569 lines
		
	
	
		
			18 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			569 lines
		
	
	
		
			18 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
| /* vi: set sw=4 ts=4: */
 | |
| /*
 | |
|  * Mini DNS server implementation for busybox
 | |
|  *
 | |
|  * Copyright (C) 2005 Roberto A. Foglietta (me@roberto.foglietta.name)
 | |
|  * Copyright (C) 2005 Odd Arild Olsen (oao at fibula dot no)
 | |
|  * Copyright (C) 2003 Paul Sheer
 | |
|  *
 | |
|  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 | |
|  *
 | |
|  * Odd Arild Olsen started out with the sheerdns [1] of Paul Sheer and rewrote
 | |
|  * it into a shape which I believe is both easier to understand and maintain.
 | |
|  * I also reused the input buffer for output and removed services he did not
 | |
|  * need.  [1] http://threading.2038bug.com/sheerdns/
 | |
|  *
 | |
|  * Some bugfix and minor changes was applied by Roberto A. Foglietta who made
 | |
|  * the first porting of oao' scdns to busybox also.
 | |
|  */
 | |
| //config:config DNSD
 | |
| //config:	bool "dnsd (9.8 kb)"
 | |
| //config:	default y
 | |
| //config:	help
 | |
| //config:	Small and static DNS server daemon.
 | |
| 
 | |
| //applet:IF_DNSD(APPLET(dnsd, BB_DIR_USR_SBIN, BB_SUID_DROP))
 | |
| 
 | |
| //kbuild:lib-$(CONFIG_DNSD) += dnsd.o
 | |
| 
 | |
| //usage:#define dnsd_trivial_usage
 | |
| //usage:       "[-dvs] [-c CONFFILE] [-t TTL_SEC] [-p PORT] [-i ADDR]"
 | |
| //usage:#define dnsd_full_usage "\n\n"
 | |
| //usage:       "Small static DNS server daemon\n"
 | |
| //usage:     "\n	-c FILE	Config file"
 | |
| //usage:     "\n	-t SEC	TTL"
 | |
| //usage:     "\n	-p PORT	Listen on PORT"
 | |
| //usage:     "\n	-i ADDR	Listen on ADDR"
 | |
| //usage:     "\n	-d	Daemonize"
 | |
| //usage:     "\n	-v	Verbose"
 | |
| //usage:     "\n	-s	Send successful replies only. Use this if you want"
 | |
| //usage:     "\n		to use /etc/resolv.conf with two nameserver lines:"
 | |
| //usage:     "\n			nameserver DNSD_SERVER"
 | |
| //usage:     "\n			nameserver NORMAL_DNS_SERVER"
 | |
| 
 | |
| #include "libbb.h"
 | |
| #include <syslog.h>
 | |
| 
 | |
| //#define DEBUG 1
 | |
| #define DEBUG 0
 | |
| 
 | |
| enum {
 | |
| 	/* can tweak this */
 | |
| 	DEFAULT_TTL = 120,
 | |
| 
 | |
| 	/* cannot get bigger packets than 512 per RFC1035. */
 | |
| 	MAX_PACK_LEN = 512,
 | |
| 	IP_STRING_LEN = sizeof(".xxx.xxx.xxx.xxx"),
 | |
| 	MAX_NAME_LEN = IP_STRING_LEN - 1 + sizeof(".in-addr.arpa"),
 | |
| 	REQ_A = 1,
 | |
| 	REQ_PTR = 12,
 | |
| };
 | |
| 
 | |
| /* the message from client and first part of response msg */
 | |
| struct dns_head {
 | |
| 	uint16_t id;
 | |
| 	uint16_t flags;
 | |
| 	uint16_t nquer;
 | |
| 	uint16_t nansw;
 | |
| 	uint16_t nauth;
 | |
| 	uint16_t nadd;
 | |
| };
 | |
| /* Structure used to access type and class fields.
 | |
|  * They are totally unaligned, but gcc 4.3.4 thinks that pointer of type uint16_t*
 | |
|  * is 16-bit aligned and replaces 16-bit memcpy (in move_from_unaligned16 macro)
 | |
|  * with aligned halfword access on arm920t!
