[PATCH v3] net: stream: add a new option to automatically reconnect

[Laurent Vivier <lvivier@redhat.com>]

In stream mode, if the server shuts down there is currently
no way to reconnect the client to a new server without removing
the NIC device and the netdev backend (or to reboot).

This patch introduces a reconnect option that specifies a delay
to try to reconnect with the same parameters.

Add a new test in qtest to test the reconnect option and the
connect/disconnect events.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
Based-on: <20230105093751.416666-1-lvivier@redhat.com>
    
v3:
- add "since 8.0" in net.json
    
v2:
- rebase

 net/stream.c                |  53 ++++++++++++++++++-
 qapi/net.json               |   7 ++-
 qemu-options.hx             |   6 +--
 tests/qtest/netdev-socket.c | 100 ++++++++++++++++++++++++++++++++++++
 4 files changed, 161 insertions(+), 5 deletions(-)

diff --git a/net/stream.c b/net/stream.c
index 37ff727e0c42..9204b4c96e40 100644
--- a/net/stream.c
+++ b/net/stream.c
@@ -39,6 +39,8 @@
 #include "io/channel-socket.h"
 #include "io/net-listener.h"
 #include "qapi/qapi-events-net.h"
+#include "qapi/qapi-visit-sockets.h"
+#include "qapi/clone-visitor.h"
 
 typedef struct NetStreamState {
     NetClientState nc;
@@ -49,11 +51,15 @@ typedef struct NetStreamState {
     guint ioc_write_tag;
     SocketReadState rs;
     unsigned int send_index;      /* number of bytes sent*/
+    uint32_t reconnect;
+    guint timer_tag;
+    SocketAddress *addr;
 } NetStreamState;
 
 static void net_stream_listen(QIONetListener *listener,
                               QIOChannelSocket *cioc,
                               void *opaque);
+static void net_stream_arm_reconnect(NetStreamState *s);
 
 static gboolean net_stream_writable(QIOChannel *ioc,
                                     GIOCondition condition,
@@ -170,6 +176,7 @@ static gboolean net_stream_send(QIOChannel *ioc,
         qemu_set_info_str(&s->nc, "%s", "");
 
         qapi_event_send_netdev_stream_disconnected(s->nc.name);
+        net_stream_arm_reconnect(s);
 
         return G_SOURCE_REMOVE;
     }
@@ -187,6 +194,14 @@ static gboolean net_stream_send(QIOChannel *ioc,
 static void net_stream_cleanup(NetClientState *nc)
 {
     NetStreamState *s = DO_UPCAST(NetStreamState, nc, nc);
+    if (s->timer_tag) {
+        g_source_remove(s->timer_tag);
+        s->timer_tag = 0;
+    }
+    if (s->addr) {
+        qapi_free_SocketAddress(s->addr);
+        s->addr = NULL;
+    }
     if (s->ioc) {
         if (QIO_CHANNEL_SOCKET(s->ioc)->fd != -1) {
             if (s->ioc_read_tag) {
@@ -346,12 +361,37 @@ static void net_stream_client_connected(QIOTask *task, gpointer opaque)
 error:
     object_unref(OBJECT(s->ioc));
     s->ioc = NULL;
+    net_stream_arm_reconnect(s);
+}
+
+static gboolean net_stream_reconnect(gpointer data)
+{
+    NetStreamState *s = data;
+    QIOChannelSocket *sioc;
+
+    s->timer_tag = 0;
+
+    sioc = qio_channel_socket_new();
+    s->ioc = QIO_CHANNEL(sioc);
+    qio_channel_socket_connect_async(sioc, s->addr,
+                                     net_stream_client_connected, s,
+                                     NULL, NULL);
+    return G_SOURCE_REMOVE;
+}
+
+static void net_stream_arm_reconnect(NetStreamState *s)
+{
+    if (s->reconnect && s->timer_tag == 0) {
+        s->timer_tag = g_timeout_add_seconds(s->reconnect,
+                                             net_stream_reconnect, s);
+    }
 }
 
 static int net_stream_client_init(NetClientState *peer,
                                   const char *model,
                                   const char *name,
                                   SocketAddress *addr,
+                                  uint32_t reconnect,
                                   Error **errp)
 {
     NetStreamState *s;
@@ -364,6 +404,10 @@ static int net_stream_client_init(NetClientState *peer,
     s->ioc = QIO_CHANNEL(sioc);
     s->nc.link_down = true;
 
