[Qemu-devel] A Patch to enable qemu-nbd run as an inetd service

[Jun Sheng <chaoseternal@gmail.com>]

From: Chaos Eternal <chaos@shlug.org>


run qemu-nbd as an inetd service has some benefits
* more scriptable, such as serve multiple images to different clients
on one ip/port
* access control using tcpd

simple usage:
#!/bin/sh
# qemu-nbd wrapper, select image file according to client ip address
IMG_FILE=`sed -n "s/$REMOTE_HOST //p" /path/to/image_list.txt`
qemu-nbd -i 10 $IMG_FILE 10<&0- 1>/tmp/log 2>/tmp/log2

#end

#xinetd.conf
service nbd
{
        flags                   = REUSE
        socket_type             = stream
        wait                    = no
        user                    = some_user
        server                  = /path/to/qemu-nbd-wrapper.sh
        log_on_failure          += USERID
        disable                 = no
}

Signed-off-by: Jun Sheng <chaoseternal@gmail.com>
---
 qemu-nbd.c | 40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index b524b34..13695e9 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -49,6 +49,7 @@ static NBDExport *exp;
 static int verbose;
 static char *srcpath;
 static char *sockpath;
+static int use_inetd = 0;
 static int persistent = 0;
 static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
 static int shared = 1;
@@ -66,6 +67,7 @@ static void usage(const char *name)
 "Connection properties:\n"
 "  -p, --port=PORT           port to listen on (default `%d')\n"
 "  -b, --bind=IFACE          interface to bind to (default `0.0.0.0')\n"
+"  -i, --inetd=FD            run as an inetd services on FD\n"
 "  -k, --socket=PATH         path to the unix socket\n"
 "                            (default '"SOCKET_PATH"')\n"
 "  -e, --shared=NUM          device can be shared by NUM clients (default '1')\n"
@@ -363,7 +365,13 @@ static void nbd_accept(void *opaque)
     struct sockaddr_in addr;
     socklen_t addr_len = sizeof(addr);
 
-    int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
+    
+    int fd ;
+    if (use_inetd == 0) 
+      fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
+    else
+      fd = server_fd;
+
     if (fd < 0) {
         perror("accept");
         return;
@@ -395,10 +403,11 @@ int main(int argc, char **argv)
     off_t fd_size;
     QemuOpts *sn_opts = NULL;
     const char *sn_id_or_name = NULL;
-    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
+    const char *sopt = "hVi:b:o:p:rsnP:c:dvk:e:f:tl:";
     struct option lopt[] = {
         { "help", 0, NULL, 'h' },
         { "version", 0, NULL, 'V' },
+	{ "inetd", 1, NULL, 'i'},
         { "bind", 1, NULL, 'b' },
         { "port", 1, NULL, 'p' },
         { "socket", 1, NULL, 'k' },
@@ -430,6 +439,7 @@ int main(int argc, char **argv)
     int partition = -1;
     int ret;
     int fd;
+    int inet_fd = 10;
     bool seen_cache = false;
     bool seen_discard = false;
 #ifdef CONFIG_LINUX_AIO
@@ -510,6 +520,16 @@ int main(int argc, char **argv)
         case 'b':
             bindto = optarg;
             break;
+	case 'i':
+  	    use_inetd = 1;
+	    inet_fd = strtol(optarg, &end, 0);
+	    if (*end) {
+                errx(EXIT_FAILURE, "Invalid inet fd `%s'", optarg);
+            }
+            if (inet_fd < 3 || inet_fd > 65535) {
+                errx(EXIT_FAILURE, "Inet fd out of range `%s', should be in [3, 65535]", optarg);
+            }
+	    break;
         case 'p':
             li = strtol(optarg, &end, 0);
             if (*end) {
@@ -729,11 +749,15 @@ int main(int argc, char **argv)
     }
 
     exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags, nbd_export_closed);
-
-    if (sockpath) {
+    
+    if (use_inetd == 0) {
+      if (sockpath) {
         fd = unix_socket_incoming(sockpath);
-    } else {
+      } else {
         fd = tcp_socket_incoming(bindto, port);
+      }
+    } else {
+      fd = inet_fd;
     }
 
     if (fd < 0) {
@@ -752,9 +776,11 @@ int main(int argc, char **argv)
         /* Shut up GCC warnings.  */
         memset(&client_thread, 0, sizeof(client_thread));
     }
-
-    qemu_set_fd_handler2(fd, nbd_can_accept, nbd_accept, NULL,
+    if (use_inetd == 0)
+      qemu_set_fd_handler2(fd, nbd_can_accept, nbd_accept, NULL,
                          (void *)(uintptr_t)fd);
+    else
+      nbd_accept((void *) (uintptr_t) fd);
 
     /* now when the initialization is (almost) complete, chdir("/")
      * to free any busy filesystems */
-- 
2.1.2