From 64bc6412188b141c010ac3b8e813b837dd991e80 Mon Sep 17 00:00:00 2001 From: Erik Andersen Date: Sun, 14 May 2000 04:16:35 +0000 Subject: Initial revision --- libc/inet/resolv.c | 892 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 892 insertions(+) create mode 100644 libc/inet/resolv.c (limited to 'libc/inet/resolv.c') diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c new file mode 100644 index 000000000..b4cfab104 --- /dev/null +++ b/libc/inet/resolv.c @@ -0,0 +1,892 @@ +/* resolv.c: DNS Resolver + * + * Copyright (C) 1998 Kenneth Albanowski , + * The Silver Hammer Group, Ltd. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Library General Public + * License as published by the Free Software Foundation; either + * version 2 of the License, or (at your option) any later version. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define DNS_SERVICE 53 +#define MAX_RECURSE 5 +#define REPLY_TIMEOUT 10 +#define MAX_RETRIES 15 + +#undef DEBUG +#ifdef DEBUG +#define DPRINTF(X,args...) printf(X,args...) +#else +#define DPRINTF(X,args...) +#endif /* DEBUG */ + +#ifdef L_encodeh +int encode_header(struct resolv_header * h, unsigned char * dest, int maxlen) +{ + if (maxlen < 12) + return -1; + + dest[0] = (h->id & 0xff00) >> 8; + dest[1] = (h->id & 0x00ff) >> 0; + dest[2] = (h->qr ? 0x80 : 0) | + ((h->opcode & 0x0f) << 3) | + (h->aa ? 0x04 : 0) | + (h->tc ? 0x02 : 0) | + (h->rd ? 0x01 : 0); + dest[3] = (h->ra ? 0x80 : 0) | + (h->rcode & 0x0f); + dest[4] = (h->qdcount & 0xff00) >> 8; + dest[5] = (h->qdcount & 0x00ff) >> 0; + dest[6] = (h->ancount & 0xff00) >> 8; + dest[7] = (h->ancount & 0x00ff) >> 0; + dest[8] = (h->nscount & 0xff00) >> 8; + dest[9] = (h->nscount & 0x00ff) >> 0; + dest[10] = (h->arcount & 0xff00) >> 8; + dest[11] = (h->arcount & 0x00ff) >> 0; + + return 12; +} +#endif + +#ifdef L_decodeh +int decode_header(unsigned char * data, struct resolv_header * h) +{ + h->id = (data[0] << 8) | data[1]; + h->qr = (data[2] & 0x80) ? 1 : 0; + h->opcode = (data[2] >> 3) & 0x0f; + h->aa = (data[2] & 0x04) ? 1 : 0; + h->tc = (data[2] & 0x02) ? 1 : 0; + h->rd = (data[2] & 0x01) ? 1 : 0; + h->ra = (data[3] & 0x80) ? 1 : 0; + h->rcode = data[3] & 0x0f; + h->qdcount = (data[4] << 8) | data[5]; + h->ancount = (data[6] << 8) | data[7]; + h->nscount = (data[8] << 8) | data[9]; + h->arcount = (data[10] << 8) | data[11]; + + return 12; +} +#endif + +#ifdef L_encoded +/* Encode a dotted string into nameserver transport-level encoding. + This routine is fairly dumb, and doesn't attempt to compress + the data */ + +int encode_dotted(const char * dotted, unsigned char * dest, int maxlen) +{ + int used=0; + + while(dotted && *dotted) { + char * c = strchr(dotted, '.'); + int l = c ? c - dotted : strlen(dotted); + + if (l >= (maxlen-used-1)) + return -1; + + dest[used++] = l; + memcpy(dest+used, dotted, l); + used += l; + + if (c) + dotted = c+1; + else + break; + } + + if (maxlen < 1) + return -1; + + dest[used++] = 0; + + return used; +} +#endif + +#ifdef L_decoded +/* Decode a dotted string from nameserver transport-level encoding. + This routine understands compressed data. */ + +int decode_dotted(const unsigned char * data, int offset, + char * dest, int maxlen) +{ + int l; + int measure=1; + int total = 0; + int used=0; + + if (!data) + return -1; + + while ((measure && total++), (l=data[offset++])) { + + if ((l & 0xc0) == (0xc0)) { + if (measure) + total++; + /* compressed item, redirect */ + offset = ((l & 0x3f) << 8) | data[offset]; + measure = 0; + continue; + } + + if ((used+l+1) >= maxlen) + return -1; + + memcpy(dest+used, data+offset, l); + offset += l; + used += l; + if (measure) + total += l; + + if (data[offset] != 0) + dest[used++] = '.'; + else + dest[used++] = '\0'; + } + + DPRINTF("Total decode len = %d\n", total); + + return total; +} +#endif + +#ifdef L_lengthd + +int length_dotted(const unsigned char * data, int offset) +{ + int orig_offset = offset; + int l; + + if (!data) + return -1; + + while ((l=data[offset++])) { + + if ((l & 0xc0) == (0xc0)) { + offset++; + break; + } + + offset += l; + } + + return offset-orig_offset; +} +#endif + +#ifdef L_encodeq +int encode_question(struct resolv_question * q, + unsigned char * dest, int maxlen) +{ + int i; + + i = encode_dotted(q->dotted, dest, maxlen); + if (i < 0) + return i; + + dest += i; + maxlen -= i; + + if (maxlen < 4) + return -1; + + dest[0] = (q->qtype & 0xff00) >> 8; + dest[1] = (q->qtype & 0x00ff) >> 0; + dest[2] = (q->qclass & 0xff00) >> 8; + dest[3] = (q->qclass & 0x00ff) >> 0; + + return i+4; +} +#endif + +#ifdef L_decodeq +int decode_question(unsigned char * message, int offset, + struct resolv_question * q) +{ + char temp[256]; + int i; + + i = decode_dotted(message, offset, temp, 256); + if (i < 0) + return i; + + offset += i; + + q->dotted = strdup(temp); + q->qtype = (message[offset+0] << 8) | message[offset+1]; + q->qclass = (message[offset+2] << 8) | message[offset+3]; + + return i+4; +} +#endif + +#ifdef L_lengthq +int length_question(unsigned char * message, int offset) +{ + int i; + + i = length_dotted(message, offset); + if (i < 0) + return i; + + return i+4; +} +#endif + +#ifdef L_encodea +int encode_answer(struct resolv_answer * a, + unsigned char * dest, int maxlen) +{ + int i; + + i = encode_dotted(a->dotted, dest, maxlen); + if (i < 0) + return i; + + dest += i; + maxlen -= i; + + if (maxlen < (10+a->rdlength)) + return -1; + + *dest++ = (a->atype & 0xff00) >> 8; + *dest++ = (a->atype & 0x00ff) >> 0; + *dest++ = (a->aclass & 0xff00) >> 8; + *dest++ = (a->aclass & 0x00ff) >> 0; + *dest++ = (a->ttl & 0xff000000) >> 24; + *dest++ = (a->ttl & 0x00ff0000) >> 16; + *dest++ = (a->ttl & 0x0000ff00) >> 8; + *dest++ = (a->ttl & 0x000000ff) >> 0; + *dest++ = (a->rdlength & 0xff00) >> 8; + *dest++ = (a->rdlength & 0x00ff) >> 0; + memcpy(dest, a->rdata, a->rdlength); + + return i+10+a->rdlength; +} +#endif + +#ifdef L_decodea +int decode_answer(unsigned char * message, int offset, + struct resolv_answer * a) +{ + char temp[256]; + int i; + + i = decode_dotted(message, offset, temp, 256); + if (i < 0) + return i; + + message += offset+i; + + a->dotted = strdup(temp); + a->atype = (message[0] << 8) | message[1]; message += 2; + a->aclass = (message[0] << 8) | message[1]; message += 2; + a->ttl = (message[0] << 24) | + (message[1] << 16) | + (message[2] << 8) | + (message[3] << 0); + message += 4; + a->rdlength = (message[0] << 8) | message[1]; message += 2; + a->rdata = message; + a->rdoffset = offset+i+10; + + DPRINTF("i=%d,rdlength=%d\n", i, a->rdlength); + + return i+10+a->rdlength; +} +#endif + +#ifdef