 | |
|  * Oh well. Slapping PACKED everywhere seems to help: */
 | |
| struct type_and_class {
 | |
| 	uint16_t type PACKED;
 | |
| 	uint16_t class PACKED;
 | |
| } PACKED;
 | |
| /* element of known name, ip address and reversed ip address */
 | |
| struct dns_entry {
 | |
| 	struct dns_entry *next;
 | |
| 	uint32_t ip;
 | |
| 	char rip[IP_STRING_LEN]; /* length decimal reversed IP */
 | |
| 	char name[1];
 | |
| };
 | |
| 
 | |
| #define OPT_verbose (option_mask32 & 1)
 | |
| #define OPT_silent  (option_mask32 & 2)
 | |
| 
 | |
| 
 | |
| /*
 | |
|  * Insert length of substrings instead of dots
 | |
|  */
 | |
| static void undot(char *rip)
 | |
| {
 | |
| 	int i = 0;
 | |
| 	int s = 0;
 | |
| 
 | |
| 	while (rip[i])
 | |
| 		i++;
 | |
| 	for (--i; i >= 0; i--) {
 | |
| 		if (rip[i] == '.') {
 | |
| 			rip[i] = s;
 | |
| 			s = 0;
 | |
| 		} else {
 | |
| 			s++;
 | |
| 		}
 | |
| 	}
 | |
| }
 | |
| 
 | |
| /*
 | |
|  * Read hostname/IP records from file
 | |
|  */
 | |
| static struct dns_entry *parse_conf_file(const char *fileconf)
 | |
| {
 | |
| 	char *token[2];
 | |
| 	parser_t *parser;
 | |
| 	struct dns_entry *m, *conf_data;
 | |
| 	struct dns_entry **nextp;
 | |
| 
 | |
| 	conf_data = NULL;
 | |
| 	nextp = &conf_data;
 | |
| 
 | |
| 	parser = config_open(fileconf);
 | |
| 	while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
 | |
| 		struct in_addr ip;
 | |
| 		uint32_t v32;
 | |
| 
 | |
| 		if (inet_aton(token[1], &ip) == 0) {
 | |
| 			bb_error_msg("error at line %u, skipping", parser->lineno);
 | |
| 			continue;
 | |
| 		}
 | |
| 
 | |
| 		if (OPT_verbose)
 | |
| 			bb_info_msg("name:%s, ip:%s", token[0], token[1]);
 | |
| 
 | |
| 		/* sizeof(*m) includes 1 byte for m->name[0] */
 | |
| 		m = xzalloc(sizeof(*m) + strlen(token[0]) + 1);
 | |
| 		/*m->next = NULL;*/
 | |
| 		*nextp = m;
 | |
| 		nextp = &m->next;
 | |
| 
 | |
| 		m->name[0] = '.';
 | |
| 		strcpy(m->name + 1, token[0]);
 | |
| 		undot(m->name);
 | |
| 		m->ip = ip.s_addr; /* in network order */
 | |
| 		v32 = ntohl(m->ip);
 | |
| 		/* inverted order */
 | |
| 		sprintf(m->rip, ".%u.%u.%u.%u",
 | |
| 			(uint8_t)(v32),
 | |
| 			(uint8_t)(v32 >> 8),
 | |
| 			(uint8_t)(v32 >> 16),
 | |
| 			(v32 >> 24)
 | |
| 		);
 | |
| 		undot(m->rip);
 | |
| 	}
 | |
| 	config_close(parser);
 | |
| 	return conf_data;
 | |
| }
 | |
| 
 | |
| /*
 | |
|  * Look query up in dns records and return answer if found.
 | |
|  */
 | |
| static char *table_lookup(struct dns_entry *d,
 | |
| 		uint16_t type,
 | |
| 		char* query_string)
 | |
| {
 | |
| 	while (d) {
 | |
| 		unsigned len = d->name[0];
 | |
| 		/* d->name[len] is the last (non NUL) char */
 | |
| #if DEBUG
 | |
| 		char *p, *q;
 | |
| 		q = query_string + 1;
 | |
| 		p = d->name + 1;
 | |
| 		fprintf(stderr, "%d/%d p:%s q:%s %d\n",
 | |
| 			(int)strlen(p), len,
 | |
| 			p, q, (int)strlen(q)
 | |
| 		);
 | |
| #endif
 | |
| 		if (type == htons(REQ_A)) {
 | |
| 			/* search by host name */
 | |
| 			if (len != 1 || d->name[1] != '*') {
 | |
| /* we are lax, hope no name component is ever >64 so that length
 | |
|  * (which will be represented as 'A','B'...) matches a lowercase letter.
 | |
|  * Actually, I think false matches are hard to construct.
 | |
|  * Example.
 | |
|  * [31] len is represented as '1', [65] as 'A', [65+32] as 'a'.
