diff options
Diffstat (limited to 'REORG.TODO/nscd/hstcache.c')
| -rw-r--r-- | REORG.TODO/nscd/hstcache.c | 619 |
1 files changed, 619 insertions, 0 deletions
diff --git a/REORG.TODO/nscd/hstcache.c b/REORG.TODO/nscd/hstcache.c new file mode 100644 index 0000000000..9f6ce979ac --- /dev/null +++ b/REORG.TODO/nscd/hstcache.c @@ -0,0 +1,619 @@ +/* Cache handling for host lookup. + Copyright (C) 1998-2017 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); +} |