* 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 tarball for details.
+ * 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.
* the first porting of oao' scdns to busybox also.
*/
+//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>
-#include "busybox.h"
//#define DEBUG 1
#define DEBUG 0
enum {
- MAX_HOST_LEN = 16, // longest host name allowed is 15
- IP_STRING_LEN = 18, // .xxx.xxx.xxx.xxx\0
-
-//must be strlen('.in-addr.arpa') larger than IP_STRING_LEN
- MAX_NAME_LEN = (IP_STRING_LEN + 13),
-
-/* Cannot get bigger packets than 512 per RFC1035
- In practice this can be set considerably smaller:
- Length of response packet is header (12B) + 2*type(4B) + 2*class(4B) +
- ttl(4B) + rlen(2B) + r (MAX_NAME_LEN =21B) +
- 2*querystring (2 MAX_NAME_LEN= 42B), all together 90 Byte
-*/
- MAX_PACK_LEN = 512 + 1,
-
- DEFAULT_TTL = 30, // increase this when not testing?
+ /* 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
-};
-
-struct dns_repl { // resource record, add 0 or 1 to accepted dns_msg in resp
- uint16_t rlen;
- uint8_t *r; // resource
- uint16_t flags;
+ REQ_PTR = 12,
};
-struct dns_head { // the message from client and first part of response mag
+/* the message from client and first part of response msg */
+struct dns_head {
uint16_t id;
uint16_t flags;
- uint16_t nquer; // accepts 0
- uint16_t nansw; // 1 in response
- uint16_t nauth; // 0
- uint16_t nadd; // 0
+ uint16_t nquer;
+ uint16_t nansw;
+ uint16_t nauth;
+ uint16_t nadd;
};
-struct dns_prop {
- uint16_t type;
- uint16_t class;
-};
-struct dns_entry { // element of known name, ip address and reversed ip address
+/* 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;
- char ip[IP_STRING_LEN]; // dotted decimal IP
- char rip[IP_STRING_LEN]; // length decimal reversed IP
- char name[MAX_HOST_LEN];
+ uint32_t ip;
+ char rip[IP_STRING_LEN]; /* length decimal reversed IP */
+ char name[1];
};
-static struct dns_entry *dnsentry;
-static uint32_t ttl = DEFAULT_TTL;
-
-static const char *fileconf = "/etc/dnsd.conf";
-
-// Must match getopt32 call
-#define OPT_daemon (option_mask32 & 0x10)
-#define OPT_verbose (option_mask32 & 0x20)
+#define OPT_verbose (option_mask32 & 1)
+#define OPT_silent (option_mask32 & 2)
/*
- * Convert host name from C-string to dns length/string.
- */
-static void convname(char *a, uint8_t *q)
-{
- int i = (q[0] == '.') ? 0 : 1;
- for (; i < MAX_HOST_LEN-1 && *q; i++, q++)
- a[i] = tolower(*q);
- a[0] = i - 1;
- a[i] = 0;
-}
-
-/*
* Insert length of substrings instead of dots
*/
-static void undot(uint8_t * rip)
+static void undot(char *rip)
{
- int i = 0, s = 0;
+ 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++;
+ } else {
+ s++;
+ }
}
}
/*
- * Read one line of hostname/IP from file
- * Returns 0 for each valid entry read, -1 at EOF
- * Assumes all host names are lower case only
- * Hostnames with more than one label are not handled correctly.
- * Presently the dot is copied into name without
- * converting to a length/string substring for that label.
+ * Read hostname/IP records from file
*/
-static int getfileentry(FILE * fp, struct dns_entry *s)
+static struct dns_entry *parse_conf_file(const char *fileconf)
{
- unsigned int a,b,c,d;
- char *line, *r, *name;
-
- restart:
- line = r = xmalloc_fgets(fp);
- if (!r)
- return -1;
- while (*r == ' ' || *r == '\t') {
- r++;
- if (!*r || *r == '#' || *r == '\n') {
- free(line);
- goto restart; /* skipping empty/blank and commented lines */
- }
- }
- name = r;
- while (*r != ' ' && *r != '\t')
- r++;
- *r++ = '\0';
- if (sscanf(r, ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4) {
- free(line);
- goto restart; /* skipping wrong lines */
- }
+ char *token[2];
+ parser_t *parser;
+ struct dns_entry *m, *conf_data;
+ struct dns_entry **nextp;
- sprintf(s->ip, ".%u.%u.%u.%u"+1, a, b, c, d);
- sprintf(s->rip, ".%u.%u.%u.%u", d, c, b, a);
- undot((uint8_t*)s->rip);
- convname(s->name, (uint8_t*)name);
+ conf_data = NULL;
+ nextp = &conf_data;
- if (OPT_verbose)
- fprintf(stderr, "\tname:%s, ip:%s\n", &(s->name[1]),s->ip);
-
- free(line);
- return 0;
-}
+ parser = config_open(fileconf);
+ while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
+ struct in_addr ip;
+ uint32_t v32;
-/*
- * Read hostname/IP records from file
- */
-static void dnsentryinit(void)
-{
- FILE *fp;
- struct dns_entry *m, *prev;
+ if (inet_aton(token[1], &ip) == 0) {
+ bb_error_msg("error at line %u, skipping", parser->lineno);
+ continue;
+ }
- prev = dnsentry = NULL;
- fp = xfopen(fileconf, "r");
+ if (OPT_verbose)
+ bb_error_msg("name:%s, ip:%s", token[0], token[1]);
- while (1) {
- m = xzalloc(sizeof(*m));
+ /* sizeof(*m) includes 1 byte for m->name[0] */
+ m = xzalloc(sizeof(*m) + strlen(token[0]) + 1);
/*m->next = NULL;*/
- if (getfileentry(fp, m))
- break;
-
- if (prev == NULL)
- dnsentry = m;
- else
- prev->next = m;
- prev = m;
+ *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);
}
- fclose(fp);
+ config_close(parser);
+ return conf_data;
}
/*
- * Look query up in dns records and return answer if found
- * qs is the query string, first byte the string length
+ * Look query up in dns records and return answer if found.