+    s->reconnect = reconnect;
+    if (reconnect) {
+        s->addr = QAPI_CLONE(SocketAddress, addr);
+    }
     qio_channel_socket_connect_async(sioc, addr,
                                      net_stream_client_connected, s,
                                      NULL, NULL);
@@ -380,7 +424,14 @@ int net_init_stream(const Netdev *netdev, const char *name,
     sock = &netdev->u.stream;
 
     if (!sock->has_server || !sock->server) {
-        return net_stream_client_init(peer, "stream", name, sock->addr, errp);
+        return net_stream_client_init(peer, "stream", name, sock->addr,
+                                      sock->has_reconnect ? sock->reconnect : 0,
+                                      errp);
+    }
+    if (sock->has_reconnect) {
+        error_setg(errp, "'reconnect' option is incompatible with "
+                         "socket in server mode");
+        return -1;
     }
     return net_stream_server_init(peer, "stream", name, sock->addr, errp);
 }
diff --git a/qapi/net.json b/qapi/net.json
index 522ac582edeb..d6eb30008be0 100644
--- a/qapi/net.json
+++ b/qapi/net.json
@@ -585,6 +585,10 @@
 # @addr: socket address to listen on (server=true)
 #        or connect to (server=false)
 # @server: create server socket (default: false)
+# @reconnect: For a client socket, if a socket is disconnected,
+#             then attempt a reconnect after the given number of seconds.
+#             Setting this to zero disables this function. (default: 0)
+#             (since 8.0)
 #
 # Only SocketAddress types 'unix', 'inet' and 'fd' are supported.
 #
@@ -593,7 +597,8 @@
 { 'struct': 'NetdevStreamOptions',
   'data': {
     'addr':   'SocketAddress',
-    '*server': 'bool' } }
+    '*server': 'bool',
+    '*reconnect': 'uint32' } }
 
 ##
 # @NetdevDgramOptions:
diff --git a/qemu-options.hx b/qemu-options.hx
index 7f99d15b231f..e8d3a384e165 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2766,9 +2766,9 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
     "-netdev socket,id=str[,fd=h][,udp=host:port][,localaddr=host:port]\n"
     "                configure a network backend to connect to another network\n"
     "                using an UDP tunnel\n"
-    "-netdev stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port[,to=maxport][,numeric=on|off][,keep-alive=on|off][,mptcp=on|off][,addr.ipv4=on|off][,addr.ipv6=on|off]\n"
-    "-netdev stream,id=str[,server=on|off],addr.type=unix,addr.path=path[,abstract=on|off][,tight=on|off]\n"
-    "-netdev stream,id=str[,server=on|off],addr.type=fd,addr.str=file-descriptor\n"
+    "-netdev stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port[,to=maxport][,numeric=on|off][,keep-alive=on|off][,mptcp=on|off][,addr.ipv4=on|off][,addr.ipv6=on|off][,reconnect=seconds]\n"
+    "-netdev stream,id=str[,server=on|off],addr.type=unix,addr.path=path[,abstract=on|off][,tight=on|off][,reconnect=seconds]\n"
+    "-netdev stream,id=str[,server=on|off],addr.type=fd,addr.str=file-descriptor[,reconnect=seconds]\n"
     "                configure a network backend to connect to another network\n"
     "                using a socket connection in stream mode.\n"
     "-netdev dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=inet,local.host=addr]\n"
diff --git a/tests/qtest/netdev-socket.c b/tests/qtest/netdev-socket.c
index a9db9fa06e79..b6db396599ae 100644
--- a/tests/qtest/netdev-socket.c
+++ b/tests/qtest/netdev-socket.c
@@ -10,6 +10,10 @@
 #include <glib/gstdio.h>
 #include "../unit/socket-helpers.h"
 #include "libqtest.h"
+#include "qapi/qmp/qstring.h"
+#include "qemu/sockets.h"
+#include "qapi/qobject-input-visitor.h"
+#include "qapi/qapi-visit-sockets.h"
 
 #define CONNECTION_TIMEOUT    5
 
@@ -141,6 +145,101 @@ static void test_stream_inet_ipv4(void)
     qtest_quit(qts0);
 }
 
