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/* Cache handling for host lookup. Copyright (C) 1998-2005, 2006, 2007 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include <alloca.h> #include <assert.h> #include <errno.h> #include <error.h> #include <libintl.h> #include <netdb.h> #include <stdbool.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> #include <unistd.h> #include <arpa/inet.h> #include <arpa/nameser.h> #include <sys/mman.h> #include <stackinfo.h> #include "nscd.h" #include "dbg_log.h" #ifdef HAVE_SENDFILE # include <kernel-features.h> #endif /* This is the standard reply in case the service is disabled. */ static const hst_response_header disabled = { .version = NSCD_VERSION, .found = -1, .h_name_len = 0, .h_aliases_cnt = 0, .h_addrtype = -1, .h_length = -1, .h_addr_list_cnt = 0, .error = NETDB_INTERNAL }; /* This is the struct describing how to write this record. */ const struct iovec hst_iov_disabled = { .iov_base = (void *) &disabled, .iov_len = sizeof (disabled) }; /* This is the standard reply in case we haven't found the dataset. */ static const hst_response_header notfound = { .version = NSCD_VERSION, .found = 0, .h_name_len = 0, .h_aliases_cnt = 0, .h_addrtype = -1, .h_length = -1, .h_addr_list_cnt = 0, .error = HOST_NOT_FOUND }; static void cache_addhst (struct database_dyn *db, int fd, request_header *req, const void *key, struct hostent *hst, uid_t owner, struct hashentry *he, struct datahead *dh, int errval) { ssize_t total; ssize_t written; time_t t = time (NULL); /* We allocate all data in one memory block: the iov vector, the response header and the dataset itself. */ struct dataset { struct datahead head; hst_response_header resp; char strdata[0]; } *dataset; assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data)); if (hst == NULL) { if (he != NULL && errval == EAGAIN) { /* If we have an old record available but cannot find one now because the service is not available we keep the old record and make sure it does not get removed. */ if (reload_count != UINT_MAX) /* Do not reset the value if we never not reload the record. */ dh->nreloads = reload_count - 1; written = total = 0; } else { /* We have no data. This means we send the standard reply for this case. */ written = total = sizeof (notfound); if (fd != -1) written = TEMP_FAILURE_RETRY (send (fd, &notfound, total, MSG_NOSIGNAL)); dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len); /* If we cannot permanently store the result, so be it. */ if (dataset != NULL) { dataset->head.allocsize = sizeof (struct dataset) + req->key_len; dataset->head.recsize = total; dataset->head.notfound = true; dataset->head.nreloads = 0; dataset->head.usable = true; /* Compute the timeout time. */ dataset->head.timeout = t + db->negtimeout; /* This is the reply. */ memcpy (&dataset->resp, &notfound, total); /* Copy the key data. */ memcpy (dataset->strdata, key, req->key_len); /* If necessary, we also propagate the data to disk. */ if (db->persistent) { // XXX async OK? uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; msync ((void *) pval, ((uintptr_t) dataset & pagesize_m1) + sizeof (struct dataset) + req->key_len, MS_ASYNC); } /* Now get the lock to safely insert the records. */ pthread_rwlock_rdlock (&db->lock); if (cache_add (req->type, &dataset->strdata, req->key_len, &dataset->head, true, db, owner) < 0) /* Ensure the data can be recovered. */ dataset->head.usable = false; pthread_rwlock_unlock (&db->lock); /* Mark the old entry as obsolete. */ if (dh != NULL) dh->usable = false; } else ++db->head->addfailed; } } else { /* Determine the I/O structure. */ size_t h_name_len = strlen (hst->h_name) + 1; size_t h_aliases_cnt; uint32_t *h_aliases_len; size_t h_addr_list_cnt; int addr_list_type; char *addresses; char *aliases; char *key_copy = NULL; char *cp; size_t cnt; /* Determine the number of aliases. */ h_aliases_cnt = 0; for (cnt = 0; hst->h_aliases[cnt] != NULL; ++cnt) ++h_aliases_cnt; /* Determine the length of all aliases. */ h_aliases_len = (uint32_t *) alloca (h_aliases_cnt * sizeof (uint32_t)); total = 0; for (cnt = 0; cnt < h_aliases_cnt; ++cnt) { h_aliases_len[cnt] = strlen (hst->h_aliases[cnt]) + 1; total += h_aliases_len[cnt]; } /* Determine the number of addresses. */ h_addr_list_cnt = 0; for (cnt = 0; hst->h_addr_list[cnt]; ++cnt) ++h_addr_list_cnt; if (h_addr_list_cnt == 0) /* Invalid entry. */ return; total += (sizeof (struct dataset) + h_name_len + h_aliases_cnt * sizeof (uint32_t) + h_addr_list_cnt * hst->h_length); written = total; /* If we refill the cache, first assume the reconrd did not change. Allocate memory on the cache since it is likely discarded anyway. If it turns out to be necessary to have a new record we can still allocate real memory. */ bool alloca_used = false; dataset = NULL; /* If the record contains more than one IP address (used