 | |
|  * [65]   <65 same chars>[31]<31 same chars>NUL
 | |
|  * [65+32]<65 same chars>1   <31 same chars>NUL
 | |
|  * This example seems to be the minimal case when false match occurs.
 | |
|  */
 | |
| 				if (strcasecmp(d->name, query_string) != 0)
 | |
| 					goto next;
 | |
| 			}
 | |
| 			return (char *)&d->ip;
 | |
| #if DEBUG
 | |
| 			fprintf(stderr, "Found IP:%x\n", (int)d->ip);
 | |
| #endif
 | |
| 			return 0;
 | |
| 		}
 | |
| 		/* search by IP-address */
 | |
| 		if ((len != 1 || d->name[1] != '*')
 | |
| 		/* we assume (do not check) that query_string
 | |
| 		 * ends in ".in-addr.arpa" */
 | |
| 		 && is_prefixed_with(query_string, d->rip)
 | |
| 		) {
 | |
| #if DEBUG
 | |
| 			fprintf(stderr, "Found name:%s\n", d->name);
 | |
| #endif
 | |
| 			return d->name;
 | |
| 		}
 | |
|  next:
 | |
| 		d = d->next;
 | |
| 	}
 | |
| 
 | |
| 	return NULL;
 | |
| }
 | |
| 
 | |
| /*
 | |
|  * Decode message and generate answer
 | |
|  */
 | |
| /* RFC 1035
 | |
| ...
 | |
| Whenever an octet represents a numeric quantity, the left most bit
 | |
| in the diagram is the high order or most significant bit.
 | |
| That is, the bit labeled 0 is the most significant bit.
 | |
| ...
 | |
| 
 | |
| 4.1.1. Header section format
 | |
|       0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                      ID                       |
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|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |QR|   OPCODE  |AA|TC|RD|RA| 0  0  0|   RCODE   |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                    QDCOUNT                    |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                    ANCOUNT                    |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                    NSCOUNT                    |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                    ARCOUNT                    |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
| ID      16 bit random identifier assigned by querying peer.
 | |
|         Used to match query/response.
 | |
| QR      message is a query (0), or a response (1).
 | |
| OPCODE  0   standard query (QUERY)
 | |
|         1   inverse query (IQUERY)
 | |
|         2   server status request (STATUS)
 | |
| AA      Authoritative Answer - this bit is valid in responses.
 | |
|         Responding name server is an authority for the domain name
 | |
|         in question section. Answer section may have multiple owner names
 | |
|         because of aliases.  The AA bit corresponds to the name which matches
 | |
|         the query name, or the first owner name in the answer section.
 | |
| TC      TrunCation - this message was truncated.
 | |
| RD      Recursion Desired - this bit may be set in a query and
 | |
|         is copied into the response.  If RD is set, it directs
 | |
|         the name server to pursue the query recursively.
 | |
|         Recursive query support is optional.
 | |
| RA      Recursion Available - this be is set or cleared in a
 | |
|         response, and denotes whether recursive query support is
 | |
|         available in the name server.
 | |
| RCODE   Response code.
 | |
|         0   No error condition
 | |
|         1   Format error
 | |
|         2   Server failure - server was unable to process the query
 | |
|             due to a problem with the name server.
 | |
|         3   Name Error - meaningful only for responses from
 | |
|             an authoritative name server. The referenced domain name
 | |
|             does not exist.
 | |
|         4   Not Implemented.
 | |
|         5   Refused.
 | |
| QDCOUNT number of entries in the question section.
 | |
| ANCOUNT number of records in the answer section.
 | |
| NSCOUNT number of records in the authority records section.
 | |
| ARCOUNT number of records in the additional records section.
 | |
| 
 | |
| 4.1.2. Question section format
 | |
| 
 | |
| The section contains QDCOUNT (usually 1) entries, each of this format:
 | |
|       0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     /                     QNAME                     /
 | |
|     /                                               /
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                     QTYPE                     |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                     QCLASS                    |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
| QNAME   a domain name represented as a sequence of labels, where
 | |
|         each label consists of a length octet followed by that
 | |
|         number of octets. The domain name terminates with the
 | |
|         zero length octet for the null label of the root. Note
 | |
|         that this field may be an odd number of octets; no
 | |
|         padding is used.
 | |
| QTYPE   a two octet type of the query.