+static void wait_stream_connected(QTestState *qts, const char *id,
+                                  SocketAddress **addr)
+{
+    QDict *resp, *data;
+    QString *qstr;
+    QObject *obj;
+    Visitor *v = NULL;
+
+    resp = qtest_qmp_eventwait_ref(qts, "NETDEV_STREAM_CONNECTED");
+    g_assert_nonnull(resp);
+    data = qdict_get_qdict(resp, "data");
+    g_assert_nonnull(data);
+
+    qstr = qobject_to(QString, qdict_get(data, "netdev-id"));
+    g_assert_nonnull(data);
+
+    g_assert(!strcmp(qstring_get_str(qstr), id));
+
+    obj = qdict_get(data, "addr");
+
+    v = qobject_input_visitor_new(obj);
+    visit_type_SocketAddress(v, NULL, addr, NULL);
+    visit_free(v);
+    qobject_unref(resp);
+}
+
+static void wait_stream_disconnected(QTestState *qts, const char *id)
+{
+    QDict *resp, *data;
+    QString *qstr;
+
+    resp = qtest_qmp_eventwait_ref(qts, "NETDEV_STREAM_DISCONNECTED");
+    g_assert_nonnull(resp);
+    data = qdict_get_qdict(resp, "data");
+    g_assert_nonnull(data);
+
+    qstr = qobject_to(QString, qdict_get(data, "netdev-id"));
+    g_assert_nonnull(data);
+
+    g_assert(!strcmp(qstring_get_str(qstr), id));
+    qobject_unref(resp);
+}
+
+static void test_stream_inet_reconnect(void)
+{
+    QTestState *qts0, *qts1;
+    int port;
+    SocketAddress *addr;
+
+    port = inet_get_free_port(false);
+    qts0 = qtest_initf("-nodefaults -M none "
+                       "-netdev stream,id=st0,server=true,addr.type=inet,"
+                       "addr.ipv4=on,addr.ipv6=off,"
+                       "addr.host=127.0.0.1,addr.port=%d", port);
+
+    EXPECT_STATE(qts0, "st0: index=0,type=stream,\r\n", 0);
+
+    qts1 = qtest_initf("-nodefaults -M none "
+                       "-netdev stream,server=false,id=st0,addr.type=inet,"
+                       "addr.ipv4=on,addr.ipv6=off,reconnect=1,"
+                       "addr.host=127.0.0.1,addr.port=%d", port);
+
+    wait_stream_connected(qts0, "st0", &addr);
+    g_assert_cmpint(addr->type, ==, SOCKET_ADDRESS_TYPE_INET);
+    g_assert_cmpstr(addr->u.inet.host, ==, "127.0.0.1");
+    qapi_free_SocketAddress(addr);
+
+    /* kill server */
+    qtest_quit(qts0);
+
+    /* check client has been disconnected */
+    wait_stream_disconnected(qts1, "st0");
+
+    /* restart server */
+    qts0 = qtest_initf("-nodefaults -M none "
+                       "-netdev stream,id=st0,server=true,addr.type=inet,"
+                       "addr.ipv4=on,addr.ipv6=off,"
+                       "addr.host=127.0.0.1,addr.port=%d", port);
+
+    /* wait connection events*/
+    wait_stream_connected(qts0, "st0", &addr);
+    g_assert_cmpint(addr->type, ==, SOCKET_ADDRESS_TYPE_INET);
+    g_assert_cmpstr(addr->u.inet.host, ==, "127.0.0.1");
+    qapi_free_SocketAddress(addr);
+
+    wait_stream_connected(qts1, "st0", &addr);
+    g_assert_cmpint(addr->type, ==, SOCKET_ADDRESS_TYPE_INET);
+    g_assert_cmpstr(addr->u.inet.host, ==, "127.0.0.1");
+    g_assert_cmpint(atoi(addr->u.inet.port), ==, port);
+    qapi_free_SocketAddress(addr);
+
+    qtest_quit(qts1);
+    qtest_quit(qts0);
+}
+
 static void test_stream_inet_ipv6(void)
 {
     QTestState *qts0, *qts1;
@@ -415,6 +514,7 @@ int main(int argc, char **argv)
         qtest_add_func("/netdev/stream/inet/ipv4", test_stream_inet_ipv4);
         qtest_add_func("/netdev/dgram/inet", test_dgram_inet);
         qtest_add_func("/netdev/dgram/mcast", test_dgram_mcast);
+        qtest_add_func("/netdev/stream/inet/reconnect", test_stream_inet_reconnect);
     }
     if (has_ipv6) {
         qtest_add_func("/netdev/stream/inet/ipv6", test_stream_inet_ipv6);
-- 
2.39.0