I/O engine: track if a fd is a file or socket, needed for Windows.

This fixes a file descriptor leak in Windows that happened in the
logging code. The most visible effect of this was if you had a
log::maxsize set then on Windows you would see:
"Max file size reached, starting new log file"
Every other line, forever (and not actually starting a new log).

fd_close() previously did not close the file descriptor of a file
on Windows because on Windows it needs to call close() for a file
and closesocket() for a socket, and it always did the latter.
On *NIX it's more easy and you can just always close() any fd.

include/fdlist.h

@@ -15,12 +15,13 @@ typedef struct fd_entry {
 	void *data;
 	time_t deadline;
 	unsigned char is_open;
+	unsigned char is_file;
 	unsigned int backend_flags;
 } FDEntry;
 
 extern MODVAR FDEntry fd_table[MAXCONNECTIONS + 1];
 
-extern int fd_open(int fd, const char *desc);
+extern int fd_open(int fd, const char *desc, int file);
 extern void fd_close(int fd);
 extern int fd_unmap(int fd);
 extern void fd_unnotify(int fd);

src/dns.c

@@ -108,7 +108,7 @@ static void unrealdns_sock_state_cb(void *data, ares_socket_t fd, int read, int
  */
 static int unrealdns_sock_create_cb(ares_socket_t fd, int type, void *data)
 {
-	fd_open(fd, "DNS Resolver Socket");
+	fd_open(fd, "DNS Resolver Socket", 0);
 	return ARES_SUCCESS;
 }
 

src/fdlist.c

@@ -24,7 +24,13 @@
  */
 FDEntry fd_table[MAXCONNECTIONS + 1];
 
-int fd_open(int fd, const char *desc)
+/** Notify I/O engine that a file descriptor opened.
+ * @param fd	The file descriptor
+ * @param desc	Description for in the fd table
+ * @param file	Set to 1 if the fd is a file, 0 otherwise (eg: socket)
+ * @returns The file descriptor 'fd' or -1 in case of fatal error.
+ */
+int fd_open(int fd, const char *desc, int file)
 {
 	FDEntry *fde;
 
@@ -46,6 +52,7 @@ int fd_open(int fd, const char *desc)
 	fde->fd = fd;
 	fde->is_open = 1;
 	fde->backend_flags = 0;
+	fde->is_file = file;
 	strlcpy(fde->desc, desc, FD_DESC_SZ);
 
 	return fde->fd;
@@ -71,13 +78,16 @@ int fd_fileopen(const char *path, unsigned int flags)
 
 	snprintf(comment, sizeof comment, "File: %s", unreal_getfilename(pathbuf));
 
-	return fd_open(fd, comment);
+	return fd_open(fd, comment, 1);
 }
 
-int fd_unmap(int fd)
+/** Internal function to unmap and optionally close the fd.
+ */
+int fd_close_ex(int fd, int close_fd)
 {
 	FDEntry *fde;
 	unsigned int befl;
+	int is_file = 0;
 
 	if ((fd < 0) || (fd >= MAXCONNECTIONS))
 	{
@@ -105,6 +115,7 @@ int fd_unmap(int fd)
 	}
 
 	befl = fde->backend_flags;
+	is_file = fde->is_file;
 	memset(fde, 0, sizeof(FDEntry));
 
 	fde->fd = fd;
@@ -112,16 +123,37 @@ int fd_unmap(int fd)
 	/* only notify the backend if it is actively tracking the FD */
 	if (befl)
 		fd_refresh(fd);
-	
+
+	/* Finally, close the file or socket if requested to do so */
+	if (close_fd)
+	{
+		if (is_file)
+			close(fd);
+		else
+			CLOSE_SOCK(fd);
+	}
+
 	return 1;
 }
 
+/** Unmap file descriptor.
+ * That is: remove it from our list, but don't actually do any
+ * close() or closesocket() call.
+ * @param fd	The file descriptor
+ * @returns 1 on success, 0 on failure
+ */
+int fd_unmap(int fd)
+{
+	return fd_close_ex(fd, 0);
+}
+
+/** Close file descriptor.
+ * That is: remove it from our list AND call close() or closesocket().
+ * @param fd	The file descriptor
+ */
 void fd_close(int fd)
 {
-	if (!fd_unmap(fd))
-		return;
-
-	CLOSE_SOCK(fd);
+	fd_close_ex(fd, 1);
 }
 
 /* Deregister I/O notification for this file descriptor */
@@ -150,7 +182,7 @@ int fd_socket(int family, int type, int protocol, const char *desc)
 	if (fd < 0)
 		return -1;
 
-	return fd_open(fd, desc);
+	return fd_open(fd, desc, 0);
 }
 
 int fd_accept(int sockfd)
@@ -162,7 +194,7 @@ int fd_accept(int sockfd)
 	if (fd < 0)
 		return -1;
 
-	return fd_open(fd, buf);
+	return fd_open(fd, buf, 0);
 }
 
 void fd_desc(int fd, const char *desc)

src/url.c

@@ -336,7 +336,7 @@ static int url_socket_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *so
 		
 		if (!fde->is_open)
 		{
-			fd_open(s, "CURL transfer");
+			fd_open(s, "CURL transfer", 0);
 		}
 
 		if (what == CURL_POLL_IN || what == CURL_POLL_INOUT)