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-rw-r--r--src/lib/net/alertsock.c295
1 files changed, 295 insertions, 0 deletions
diff --git a/src/lib/net/alertsock.c b/src/lib/net/alertsock.c
new file mode 100644
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+++ b/src/lib/net/alertsock.c
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+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file alertsock.c
+ *
+ * \brief Use a socket to alert the main thread from a worker thread.
+ *
+ * Because our main loop spends all of its time in select, epoll, kqueue, or
+ * etc, we need a way to wake up the main loop from another thread. This code
+ * tries to provide the fastest reasonable way to do that, depending on our
+ * platform.
+ **/
+
+#include "orconfig.h"
+#include "lib/net/alertsock.h"
+#include "lib/net/socket.h"
+#include "lib/log/util_bug.h"
+
+#ifdef HAVE_SYS_EVENTFD_H
+#include <sys/eventfd.h>
+#endif
+#ifdef HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#ifdef HAVE_SYS_SOCKET_H
+#include <sys/socket.h>
+#endif
+#ifdef _WIN32
+#include <winsock2.h>
+#endif
+
+#if defined(HAVE_EVENTFD) || defined(HAVE_PIPE)
+/* As write(), but retry on EINTR, and return the negative error code on
+ * error. */
+static int
+write_ni(int fd, const void *buf, size_t n)
+{
+ int r;
+ again:
+ r = (int) write(fd, buf, n);
+ if (r < 0) {
+ if (errno == EINTR)
+ goto again;
+ else
+ return -errno;
+ }
+ return r;
+}
+/* As read(), but retry on EINTR, and return the negative error code on error.
+ */
+static int
+read_ni(int fd, void *buf, size_t n)
+{
+ int r;
+ again:
+ r = (int) read(fd, buf, n);
+ if (r < 0) {
+ if (errno == EINTR)
+ goto again;
+ else
+ return -errno;
+ }
+ return r;
+}
+#endif /* defined(HAVE_EVENTFD) || defined(HAVE_PIPE) */
+
+/** As send(), but retry on EINTR, and return the negative error code on
+ * error. */
+static int
+send_ni(int fd, const void *buf, size_t n, int flags)
+{
+ int r;
+ again:
+ r = (int) send(fd, buf, n, flags);
+ if (r < 0) {
+ int error = tor_socket_errno(fd);
+ if (ERRNO_IS_EINTR(error))
+ goto again;
+ else
+ return -error;
+ }
+ return r;
+}
+
+/** As recv(), but retry on EINTR, and return the negative error code on
+ * error. */
+static int
+recv_ni(int fd, void *buf, size_t n, int flags)
+{
+ int r;
+ again:
+ r = (int) recv(fd, buf, n, flags);
+ if (r < 0) {
+ int error = tor_socket_errno(fd);
+ if (ERRNO_IS_EINTR(error))
+ goto again;
+ else
+ return -error;
+ }
+ return r;
+}
+
+#ifdef HAVE_EVENTFD
+/* Increment the event count on an eventfd <b>fd</b> */
+static int
+eventfd_alert(int fd)
+{
+ uint64_t u = 1;
+ int r = write_ni(fd, (void*)&u, sizeof(u));
+ if (r < 0 && -r != EAGAIN)
+ return -1;
+ return 0;
+}
+
+/* Drain all events from an eventfd <b>fd</b>. */
+static int
+eventfd_drain(int fd)
+{
+ uint64_t u = 0;
+ int r = read_ni(fd, (void*)&u, sizeof(u));
+ if (r < 0 && -r != EAGAIN)
+ return r;
+ return 0;
+}
+#endif /* defined(HAVE_EVENTFD) */
+
+#ifdef HAVE_PIPE
+/** Send a byte over a pipe. Return 0 on success or EAGAIN; -1 on error */
+static int
+pipe_alert(int fd)
+{
+ ssize_t r = write_ni(fd, "x", 1);
+ if (r < 0 && -r != EAGAIN)
+ return (int)r;
+ return 0;
+}
+
+/** Drain all input from a pipe <b>fd</b> and ignore it. Return 0 on
+ * success, -1 on error. */
+static int
+pipe_drain(int fd)
+{
+ char buf[32];
+ ssize_t r;
+ do {
+ r = read_ni(fd, buf, sizeof(buf));
+ } while (r > 0);
+ if (r < 0 && errno != EAGAIN)
+ return -errno;
+ /* A value of r = 0 means EOF on the fd so successfully drained. */
+ return 0;
+}
+#endif /* defined(HAVE_PIPE) */
+
+/** Send a byte on socket <b>fd</b>t. Return 0 on success or EAGAIN,
+ * -1 on error. */
+static int
+sock_alert(tor_socket_t fd)
+{
+ ssize_t r = send_ni(fd, "x", 1, 0);
+ if (r < 0 && !ERRNO_IS_EAGAIN(-r))
+ return (int)r;
+ return 0;
+}
+
+/** Drain all the input from a socket <b>fd</b>, and ignore it. Return 0 on
+ * success, -errno on error. */
+static int
+sock_drain(tor_socket_t fd)
+{
+ char buf[32];
+ ssize_t r;
+ do {
+ r = recv_ni(fd, buf, sizeof(buf), 0);
+ } while (r > 0);
+ if (r < 0 && !ERRNO_IS_EAGAIN(-r))
+ return (int)r;
+ /* A value of r = 0 means EOF on the fd so successfully drained. */
+ return 0;
+}
+
+/** Allocate a new set of alert sockets, and set the appropriate function
+ * pointers, in <b>socks_out</b>. */
+int
+alert_sockets_create(alert_sockets_t *socks_out, uint32_t flags)
+{
+ tor_socket_t socks[2] = { TOR_INVALID_SOCKET, TOR_INVALID_SOCKET };
+
+#ifdef HAVE_EVENTFD
+ /* First, we try the Linux eventfd() syscall. This gives a 64-bit counter
+ * associated with a single file descriptor. */
+#if defined(EFD_CLOEXEC) && defined(EFD_NONBLOCK)
+ if (!(flags & ASOCKS_NOEVENTFD2))
+ socks[0] = eventfd(0, EFD_CLOEXEC|EFD_NONBLOCK);
+#endif
+ if (socks[0] < 0 && !(flags & ASOCKS_NOEVENTFD)) {
+ socks[0] = eventfd(0,0);
+ if (socks[0] >= 0) {
+ if (fcntl(socks[0], F_SETFD, FD_CLOEXEC) < 0 ||
+ set_socket_nonblocking(socks[0]) < 0) {
+ // LCOV_EXCL_START -- if eventfd succeeds, fcntl will.
