERIMENTAL) 283 10 a null RR (EXPERIMENTAL) 284 11 a well known service description 285 12 a domain name pointer [REQ_PTR const] 286 13 host information 287 14 mailbox or mail list information 288 15 mail exchange 289 16 text strings 290 0x1c IPv6? 291 252 a request for a transfer of an entire zone 292 253 a request for mailbox-related records (MB, MG or MR) 293 254 a request for mail agent RRs (Obsolete - see MX) 294 255 a request for all records 295 QCLASS a two octet code that specifies the class of the query. 296 1 the Internet 297 (others are historic only) 298 255 any class 299 300 4.1.3. Resource Record format 301 302 The answer, authority, and additional sections all share the same format: 303 a variable number of resource records, where the number of records 304 is specified in the corresponding count field in the header. 305 Each resource record has this format: 306 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 307 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 308 / / 309 / NAME / 310 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 311 | TYPE | 312 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 313 | CLASS | 314 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 315 | TTL | 316 | | 317 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 318 | RDLENGTH | 319 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--| 320 / RDATA / 321 / / 322 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 323 NAME a domain name to which this resource record pertains. 324 TYPE two octets containing one of the RR type codes. This 325 field specifies the meaning of the data in the RDATA field. 326 CLASS two octets which specify the class of the data in the RDATA field. 327 TTL a 32 bit unsigned integer that specifies the time interval 328 (in seconds) that the record may be cached. 329 RDLENGTH a 16 bit integer, length in octets of the RDATA field. 330 RDATA a variable length string of octets that describes the resource. 331 The format of this information varies according to the TYPE 332 and CLASS of the resource record. 333 If the TYPE is A and the CLASS is IN, it's a 4 octet IP address. 334 335 4.1.4. Message compression 336 337 In order to reduce the size of messages, domain names coan be compressed. 338 An entire domain name or a list of labels at the end of a domain name 339 is replaced with a pointer to a prior occurance of the same name. 340 341 The pointer takes the form of a two octet sequence: 342 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 343 | 1 1| OFFSET | 344 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 345 The first two bits are ones. This allows a pointer to be distinguished 346 from a label, since the label must begin with two zero bits because 347 labels are restricted to 63 octets or less. The OFFSET field specifies 348 an offset from the start of the message (i.e., the first octet 349 of the ID field in the domain header). 