Move accepting connections to a utility function

Accepting connections from an array of file descriptors is a bit
fiddly.  Move all that code out to a utility function that we can
reuse and simplify the server code.

2 files changed, 59 insertions, 0 deletions

diff --git a/util/network.c b/util/network.c
index 51b6ef1..50d7f8d 100644
--- a/util/network.c
+++ b/util/network.c
@@ -285,6 +285,53 @@ network_bind_all(unsigned short port, socket_type **fds, unsigned int *count)
 
 
 /*
+ * Given an array of file descriptors and the length of that array (the same
+ * data that's returned by network_bind_all), wait for an incoming connection
+ * on any of those sockets, accept the connection with accept(), and return
+ * the new file descriptor.
+ *
+ * This is essentially a replacement for accept() with a single socket for
+ * daemons that are listening to multiple separate bound sockets, possibly
+ * because they need to listen to specific interfaces or possibly because
+ * they're listening for both IPv4 and IPv6 connections.
+ *
+ * Returns the new socket on success or INVALID_SOCKET on failure.  On
+ * success, fills out the arguments with the address and address length of the
+ * accepted client.  No error will be reported, so the caller should do that.
+ * Note that INVALID_SOCKET may be returned if the timeout is interrupted by a
+ * signal, which is not, precisely speaking, an error condition.  In this
+ * case, errno will be set to EINTR.
+ */
+socket_type
+network_accept_any(socket_type fds[], unsigned int count,
+                   struct sockaddr *addr, socklen_t *addrlen)
+{
+    fd_set readfds;
+    socket_type maxfd, fd;
+    unsigned int i;
+    int status;
+
+    FD_ZERO(&readfds);
+    maxfd = -1;
+    for (i = 0; i < count; i++) {
+        FD_SET(fds[i], &readfds);
+        if (fds[i] > maxfd)
+            maxfd = fds[i];
+    }
+    status = select(maxfd + 1, &readfds, NULL, NULL, NULL);
+    if (status < 0)
+        return INVALID_SOCKET;
+    fd = INVALID_SOCKET;
+    for (i = 0; i < count; i++)
+        if (FD_ISSET(fds[i], &readfds)) {
+            fd = fds[i];
+            break;
+        }
+    return accept(fd, addr, addrlen);
+}
+
+
+/*
  * Binds the given socket to an appropriate source address for its family
  * using the provided source address.  Returns true on success and false on
  * failure.
diff --git a/util/network.h b/util/network.h
index 3631e9d..67cd403 100644
--- a/util/network.h
+++ b/util/network.h
@@ -63,6 +63,18 @@ void network_bind_all(unsigned short port, socket_type **fds,
     __attribute__((__nonnull__));
 
 /*
+ * Accept an incoming connection from any file descriptor in an array.  This
+ * is a blocking accept that will wait until there is an incoming connection,
+ * unless interrupted by receipt of a signal.  Returns the new socket or
+ * INVALID_SOCKET, and fills out the arguments with the address of the remote
+ * client.  If the wait for a connection was interrupted by a signal, returns
+ * INVALID_SOCKET with errno set to EINTR.
+ */
+socket_type network_accept_any(socket_type fds[], unsigned int count,
+                               struct sockaddr *addr, socklen_t *addrlen)
+    __attribute__((__nonnull__(1)));
+
+/*
  * Create a socket and connect it to the remote service given by the linked
  * list of addrinfo structs.  Returns the new file descriptor on success and
  * -1 on failure, with the error left in errno.  Takes an optional source