diff options
Diffstat (limited to 'REORG.TODO/nscd/nscd_helper.c')
| -rw-r--r-- | REORG.TODO/nscd/nscd_helper.c | 564 |
1 files changed, 564 insertions, 0 deletions
diff --git a/REORG.TODO/nscd/nscd_helper.c b/REORG.TODO/nscd/nscd_helper.c new file mode 100644 index 0000000000..22905d0b83 --- /dev/null +++ b/REORG.TODO/nscd/nscd_helper.c @@ -0,0 +1,564 @@ +/* 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. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <assert.h> +#include <errno.h> +#include <fcntl.h> +#include <stdbool.h> +#include <stddef.h> +#include <stdlib.h> +#include <string.h> +#include <time.h> +#include <unistd.h> +#include <stdint.h> +#include <sys/mman.h> +#include <sys/poll.h> +#include <sys/socket.h> +#include <sys/stat.h> +#include <sys/time.h> +#include <sys/uio.h> +#include <sys/un.h> +#include <not-cancel.h> +#include <nis/rpcsvc/nis.h> +#include <kernel-features.h> + +#include "nscd-client.h" + + +/* Extra time we wait if the socket is still receiving data. This + value is in milliseconds. Note that the other side is nscd on the + local machine and it is already transmitting data. So the wait + time need not be long. */ +#define EXTRA_RECEIVE_TIME 200 + + +static int +wait_on_socket (int sock, long int usectmo) +{ + struct pollfd fds[1]; + fds[0].fd = sock; + fds[0].events = POLLIN | POLLERR | POLLHUP; + int n = __poll (fds, 1, usectmo); + if (n == -1 && __builtin_expect (errno == EINTR, 0)) + { + /* Handle the case where the poll() call is interrupted by a + signal. We cannot just use TEMP_FAILURE_RETRY since it might + lead to infinite loops. */ + struct timeval now; + (void) __gettimeofday (&now, NULL); + long int end = now.tv_sec * 1000 + usectmo + (now.tv_usec + 500) / 1000; + long int timeout = usectmo; + while (1) + { + n = __poll (fds, 1, timeout); + if (n != -1 || errno != EINTR) + break; + + /* Recompute the timeout time. */ + (void) __gettimeofday (&now, NULL); + timeout = end - (now.tv_sec * 1000 + (now.tv_usec + 500) / 1000); + } + } + + return n; +} + + +ssize_t +__readall (int fd, void *buf, size_t len) +{ + size_t n = len; + ssize_t ret; + do + { + again: + ret = TEMP_FAILURE_RETRY (__read (fd, buf, n)); + if (ret <= 0) + { + if (__builtin_expect (ret < 0 && errno == EAGAIN, 0) + /* The socket is still receiving data. Wait a bit more. */ + && wait_on_socket (fd, EXTRA_RECEIVE_TIME) > 0) + goto again; + + break; + } + buf = (char *) buf + ret; + n -= ret; + } + while (n > 0); + return ret < 0 ? ret : len - n; +} + + +ssize_t +__readvall (int fd, const struct iovec *iov, int iovcnt) +{ + ssize_t ret = TEMP_FAILURE_RETRY (__readv (fd, iov, iovcnt)); + if (ret <= 0) + { + if (__glibc_likely (ret == 0 || errno != EAGAIN)) + /* A genuine error or no data to read. */ + return ret; + + /* The data has not all yet been received. Do as if we have not + read anything yet. */ + ret = 0; + } + + size_t total = 0; + for (int i = 0; i < iovcnt; ++i) + total += iov[i].iov_len; + + if (ret < total) + { + struct iovec iov_buf[iovcnt]; + ssize_t r = ret; + + struct iovec *iovp = memcpy (iov_buf, iov, iovcnt * sizeof (*iov)); + do + { + while (iovp->iov_len <= r) + { + r -= iovp->iov_len; + --iovcnt; + ++iovp; + } + iovp->iov_base = (char *) iovp->iov_base + r; + iovp->iov_len -= r; + again: + r = TEMP_FAILURE_RETRY (__readv (fd, iovp, iovcnt)); + if (r <= 0) + { + if (__builtin_expect (r < 0 && errno == EAGAIN, 0) + /* The socket is still receiving data. Wait a bit more. */ + && wait_on_socket (fd, EXTRA_RECEIVE_TIME) > 0) + goto again; + + break; + } + ret += r; + } + while (ret < total); + if (r < 0) + ret = r; + } + return