 | |
|           1 a host address [REQ_A const]
 | |
|           2 an authoritative name server
 | |
|           3 a mail destination (Obsolete - use MX)
 | |
|           4 a mail forwarder (Obsolete - use MX)
 | |
|           5 the canonical name for an alias
 | |
|           6 marks the start of a zone of authority
 | |
|           7 a mailbox domain name (EXPERIMENTAL)
 | |
|           8 a mail group member (EXPERIMENTAL)
 | |
|           9 a mail rename domain name (EXPERIMENTAL)
 | |
|          10 a null RR (EXPERIMENTAL)
 | |
|          11 a well known service description
 | |
|          12 a domain name pointer [REQ_PTR const]
 | |
|          13 host information
 | |
|          14 mailbox or mail list information
 | |
|          15 mail exchange
 | |
|          16 text strings
 | |
|        0x1c IPv6?
 | |
|         252 a request for a transfer of an entire zone
 | |
|         253 a request for mailbox-related records (MB, MG or MR)
 | |
|         254 a request for mail agent RRs (Obsolete - see MX)
 | |
|         255 a request for all records
 | |
| QCLASS  a two octet code that specifies the class of the query.
 | |
|           1 the Internet
 | |
|         (others are historic only)
 | |
|         255 any class
 | |
| 
 | |
| 4.1.3. Resource Record format
 | |
| 
 | |
| The answer, authority, and additional sections all share the same format:
 | |
| a variable number of resource records, where the number of records
 | |
| is specified in the corresponding count field in the header.
 | |
| Each resource record has this format:
 | |
|       0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     /                                               /
 | |
|     /                      NAME                     /
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                      TYPE                     |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                     CLASS                     |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                      TTL                      |
 | |
|     |                                               |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     |                   RDLENGTH                    |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
 | |
|     /                     RDATA                     /
 | |
|     /                                               /
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
| NAME    a domain name to which this resource record pertains.
 | |
| TYPE    two octets containing one of the RR type codes.  This
 | |
|         field specifies the meaning of the data in the RDATA field.
 | |
| CLASS   two octets which specify the class of the data in the RDATA field.
 | |
| TTL     a 32 bit unsigned integer that specifies the time interval
 | |
|         (in seconds) that the record may be cached.
 | |
| RDLENGTH a 16 bit integer, length in octets of the RDATA field.
 | |
| RDATA   a variable length string of octets that describes the resource.
 | |
|         The format of this information varies according to the TYPE
 | |
|         and CLASS of the resource record.
 | |
|         If the TYPE is A and the CLASS is IN, it's a 4 octet IP address.
 | |
| 
 | |
| 4.1.4. Message compression
 | |
| 
 | |
| In order to reduce the size of messages, domain names coan be compressed.
 | |
| An entire domain name or a list of labels at the end of a domain name
 | |
| is replaced with a pointer to a prior occurrence of the same name.
 | |
| 
 | |
| The pointer takes the form of a two octet sequence:
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
|     | 1  1|                OFFSET                   |
 | |
|     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 | |
| The first two bits are ones.  This allows a pointer to be distinguished
 | |
| from a label, since the label must begin with two zero bits because
 | |
| labels are restricted to 63 octets or less.  The OFFSET field specifies
 | |
| an offset from the start of the message (i.e., the first octet
 | |
| of the ID field in the domain header).
 | |
| A zero offset specifies the first byte of the ID field, etc.
