| /* Cache handling for host lookup. |
| Copyright (C) 1998-2016 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 as published |
| by the Free Software Foundation; version 2 of the License, or |
| (at your option) any later version. |
| |
| 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, see <http://www.gnu.org/licenses/>. */ |
| |
| #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 <stdint.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 |
| }; |
| |
| |
| /* This is the standard reply in case there are temporary problems. */ |
| static const hst_response_header tryagain = |
| { |
| .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 = TRY_AGAIN |
| }; |
| |
| |
| static time_t |
| cache_addhst (struct database_dyn *db, int fd, request_header *req, |
| const void *key, struct hostent *hst, uid_t owner, |
| struct hashentry *const he, struct datahead *dh, int errval, |
| int32_t ttl) |
| { |
| bool all_written = true; |
| 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)); |
| |
| time_t timeout = MAX_TIMEOUT_VALUE; |
| 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; |
| |
| /* Reload with the same time-to-live value. */ |
| timeout = dh->timeout = t + dh->ttl; |
| } |
| else |
| { |
| /* We have no data. This means we send the standard reply for this |
| case. Possibly this is only temporary. */ |
| ssize_t total = sizeof (notfound); |
| assert (sizeof (notfound) == sizeof (tryagain)); |
| |
| const hst_response_header *resp = (errval == EAGAIN |
| ? &tryagain : ¬found); |
| |
| if (fd != -1 && |
| TEMP_FAILURE_RETRY (send (fd, resp, total, |
| MSG_NOSIGNAL)) != total) |
| all_written = false; |
| |
| /* If we have a transient error or cannot permanently store |
| the result, so be it. */ |
| if (errval == EAGAIN || __builtin_expect (db->negtimeout == 0, 0)) |
| { |
| /* Mark the old entry as obsolete. */ |
| if (dh != NULL) |
| dh->usable = false; |
| } |
| else if ((dataset = mempool_alloc (db, (sizeof (struct dataset) |
| + req->key_len), 1)) != NULL) |
| { |
| timeout = datahead_init_neg (&dataset->head, |
| (sizeof (struct dataset) |
| + req->key_len), total, |
| (ttl == INT32_MAX |
| ? db->negtimeout : ttl)); |
| |
| /* This is the reply. */ |
| memcpy (&dataset->resp, resp, 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); |
| } |
| |
| (void) cache_add (req->type, &dataset->strdata, req->key_len, |
| &dataset->head, true, db, owner, he == NULL); |
| |
| pthread_rwlock_unlock (&db->lock); |
| |
| /* Mark the old entry as obsolete. */ |
| if (dh != NULL) |
| dh->usable = false; |
| } |
| } |
| } |
| 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; |
| char *addresses; |
| char *aliases; |
| char *key_copy = NULL; |
| char *cp; |
| size_t cnt; |
| ssize_t total; |
| |
| /* 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; |
| while (hst->h_addr_list[h_addr_list_cnt] != NULL) |
| ++h_addr_list_cnt; |
| |
| if (h_addr_list_cnt == 0) |
| /* Invalid entry. */ |
| return MAX_TIMEOUT_VALUE; |
| |
| total += (sizeof (struct dataset) |
| + h_name_len |
| + h_aliases_cnt * sizeof (uint32_t) |
| + h_addr_list_cnt * hst->h_length); |
| |
| /* 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 && h_addr_list_cnt == 1) |
| dataset = (struct dataset *) mempool_alloc (db, total + req->key_len, |
| 1); |
| |
| 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; |
| } |
| |
| timeout = datahead_init_pos (&dataset->head, total + req->key_len, |
| total - offsetof (struct dataset, resp), |
| he == NULL ? 0 : dh->nreloads + 1, |
| ttl == INT32_MAX ? db->postimeout : ttl); |
| |
| 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; |
| |
| /* Make sure there is no gap. */ |
| assert ((char *) (&dataset->resp.error + 1) == dataset->strdata); |
| |
| 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); |
| |
| assert ((char *) &dataset->resp + dataset->head.recsize == cp); |
| |
| /* 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. */ |
| assert (h_addr_list_cnt == 1); |
| dh->ttl = dataset->head.ttl; |
| dh->timeout = dataset->head.timeout; |
| ++dh->nreloads; |
| } |
