diff options
Diffstat (limited to 'ares_search.c')
| -rw-r--r-- | ares_search.c | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/ares_search.c b/ares_search.c new file mode 100644 index 0000000..1877c19 --- /dev/null +++ b/ares_search.c @@ -0,0 +1,321 @@ + +/* 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" + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <ctype.h> + +#ifdef HAVE_STRINGS_H +# include <strings.h> +#endif + +#include "ares.h" +#include "ares_private.h" + +struct search_query { + /* Arguments passed to ares_search */ + ares_channel channel; + char *name; /* copied into an allocated buffer */ + int dnsclass; + int type; + ares_callback callback; + void *arg; + + int status_as_is; /* error status from trying as-is */ + int next_domain; /* next search domain to try */ + int trying_as_is; /* current query is for name as-is */ + int timeouts; /* number of timeouts we saw for this request */ + int ever_got_nodata; /* did we ever get ARES_ENODATA along the way? */ +}; + +static void search_callback(void *arg, int status, int timeouts, + unsigned char *abuf, int alen); +static void end_squery(struct search_query *squery, int status, + unsigned char *abuf, int alen); +static int cat_domain(const char *name, const char *domain, char **s); +static int single_domain(ares_channel channel, const char *name, char **s); + +void ares_search(ares_channel channel, const char *name, int dnsclass, + int type, ares_callback callback, void *arg) +{ + struct search_query *squery; + char *s; + const char *p; + int status, ndots; + + /* If name only yields one domain to search, then we don't have + * to keep extra state, so just do an ares_query(). + */ + status = single_domain(channel, name, &s); + if (status != ARES_SUCCESS) + { + callback(arg, status, 0, NULL, 0); + return; + } + if (s) + { + ares_query(channel, s, dnsclass, type, callback, arg); + free(s); + return; + } + + /* Allocate a search_query structure to hold the state necessary for + * doing multiple lookups. + */ + squery = malloc(sizeof(struct search_query)); + if (!squery) + { + callback(arg, ARES_ENOMEM, 0, NULL, 0); + return; + } + squery->channel = channel; + squery->name = strdup(name); + if (!squery->name) + { + free(squery); + callback(arg, ARES_ENOMEM, 0, NULL, 0); + return; + } + squery->dnsclass = dnsclass; + squery->type = type; + squery->status_as_is = -1; + squery->callback = callback; + squery->arg = arg; + squery->timeouts = 0; + squery->ever_got_nodata = 0; + + /* Count the number of dots in name. */ + ndots = 0; + for (p = name; *p; p++) + { + if (*p == '.') + ndots++; + } + + /* If ndots is at least the channel ndots threshold (usually 1), + * then we try the name as-is first. Otherwise, we try the name + * as-is last. + */ + if (ndots >= channel->ndots) + { + /* Try the name as-is first. */ + squery->next_domain = 0; + squery->trying_as_is = 1; + ares_query(channel, name, dnsclass, type, search_callback, squery); + } + else + { + /* Try the name as-is last; start with the first search domain. */ + squery->next_domain = 1; + squery->trying_as_is = 0; + status = cat_domain(name, channel->domains[0], &s); + if (status == ARES_SUCCESS) + { + ares_query(channel, s, dnsclass, type, search_callback, squery); + free(s); + } + else + { + /* failed, free the malloc()ed memory */ + free(squery->name); + free(squery); + callback(arg, status, 0, NULL, 0); + } + } +} + +static void search_callback(void *arg, int status, int timeouts, + unsigned char *abuf, int alen) +{ + struct search_query *squery = (struct search_query *) arg; + ares_channel channel = squery->channel; + char *s; + + squery->timeouts += timeouts; + + /* Stop searching unless we got a non-fatal error. */ + if (status != ARES_ENODATA && status != ARES_ESERVFAIL + && status != ARES_ENOTFOUND) + end_squery(squery, status, abuf, alen); + else + { + /* Save the status if we were trying as-is. */ + if (squery->trying_as_is) + squery->status_as_is = status; + + /* + * If we ever get ARES_ENODATA along the way, record that; if the search + * should run to the very end and we got at least one ARES_ENODATA, + * then callers like ares_gethostbyname() may want to try a T_A search + * even if the last domain we queried for T_AAAA resource records + * returned ARES_ENOTFOUND. + */ + if (status == ARES_ENODATA) + squery->ever_got_nodata = 1; + + if (squery->next_domain < channel->ndomains) + { + /* Try the next domain. */ + status = cat_domain(squery->name, + channel->domains[squery->next_domain], &s); + if (status != ARES_SUCCESS) + end_squery(squery, status, NULL, 0); + else + { + squery->trying_as_is = 0; + squery->next_domain++; + ares_query(channel, s, squery->dnsclass, squery->type, + search_callback, squery); + free(s); + } + } + else if (squery->status_as_is == -1) + { + /* Try the name as-is at the end. */ + squery->trying_as_is = 1; + ares_query(channel, squery->name, squery->dnsclass, squery->type, + search_callback, squery); + } + else { + if (squery->status_as_is == ARES_ENOTFOUND && squery->ever_got_nodata) { + end_squery(squery, ARES_ENODATA, NULL, 0); + } + else + end_squery(squery, squery->status_as_is, NULL, 0); + } + } +} + +static void end_squery(struct search_query *squery, int status, + unsigned char *abuf, int alen) +{ + squery->callback(squery->arg, status, squery->timeouts, abuf, alen); + free(squery->name); + free(squery); +} + +/* Concatenate two domains. */ +static int cat_domain(const char *name, const char *domain, char **s) +{ + size_t nlen = strlen(name); + size_t dlen = strlen(domain); + + *s = malloc(nlen + 1 + dlen + 1); + if (!*s) + return ARES_ENOMEM; + memcpy(*s, name, nlen); + (*s)[nlen] = '.'; + memcpy(*s + nlen + 1, domain, dlen); + (*s)[nlen + 1 + dlen] = 0; + return ARES_SUCCESS; +} + +/* Determine if this name only yields one query. If it does, set *s to + * the string we should query, in an allocated buffer. If not, set *s + * to NULL. + */ +static int single_domain(ares_channel channel, const char *name, char **s) +{ + size_t len = strlen(name); + const char *hostaliases; + FILE *fp; + char *line = NULL; + int status; + size_t linesize; + const char *p, *q; + int error; + + /* If the name contains a trailing dot, then the single query is the name + * sans the trailing dot. + */ + if (name[len - 1] == '.') + { + *s = strdup(name); + return (*s) ? ARES_SUCCESS : ARES_ENOMEM; + } + + if (!(channel->flags & ARES_FLAG_NOALIASES) && !strchr(name, '.')) + { + /* The name might be a host alias. */ + hostaliases = getenv("HOSTALIASES"); + if (hostaliases) + { + fp = fopen(hostaliases, "r"); + if (fp) + { + while ((status = ares__read_line(fp, &line, &linesize)) + == ARES_SUCCESS) + { + if (strncasecmp(line, name, len) != 0 || + !ISSPACE(line[len])) + continue; + p = line + len; + while (ISSPACE(*p)) + p++; + if (*p) + { + q = p + 1; + while (*q && !ISSPACE(*q)) + q++; + *s = malloc(q - p + 1); + if (*s) + { + memcpy(*s, p, q - p); + (*s)[q - p] = 0; + } + free(line); + fclose(fp); + return (*s) ? ARES_SUCCESS : ARES_ENOMEM; + } + } + free(line); + fclose(fp); + if (status != ARES_SUCCESS && status != ARES_EOF) + return status; + } + else + { + error = ERRNO; + switch(error) + { + case ENOENT: + case ESRCH: + break; + default: + DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n", + error, strerror(error))); + DEBUGF(fprintf(stderr, "Error opening file: %s\n", + hostaliases)); + *s = NULL; + return ARES_EFILE; + } + } + } + } + + if (channel->flags & ARES_FLAG_NOSEARCH || channel->ndomains == 0) + { + /* No domain search to do; just try the name as-is. */ + *s = strdup(name); + return (*s) ? ARES_SUCCESS : ARES_ENOMEM; + } + + *s = NULL; + return ARES_SUCCESS; +} |