 | |
| Domain name in a message can be represented as either:
 | |
|    - a sequence of labels ending in a zero octet
 | |
|    - a pointer
 | |
|    - a sequence of labels ending with a pointer
 | |
|  */
 | |
| static int process_packet(struct dns_entry *conf_data,
 | |
| 		uint32_t conf_ttl,
 | |
| 		uint8_t *buf)
 | |
| {
 | |
| 	struct dns_head *head;
 | |
| 	struct type_and_class *unaligned_type_class;
 | |
| 	const char *err_msg;
 | |
| 	char *query_string;
 | |
| 	char *answstr;
 | |
| 	uint8_t *answb;
 | |
| 	uint16_t outr_rlen;
 | |
| 	uint16_t outr_flags;
 | |
| 	uint16_t type;
 | |
| 	uint16_t class;
 | |
| 	int query_len;
 | |
| 
 | |
| 	head = (struct dns_head *)buf;
 | |
| 	if (head->nquer == 0) {
 | |
| 		bb_error_msg("packet has 0 queries, ignored");
 | |
| 		return 0; /* don't reply */
 | |
| 	}
 | |
| 	if (head->flags & htons(0x8000)) { /* QR bit */
 | |
| 		bb_error_msg("response packet, ignored");
 | |
| 		return 0; /* don't reply */
 | |
| 	}
 | |
| 	/* QR = 1 "response", RCODE = 4 "Not Implemented" */
 | |
| 	outr_flags = htons(0x8000 | 4);
 | |
| 	err_msg = NULL;
 | |
| 
 | |
| 	/* start of query string */
 | |
| 	query_string = (void *)(head + 1);
 | |
| 	/* caller guarantees strlen is <= MAX_PACK_LEN */
 | |
| 	query_len = strlen(query_string) + 1;
 | |
| 	/* may be unaligned! */
 | |
| 	unaligned_type_class = (void *)(query_string + query_len);
 | |
| 	query_len += sizeof(*unaligned_type_class);
 | |
| 	/* where to append answer block */
 | |
| 	answb = (void *)(unaligned_type_class + 1);
 | |
| 
 | |
| 	/* OPCODE != 0 "standard query"? */
 | |
| 	if ((head->flags & htons(0x7800)) != 0) {
 | |
| 		err_msg = "opcode != 0";
 | |
| 		goto empty_packet;
 | |
| 	}
 | |
| 	move_from_unaligned16(class, &unaligned_type_class->class);
 | |
| 	if (class != htons(1)) { /* not class INET? */
 | |
| 		err_msg = "class != 1";
 | |
| 		goto empty_packet;
 | |
| 	}
 | |
| 	move_from_unaligned16(type, &unaligned_type_class->type);
 | |
| 	if (type != htons(REQ_A) && type != htons(REQ_PTR)) {
 | |
| 		/* we can't handle this query type */
 | |
| //TODO: happens all the time with REQ_AAAA (0x1c) requests - implement those?
 | |
| 		err_msg = "type is !REQ_A and !REQ_PTR";
 | |
| 		goto empty_packet;
 | |
| 	}
 | |
| 
 | |
| 	/* look up the name */
 | |
| 	answstr = table_lookup(conf_data, type, query_string);
 | |
| #if DEBUG
 | |
| 	/* Shows lengths instead of dots, unusable for !DEBUG */
 | |
| 	bb_info_msg("'%s'->'%s'", query_string, answstr);
 | |
| #endif
 | |
| 	outr_rlen = 4;
 | |
| 	if (answstr && type == htons(REQ_PTR)) {
 | |
| 		/* returning a host name */
 | |
| 		outr_rlen = strlen(answstr) + 1;
 | |
| 	}
 | |
| 	if (!answstr
 | |
| 	 || (unsigned)(answb - buf) + query_len + 4 + 2 + outr_rlen > MAX_PACK_LEN
 | |
| 	) {
 | |
| 		/* QR = 1 "response"
 | |
| 		 * AA = 1 "Authoritative Answer"
 | |
| 		 * RCODE = 3 "Name Error" */
 | |
| 		err_msg = "name is not found";
 | |
| 		outr_flags = htons(0x8000 | 0x0400 | 3);
 | |
| 		goto empty_packet;
 | |
| 	}
 | |
| 
 | |
| 	/* Append answer Resource Record */
 | |
| 	memcpy(answb, query_string, query_len); /* name, type, class */
 | |
| 	answb += query_len;
 | |
| 	move_to_unaligned32((uint32_t *)answb, htonl(conf_ttl));
 | |
| 	answb += 4;
 | |
| 	move_to_unaligned16((uint16_t *)answb, htons(outr_rlen));
 | |
| 	answb += 2;
 | |
| 	memcpy(answb, answstr, outr_rlen);
 | |
| 	answb += outr_rlen;
 | |
| 
 | |
| 	/* QR = 1 "response",
 | |
| 	 * AA = 1 "Authoritative Answer",
 | |
| 	 * TODO: need to set RA bit 0x80? One user says nslookup complains
 | |
| 	 * "Got recursion not available from SERVER, trying next server"
 | |
| 	 * "** server can't find HOSTNAME"
 | |
| 	 * RCODE = 0 "success"
 | |
| 	 */
 | |
| 	if (OPT_verbose)
 | |
| 		bb_info_msg("returning positive reply");
 | |
| 	outr_flags = htons(0x8000 | 0x0400 | 0);
 | |
| 	/* we have one answer */
 | |
| 	head->nansw = htons(1);
 | |
| 
 | |
|  empty_packet:
 | |
| 	if ((outr_flags & htons(0xf)) != 0) { /* not a positive response */
 | |
| 		if (OPT_verbose) {
 | |
| 			bb_error_msg("%s, %s",
 | |
| 				err_msg,
 | |
| 				OPT_silent ? "dropping query" : "sending error reply"
 | |
| 			);
 | |
| 		}
 | |
| 		if (OPT_silent)
 | |
| 			return 0;
 | |
| 	}
 | |
| 	head->flags |= outr_flags;
 | |
| 	head->nauth = head->nadd = 0;
 | |
| 	head->nquer = htons(1); // why???