*/
-static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs)
+static char *table_lookup(struct dns_entry *d,
+ uint16_t type,
+ char* query_string)
{
- int i;
- struct dns_entry *d = dnsentry;
-
- do {
+ while (d) {
+ unsigned len = d->name[0];
+ /* d->name[len] is the last (non NUL) char */
#if DEBUG
- char *p,*q;
- q = (char *)&(qs[1]);
- p = &(d->name[1]);
- fprintf(stderr, "\n%s: %d/%d p:%s q:%s %d",
- __FUNCTION__, (int)strlen(p), (int)(d->name[0]),
- p, q, (int)strlen(q));
+ 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 == REQ_A) { /* search by host name */
- for (i = 1; i <= (int)(d->name[0]); i++)
- if (tolower(qs[i]) != d->name[i])
- break;
- if (i > (int)(d->name[0])) {
- strcpy((char *)as, d->ip);
+ 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, " OK as:%s\n", as);
+ fprintf(stderr, "Found IP:%x\n", (int)d->ip);
#endif
- return 0;
- }
- } else if (type == REQ_PTR) { /* search by IP-address */
- if (!strncmp((char*)&d->rip[1], (char*)&qs[1], strlen(d->rip)-1)) {
- strcpy((char *)as, d->name);
- return 0;
- }
+ 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" */
+ && strncmp(d->rip, query_string, strlen(d->rip)) == 0
+ ) {
+#if DEBUG
+ fprintf(stderr, "Found name:%s\n", d->name);
+#endif
+ return d->name;
+ }
+ next:
d = d->next;
- } while (d);
- return -1;
-}
+ }
+ return NULL;
+}
/*
* Decode message and generate answer
*/
-static int process_packet(uint8_t * buf)
+/* 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 |
+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ |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 occurance 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 dns_prop *qprop;
- struct dns_repl outr;
- void *next, *from, *answb;
-
- uint8_t answstr[MAX_NAME_LEN + 1];
- int lookup_result, type, len, packet_len;
- uint16_t flags;
-
- answstr[0] = '\0';
+ 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("no queries");
- return -1;
+ bb_error_msg("packet has 0 queries, ignored");
+ return 0; /* don't reply */
}
-
- if (head->flags & 0x8000) {
- bb_error_msg("ignoring response packet");
- return -1;
+ if (head->flags & htons(0x8000)) { /* QR bit */
+ bb_error_msg("response packet, ignored");
+ return 0; /* don't reply */
}
-
- from = (void *)&head[1]; // start of query string
- next = answb = from + strlen((char *)from) + 1 + sizeof(struct dns_prop); // where to append answer block
-
- outr.rlen = 0; // may change later
- outr.r = NULL;
- outr.flags = 0;
-
- qprop = (struct dns_prop *)(answb - 4);
- type = ntohs(qprop->type);
-
- // only let REQ_A and REQ_PTR pass
- if (!(type == REQ_A || type == REQ_PTR)) {
- goto empty_packet; /* we can't handle the query type */
+ /* 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;
}
-
- if (ntohs(qprop->class) != 1 /* class INET */ ) {
- outr.flags = 4; /* not supported */
+ move_from_unaligned16(class, &unaligned_type_class->class);
+ if (class != htons(1)) { /* not class INET? */
+ err_msg = "class != 1";
goto empty_packet;
}
- /* we only support standard queries */
-
- if ((ntohs(head->flags) & 0x7800) != 0)
+ 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;
+ }
- // We have a standard query
- bb_info_msg("%s", (char *)from);
- lookup_result = table_lookup(type, answstr, (uint8_t*)from);
- if (lookup_result != 0) {
- outr.flags = 3 | 0x0400; //name do not exist and auth
+ /* look up the name */
+ answstr = table_lookup(conf_data, type, query_string);
+#if DEBUG
+ /* Shows lengths instead of dots, unusable for !DEBUG */
+ bb_error_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;
}
- if (type == REQ_A) { // return an address
- struct in_addr a;
- if (!inet_aton((char*)answstr, &a)) {//dotted dec to long conv
- outr.flags = 1; /* Frmt err */
- goto empty_packet;
- }
- memcpy(answstr, &a.s_addr, 4); // save before a disappears
- outr.rlen = 4; // uint32_t IP
- } else
- outr.rlen = strlen((char *)answstr) + 1; // a host name
- outr.r = answstr; // 32 bit ip or a host name
- outr.flags |= 0x0400; /* authority-bit */
- // we have an answer
- head->nansw = htons(1);
-
- // copy query block to answer block
- len = answb - from;
- memcpy(answb, from, len);
- next += len;
- // and append answer rr
- *(uint32_t *) next = htonl(ttl);
- next += 4;
- *(uint16_t *) next = htons(outr.rlen);
- next += 2;
- memcpy(next, (void *)answstr, outr.rlen);
- next += outr.rlen;
+ /* 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_error_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???