+ tor_assert_nonfatal_unreached();
+ close(socks[0]);
+ return -1;
+ // LCOV_EXCL_STOP
+ }
+ }
+ }
+ if (socks[0] >= 0) {
+ socks_out->read_fd = socks_out->write_fd = socks[0];
+ socks_out->alert_fn = eventfd_alert;
+ socks_out->drain_fn = eventfd_drain;
+ return 0;
+ }
+#endif /* defined(HAVE_EVENTFD) */
+
+#ifdef HAVE_PIPE2
+ /* Now we're going to try pipes. First type the pipe2() syscall, if we
+ * have it, so we can save some calls... */
+ if (!(flags & ASOCKS_NOPIPE2) &&
+ pipe2(socks, O_NONBLOCK|O_CLOEXEC) == 0) {
+ socks_out->read_fd = socks[0];
+ socks_out->write_fd = socks[1];
+ socks_out->alert_fn = pipe_alert;
+ socks_out->drain_fn = pipe_drain;
+ return 0;
+ }
+#endif /* defined(HAVE_PIPE2) */
+
+#ifdef HAVE_PIPE
+ /* Now try the regular pipe() syscall. Pipes have a bit lower overhead than
+ * socketpairs, fwict. */
+ if (!(flags & ASOCKS_NOPIPE) &&
+ pipe(socks) == 0) {
+ if (fcntl(socks[0], F_SETFD, FD_CLOEXEC) < 0 ||
+ fcntl(socks[1], F_SETFD, FD_CLOEXEC) < 0 ||
+ set_socket_nonblocking(socks[0]) < 0 ||
+ set_socket_nonblocking(socks[1]) < 0) {
+ // LCOV_EXCL_START -- if pipe succeeds, you can fcntl the output
+ tor_assert_nonfatal_unreached();
+ close(socks[0]);
+ close(socks[1]);
+ return -1;
+ // LCOV_EXCL_STOP
+ }
+ socks_out->read_fd = socks[0];
+ socks_out->write_fd = socks[1];
+ socks_out->alert_fn = pipe_alert;
+ socks_out->drain_fn = pipe_drain;
+ return 0;
+ }
+#endif /* defined(HAVE_PIPE) */
+
+ /* If nothing else worked, fall back on socketpair(). */
+ if (!(flags & ASOCKS_NOSOCKETPAIR) &&
+ tor_socketpair(AF_UNIX, SOCK_STREAM, 0, socks) == 0) {
+ if (set_socket_nonblocking(socks[0]) < 0 ||
+ set_socket_nonblocking(socks[1])) {
+ // LCOV_EXCL_START -- if socketpair worked, you can make it nonblocking.
+ tor_assert_nonfatal_unreached();
+ tor_close_socket(socks[0]);
+ tor_close_socket(socks[1]);
+ return -1;
+ // LCOV_EXCL_STOP
+ }
+ socks_out->read_fd = socks[0];
+ socks_out->write_fd = socks[1];
+ socks_out->alert_fn = sock_alert;
+ socks_out->drain_fn = sock_drain;
+ return 0;
+ }
+ return -1;
+}
+
+/** Close the sockets in <b>socks</b>. */
+void
+alert_sockets_close(alert_sockets_t *socks)
+{
+ if (socks->alert_fn == sock_alert) {
+ /* they are sockets. */
+ tor_close_socket(socks->read_fd);
+ tor_close_socket(socks->write_fd);
+ } else {
+ close(socks->read_fd);
+ if (socks->write_fd != socks->read_fd)
+ close(socks->write_fd);
+ }
+ socks->read_fd = socks->write_fd = -1;
+}
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