NBD patches for 2025-02-11

- Add --handshake-limit option to qemu-nbd
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Merge tag 'pull-nbd-2025-02-11' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2025-02-11

- Add --handshake-limit option to qemu-nbd

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# gpg: Signature made Tue 11 Feb 2025 15:23:59 EST
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# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg:                 aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* tag 'pull-nbd-2025-02-11' of https://repo.or.cz/qemu/ericb:
  nbd/server: Allow users to adjust handshake limit in QMP
  qemu-nbd: Allow users to adjust handshake limit

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/monitor/block-hmp-cmds.c

@@ -402,8 +402,8 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
         goto exit;
     }
 
-    nbd_server_start(addr, NULL, NULL, NBD_DEFAULT_MAX_CONNECTIONS,
+    nbd_server_start(addr, NBD_DEFAULT_HANDSHAKE_MAX_SECS, NULL, NULL,
-                     &local_err);
+                     NBD_DEFAULT_MAX_CONNECTIONS, &local_err);
     qapi_free_SocketAddress(addr);
     if (local_err != NULL) {
         goto exit;

blockdev-nbd.c

@@ -28,6 +28,7 @@ typedef struct NBDConn {
 
 typedef struct NBDServerData {
     QIONetListener *listener;
+    uint32_t handshake_max_secs;
     QCryptoTLSCreds *tlscreds;
     char *tlsauthz;
     uint32_t max_connections;
@@ -84,8 +85,7 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
     nbd_update_server_watch(nbd_server);
 
     qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
-    /* TODO - expose handshake timeout as QMP option */
+    nbd_client_new(cioc, nbd_server->handshake_max_secs,
-    nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS,
                    nbd_server->tlscreds, nbd_server->tlsauthz,
                    nbd_blockdev_client_closed, conn);
 }
@@ -162,9 +162,9 @@ static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
 }
 
 
-void nbd_server_start(SocketAddress *addr, const char *tls_creds,
+void nbd_server_start(SocketAddress *addr, uint32_t handshake_max_secs,
-                      const char *tls_authz, uint32_t max_connections,
+                      const char *tls_creds, const char *tls_authz,
-                      Error **errp)
+                      uint32_t max_connections, Error **errp)
 {
     if (nbd_server) {
         error_setg(errp, "NBD server already running");
@@ -173,6 +173,7 @@ void nbd_server_start(SocketAddress *addr, const char *tls_creds,
 
     nbd_server = g_new0(NBDServerData, 1);
     nbd_server->max_connections = max_connections;
+    nbd_server->handshake_max_secs = handshake_max_secs;
     nbd_server->listener = qio_net_listener_new();
 
     qio_net_listener_set_name(nbd_server->listener,
@@ -210,12 +211,17 @@ void nbd_server_start_options(NbdServerOptions *arg, Error **errp)
     if (!arg->has_max_connections) {
         arg->max_connections = NBD_DEFAULT_MAX_CONNECTIONS;
     }
+    if (!arg->has_handshake_max_seconds) {
+        arg->handshake_max_seconds = NBD_DEFAULT_HANDSHAKE_MAX_SECS;
+    }
 
-    nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz,
+    nbd_server_start(arg->addr, arg->handshake_max_seconds, arg->tls_creds,
-                     arg->max_connections, errp);
+                     arg->tls_authz, arg->max_connections, errp);
 }
 
 void qmp_nbd_server_start(SocketAddressLegacy *addr,
+                          bool has_handshake_max_secs,
+                          uint32_t handshake_max_secs,
                           const char *tls_creds,
                           const char *tls_authz,
                           bool has_max_connections, uint32_t max_connections,
@@ -226,8 +232,12 @@ void qmp_nbd_server_start(SocketAddressLegacy *addr,
     if (!has_max_connections) {
         max_connections = NBD_DEFAULT_MAX_CONNECTIONS;
     }
+    if (!has_handshake_max_secs) {
+        handshake_max_secs = NBD_DEFAULT_HANDSHAKE_MAX_SECS;
+    }
 
-    nbd_server_start(addr_flat, tls_creds, tls_authz, max_connections, errp);
+    nbd_server_start(addr_flat, handshake_max_secs, tls_creds, tls_authz,
+                     max_connections, errp);
     qapi_free_SocketAddress(addr_flat);
 }
 

docs/tools/qemu-nbd.rst

@@ -156,6 +156,11 @@ driver options if :option:`--image-opts` is specified.
   Set the NBD volume export description, as a human-readable
   string.
 
