Drop support for nscd

nscd is known to be racy [1] and it was already deprecated and later dropped in
Fedora a while back [1,2]. We don't need to support obsolete stuff in systemd,
and the cache in systemd-resolved provides a better solution anyway.

We announced the plan to drop nscd in d44934f3785ad9ca4aab757beb80a9b11ba4bc04.

[1] https://fedoraproject.org/wiki/Changes/DeprecateNSCD
[2] https://fedoraproject.org/wiki/Changes/RemoveNSCD

The option is kept as a stub without any effect to make the transition easier.

3 files changed, 0 insertions, 154 deletions

diff --git a/src/shared/meson.build b/src/shared/meson.build
index eac5b83972..b7ae5959e8 100644
--- a/src/shared/meson.build
+++ b/src/shared/meson.build
@@ -247,10 +247,6 @@ if conf.get('HAVE_PAM') == 1
         shared_sources += files('pam-util.c')
 endif
 
-if conf.get('ENABLE_NSCD') == 1
-        shared_sources += files('nscd-flush.c')
-endif
-
 if conf.get('HAVE_LIBFIDO2') == 1 and conf.get('HAVE_LIBCRYPTSETUP') == 1
         shared_sources += files('cryptsetup-fido2.c')
 endif
diff --git a/src/shared/nscd-flush.c b/src/shared/nscd-flush.c
deleted file mode 100644
index 3d47ae3655..0000000000
--- a/src/shared/nscd-flush.c
+++ /dev/null
@@ -1,142 +0,0 @@
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-
-#include <fcntl.h>
-#include <poll.h>
-
-#include "fd-util.h"
-#include "io-util.h"
-#include "nscd-flush.h"
-#include "socket-util.h"
-#include "strv.h"
-#include "time-util.h"
-
-#define NSCD_FLUSH_CACHE_TIMEOUT_USEC (5*USEC_PER_SEC)
-
-struct nscdInvalidateRequest {
-        int32_t version;
-        int32_t type; /* in glibc this is an enum. We don't replicate this here 1:1. Also, wtf, how unportable is that
-                       * even? */
-        int32_t key_len;
-        char dbname[];
-};
-
-static int nscd_flush_cache_one(const char *database, usec_t end) {
-        size_t req_size, has_written = 0, has_read = 0, l;
-        struct nscdInvalidateRequest *req;
-        _cleanup_close_ int fd = -EBADF;
-        int32_t resp;
-        int events, r;
-
-        assert(database);
-
-        l = strlen(database);
-        req_size = offsetof(struct nscdInvalidateRequest, dbname) + l + 1;
-
-        req = alloca_safe(req_size);
-        *req = (struct nscdInvalidateRequest) {
-                .version = 2,
-                .type = 10,
-                .key_len = l + 1,
-        };
-
-        strcpy(req->dbname, database);
-
-        fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
-        if (fd < 0)
-                return log_debug_errno(errno, "Failed to allocate nscd socket: %m");
-
-        /* Note: connect() returns EINPROGRESS if O_NONBLOCK is set and establishing a connection takes time. The
-         * kernel lets us know this way that the connection is now being established, and we should watch with poll()
-         * to learn when it is fully established. That said, AF_UNIX on Linux never triggers this IRL (connect() is
-         * always instant on AF_UNIX), hence handling this is mostly just an exercise in defensive, protocol-agnostic
-         * programming.
-         *
-         * connect() returns EAGAIN if the socket's backlog limit has been reached. When we see this we give up right
-         * away, after all this entire function here is written in a defensive style so that a non-responding nscd
-         * doesn't stall us for good. (Even if we wanted to handle this better: the Linux kernel doesn't really have a
-         * nice way to connect() to a server synchronously with a time limit that would also cover dealing with the
-         * backlog limit. After all SO_RCVTIMEO and SR_SNDTIMEO don't apply to connect(), and alarm() is frickin' ugly
-         * and not really reasonably usable from threads-aware code.) */
-        r = connect_unix_path(fd, AT_FDCWD, "/run/nscd/socket");
-        if (r < 0) {
-                if (r == -EAGAIN)
-                        return log_debug_errno(r, "nscd is overloaded (backlog limit reached) and refuses to take further connections: %m");
-                if (r != -EINPROGRESS)
-                        return log_debug_errno(r, "Failed to connect to nscd socket: %m");