350 A zero offset specifies the first byte of the ID field, etc. 351 Domain name in a message can be represented as either: 352 - a sequence of labels ending in a zero octet 353 - a pointer 354 - a sequence of labels ending with a pointer 355 */ 356 static int process_packet(struct dns_entry *conf_data, 357 uint32_t conf_ttl, 358 uint8_t *buf) 226 359 { 227 360 struct dns_head *head; 228 struct dns_prop *qprop; 229 struct dns_repl outr; 230 void *next, *from, *answb; 231 232 uint8_t answstr[MAX_NAME_LEN + 1]; 233 int lookup_result, type, len, packet_len; 234 uint16_t flags; 235 236 answstr[0] = '\0'; 361 struct type_and_class *unaligned_type_class; 362 const char *err_msg; 363 char *query_string; 364 char *answstr; 365 uint8_t *answb; 366 uint16_t outr_rlen; 367 uint16_t outr_flags; 368 uint16_t type; 369 uint16_t class; 370 int query_len; 237 371 238 372 head = (struct dns_head *)buf; 239 373 if (head->nquer == 0) { 240 bb_error_msg("no queries"); 241 return -1; 242 } 243 244 if (head->flags & 0x8000) { 245 bb_error_msg("ignoring response packet"); 246 return -1; 247 } 248 249 from = (void *)&head[1]; // start of query string 250 next = answb = from + strlen((char *)from) + 1 + sizeof(struct dns_prop); // where to append answer block 251 252 outr.rlen = 0; // may change later 253 outr.r = NULL; 254 outr.flags = 0; 255 256 qprop = (struct dns_prop *)(answb - 4); 257 type = ntohs(qprop->type); 258 259 // only let REQ_A and REQ_PTR pass 260 if (!(type == REQ_A || type == REQ_PTR)) { 261 goto empty_packet; /* we can't handle the query type */ 262 } 263 264 if (ntohs(qprop->class) != 1 /* class INET */ ) { 265 outr.flags = 4; /* not supported */ 374 bb_error_msg("packet has 0 queries, ignored"); 375 return 0; /* don't reply */ 376 } 377 if (head->flags & htons(0x8000)) { /* QR bit */ 378 bb_error_msg("response packet, ignored"); 379 return 0; /* don't reply */ 380 } 381 /* QR = 1 "response", RCODE = 4 "Not Implemented" */ 382 outr_flags = htons(0x8000 | 4); 383 err_msg = NULL; 384 385 /* start of query string */ 386 query_string = (void *)(head + 1); 387 /* caller guarantees strlen is <= MAX_PACK_LEN */ 388 query_len = strlen(query_string) + 1; 389 /* may be unaligned! */ 390 unaligned_type_class = (void *)(query_string + query_len); 391 query_len += sizeof(*unaligned_type_class); 392 /* where to append answer block */ 393 answb = (void *)(unaligned_type_class + 1); 394 395 /* OPCODE != 0 "standard query"? */ 396 if ((head->flags & htons(0x7800)) != 0) { 397 err_msg = "opcode != 0"; 266 398 goto empty_packet; 267 399 } 268 /* we only support standard queries */269 270 if ((ntohs(head->flags) & 0x7800) != 0)400 move_from_unaligned16(class, &unaligned_type_class->class); 401 if (class != htons(1)) { /* not class INET? */ 402 err_msg = "class != 1"; 271 403 goto empty_packet; 272 273 // We have a standard query274 bb_info_msg("%s", (char *)from);275 lookup_result = table_lookup(type, answstr, (uint8_t*)from);276 if (lookup_result != 0) { 277 outr.flags = 3 | 0x0400; //name do not exist and auth404 } 405 move_from_unaligned16(type, &unaligned_type_class->type); 406 if (type != htons(REQ_A) && type != htons(REQ_PTR)) { 407 /* we can't handle this query type */ 408 //TODO: happens all the time with REQ_AAAA (0x1c) requests - implement those? 409 err_msg = "type is !REQ_A and !REQ_PTR"; 278 410 goto empty_packet; 279 411 } 280 if (type == REQ_A) { // return an address 281 struct in_addr a; 282 if (!inet_aton((char*)answstr, &a)) {//dotted dec to long conv 283 outr.flags = 1; /* Frmt err */ 284 goto empty_packet; 412 413 /* look up the name */ 414 answstr = table_lookup(conf_data, type, query_string); 415 #if DEBUG 416 /* Shows lengths instead of dots, unusable for !DEBUG */ 417 bb_error_msg("'%s'->'%s'", query_string, answstr); 418 #endif 419 outr_rlen = 4; 420 if (answstr && type == htons(REQ_PTR)) { 421 /* returning a host name */ 422 outr_rlen = strlen(answstr) + 1; 423 } 424 if (!answstr 425 || (unsigned)(answb - buf) + query_len + 4 + 2 + outr_rlen > MAX_PACK_LEN 426 ) { 427 /* QR = 1 "response" 428 * AA = 1 "Authoritative Answer" 429 * RCODE = 3 "Name Error" */ 430 err_msg = "name is not found"; 431 outr_flags = htons(0x8000 | 0x0400 | 3); 432 goto empty_packet; 433 } 434 435 /* Append answer Resource Record */ 436 memcpy(answb, query_string, query_len); /* name, type, class */ 437 answb += query_len; 438 move_to_unaligned32((uint32_t *)answb, htonl(conf_ttl)); 439 answb += 4; 440 move_to_unaligned16((uint16_t *)answb, htons(outr_rlen)); 441 answb += 2; 442 memcpy(answb, answstr, outr_rlen); 443 answb += outr_rlen; 444 445 /* QR = 1 "response", 446 * AA = 1 "Authoritative Answer", 447 * TODO: need to set RA bit 0x80? One user says nslookup complains 448 * "Got recursion not available from SERVER, trying next server" 449 * "** server can't find HOSTNAME" 450 * RCODE = 0 "success" 451 */ 452 if (OPT_verbose) 453 bb_error_msg("returning positive reply"); 454 outr_flags = htons(0x8000 | 0x0400 | 0); 455 /* we have one answer */ 456 head->nansw = htons(1); 457 458 empty_packet: 459 if ((outr_flags & htons(0xf)) != 0) { /* not a positive response */ 460 if (OPT_verbose) { 461 bb_error_msg("%s, %s", 462 err_msg, 463 OPT_silent ? "dropping query" : "sending error reply" 464 ); 285 465 } 286 memcpy(answstr, &a.s_addr, 4); // save before a disappears 287 outr.rlen = 4; // uint32_t IP 288 } else 289 outr.rlen = strlen((char *)answstr) + 1; // a host name 290 outr.r = answstr; // 32 bit ip or a host name 291 outr.flags |= 0x0400; /* authority-bit */ 292 // we have an answer 293 head->nansw = htons(1); 294 295 // copy query block to answer block 296 len = answb - from; 297 memcpy(answb, from, len); 298 next += len; 299 300 // and append answer rr 301 *(uint32_t *) next = htonl(ttl); 302 next += 4; 303 *(uint16_t *) next = htons(outr.rlen); 304 next += 2; 305 memcpy(next, (void *)answstr, outr.rlen); 306 next += outr.rlen; 307 308 empty_packet: 309 310 flags = ntohs(head->flags); 311 // clear rcode and RA, set responsebit and our new flags 312 flags |= (outr.flags & 0xff80) | 0x8000; 313 head->flags = htons(flags); 314 head->nauth = head->nadd = htons(0); 315 head->nquer = htons(1); 316 317 packet_len = (uint8_t *)next - buf; 318 return packet_len; 466 if (OPT_silent) 467 return 0; 468 } 469 head->flags |= outr_flags; 470 head->nauth = head->nadd = 0; 471 head->nquer = htons(1); // why??? 472 473 return answb - buf; 319 474 } 320 475 321 /* 322 * Exit on signal 323 */ 324 static void interrupt(int x) 325 { 326 /* unlink("/var/run/dnsd.lock"); */ 327 bb_error_msg("interrupt, exiting\n"); 328 exit(2); 329 } 330 331 int dnsd_main(int argc, char **argv); 332 int dnsd_main(int argc, char **argv) 476 int dnsd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 477 int dnsd_main(int argc UNUSED_PARAM, char **argv) 333 478 { 334 479 const char *listen_interface = "0.0.0.0"; 480 const char *fileconf = "/etc/dnsd.conf"; 481 struct dns_entry *conf_data; 482 uint32_t conf_ttl = DEFAULT_TTL; 335 483 char *sttl, *sport; 336 len_and_sockaddr *lsa; 337 int udps; 484 len_and_sockaddr *lsa, *from, *to; 485 unsigned lsa_size; 486 int udps, opts; 338 487 uint16_t port = 53; 339 uint8_t buf[MAX_PACK_LEN]; 340 341 getopt32(argv, "i:c:t:p:dv", &listen_interface, &fileconf, &sttl, &sport); 342 //if (option_mask32 & 0x1) // -i 343 //if (option_mask32 & 0x2) // -c 344 if (option_mask32 & 0x4) // -t 345 ttl = xatou_range(sttl, 