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Diffstat (limited to 'i/pc104/initrd/conf/busybox/networking/dnsd.c')
-rw-r--r--i/pc104/initrd/conf/busybox/networking/dnsd.c426
1 files changed, 426 insertions, 0 deletions
diff --git a/i/pc104/initrd/conf/busybox/networking/dnsd.c b/i/pc104/initrd/conf/busybox/networking/dnsd.c
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+++ b/i/pc104/initrd/conf/busybox/networking/dnsd.c
@@ -0,0 +1,426 @@
+/* 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 tarball for details.
+ *
+ * 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.
+ */
+
+#include "busybox.h"
+
+static const char *fileconf = "/etc/dnsd.conf";
+#define LOCK_FILE "/var/run/dnsd.lock"
+
+// Must match getopt32 call
+#define OPT_daemon (option_mask32 & 0x10)
+#define OPT_verbose (option_mask32 & 0x20)
+
+//#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?
+
+ 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;
+};
+
+struct dns_head { // the message from client and first part of response mag
+ 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
+};
+struct dns_prop {
+ uint16_t type;
+ uint16_t class;
+};
+struct dns_entry { // element of known name, ip address and reversed ip address
+ 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];
+};
+
+static struct dns_entry *dnsentry = NULL;
+static uint32_t ttl = DEFAULT_TTL;
+
+/*
+ * 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)
+{
+ int i = 0, s = 0;
+ while (rip[i])
+ i++;
+ for (--i; i >= 0; i--) {
+ if (rip[i] == '.') {
+ rip[i] = s;
+ s = 0;
+ } 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.
+ */
+
+static int getfileentry(FILE * fp, struct dns_entry *s)
+{
+ 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", &a, &b, &c, &d) != 4) {
+ free(line);
+ goto restart; /* skipping wrong lines */
+ }
+
+ sprintf(s->ip, "%u.%u.%u.%u", 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);
+
+ if (OPT_verbose)
+ fprintf(stderr, "\tname:%s, ip:%s\n", &(s->name[1]),s->ip);
+
+ free(line);
+ return 0;
+}
+
+/*
+ * Read hostname/IP records from file
+ */
+static void dnsentryinit(void)
+{
+ FILE *fp;
+ struct dns_entry *m, *prev;
+
+ prev = dnsentry = NULL;
+ fp = xfopen(fileconf, "r");
+
+ while (1) {
+ m = xzalloc(sizeof(*m));
+ /*m->next = NULL;*/
+ if (getfileentry(fp, m))
+ break;
+
+ if (prev == NULL)
+ dnsentry = m;
+ else
+ prev->next = m;
+ prev = m;
+ }
+ fclose(fp);
+}
+
+/*
+ * Look query up in dns records and return answer if found
+ * qs is the query string, first byte the string length
+ */
+static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs)
+{
+ int i;
+ struct dns_entry *d=dnsentry;
+
+ do {
+#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));
+#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])) {
+#if DEBUG
+ fprintf(stderr, " OK");
+#endif
+ strcpy((char *)as, d->ip);
+#if DEBUG
+ fprintf(stderr, " as:%s\n", as);
+#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;
+ }
+ }
+ d = d->next;
+ } while (d);
+ return -1;
+}
+
+
+/*
+ * Decode message and generate answer
+ */
+#define eret(s) do { fputs(s, stderr); return -1; } while (0)
+static int process_packet(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';
+
+ head = (struct dns_head *)buf;
+ if (head->nquer == 0)
+ eret("no queries\n");
+
+ if (head->flags & 0x8000)
+ eret("ignoring response packet\n");
+
+ 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 */
+ }
+
+ if (ntohs(qprop->class) != 1 /* class INET */ ) {
+ outr.flags = 4; /* not supported */
+ goto empty_packet;
+ }
+ /* we only support standard queries */
+
+ if ((ntohs(head->flags) & 0x7800) != 0)
+ 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
+ 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;
+
+ empty_packet:
+
+ 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 = next - (void *)buf;
+ return packet_len;
+}
+
+/*
+ * Exit on signal
+ */
+static void interrupt(int x)
+{
+ unlink(LOCK_FILE);
+ bb_error_msg("interrupt, exiting\n");
+ exit(2);
+}
+
+int dnsd_main(int argc, char **argv);
+int dnsd_main(int argc, char **argv)
+{
+ char *listen_interface = NULL;
+ char *sttl, *sport;
+ len_and_sockaddr *lsa;
+ int udps;
+ 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
+ port = xatou_range(sttl, 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) {
+//FIXME: NOMMU will NOT set LOGMODE_SYSLOG!
+#ifdef BB_NOMMU
+ /* reexec for vfork() do continue parent */
+ vfork_daemon_rexec(1, 0, argc, argv, "-d");
+#else
+ xdaemon(1, 0);
+#endif
+ logmode = LOGMODE_SYSLOG;
+ }
+
+ dnsentryinit();
+
+ signal(SIGINT, interrupt);
+ signal(SIGPIPE, SIG_IGN);
+ signal(SIGHUP, SIG_IGN);
+#ifdef SIGTSTP
+ signal(SIGTSTP, SIG_IGN);
+#endif
+#ifdef SIGURG
+ signal(SIGURG, SIG_IGN);
+#endif
+
+ lsa = xhost2sockaddr(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));
+
+ while (1) {
+ fd_set fdset;
+ int r;
+
+ FD_ZERO(&fdset);
+ FD_SET(udps, &fdset);
+ // Block until a message arrives
+// FIXME: Fantastic. select'ing on just one fd??
+// Why no just block on it doing recvfrom() ?
+ r = select(udps + 1, &fdset, NULL, NULL, NULL);
+ if (r < 0)
+ bb_perror_msg_and_die("select error");
+ if (r == 0)
+ bb_perror_msg_and_die("select spurious return");
+
+ /* Can this test ever be false? - yes */
+ if (FD_ISSET(udps, &fdset)) {
+ 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");
+ continue;
+ }
+ if (r <= 0)
+ continue;
+ r = process_packet(buf);
+ if (r <= 0)
+ continue;
+ sendto(udps, buf, r, 0, &lsa->sa, fromlen);
+ }
+ }
+}