ret; +} + + +static int +open_socket (request_type type, const char *key, size_t keylen) +{ + int sock; + + sock = __socket (PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0); + if (sock < 0) + return -1; + + size_t real_sizeof_reqdata = sizeof (request_header) + keylen; + struct + { + request_header req; + char key[]; + } *reqdata = alloca (real_sizeof_reqdata); + + struct sockaddr_un sun; + sun.sun_family = AF_UNIX; + strcpy (sun.sun_path, _PATH_NSCDSOCKET); + if (__connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0 + && errno != EINPROGRESS) + goto out; + + reqdata->req.version = NSCD_VERSION; + reqdata->req.type = type; + reqdata->req.key_len = keylen; + + memcpy (reqdata->key, key, keylen); + + bool first_try = true; + struct timeval tvend; + /* Fake initializing tvend. */ + asm ("" : "=m" (tvend)); + while (1) + { +#ifndef MSG_NOSIGNAL +# define MSG_NOSIGNAL 0 +#endif + ssize_t wres = TEMP_FAILURE_RETRY (__send (sock, reqdata, + real_sizeof_reqdata, + MSG_NOSIGNAL)); + if (__glibc_likely (wres == (ssize_t) real_sizeof_reqdata)) + /* We managed to send the request. */ + return sock; + + if (wres != -1 || errno != EAGAIN) + /* Something is really wrong, no chance to continue. */ + break; + + /* The daemon is busy wait for it. */ + int to; + struct timeval now; + (void) __gettimeofday (&now, NULL); + if (first_try) + { + tvend.tv_usec = now.tv_usec; + tvend.tv_sec = now.tv_sec + 5; + to = 5 * 1000; + first_try = false; + } + else + to = ((tvend.tv_sec - now.tv_sec) * 1000 + + (tvend.tv_usec - now.tv_usec) / 1000); + + struct pollfd fds[1]; + fds[0].fd = sock; + fds[0].events = POLLOUT | POLLERR | POLLHUP; + if (__poll (fds, 1, to) <= 0) + /* The connection timed out or broke down. */ + break; + + /* We try to write again. */ + } + + out: + close_not_cancel_no_status (sock); + + return -1; +} + + +void +__nscd_unmap (struct mapped_database *mapped) +{ + assert (mapped->counter == 0); + __munmap ((void *) mapped->head, mapped->mapsize); + free (mapped); +} + + +/* Try to get a file descriptor for the shared meory segment + containing the database. */ +struct mapped_database * +__nscd_get_mapping (request_type type, const char *key, + struct mapped_database **mappedp) +{ + struct mapped_database *result = NO_MAPPING; +#ifdef SCM_RIGHTS + const size_t keylen = strlen (key) + 1; + int saved_errno = errno; + + int mapfd = -1; + char resdata[keylen]; + + /* Open a socket and send the request. */ + int sock = open_socket (type, key, keylen); + if (sock < 0) + goto out; + + /* Room for the data sent along with the file descriptor. We expect + the key name back. */ + uint64_t mapsize; + struct iovec iov[2]; + iov[0].iov_base = resdata; + iov[0].iov_len = keylen; + iov[1].iov_base = &mapsize; + iov[1].iov_len = sizeof (mapsize); + + union + { + struct cmsghdr hdr; + char bytes[CMSG_SPACE (sizeof (int))]; + } buf; + struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 2, + .msg_control = buf.bytes, + .msg_controllen = sizeof (buf) }; + struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg); + + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_RIGHTS; + cmsg->cmsg_len = CMSG_LEN (sizeof (int)); + + /* This access is well-aligned since BUF is correctly aligned for an + int and CMSG_DATA preserves this alignment. */ + memset (CMSG_DATA (cmsg), '\xff', sizeof (int)); + + msg.msg_controllen = cmsg->cmsg_len; + + if (wait_on_socket (sock, 5 * 1000) <= 0) + goto out_close2; + +# ifndef MSG_CMSG_CLOEXEC +# define MSG_CMSG_CLOEXEC 0 +# endif + ssize_t n = TEMP_FAILURE_RETRY (__recvmsg (sock, &msg, MSG_CMSG_CLOEXEC)); + + if (__builtin_expect (CMSG_FIRSTHDR (&msg) == NULL + || (CMSG_FIRSTHDR (&msg)->cmsg_len + != CMSG_LEN (sizeof (int))), 0)) + goto out_close2; + + int *ip = (void *) CMSG_DATA (cmsg); + mapfd = *ip; + + if (__glibc_unlikely (n != keylen && n != keylen + sizeof (mapsize))) + goto out_close; + + if (__glibc_unlikely (strcmp (resdata, key) != 0)) + goto out_close; + + if (__glibc_unlikely (n == keylen)) + { + struct stat64 st; + if (__builtin_expect (fstat64 (mapfd, &st) != 0, 0) + || __builtin_expect (st.st_size < sizeof (struct database_pers_head), + 0)) + goto out_close; + + mapsize = st.st_size; + } + + /* The file is large enough, map it now. */ + void *mapping = __mmap (NULL, mapsize, PROT_READ, MAP_SHARED, mapfd, 0); + if (__glibc_likely (mapping != MAP_FAILED)) + { + /* Check whether the database is correct and up-to-date. */ + struct database_pers_head *head = mapping; + + if (__builtin_expect (head->version != DB_VERSION, 0) + || __builtin_expect (head->header_size != sizeof (*head), 0) + /* Catch some misconfiguration. The server should catch + them now but some older versions did not. */ + || __builtin_expect (head->module == 0, 0) + /* This really should not happen but who knows, maybe the update + thread got stuck. */ + || __builtin_expect (! head->nscd_certainly_running + && (head->timestamp + MAPPING_TIMEOUT + < time (NULL)), 0)) + { + out_unmap: + __munmap (mapping, mapsize); + goto out_close; + } + + size_t size = (sizeof (*head) + roundup (head->module * sizeof (ref_t), + ALIGN) + + head->data_size); + + if (__glibc_unlikely (mapsize < size)) + goto out_unmap; + + /* Allocate a record for the mapping. */ + struct mapped_database *newp = malloc (sizeof (*newp)); + if (newp == NULL) + /* Ugh, after all we went through the memory allocation failed. */ + goto out_unmap; + + newp->head = mapping; + newp->data = ((char *) mapping + head->header_size + + roundup (head->module * sizeof (ref_t), ALIGN)); + newp->mapsize = size; + newp->datasize = head->data_size; + /* Set counter to 1 to show it is usable. */ + newp->counter = 1; + + result = newp; + } + + out_close: + __close (mapfd); + out_close2: + __close (sock); + out: + __set_errno (saved_errno); +#endif /* SCM_RIGHTS */ + + struct mapped_database *oldval = *mappedp; + *mappedp = result; + + if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0) + __nscd_unmap (oldval); + + return result; +} + +struct mapped_database * +__nscd_get_map_ref (request_type type, const char *name, + volatile struct locked_map_ptr *mapptr, int *gc_cyclep) +{ + struct mapped_database *cur = mapptr->mapped; + if (cur == NO_MAPPING) + return cur; + + if (!__nscd_acquire_maplock (mapptr)) + return NO_MAPPING; + + cur = mapptr->mapped; + + if (__glibc_likely (cur != NO_MAPPING)) + { + /* If not mapped or timestamp not updated, request new map. */ + if (cur == NULL + || (cur->head->nscd_certainly_running == 0 + && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL)) + || cur->head->data_size > cur->datasize) + cur = __nscd_get_mapping (type, name, + (struct mapped_database **) &mapptr->mapped); + + if (__glibc_likely (cur != NO_MAPPING)) + { + if (__builtin_expect (((*gc_cyclep = cur->head->gc_cycle) & 1) != 0, + 0)) + cur = NO_MAPPING; + else + atomic_increment (&cur->counter); + } + } + + mapptr->lock = 0; + + return cur; +} + + +/* Using sizeof (hashentry) is not always correct to determine the size of + the data structure as found in the nscd cache. The program could be + a 64-bit process and nscd could be a 32-bit process. In this case + sizeof (hashentry) would overestimate the size. The following is + the minimum size of