| else |
| { |
| if (h_addr_list_cnt == 1) |
| { |
| /* 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, |
| 1); |
| 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 - (char *) db->head |
| + total |
| <= (sizeof (struct database_pers_head) |
| + db->head->module * sizeof (ref_t) |
| + db->head->data_size)); |
| ssize_t written = sendfileall (fd, db->wr_fd, |
| (char *) &dataset->resp |
| - (char *) db->head, |
| dataset->head.recsize); |
| if (written != dataset->head.recsize) |
| { |
| # ifndef __ASSUME_SENDFILE |
| if (written == -1 && errno == ENOSYS) |
| goto use_write; |
| # endif |
| all_written = false; |
| } |
| } |
| else |
| # ifndef __ASSUME_SENDFILE |
| use_write: |
| # endif |
| #endif |
| if (writeall (fd, &dataset->resp, dataset->head.recsize) |
| != dataset->head.recsize) |
| all_written = false; |
| } |
| |
| /* 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); |
| } |
| |
| /* 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); |
| |
| (void) cache_add (req->type, key_copy, req->key_len, |
| &dataset->head, true, db, owner, he == NULL); |
| |
| pthread_rwlock_unlock (&db->lock); |
| } |
| } |
| |
| if (__builtin_expect (!all_written, 0) && debug_level > 0) |
| { |
| char buf[256]; |
| dbg_log (_("short write in %s: %s"), __FUNCTION__, |
| strerror_r (errno, buf, sizeof (buf))); |
| } |
| |
| return timeout; |
| } |
| |
| |
| static int |
| lookup (int type, void *key, struct hostent *resultbufp, char *buffer, |
| size_t buflen, struct hostent **hst, int32_t *ttlp) |
| { |
| if (type == GETHOSTBYNAME) |
| return __gethostbyname3_r (key, AF_INET, resultbufp, buffer, buflen, hst, |
| &h_errno, ttlp, NULL); |
| if (type == GETHOSTBYNAMEv6) |
| return __gethostbyname3_r (key, AF_INET6, resultbufp, buffer, buflen, hst, |
| &h_errno, ttlp, NULL); |
| if (type == GETHOSTBYADDR) |
| return __gethostbyaddr2_r (key, NS_INADDRSZ, AF_INET, resultbufp, buffer, |
| buflen, hst, &h_errno, ttlp); |
| return __gethostbyaddr2_r (key, NS_IN6ADDRSZ, AF_INET6, resultbufp, buffer, |
| buflen, hst, &h_errno, ttlp); |
| } |
| |
| |
| static time_t |
| 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; |
| int32_t ttl = INT32_MAX; |
| |
| if (__glibc_unlikely (debug_level > 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, &ttl) != 0 |
| && h_errno == NETDB_INTERNAL |
| && (errval = errno) == ERANGE) |
| { |
| errno = 0; |
| |
| if (__glibc_unlikely (buflen > 32768)) |
| { |
| 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. */ |
| h_errno = TRY_AGAIN; |
| 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); |
| } |
| |
| time_t timeout = cache_addhst (db, fd, req, key, hst, uid, he, dh, |
| h_errno == TRY_AGAIN ? errval : 0, ttl); |
| |
| if (use_malloc) |
| free (buffer); |
| |
| return timeout; |
| } |
| |
| |
| void |
| addhstbyname (struct database_dyn *db, int fd, request_header *req, |
| void *key, uid_t uid) |
| { |
| addhstbyX (db, fd, req, key, uid, NULL, NULL); |
| } |
| |
| |
| time_t |
| readdhstbyname (struct database_dyn *db, struct hashentry *he, |
| struct datahead *dh) |
| { |
| request_header req = |
| { |
| .type = GETHOSTBYNAME, |
| .key_len = he->len |
| }; |
| |
| return 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); |
| } |
| |
| |
| time_t |
| readdhstbyaddr (struct database_dyn *db, struct hashentry *he, |
| struct datahead *dh) |
| { |
| request_header req = |
| { |
| .type = GETHOSTBYADDR, |
| .key_len = he->len |
| }; |
| |
| return 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); |
| } |
| |
| |
| time_t |
| readdhstbynamev6 (struct database_dyn *db, struct hashentry *he, |
| struct datahead *dh) |
| { |
| request_header req = |
| { |
| .type = GETHOSTBYNAMEv6, |
| .key_len = he->len |
| }; |
| |
| return 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); |
| } |
| |
| |
| time_t |
| readdhstbyaddrv6 (struct database_dyn *db, struct hashentry *he, |
| struct datahead *dh) |
| { |
| request_header req = |
| { |
| .type = GETHOSTBYADDRv6, |
| .key_len = he->len |
| }; |
| |
| return addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); |
| } |