for load balancing etc) don't cache the entry. This is something the current cache handling cannot handle and it is more than questionable whether it is worthwhile complicating the cache handling just for handling such a special case. */ if (he == NULL && hst->h_addr_list[1] == NULL) { dataset = (struct dataset *) mempool_alloc (db, total + req->key_len); if (dataset == NULL) ++db->head->addfailed; } if (dataset == NULL) { /* We cannot permanently add the result in the moment. But we can provide the result as is. Store the data in some temporary memory. */ dataset = (struct dataset *) alloca (total + req->key_len); /* We cannot add this record to the permanent database. */ alloca_used = true; } dataset->head.allocsize = total + req->key_len; dataset->head.recsize = total - offsetof (struct dataset, resp); dataset->head.notfound = false; dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1); dataset->head.usable = true; /* Compute the timeout time. */ dataset->head.timeout = t + db->postimeout; dataset->resp.version = NSCD_VERSION; dataset->resp.found = 1; dataset->resp.h_name_len = h_name_len; dataset->resp.h_aliases_cnt = h_aliases_cnt; dataset->resp.h_addrtype = hst->h_addrtype; dataset->resp.h_length = hst->h_length; dataset->resp.h_addr_list_cnt = h_addr_list_cnt; dataset->resp.error = NETDB_SUCCESS; cp = dataset->strdata; cp = mempcpy (cp, hst->h_name, h_name_len); cp = mempcpy (cp, h_aliases_len, h_aliases_cnt * sizeof (uint32_t)); /* The normal addresses first. */ addresses = cp; for (cnt = 0; cnt < h_addr_list_cnt; ++cnt) cp = mempcpy (cp, hst->h_addr_list[cnt], hst->h_length); /* Then the aliases. */ aliases = cp; for (cnt = 0; cnt < h_aliases_cnt; ++cnt) cp = mempcpy (cp, hst->h_aliases[cnt], h_aliases_len[cnt]); assert (cp == dataset->strdata + total - offsetof (struct dataset, strdata)); /* If we are adding a GETHOSTBYNAME{,v6} entry we must be prepared that the answer we get from the NSS does not contain the key itself. This is the case if the resolver is used and the name is extended by the domainnames from /etc/resolv.conf. Therefore we explicitly add the name here. */ key_copy = memcpy (cp, key, req->key_len); /* Now we can determine whether on refill we have to create a new record or not. */ if (he != NULL) { assert (fd == -1); if (total + req->key_len == dh->allocsize && total - offsetof (struct dataset, resp) == dh->recsize && memcmp (&dataset->resp, dh->data, dh->allocsize - offsetof (struct dataset, resp)) == 0) { /* The data has not changed. We will just bump the timeout value. Note that the new record has been allocated on the stack and need not be freed. */ dh->timeout = dataset->head.timeout; ++dh->nreloads; } else { /* We have to create a new record. Just allocate appropriate memory and copy it. */ struct dataset *newp = (struct dataset *) mempool_alloc (db, total + req->key_len); if (newp != NULL) { /* Adjust pointers into the memory block. */ addresses = (char *) newp + (addresses - (char *) dataset); aliases = (char *) newp + (aliases - (char *) dataset); assert (key_copy != NULL); key_copy = (char *) newp + (key_copy - (char *) dataset); dataset = memcpy (newp, dataset, total + req->key_len); alloca_used = false; } /* Mark the old record as obsolete. */ dh->usable = false; } } else { /* We write the dataset before inserting it to the database since while inserting this thread might block and so would unnecessarily keep the receiver waiting. */ assert (fd != -1); #ifdef HAVE_SENDFILE if (__builtin_expect (db->mmap_used, 1) && !alloca_used) { assert (db->wr_fd != -1); assert ((char *) &dataset->resp > (char *) db->data); assert ((char *) &dataset->resp - (char *) db->head + total <= (sizeof (struct database_pers_head) + db->head->module * sizeof (ref_t) + db->head->data_size)); written = sendfileall (fd, db->wr_fd, (char *) &dataset->resp - (char *) db->head, total); # ifndef __ASSUME_SENDFILE if (written == -1 && errno == ENOSYS) goto use_write; # endif } else # ifndef __ASSUME_SENDFILE use_write: # endif #endif written = writeall (fd, &dataset->resp, total); } /* Add the record to the database. But only if it has not been stored on the stack. If the record contains more than one IP address (used for load balancing etc) don't cache the entry. This is something the current cache handling cannot handle and it is more than questionable whether it is worthwhile complicating the cache handling just for handling such a special case. */ if (! alloca_used) { /* If necessary, we also propagate the data to disk. */ if (db->persistent) { // XXX async OK? uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; msync ((void *) pval, ((uintptr_t) dataset & pagesize_m1) + total + req->key_len, MS_ASYNC); } addr_list_type = (hst->h_length == NS_INADDRSZ ? GETHOSTBYADDR : GETHOSTBYADDRv6); /* Now get the lock to safely insert the records. */ pthread_rwlock_rdlock (&db->lock); /* NB: the following code is really complicated. It has seemlingly duplicated code paths which do the same. The problem is that we always must add the hash table entry with the FIRST flag set first. Otherwise we get dangling pointers in case memory allocation fails. */ assert (hst->h_addr_list[1] == NULL); /* Avoid adding names if more than one address is available. See above for more info. */ assert (req->type == GETHOSTBYNAME || req->type == GETHOSTBYNAMEv6 || req->type == GETHOSTBYADDR || req->type == GETHOSTBYADDRv6); if (cache_add (req->type, key_copy, req->key_len, &dataset->head, true, db, owner) < 0) /* Could not allocate memory. Make sure the data gets discarded. */ dataset->head.usable = false; pthread_rwlock_unlock (&db->lock); } } if (__builtin_expect (written != total, 0) && debug_level > 0) { char buf[256]; dbg_log (_("short write in %s: %s"), __FUNCTION__, strerror_r (errno, buf, sizeof (buf))); } } static int lookup (int type, void *key, struct hostent *resultbufp, char *buffer, size_t buflen, struct hostent **hst) { if (type == GETHOSTBYNAME) return __gethostbyname2_r (key, AF_INET, resultbufp, buffer, buflen, hst, &h_errno); if (type == GETHOSTBYNAMEv6) return __gethostbyname2_r (key, AF_INET6, resultbufp, buffer, buflen, hst, &h_errno); if (type == GETHOSTBYADDR) return __gethostbyaddr_r (key, NS_INADDRSZ, AF_INET, resultbufp, buffer, buflen, hst, &h_errno); return __gethostbyaddr_r (key, NS_IN6ADDRSZ, AF_INET6, resultbufp, buffer, buflen, hst, &h_errno); } static void addhstbyX (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid, struct hashentry *he, struct datahead *dh) { /* Search for the entry matching the key. Please note that we don't look again in the table whether the dataset is now available. We simply insert it. It does not matter if it is in there twice. The pruning function only will look at the timestamp. */ int buflen = 1024; char *buffer = (char *) alloca (buflen); struct hostent resultbuf; struct hostent *hst; bool use_malloc = false; int errval = 0; if (__builtin_expect (debug_level > 0, 0)) { const char *str; char buf[INET6_ADDRSTRLEN + 1]; if (req->type == GETHOSTBYNAME || req->type == GETHOSTBYNAMEv6) str = key; else str = inet_ntop (req->type == GETHOSTBYADDR ? AF_INET : AF_INET6, key, buf, sizeof (buf)); if (he == NULL) dbg_log (_("Haven't found \"%s\" in hosts cache!"), (char *) str); else dbg_log (_("Reloading \"%s\" in hosts cache!"), (char *) str); } while (lookup (req->type, key, &resultbuf, buffer, buflen, &hst) != 0 && h_errno == NETDB_INTERNAL && (errval = errno) == ERANGE) { errno = 0; if (__builtin_expect (buflen > 32768, 0)) { char *old_buffer = buffer; buflen *= 2; buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen); if (buffer == NULL) { /* We ran out of memory. We cannot do anything but sending a negative response. In reality this should never happen. */ hst = NULL; buffer = old_buffer; /* We set the error to indicate this is (possibly) a temporary error and that it does not mean the entry is not available at all. */ errval = EAGAIN; break; } use_malloc = true; } else /* Allocate a new buffer on the stack. If possible combine it with the previously allocated buffer. */ buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen); } cache_addhst (db, fd, req, key, hst, uid, he, dh, h_errno == TRY_AGAIN ? errval : 0); if (use_malloc) free (buffer); } void addhstbyname (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid) { addhstbyX (db, fd, req, key, uid, NULL, NULL); } void readdhstbyname (struct database_dyn *db, struct hashentry *he, struct datahead *dh) { request_header req = { .type = GETHOSTBYNAME, .key_len = he->len }; addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); } void addhstbyaddr (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid) { addhstbyX (db, fd, req, key, uid, NULL, NULL); } void readdhstbyaddr (struct database_dyn *db, struct hashentry *he, struct datahead *dh) { request_header req = { .type = GETHOSTBYADDR, .key_len = he->len }; addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); } void addhstbynamev6 (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid) { addhstbyX (db, fd, req, key, uid, NULL, NULL); } void readdhstbynamev6 (struct database_dyn *db, struct hashentry *he, struct datahead *dh) { request_header req = { .type = GETHOSTBYNAMEv6, .key_len = he->len }; addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); } void addhstbyaddrv6 (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid) { addhstbyX (db, fd, req, key, uid, NULL, NULL); } void readdhstbyaddrv6 (struct database_dyn *db, struct hashentry *he, struct datahead *dh) { request_header req = { .type = GETHOSTBYADDRv6, .key_len = he->len }; addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); }


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