such an entry, good enough for our tests here. */ +#define MINIMUM_HASHENTRY_SIZE \ + (offsetof (struct hashentry, dellist) + sizeof (int32_t)) + + +/* Don't return const struct datahead *, as eventhough the record + is normally constant, it can change arbitrarily during nscd + garbage collection. */ +struct datahead * +__nscd_cache_search (request_type type, const char *key, size_t keylen, + const struct mapped_database *mapped, size_t datalen) +{ + unsigned long int hash = __nis_hash (key, keylen) % mapped->head->module; + size_t datasize = mapped->datasize; + + ref_t trail = mapped->head->array[hash]; + trail = atomic_forced_read (trail); + ref_t work = trail; + size_t loop_cnt = datasize / (MINIMUM_HASHENTRY_SIZE + + offsetof (struct datahead, data) / 2); + int tick = 0; + + while (work != ENDREF && work + MINIMUM_HASHENTRY_SIZE <= datasize) + { + struct hashentry *here = (struct hashentry *) (mapped->data + work); + ref_t here_key, here_packet; + +#if !_STRING_ARCH_unaligned + /* Although during garbage collection when moving struct hashentry + records around we first copy from old to new location and then + adjust pointer from previous hashentry to it, there is no barrier + between those memory writes. It is very unlikely to hit it, + so check alignment only if a misaligned load can crash the + application. */ + if ((uintptr_t) here & (__alignof__ (*here) - 1)) + return NULL; +#endif + + if (type == here->type + && keylen == here->len + && (here_key = atomic_forced_read (here->key)) + keylen <= datasize + && memcmp (key, mapped->data + here_key, keylen) == 0 + && ((here_packet = atomic_forced_read (here->packet)) + + sizeof (struct datahead) <= datasize)) + { + /* We found the entry. Increment the appropriate counter. */ + struct datahead *dh + = (struct datahead *) (mapped->data + here_packet); + +#if !_STRING_ARCH_unaligned + if ((uintptr_t) dh & (__alignof__ (*dh) - 1)) + return NULL; +#endif + + /* See whether we must ignore the entry or whether something + is wrong because garbage collection is in progress. */ + if (dh->usable + && here_packet + dh->allocsize <= datasize + && (here_packet + offsetof (struct datahead, data) + datalen + <= datasize)) + return dh; + } + + work = atomic_forced_read (here->next); + /* Prevent endless loops. This should never happen but perhaps + the database got corrupted, accidentally or deliberately. */ + if (work == trail || loop_cnt-- == 0) + break; + if (tick) + { + struct hashentry *trailelem; + trailelem = (struct hashentry *) (mapped->data + trail); + +#if !_STRING_ARCH_unaligned + /* We have to redo the checks. Maybe the data changed. */ + if ((uintptr_t) trailelem & (__alignof__ (*trailelem) - 1)) + return NULL; +#endif + + if (trail + MINIMUM_HASHENTRY_SIZE > datasize) + return NULL; + + trail = atomic_forced_read (trailelem->next); + } + tick = 1 - tick; + } + + return NULL; +} + + +/* Create a socket connected to a name. */ +int +__nscd_open_socket (const char *key, size_t keylen, request_type type, + void *response, size_t responselen) +{ + /* This should never happen and it is something the nscd daemon + enforces, too. He it helps to limit the amount of stack + used. */ + if (keylen > MAXKEYLEN) + return -1; + + int saved_errno = errno; + + int sock = open_socket (type, key, keylen); + if (sock >= 0) + { + /* Wait for data. */ + if (wait_on_socket (sock, 5 * 1000) > 0) + { + ssize_t nbytes = TEMP_FAILURE_RETRY (__read (sock, response, + responselen)); + if (nbytes == (ssize_t) responselen) + return sock; + } + + close_not_cancel_no_status (sock); + } + + __set_errno (saved_errno); + + return -1; +} |