/* $Id: ares_gethostbyname.c,v 1.50 2009-11-02 11:55:53 yangtse Exp $ */ /* Copyright 1998 by the Massachusetts Institute of Technology. * * Permission to use, copy, modify, and distribute this * software and its documentation for any purpose and without * fee is hereby granted, provided that the above copyright * notice appear in all copies and that both that copyright * notice and this permission notice appear in supporting * documentation, and that the name of M.I.T. not be used in * advertising or publicity pertaining to distribution of the * software without specific, written prior permission. * M.I.T. makes no representations about the suitability of * this software for any purpose. It is provided "as is" * without express or implied warranty. */ #include "ares_setup.h" #ifdef HAVE_SYS_SOCKET_H # include <sys/socket.h> #endif #ifdef HAVE_NETINET_IN_H # include <netinet/in.h> #endif #ifdef HAVE_NETDB_H # include <netdb.h> #endif #ifdef HAVE_ARPA_INET_H # include <arpa/inet.h> #endif #ifdef HAVE_ARPA_NAMESER_H # include <arpa/nameser.h> #else # include "nameser.h" #endif #ifdef HAVE_ARPA_NAMESER_COMPAT_H # include <arpa/nameser_compat.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> #ifdef HAVE_STRINGS_H #include <strings.h> #endif #include "ares.h" #include "inet_net_pton.h" #include "bitncmp.h" #include "ares_private.h" #ifdef WATT32 #undef WIN32 #endif struct host_query { /* Arguments passed to ares_gethostbyname() */ ares_channel channel; char *name; ares_host_callback callback; void *arg; int sent_family; /* this family is what was is being used */ int want_family; /* this family is what is asked for in the API */ const char *remaining_lookups; int timeouts; }; static void next_lookup(struct host_query *hquery, int status_code); static void host_callback(void *arg, int status, int timeouts, unsigned char *abuf, int alen); static void end_hquery(struct host_query *hquery, int status, struct hostent *host); static int fake_hostent(const char *name, int family, ares_host_callback callback, void *arg); static int file_lookup(const char *name, int family, struct hostent **host); static void sort_addresses(struct hostent *host, const struct apattern *sortlist, int nsort); static void sort6_addresses(struct hostent *host, const struct apattern *sortlist, int nsort); static int get_address_index(const struct in_addr *addr, const struct apattern *sortlist, int nsort); static int get6_address_index(const struct in6_addr *addr, const struct apattern *sortlist, int nsort); void ares_gethostbyname(ares_channel channel, const char *name, int family, ares_host_callback callback, void *arg) { struct host_query *hquery; /* Right now we only know how to look up Internet addresses - and unspec means try both basically. */ switch (family) { case AF_INET: case AF_INET6: case AF_UNSPEC: break; default: callback(arg, ARES_ENOTIMP, 0, NULL); return; } if (fake_hostent(name, family, callback, arg)) return; /* Allocate and fill in the host query structure. */ hquery = malloc(sizeof(struct host_query)); if (!hquery) { callback(arg, ARES_ENOMEM, 0, NULL); return; } hquery->channel = channel; hquery->name = strdup(name); hquery->want_family = family; hquery->sent_family = -1; /* nothing is sent yet */ if (!hquery->name) { free(hquery); callback(arg, ARES_ENOMEM, 0, NULL); return; } hquery->callback = callback; hquery->arg = arg; hquery->remaining_lookups = channel->lookups; hquery->timeouts = 0; /* Start performing lookups according to channel->lookups. */ next_lookup(hquery, ARES_ECONNREFUSED /* initial error code */); } static void next_lookup(struct host_query *hquery, int status_code) { const char *p; struct hostent *host; int status = status_code; for (p = hquery->remaining_lookups; *p; p++) { switch (*p) { case 'b': /* DNS lookup */ hquery->remaining_lookups = p + 1; if ((hquery->want_family == AF_INET6) || (hquery->want_family == AF_UNSPEC)) { /* if inet6 or unspec, start out with AAAA */ hquery->sent_family = AF_INET6; ares_search(hquery->channel, hquery->name, C_IN, T_AAAA, host_callback, hquery); } else { hquery->sent_family = AF_INET; ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback, hquery); } return; case 'f': /* Host file lookup */ status = file_lookup(hquery->name, hquery->want_family, &host); /* this status check below previously checked for !ARES_ENOTFOUND, but we should not assume that this single error code is the one that can occur, as that is in fact no longer the case */ if (status == ARES_SUCCESS) { end_hquery(hquery, status, host); return; } status = status_code; /* Use original status code */ break; } } end_hquery(hquery, status, NULL); } static void host_callback(void *arg, int status, int timeouts, unsigned char *abuf, int alen) { struct host_query *hquery = (struct host_query *) arg; ares_channel channel = hquery->channel; struct hostent *host = NULL; hquery->timeouts += timeouts; if (status == ARES_SUCCESS) { if (hquery->sent_family == AF_INET) { status = ares_parse_a_reply(abuf, alen, &host, NULL, NULL); if (host && channel->nsort) sort_addresses(host, channel->sortlist, channel->nsort); } else if (hquery->sent_family == AF_INET6) { status = ares_parse_aaaa_reply(abuf, alen, &host, NULL, NULL); if (status == ARES_ENODATA || status == ARES_EBADRESP) { /* The query returned something but either there were no AAAA records (e.g. just CNAME) or the response was malformed. Try looking up A instead. We should possibly limit this attempt-next logic to AF_UNSPEC lookups only. */ hquery->sent_family = AF_INET; ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback, hquery); return; } if (host && channel->nsort) sort6_addresses(host, channel->sortlist, channel->nsort); } end_hquery(hquery, status, host); } else if ((status == ARES_ENODATA || status == ARES_EBADRESP || status == ARES_ETIMEOUT) && hquery->sent_family == AF_INET6) { /* The AAAA query yielded no useful result. Now look up an A instead. We should possibly limit this attempt-next logic to AF_UNSPEC lookups only. */ hquery->sent_family = AF_INET; ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback, hquery); } else if (status == ARES_EDESTRUCTION) end_hquery(hquery, status, NULL); else next_lookup(hquery, status); } static void end_hquery(struct host_query *hquery, int status, struct hostent *host) { hquery->callback(hquery->arg, status, hquery->timeouts, host); if (host) ares_free_hostent(host); free(hquery->name); free(hquery); } /* If the name looks like an IP address, fake up a host entry, end the * query immediately, and return true. Otherwise return false. */ static int fake_hostent(const char *name, int family, ares_host_callback callback, void *arg) { struct hostent hostent; char *aliases[1] = { NULL }; char *addrs[2]; int result = 0; struct in_addr in; struct in6_addr in6; if (family == AF_INET || family == AF_INET6) { /* It only looks like an IP address if it's all numbers and dots. */ int numdots = 0, valid = 1; const char *p; for (p = name; *p; p++) { if (!ISDIGIT(*p) && *p != '.') { valid = 0; break; } else if (*p == '.') { numdots++; } } /* if we don't have 3 dots, it is illegal * (although inet_addr doesn't think so). */ if (numdots != 3 || !valid) result = 0; else result = ((in.s_addr = inet_addr(name)) == INADDR_NONE ? 0 : 1); if (result) family = AF_INET; } if (family == AF_INET6) result = (ares_inet_pton(AF_INET6, name, &in6) < 1 ? 0 : 1); if (!result) return 0; if (family == AF_INET) { hostent.h_length = (int)sizeof(struct in_addr); addrs[0] = (char *)∈ } else if (family == AF_INET6) { hostent.h_length = (int)sizeof(struct in6_addr); addrs[0] = (char *)&in6; } /* Duplicate the name, to avoid a constness violation. */ hostent.h_name = strdup(name); if (!hostent.h_name) { callback(arg, ARES_ENOMEM, 0, NULL); return 1; } /* Fill in the rest of the host structure and terminate the query. */ addrs[1] = NULL; hostent.h_aliases = aliases; hostent.h_addrtype = family; hostent.h_addr_list = addrs; callback(arg, ARES_SUCCESS, 0, &hostent); free((char *)(hostent.h_name)); return 1; } /* This is an API method */ int ares_gethostbyname_file(ares_channel channel, const char *name, int family, struct hostent **host) { int result; /* We only take the channel to ensure that ares_init() been called. */ if(channel == NULL) { /* Anything will do, really. This seems fine, and is consistent with other error cases. */ *host = NULL; return ARES_ENOTFOUND; } /* Just chain to the internal implementation we use here; it's exactly * what we want. */ result = file_lookup(name, family, host); if(result != ARES_SUCCESS) { /* We guarantee a NULL hostent on failure. */ *host = NULL; } return result; } static int file_lookup(const char *name, int family, struct hostent **host) { FILE *fp; char **alias; int status; int error; #ifdef WIN32 char PATH_HOSTS[MAX_PATH]; if (IS_NT()) { char tmp[MAX_PATH]; HKEY hkeyHosts; if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ, &hkeyHosts) == ERROR_SUCCESS) { DWORD dwLength = MAX_PATH; RegQueryValueEx(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp, &dwLength); ExpandEnvironmentStrings(tmp, PATH_HOSTS, MAX_PATH); RegCloseKey(hkeyHosts); } } else GetWindowsDirectory(PATH_HOSTS, MAX_PATH); strcat(PATH_HOSTS, WIN_PATH_HOSTS); #elif defined(WATT32) extern const char *_w32_GetHostsFile (void); const char *PATH_HOSTS = _w32_GetHostsFile(); if (!PATH_HOSTS) return ARES_ENOTFOUND; #endif fp = fopen(PATH_HOSTS, "r"); if (!fp) { error = ERRNO; switch(error) { case ENOENT: case ESRCH: return ARES_ENOTFOUND; default: DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n", error, strerror(error))); DEBUGF(fprintf(stderr, "Error opening file: %s\n", PATH_HOSTS)); *host = NULL; return ARES_EFILE; } } while ((status = ares__get_hostent(fp, family, host)) == ARES_SUCCESS) { if (strcasecmp((*host)->h_name, name) == 0) break; for (alias = (*host)->h_aliases; *alias; alias++) { if (strcasecmp(*alias, name) == 0) break; } if (*alias) break; ares_free_hostent(*host); } fclose(fp); if (status == ARES_EOF) status = ARES_ENOTFOUND; if (status != ARES_SUCCESS) *host = NULL; return status; } static void sort_addresses(struct hostent *host, const struct apattern *sortlist, int nsort) { struct in_addr a1, a2; int i1, i2, ind1, ind2; /* This is a simple insertion sort, not optimized at all. i1 walks * through the address list, with the loop invariant that everything * to the left of i1 is sorted. In the loop body, the value at i1 is moved * back through the list (via i2) until it is in sorted order. */ for (i1 = 0; host->h_addr_list[i1]; i1++) { memcpy(&a1, host->h_addr_list[i1], sizeof(struct in_addr)); ind1 = get_address_index(&a1, sortlist, nsort); for (i2 = i1 - 1; i2 >= 0; i2--) { memcpy(&a2, host->h_addr_list[i2], sizeof(struct in_addr)); ind2 = get_address_index(&a2, sortlist, nsort); if (ind2 <= ind1) break; memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in_addr)); } memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in_addr)); } } /* Find the first entry in sortlist which matches addr. Return nsort * if none of them match. */ static int get_address_index(const struct in_addr *addr, const struct apattern *sortlist, int nsort) { int i; for (i = 0; i < nsort; i++) { if (sortlist[i].family != AF_INET) continue; if (sortlist[i].type == PATTERN_MASK) { if ((addr->s_addr & sortlist[i].mask.addr4.s_addr) == sortlist[i].addrV4.s_addr) break; } else { if (!ares_bitncmp(&addr->s_addr, &sortlist[i].addrV4.s_addr, sortlist[i].mask.bits)) break; } } return i; } static void sort6_addresses(struct hostent *host, const struct apattern *sortlist, int nsort) { struct in6_addr a1, a2; int i1, i2, ind1, ind2; /* This is a simple insertion sort, not optimized at all. i1 walks * through the address list, with the loop invariant that everything * to the left of i1 is sorted. In the loop body, the value at i1 is moved * back through the list (via i2) until it is in sorted order. */ for (i1 = 0; host->h_addr_list[i1]; i1++) { memcpy(&a1, host->h_addr_list[i1], sizeof(struct in6_addr)); ind1 = get6_address_index(&a1, sortlist, nsort); for (i2 = i1 - 1; i2 >= 0; i2--) { memcpy(&a2, host->h_addr_list[i2], sizeof(struct in6_addr)); ind2 = get6_address_index(&a2, sortlist, nsort); if (ind2 <= ind1) break; memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in6_addr)); } memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in6_addr)); } } /* Find the first entry in sortlist which matches addr. Return nsort * if none of them match. */ static int get6_address_index(const struct in6_addr *addr, const struct apattern *sortlist, int nsort) { int i; for (i = 0; i < nsort; i++) { if (sortlist[i].family != AF_INET6) continue; if (!ares_bitncmp(&addr->s6_addr, &sortlist[i].addrV6.s6_addr, sortlist[i].mask.bits)) break; } return i; }