- flags = ntohs(head->flags);
- // clear rcode and RA, set responsebit and our new flags
- flags |= (outr.flags & 0xff80) | 0x8000;
- head->flags = htons(flags);
- head->nauth = head->nadd = htons(0);
- head->nquer = htons(1);
-
- packet_len = (uint8_t *)next - buf;
- return packet_len;
+ return answb - buf;
}
-/*
- * Exit on signal
- */
-static void interrupt(int x)
-{
- /* unlink("/var/run/dnsd.lock"); */
- bb_error_msg("interrupt, exiting\n");
- exit(2);
-}
-
-int dnsd_main(int argc, char **argv);
-int dnsd_main(int argc, char **argv)
+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;
- int udps;
+ len_and_sockaddr *lsa, *from, *to;
+ unsigned lsa_size;
+ int udps, opts;
uint16_t port = 53;
- uint8_t buf[MAX_PACK_LEN];
-
- getopt32(argc, argv, "i:c:t:p:dv", &listen_interface, &fileconf, &sttl, &sport);
- //if (option_mask32 & 0x1) // -i
- //if (option_mask32 & 0x2) // -c
- if (option_mask32 & 0x4) // -t
- ttl = xatou_range(sttl, 1, 0xffffffff);
- if (option_mask32 & 0x8) // -p
+ /* 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 (OPT_verbose) {
- bb_info_msg("listen_interface: %s", listen_interface);
- bb_info_msg("ttl: %d, port: %d", ttl, port);
- bb_info_msg("fileconf: %s", fileconf);
- }
-
- if (OPT_daemon) {
+ if (opts & (1 << 6)) { // -d
bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
openlog(applet_name, LOG_PID, LOG_DAEMON);
logmode = LOGMODE_SYSLOG;
}
- dnsentryinit();
-
- signal(SIGINT, interrupt);
- /* why? signal(SIGPIPE, SIG_IGN); */
- signal(SIGHUP, SIG_IGN);
-#ifdef SIGTSTP
- signal(SIGTSTP, SIG_IGN);
-#endif
-#ifdef SIGURG
- signal(SIGURG, SIG_IGN);
-#endif
+ conf_data = parse_conf_file(fileconf);
lsa = xdotted2sockaddr(listen_interface, port);
- udps = xsocket(lsa->sa.sa_family, SOCK_DGRAM, 0);
- xbind(udps, &lsa->sa, lsa->len);
- /* xlisten(udps, 50); - ?!! DGRAM sockets are never listened on I think? */
- bb_info_msg("Accepting UDP packets on %s",
- xmalloc_sockaddr2dotted(&lsa->sa, lsa->len));
+ 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_error_msg("accepting UDP packets on %s", p);
+ free(p);
+ }
while (1) {
int r;
- socklen_t fromlen = lsa->len;
-// FIXME: need 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)
- r = recvfrom(udps, buf, sizeof(buf), 0, &lsa->sa, &fromlen);
- if (OPT_verbose)
- bb_info_msg("Got UDP packet");
- if (r < 12 || r > 512) {
- bb_error_msg("invalid packet size");
+ /* 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;
}
- r = process_packet(buf);
+ if (OPT_verbose)
+ bb_error_msg("got UDP packet");
+ buf[r] = '\0'; /* paranoia */
+ r = process_packet(conf_data, conf_ttl, buf);
if (r <= 0)
continue;
- sendto(udps, buf, r, 0, &lsa->sa, fromlen);
+ send_to_from(udps, buf, r, 0, &from->u.sa, &to->u.sa, lsa->len);
}
return 0;
}
projects / platform / upstream / busybox.git / blobdiff