-
-                /* Continue in case of EINPROGRESS, but don't bother with send() or recv() until being notified that
-                 * establishing the connection is complete. */
-                events = 0;
-        } else
-                events = POLLIN|POLLOUT; /* Let's assume initially that we can write and read to the fd, to suppress
-                                          * one poll() invocation */
-        for (;;) {
-                usec_t p;
-
-                if (events & POLLOUT) {
-                        ssize_t m;
-
-                        assert(has_written < req_size);
-
-                        m = send(fd, (uint8_t*) req + has_written, req_size - has_written, MSG_NOSIGNAL);
-                        if (m < 0) {
-                                if (errno != EAGAIN) /* Note that EAGAIN is returned by the kernel whenever it can't
-                                                      * take the data right now, and that includes if the connect() is
-                                                      * asynchronous and we saw EINPROGRESS on it, and it hasn't
-                                                      * completed yet. */
-                                        return log_debug_errno(errno, "Failed to write to nscd socket: %m");
-                        } else
-                                has_written += m;
-                }
-
-                if (events & (POLLIN|POLLERR|POLLHUP)) {
-                        ssize_t m;
-
-                        if (has_read >= sizeof(resp))
-                                return log_debug_errno(SYNTHETIC_ERRNO(EIO), "Response from nscd longer than expected.");
-
-                        m = recv(fd, (uint8_t*) &resp + has_read, sizeof(resp) - has_read, 0);
-                        if (m < 0) {
-                                if (errno != EAGAIN)
-                                        return log_debug_errno(errno, "Failed to read from nscd socket: %m");
-                        } else if (m == 0) { /* EOF */
-                                if (has_read == 0 && has_written >= req_size) /* Older nscd immediately terminated the
-                                                                               * connection, accept that as OK */
-                                        return 1;
-
-                                return log_debug_errno(SYNTHETIC_ERRNO(EIO), "nscd prematurely ended connection.");
-                        } else
-                                has_read += m;
-                }
-
-                if (has_written >= req_size && has_read >= sizeof(resp)) { /* done? */
-                        if (resp < 0)
-                                return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG), "nscd sent us a negative error number: %i", resp);
-                        if (resp > 0)
-                                return log_debug_errno(resp, "nscd return failure code on invalidating '%s'.", database);
-                        return 1;
-                }
-
-                p = now(CLOCK_MONOTONIC);
-                if (p >= end)
-                        return -ETIMEDOUT;
-
-                events = fd_wait_for_event(fd, POLLIN | (has_written < req_size ? POLLOUT : 0), end - p);
-                if (events < 0)
-                        return events;
-        }
-}
-
-int nscd_flush_cache(char **databases) {
-        int r = 0;
-
-        /* Tries to invalidate the specified database in nscd. We do this carefully, with a 5s timeout,
-         * so that we don't block indefinitely on another service. */
-
-        usec_t end = usec_add(now(CLOCK_MONOTONIC), NSCD_FLUSH_CACHE_TIMEOUT_USEC);
-
-        STRV_FOREACH(i, databases)
-                RET_GATHER(r, nscd_flush_cache_one(*i, end));
-
-        return r;
-}
diff --git a/src/shared/nscd-flush.h b/src/shared/nscd-flush.h
deleted file mode 100644
index dac223e658..0000000000
--- a/src/shared/nscd-flush.h
+++ /dev/null
@@ -1,8 +0,0 @@
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-#pragma once
-
-#if ENABLE_NSCD
-int nscd_flush_cache(char **databases);
-#else
-static inline void nscd_flush_cache(char **databases) {}
-#endif