L_encodep +int encode_packet(struct resolv_header * h, + struct resolv_question ** q, + struct resolv_question ** an, + struct resolv_question ** ns, + struct resolv_question ** ar, + unsigned char * dest, int maxlen) +{ + int i, total=0; + int j; + + i = encode_header(h, dest, maxlen); + if (i < 0) + return i; + + dest += i; + maxlen -= i; + total += i; + + for(j=0;jqdcount;j++) { + i = encode_question(q[j], dest, maxlen); + if (i < 0) + return i; + dest += i; + maxlen -= i; + total += i; + } + + for(j=0;jancount;j++) { + i = encode_answer(an[j], dest, maxlen); + if (i < 0) + return i; + dest += i; + maxlen -= i; + total += i; + } + for(j=0;jnscount;j++) { + i = encode_answer(ns[j], dest, maxlen); + if (i < 0) + return i; + dest += i; + maxlen -= i; + total += i; + } + for(j=0;jarcount;j++) { + i = encode_answer(ar[j], dest, maxlen); + if (i < 0) + return i; + dest += i; + maxlen -= i; + total += i; + } + + return total; +} +#endif + +#ifdef L_decodep +int decode_packet(unsigned char * data, struct resolv_header * h) +{ + return decode_header(data, h); +} +#endif + +#ifdef L_formquery +int form_query(int id, const char * name, int type, unsigned char * packet, int maxlen) +{ + struct resolv_header h; + struct resolv_question q; + int i,j; + + memset(&h, 0, sizeof(h)); + h.id = id; + h.qdcount = 1; + + q.dotted = (char*)name; + q.qtype = type; + q.qclass = 1 /*CLASS_IN*/; + + i = encode_header(&h, packet, maxlen); + if (i < 0) + return i; + + j = encode_question(&q, packet+i, maxlen-i); + if (j < 0) + return j; + + return i+j; +} +#endif + +#ifdef L_dnslookup + +int dns_caught_signal = 0; +void dns_catch_signal(int signo) { + dns_caught_signal = 1; +} + +int dns_lookup(const char * name, int type, int nscount, const char ** nsip, + unsigned char ** outpacket, struct resolv_answer * a) +{ + static int id=1; + int i,j,len; + int fd; + int pos; + static int ns = 0; + struct sockaddr_in sa; + int oldalarm; + __sighandler_t oldhandler; + struct resolv_header h; + struct resolv_question q; + int retries = 0; + unsigned char * packet = malloc(512); + + if (!packet) + goto fail1; + + DPRINTF("Looking up type %d answer for '%s'\n", type, name); + + + if (!nscount) + goto fail1; + + ns %= nscount; + + fd = -1; + + while (retries++ < MAX_RETRIES) { + + if (fd != -1) + close(fd); + + fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); + + if (fd==-1) + goto fail2; + + + memset(packet, 0, 512); + + memset(&h, 0, sizeof(h)); + h.id = ++id; + h.qdcount = 1; + h.rd = 1; + + DPRINTF("encoding header\n"); + + i = encode_header(&h, packet, 512); + if (i < 0) + goto fail3; + + q.dotted = (char*)name; + q.qtype = type; + q.qclass = 1 /*CLASS_IN*/; + + j = encode_question(&q, packet+i, 512-i); + if (j < 0) + goto fail3; + + len = i+j; + + DPRINTF("On try %d, sending query to port %d of machine %s\n", + retries, DNS_SERVICE, nsip[ns]); + + sa.sin_family = AF_INET; + sa.sin_port = htons(DNS_SERVICE); + sa.sin_addr.s_addr = inet_addr(nsip[ns]); + + if (connect(fd, (struct sockaddr*)&sa, sizeof(sa))==-1) { + if (errno == ENETUNREACH) { + /* routing error, presume not transient */ + goto tryall; + } else + /* retry */ + break; + } + + DPRINTF("Transmitting packet of length %d, id=%d, qr=%d\n", + len, h.id, h.qr); + + send(fd, packet, len, 0); + + dns_caught_signal = 0; + oldalarm = alarm(REPLY_TIMEOUT); + oldhandler = signal(SIGALRM, dns_catch_signal); + + i = recv(fd, packet, 512, 0); + + alarm(0); + signal(SIGALRM, oldhandler); + alarm(oldalarm); + + DPRINTF("Timeout=%d, len=%d\n", + dns_caught_signal, i); + + if (dns_caught_signal) + /* timed out, so retry send and receive, + to next nameserver on queue */ + goto again; + + if (i < 12) + /* too short ! */ + goto again; + + decode_header(packet, &h); + + DPRINTF("id = %d, qr = %d\n", + h.id, h.qr); + + if ((h.id != id) || (!h.qr)) + /* unsolicited */ + goto again; + + DPRINTF("Got response (i think)!\n"); + DPRINTF("qrcount=%d,ancount=%d,nscount=%d,arcount=%d\n", + h.qdcount, h.ancount, h.nscount, h.arcount); + DPRINTF("opcode=%d,aa=%d,tc=%d,rd=%d,ra=%d,rcode=%d\n", + h.opcode,h.aa,h.tc,h.rd,h.ra,h.rcode); + + if ((h.rcode) || (h.ancount < 1)) { + /* negative result, not present */ + goto tryall; + } + + pos = 12; + + for(j=0;jdotted); + DPRINTF("Answer type = |%d|\n", a->atype); + + close(fd); + + if (outpacket) + *outpacket = packet; + else + free(packet); + return (0); /* success! */ + + tryall: + /* if there are other nameservers, give them a go, + otherwise return with error */ + if (retries >= nscount) + break; + again: + ns = (ns + 1) % nscount; + continue; + } + + + +fail3: + close(fd); +fail2: + free(packet); +fail1: + return -1; +} +#endif + +#ifdef L_resolveaddress + +int resolve_address(const char * address, + int nscount, const char ** nsip, + struct in_addr * in) +{ + unsigned char * packet; + struct resolv_answer a; + char temp[256]; + int i; + int nest=0; + + if (!address || !in) + return -1; + + strcpy(temp, address); + + for(;;) { + + i = dns_lookup(temp, 1, nscount, nsip, &packet, &a); + + if (i<0) + return -1; + + free(a.dotted); + + if (a.atype == 5) { /* CNAME*/ + i = decode_dotted(packet, a.rdoffset, temp, 256); + free(packet); + + if (i <0) + return -1; + if (++nest > MAX_RECURSE) + return -1; + continue; + } else if (a.atype == 1) { /* ADDRESS */ + free(packet); + break; + } else { + free(packet); + return -1; + } + } + + if (in) + memcpy(in, a.rdata, 4); + + return 0; +} +#endif + +#ifdef L_resolvemailbox + +int resolve_mailbox(const char * address, + int nscount, const char ** nsip, + struct in_addr * in) +{ + struct resolv_answer a; + unsigned char * packet; + char temp[256]; + int nest=0; + int i; + + if (!address || !in) + return -1; + + /* look up mail exchange */ + i = dns_lookup(address, 15, nscount, nsip, &packet, &a); + + strcpy(temp, address); + + if (i>=0) { + i = decode_dotted(packet, a.rdoffset+2, temp, 256); + free(packet); + } + + for(;;) { + + i = dns_lookup(temp, 1, nscount, nsip, &packet, &a); + + if (i<0) + return -1; + + free(a.dotted); + + if (a.atype == 5) { /* CNAME*/ + i = decode_dotted(packet, a.rdoffset, temp, 256); + free(packet); + if (i<0) + return i; + if (++nest > MAX_RECURSE) + return -1; + continue; + } else if (a.atype == 1) { /* ADDRESS */ + free(packet); + break; + } else { + free(packet); + return -1; + } + } + + if (in) + memcpy(in, a.rdata, 4); + + return 0; +} +#endif + +extern int nameservers; +extern const char * nameserver[3]; + +#ifdef L_opennameservers + +int nameservers; +const char * nameserver[3]; + +int open_nameservers() +{ + FILE *fp; + char **arg; + int i; + + if (fp = fopen("/etc/resolv.conf", "r")) { + if (arg = cfgfind(fp, "nameserver")) { + for (i=1; arg[i]; i++) { + nameserver[nameservers++] = strdup(arg[i]); + } + } + fclose(fp); + } + return 0; +} +#endif + +#ifdef L_closenameservers +void close_nameservers(void) { + + while(nameservers>0) + free(nameserver[--nameservers]); +} +#endif + + +#ifdef L_resolvename + +char * resolve_name(const char * name, int mailbox) +{ + struct in_addr in; + int i; + + /* shortcut: is it a valid IP address to begin with? */ + if (inet_aton(name, &in)) + return name; + + open_nameservers(); + + DPRINTF("looking up '%s', mailbox=%d, nameservers=%d\n", + name, mailbox, nameservers); + + if (mailbox) + i = resolve_mailbox(name, nameservers, nameserver, &in); + else + i = resolve_address(name, nameservers, nameserver, &in); + + if (i<0) + return 0; + + DPRINTF("success = '%s'\n", inet_ntoa(in)); + + return inet_ntoa(in); +} +#endif + +#ifdef L_gethostbyname + +struct hostent * gethostbyname(const char * name) +{ + static struct hostent h; + static char namebuf[256]; + static struct in_addr in; + static struct in_addr *addr_list[2]; + unsigned char * packet; + struct resolv_answer a; + int i; + int nest=0; + + open_nameservers(); + + if (!name) + return 0; + + memset(&h, 0, sizeof(h)); + + addr_list[0] = ∈ + addr_list[1] = 0; + + strcpy(namebuf, name); + + for(;;) { + + i = dns_lookup(namebuf, 1, nameservers, nameserver, &packet, &a); + + if (i<0) + return 0; + + strcpy(namebuf, a.dotted); + free(a.dotted); + + + if (a.atype == 5) { /* CNAME*/ + i = decode_dotted(packet, a.rdoffset, namebuf, 256); + free(packet); + + if (i <0) + return 0; + if (++nest > MAX_RECURSE) + return 0; + continue; + } else if (a.atype == 1) { /* ADDRESS */ + memcpy(&in, a.rdata, sizeof(in)); + h.h_name = namebuf; + h.h_addrtype = AF_INET; + h.h_length = sizeof(in); + h.h_addr_list = (char**)addr_list; + free(packet); + break; + } else { + free(packet); + return 0; + } + } + + return &h; +} +#endif + +#ifdef L_gethostbyaddr + +struct hostent * gethostbyaddr(const char * addr, int len, int type) +{ + static struct hostent h; + static char namebuf[256]; + static struct in_addr in; + static struct in_addr *addr_list[2]; + unsigned char * packet; + struct resolv_answer a; + int i; + int nest=0; + + if (!addr || (len != sizeof(in)) || (type != AF_INET)) + return 0; + + memcpy(&in.s_addr, addr, len); + + open_nameservers(); + + memset(&h, 0, sizeof(h)); + + addr_list[0] = ∈ + addr_list[1] = 0; + + sprintf(namebuf, "%d.%d.%d.%d.in-addr.arpa", + (in.s_addr >> 24) & 0xff, + (in.s_addr >> 16) & 0xff, + (in.s_addr >> 8) & 0xff, + (in.s_addr >> 0) & 0xff + ); + + for(;;) { + + i = dns_lookup(namebuf, 12, nameservers, nameserver, &packet, &a); + + if (i<0) + return 0; + + strcpy(namebuf, a.dotted); + free(a.dotted); + + if (a.atype == 5) { /* CNAME*/ + i = decode_dotted(packet, a.rdoffset, namebuf, 256); + free(packet); + + if (i <0) + return 0; + if (++nest > MAX_RECURSE) + return 0; + continue; + } else if (a.atype == 12) { /* ADDRESS */ + i = decode_dotted(packet, a.rdoffset, namebuf, 256); + free(packet); + + h.h_name = namebuf; + h.h_addrtype = AF_INET; + h.h_length = sizeof(in); + h.h_addr_list = (char**)addr_list; + break; + } else { + free(packet); + return 0; + } + } + + return &h; +} +#endif -- cgit v1.2.3