Extract the alert-socket code into lib/net.

This code was in compat_threads, since it was _used_ for efficiently
notifying the main libevent thread from another thread.  But in
spite of its usage, it's fundamentally a part of the network code.

3 files changed, 1 insertions, 296 deletions

diff --git a/src/common/compat_threads.c b/src/common/compat_threads.c
index e66143b35c..87833c6cfa 100644
--- a/src/common/compat_threads.c
+++ b/src/common/compat_threads.c
@@ -19,16 +19,6 @@
 #include "common/util.h"
 #include "lib/log/torlog.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
-
 /** Allocate and return a new condition variable. */
 tor_cond_t *
 tor_cond_new(void)
@@ -66,265 +56,6 @@ in_main_thread(void)
   return main_thread_id == tor_get_thread_id();
 }
 
-#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;
-}
-
 #ifndef HAVE_STDATOMIC_H
 /** Initialize a new atomic counter with the value 0 */
 void
diff --git a/src/common/compat_threads.h b/src/common/compat_threads.h
index d1fdfc96cc..69350421b5 100644
--- a/src/common/compat_threads.h
+++ b/src/common/compat_threads.h
@@ -52,32 +52,6 @@ int tor_cond_wait(tor_cond_t *cond, tor_mutex_t *mutex,
 void tor_cond_signal_one(tor_cond_t *cond);
 void tor_cond_signal_all(tor_cond_t *cond);
 
-/** Helper type used to manage waking up the main thread while it's in
- * the libevent main loop.  Used by the work queue code. */
-typedef struct alert_sockets_s {
-  /* XXXX This structure needs a better name. */
-  /** Socket that the main thread should listen for EV_READ events on.
-   * Note that this socket may be a regular fd on a non-Windows platform.
-   */
-  tor_socket_t read_fd;
-  /** Socket to use when alerting the main thread. */
-  tor_socket_t write_fd;
-  /** Function to alert the main thread */
-  int (*alert_fn)(tor_socket_t write_fd);
-  /** Function to make the main thread no longer alerted. */
-  int (*drain_fn)(tor_socket_t read_fd);
-} alert_sockets_t;
-
-/* Flags to disable one or more alert_sockets backends. */
-#define ASOCKS_NOEVENTFD2   (1u<<0)
-#define ASOCKS_NOEVENTFD    (1u<<1)
-#define ASOCKS_NOPIPE2      (1u<<2)
-#define ASOCKS_NOPIPE       (1u<<3)
-#define ASOCKS_NOSOCKETPAIR (1u<<4)
-
-int alert_sockets_create(alert_sockets_t *socks_out, uint32_t flags);
-void alert_sockets_close(alert_sockets_t *socks);
-
 typedef struct tor_threadlocal_s {
 #ifdef _WIN32
   DWORD index;
diff --git a/src/common/workqueue.c b/src/common/workqueue.c
index 84945882d6..fd31ccd7fd 100644
--- a/src/common/workqueue.c
+++ b/src/common/workqueue.c
@@ -31,6 +31,7 @@
 #include "common/util.h"
 #include "common/workqueue.h"
 #include "tor_queue.h"
+#include "lib/net/alertsock.h"
 #include "lib/log/torlog.h"
 
 #include <event2/event.h>
@@ -675,4 +676,3 @@ replyqueue_process(replyqueue_t *queue)
 
   tor_mutex_release(&queue->lock);
 }
-