 | |
| 
 | |
| 	return answb - buf;
 | |
| }
 | |
| 
 | |
| int dnsd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 | |
| int dnsd_main(int argc UNUSED_PARAM, char **argv)
 | |
| {
 | |
| 	const char *listen_interface = "0.0.0.0";
 | |
| 	const char *fileconf = "/etc/dnsd.conf";
 | |
| 	struct dns_entry *conf_data;
 | |
| 	uint32_t conf_ttl = DEFAULT_TTL;
 | |
| 	char *sttl, *sport;
 | |
| 	len_and_sockaddr *lsa, *from, *to;
 | |
| 	unsigned lsa_size;
 | |
| 	int udps, opts;
 | |
| 	uint16_t port = 53;
 | |
| 	/* Ensure buf is 32bit aligned (we need 16bit, but 32bit can't hurt) */
 | |
| 	uint8_t buf[MAX_PACK_LEN + 1] ALIGN4;
 | |
| 
 | |
| 	opts = getopt32(argv, "vsi:c:t:p:d", &listen_interface, &fileconf, &sttl, &sport);
 | |
| 	//if (opts & (1 << 0)) // -v
 | |
| 	//if (opts & (1 << 1)) // -s
 | |
| 	//if (opts & (1 << 2)) // -i
 | |
| 	//if (opts & (1 << 3)) // -c
 | |
| 	if (opts & (1 << 4)) // -t
 | |
| 		conf_ttl = xatou_range(sttl, 1, 0xffffffff);
 | |
| 	if (opts & (1 << 5)) // -p
 | |
| 		port = xatou_range(sport, 1, 0xffff);
 | |
| 	if (opts & (1 << 6)) { // -d
 | |
| 		bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
 | |
| 		openlog(applet_name, LOG_PID, LOG_DAEMON);
 | |
| 		logmode = LOGMODE_SYSLOG;
 | |
| 	}
 | |
| 
 | |
| 	conf_data = parse_conf_file(fileconf);
 | |
| 
 | |
| 	lsa = xdotted2sockaddr(listen_interface, port);
 | |
| 	udps = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0);
 | |
| 	xbind(udps, &lsa->u.sa, lsa->len);
 | |
| 	socket_want_pktinfo(udps); /* needed for recv_from_to to work */
 | |
| 	lsa_size = LSA_LEN_SIZE + lsa->len;
 | |
| 	from = xzalloc(lsa_size);
 | |
| 	to = xzalloc(lsa_size);
 | |
| 
 | |
| 	{
 | |
| 		char *p = xmalloc_sockaddr2dotted(&lsa->u.sa);
 | |
| 		bb_info_msg("accepting UDP packets on %s", p);
 | |
| 		free(p);
 | |
| 	}
 | |
| 
 | |
| 	while (1) {
 | |
| 		int r;
 | |
| 		/* Try to get *DEST* address (to which of our addresses
 | |
| 		 * this query was directed), and reply from the same address.
 | |
| 		 * Or else we can exhibit usual UDP ugliness:
 | |
| 		 * [ip1.multihomed.ip2] <=  query to ip1  <= peer
 | |
| 		 * [ip1.multihomed.ip2] => reply from ip2 => peer (confused) */
 | |
| 		memcpy(to, lsa, lsa_size);
 | |
| 		r = recv_from_to(udps, buf, MAX_PACK_LEN + 1, 0, &from->u.sa, &to->u.sa, lsa->len);
 | |
| 		if (r < 12 || r > MAX_PACK_LEN) {
 | |
| 			bb_error_msg("packet size %d, ignored", r);
 | |
| 			continue;
 | |
| 		}
 | |
| 		if (OPT_verbose)
 | |
| 			bb_info_msg("got UDP packet");
 | |
| 		buf[r] = '\0'; /* paranoia */
 | |
| 		r = process_packet(conf_data, conf_ttl, buf);
 | |
| 		if (r <= 0)
 | |
| 			continue;
 | |
| 		send_to_from(udps, buf, r, 0, &from->u.sa, &to->u.sa, lsa->len);
 | |
| 	}
 | |
| 	return 0;
 | |
| }
 | 