+.. option:: --handshake-limit=N
+
+  Set the timeout for a client to successfully complete its handshake
+  to N seconds (default 10), or 0 for no limit.
+
 .. option:: -L, --list
 
   Connect as a client and list all details about the exports exposed by

include/block/nbd.h

@@ -428,9 +428,9 @@ void nbd_client_put(NBDClient *client);
 void nbd_server_is_qemu_nbd(int max_connections);
 bool nbd_server_is_running(void);
 int nbd_server_max_connections(void);
-void nbd_server_start(SocketAddress *addr, const char *tls_creds,
+void nbd_server_start(SocketAddress *addr, uint32_t handshake_max_secs,
-                      const char *tls_authz, uint32_t max_connections,
+                      const char *tls_creds, const char *tls_authz,
-                      Error **errp);
+                      uint32_t max_connections, Error **errp);
 void nbd_server_start_options(NbdServerOptions *arg, Error **errp);
 
 /* nbd_read

qapi/block-export.json

@@ -17,6 +17,10 @@
 #
 # @addr: Address on which to listen.
 #
+# @handshake-max-seconds: Time limit, in seconds, at which a client
+#     that has not completed the negotiation handshake will be
+#     disconnected, 0 for no limit (since 10.0; default: 10).
+#
 # @tls-creds: ID of the TLS credentials object (since 2.6).
 #
 # @tls-authz: ID of the QAuthZ authorization object used to validate
@@ -34,6 +38,7 @@
 ##
 { 'struct': 'NbdServerOptions',
   'data': { 'addr': 'SocketAddress',
+            '*handshake-max-seconds': 'uint32',
             '*tls-creds': 'str',
             '*tls-authz': 'str',
             '*max-connections': 'uint32' } }
@@ -52,6 +57,10 @@
 #
 # @addr: Address on which to listen.
 #
+# @handshake-max-seconds: Time limit, in seconds, at which a client
+#     that has not completed the negotiation handshake will be
+#     disconnected, or 0 for no limit (since 10.0; default: 10).
+#
 # @tls-creds: ID of the TLS credentials object (since 2.6).
 #
 # @tls-authz: ID of the QAuthZ authorization object used to validate
@@ -72,6 +81,7 @@
 ##
 { 'command': 'nbd-server-start',
   'data': { 'addr': 'SocketAddressLegacy',
+            '*handshake-max-seconds': 'uint32',
             '*tls-creds': 'str',
             '*tls-authz': 'str',
             '*max-connections': 'uint32' },

qemu-nbd.c

@@ -70,6 +70,7 @@
 #define QEMU_NBD_OPT_PID_FILE        265
 #define QEMU_NBD_OPT_SELINUX_LABEL   266
 #define QEMU_NBD_OPT_TLSHOSTNAME     267
+#define QEMU_NBD_OPT_HANDSHAKE_LIMIT 268
 
 #define MBR_SIZE 512
 
@@ -80,6 +81,7 @@ static int nb_fds;
 static QIONetListener *server;
 static QCryptoTLSCreds *tlscreds;
 static const char *tlsauthz;
+static int handshake_limit = NBD_DEFAULT_HANDSHAKE_MAX_SECS;
 
 static void usage(const char *name)
 {
@@ -101,6 +103,7 @@ static void usage(const char *name)
 "  -v, --verbose             display extra debugging information\n"
 "  -x, --export-name=NAME    expose export by name (default is empty string)\n"
 "  -D, --description=TEXT    export a human-readable description\n"
+"      --handshake-limit=N   limit client's handshake to N seconds (default 10)\n"
 "\n"
 "Exposing part of the image:\n"
 "  -o, --offset=OFFSET       offset into the image\n"
@@ -390,8 +393,7 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
 
     nb_fds++;
     nbd_update_server_watch();
-    /* TODO - expose handshake timeout as command line option */
+    nbd_client_new(cioc, handshake_limit,
-    nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS,
                    tlscreds, tlsauthz, nbd_client_closed, NULL);
 }
 
@@ -569,6 +571,8 @@ int main(int argc, char **argv)
         { "object", required_argument, NULL, QEMU_NBD_OPT_OBJECT },
         { "export-name", required_argument, NULL, 'x' },
         { "description", required_argument, NULL, 'D' },
+        { "handshake-limit", required_argument, NULL,
+          QEMU_NBD_OPT_HANDSHAKE_LIMIT },
         { "tls-creds", required_argument, NULL, QEMU_NBD_OPT_TLSCREDS },
         { "tls-hostname", required_argument, NULL, QEMU_NBD_OPT_TLSHOSTNAME },
         { "tls-authz", required_argument, NULL, QEMU_NBD_OPT_TLSAUTHZ },
@@ -815,6 +819,13 @@ int main(int argc, char **argv)
         case QEMU_NBD_OPT_SELINUX_LABEL:
             selinux_label = optarg;
             break;
+        case QEMU_NBD_OPT_HANDSHAKE_LIMIT:
+            if (qemu_strtoi(optarg, NULL, 0, &handshake_limit) < 0 ||
+                handshake_limit < 0) {
+                error_report("Invalid handshake limit '%s'", optarg);
+                exit(EXIT_FAILURE);
+            }
+            break;
         }
     }