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/* Cache handling for services lookup. Copyright (C) 2007 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper <drepper@drepper.com>, 2007. 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 <libintl.h> #include <netdb.h> #include <unistd.h> #include <sys/mman.h> #include "nscd.h" #include "dbg_log.h" /* This is the standard reply in case the service is disabled. */ static const serv_response_header disabled = { .version = NSCD_VERSION, .found = -1, .s_name_len = 0, .s_proto_len = 0, .s_aliases_cnt = 0, .s_port = -1 }; /* This is the struct describing how to write this record. */ const struct iovec serv_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 serv_response_header notfound = { .version = NSCD_VERSION, .found = 0, .s_name_len = 0, .s_proto_len = 0, .s_aliases_cnt = 0, .s_port = -1 }; static void cache_addserv (struct database_dyn *db, int fd, request_header *req, const void *key, struct servent *serv, 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; serv_response_header resp; char strdata[0]; } *dataset; assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data)); if (serv == 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. */ total = sizeof (notfound); written = TEMP_FAILURE_RETRY (send (fd, ¬found, 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, ¬found, 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 s_name_len = strlen (serv->s_name) + 1; size_t s_proto_len = strlen (serv->s_proto) + 1; uint32_t *s_aliases_len; size_t s_aliases_cnt; char *aliases; char *cp; size_t cnt; /* Determine the number of aliases. */ s_aliases_cnt = 0; for (cnt = 0; serv->s_aliases[cnt] != NULL; ++cnt) ++s_aliases_cnt; /* Determine the length of all aliases. */ s_aliases_len = (uint32_t *) alloca (s_aliases_cnt * sizeof (uint32_t)); total = 0; for (cnt = 0; cnt < s_aliases_cnt; ++cnt) { s_aliases_len[cnt] = strlen (serv->s_aliases[cnt]) + 1; total += s_aliases_len[cnt]; } total += (sizeof (struct dataset) + s_name_len + s_proto_len + s_aliases_cnt * sizeof (uint32_t)); 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 (he == 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.s_name_len = s_name_len; dataset->resp.s_proto_len = s_proto_len; dataset->resp.s_port = serv->s_port; dataset->resp.s_aliases_cnt = s_aliases_cnt; cp = dataset->strdata; cp = mempcpy (cp, serv->s_name, s_name_len); cp = mempcpy (cp, serv->s_proto, s_proto_len); cp = mempcpy (cp, s_aliases_len, s_aliases_cnt * sizeof (uint32_t)); /* Then the aliases. */ aliases = cp; for (cnt = 0; cnt < s_aliases_cnt; ++cnt) cp = mempcpy (cp, serv->s_aliases[cnt], s_aliases_len[cnt]); assert (cp == dataset->strdata + total - offsetof (struct dataset, strdata)); char *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. */ 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 (! 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); } /* Now get the lock to safely insert the records. */ pthread_rwlock_rdlock (&db->lock); 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, char *key, struct servent *resultbufp, char *buffer, size_t buflen, struct servent **serv) { char *proto = strrchr (key, '/'); if (proto != NULL && proto != key) { key = strndupa (key, proto - key); if (proto[1] == '\0') proto = NULL; else ++proto; } if (type == GETSERVBYNAME) return __getservbyname_r (key, proto, resultbufp, buffer, buflen, serv); assert (type == GETSERVBYPORT); return __getservbyport_r (atol (key), proto, resultbufp, buffer, buflen, serv); } static void addservbyX (struct database_dyn *db, int fd, request_header *req, char *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. */ size_t buflen = 1024; char *buffer = (char *) alloca (buflen); struct servent resultbuf; struct servent *serv; bool use_malloc = false; int errval = 0; if (__builtin_expect (debug_level > 0, 0)) { if (he == NULL) dbg_log (_("Haven't found \"%s\" in services cache!"), key); else dbg_log (_("Reloading \"%s\" in services cache!"), key); } while (lookup (req->type, key, &resultbuf, buffer, buflen, &serv) != 0 && (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. */ serv = 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_addserv (db, fd, req, key, serv, uid, he, dh, errval); if (use_malloc) free (buffer); } void addservbyname (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid) { addservbyX (db, fd, req, key, uid, NULL, NULL); } void readdservbyname (struct database_dyn *db, struct hashentry *he, struct datahead *dh) { request_header req = { .type = GETSERVBYNAME, .key_len = he->len }; addservbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); } void addservbyport (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid) { addservbyX (db, fd, req, key, uid, NULL, NULL); } void readdservbyport (struct database_dyn *db, struct hashentry *he, struct datahead *dh) { request_header req = { .type = GETSERVBYPORT, .key_len = he->len }; addservbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); }
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