1, 0xffffffff); 346 if (option_mask32 & 0x8) // -p 488 /* Ensure buf is 32bit aligned (we need 16bit, but 32bit can't hurt) */ 489 uint8_t buf[MAX_PACK_LEN + 1] ALIGN4; 490 491 opts = getopt32(argv, "vsi:c:t:p:d", &listen_interface, &fileconf, &sttl, &sport); 492 //if (opts & (1 << 0)) // -v 493 //if (opts & (1 << 1)) // -s 494 //if (opts & (1 << 2)) // -i 495 //if (opts & (1 << 3)) // -c 496 if (opts & (1 << 4)) // -t 497 conf_ttl = xatou_range(sttl, 1, 0xffffffff); 498 if (opts & (1 << 5)) // -p 347 499 port = xatou_range(sport, 1, 0xffff); 348 349 if (OPT_verbose) { 350 bb_info_msg("listen_interface: %s", listen_interface); 351 bb_info_msg("ttl: %d, port: %d", ttl, port); 352 bb_info_msg("fileconf: %s", fileconf); 353 } 354 355 if (OPT_daemon) { 500 if (opts & (1 << 6)) { // -d 356 501 bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv); 357 502 openlog(applet_name, LOG_PID, LOG_DAEMON); … … 359 504 } 360 505 361 dnsentryinit(); 362 363 signal(SIGINT, interrupt); 364 /* why? signal(SIGPIPE, SIG_IGN); */ 365 signal(SIGHUP, SIG_IGN); 366 #ifdef SIGTSTP 367 signal(SIGTSTP, SIG_IGN); 368 #endif 369 #ifdef SIGURG 370 signal(SIGURG, SIG_IGN); 371 #endif 506 conf_data = parse_conf_file(fileconf); 372 507 373 508 lsa = xdotted2sockaddr(listen_interface, port); 374 udps = xsocket(lsa->sa.sa_family, SOCK_DGRAM, 0); 375 xbind(udps, &lsa->sa, lsa->len); 376 /* xlisten(udps, 50); - ?!! DGRAM sockets are never listened on I think? */ 377 bb_info_msg("Accepting UDP packets on %s", 378 xmalloc_sockaddr2dotted(&lsa->sa)); 509 udps = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0); 510 xbind(udps, &lsa->u.sa, lsa->len); 511 socket_want_pktinfo(udps); /* needed for recv_from_to to work */ 512 lsa_size = LSA_LEN_SIZE + lsa->len; 513 from = xzalloc(lsa_size); 514 to = xzalloc(lsa_size); 515 516 { 517 char *p = xmalloc_sockaddr2dotted(&lsa->u.sa); 518 bb_error_msg("accepting UDP packets on %s", p); 519 free(p); 520 } 379 521 380 522 while (1) { 381 523 int r; 382 socklen_t fromlen = lsa->len; 383 // FIXME: need to get *DEST* address (to which of our addresses 384 // this query was directed), and reply from the same address. 385 // Or else we can exhibit usual UDP ugliness: 386 // [ip1.multihomed.ip2] <= query to ip1 <= peer 387 // [ip1.multihomed.ip2] => reply from ip2 => peer (confused) 388 r = recvfrom(udps, buf, sizeof(buf), 0, &lsa->sa, &fromlen); 389 if (OPT_verbose) 390 bb_info_msg("Got UDP packet"); 391 if (r < 12 || r > 512) { 392 bb_error_msg("invalid packet size"); 524 /* Try to get *DEST* address (to which of our addresses 525 * this query was directed), and reply from the same address. 526 * Or else we can exhibit usual UDP ugliness: 527 * [ip1.multihomed.ip2] <= query to ip1 <= peer 528 * [ip1.multihomed.ip2] => reply from ip2 => peer (confused) */ 529 memcpy(to, lsa, lsa_size); 530 r = recv_from_to(udps, buf, MAX_PACK_LEN + 1, 0, &from->u.sa, &to->u.sa, lsa->len); 531 if (r < 12 || r > MAX_PACK_LEN) { 532 bb_error_msg("packet size %d, ignored", r); 393 533 continue; 394 534 } 395 r = process_packet(buf); 535 if (OPT_verbose) 536 bb_error_msg("got UDP packet"); 537 buf[r] = '\0'; /* paranoia */ 538 r = process_packet(conf_data, conf_ttl, buf); 396 539 if (r <= 0) 397 540 continue; 398 send to(udps, buf, r, 0, &lsa->sa, fromlen);541 send_to_from(udps, buf, r, 0, &from->u.sa, &to->u.sa, lsa->len); 399 542 } 400 543 return 0;
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