Add support for UNIX sockets in the abstract namespace

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Merge remote-tracking branch 'remotes/berrange/tags/socket-next-pull-request' into staging

Add support for UNIX sockets in the abstract namespace

# gpg: Signature made Wed 20 May 2020 13:58:43 BST
# gpg:                using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>" [full]
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/socket-next-pull-request:
  qemu-options: updates for abstract unix sockets
  tests/util-sockets: add abstract unix socket cases
  qemu-sockets: add abstract UNIX domain socket support

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

chardev/char-socket.c

@@ -1380,6 +1380,8 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
     const char *host = qemu_opt_get(opts, "host");
     const char *port = qemu_opt_get(opts, "port");
     const char *fd = qemu_opt_get(opts, "fd");
+    bool tight = qemu_opt_get_bool(opts, "tight", true);
+    bool abstract = qemu_opt_get_bool(opts, "abstract", false);
     SocketAddressLegacy *addr;
     ChardevSocket *sock;
 
@@ -1431,6 +1433,8 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
         addr->type = SOCKET_ADDRESS_LEGACY_KIND_UNIX;
         q_unix = addr->u.q_unix.data = g_new0(UnixSocketAddress, 1);
         q_unix->path = g_strdup(path);
+        q_unix->tight = tight;
+        q_unix->abstract = abstract;
     } else if (host) {
         addr->type = SOCKET_ADDRESS_LEGACY_KIND_INET;
         addr->u.inet.data = g_new(InetSocketAddress, 1);

chardev/char.c

@@ -939,6 +939,13 @@ QemuOptsList qemu_chardev_opts = {
         },{
             .name = "logappend",
             .type = QEMU_OPT_BOOL,
+        },{
+            .name = "tight",
+            .type = QEMU_OPT_BOOL,
+            .def_value_str = "on",
+        },{
+            .name = "abstract",
+            .type = QEMU_OPT_BOOL,
         },
         { /* end of list */ }
     },

qapi/sockets.json

@@ -73,12 +73,18 @@
 # Captures a socket address in the local ("Unix socket") namespace.
 #
 # @path: filesystem path to use
+# @tight: pass a socket address length confined to the minimum length of the
+#         abstract string, rather than the full sockaddr_un record length
+#         (only matters for abstract sockets, default true). (Since 5.1)
+# @abstract: whether this is an abstract address, default false. (Since 5.1)
 #
 # Since: 1.3
 ##
 { 'struct': 'UnixSocketAddress',
   'data': {
-    'path': 'str' } }
+    'path': 'str',
+    '*tight': 'bool',
+    '*abstract': 'bool' } }
 
 ##
 # @VsockSocketAddress:

qemu-options.hx

@@ -2938,7 +2938,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
     "         [,server][,nowait][,telnet][,websocket][,reconnect=seconds][,mux=on|off]\n"
     "         [,logfile=PATH][,logappend=on|off][,tls-creds=ID][,tls-authz=ID] (tcp)\n"
     "-chardev socket,id=id,path=path[,server][,nowait][,telnet][,websocket][,reconnect=seconds]\n"
-    "         [,mux=on|off][,logfile=PATH][,logappend=on|off] (unix)\n"
+    "         [,mux=on|off][,logfile=PATH][,logappend=on|off][,abstract=on|off][,tight=on|off] (unix)\n"
     "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
     "         [,localport=localport][,ipv4][,ipv6][,mux=on|off]\n"
     "         [,logfile=PATH][,logappend=on|off]\n"
@@ -3105,9 +3105,13 @@ The available backends are:
 
         ``nodelay`` disables the Nagle algorithm.
 
-    ``unix options: path=path``
+    ``unix options: path=path[,abstract=on|off][,tight=on|off]``
         ``path`` specifies the local path of the unix socket. ``path``
         is required.
+        ``abstract`` specifies the use of the abstract socket namespace,
+        rather than the filesystem.  Optional, defaults to false.
+        ``tight`` sets the socket length of abstract sockets to their minimum,
+        rather than the full sun_path length.  Optional, defaults to true.
 
 ``-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4][,ipv6]``
     Sends all traffic from the guest to a remote host over UDP.

tests/test-util-sockets.c

@@ -227,6 +227,93 @@ static void test_socket_fd_pass_num_nocli(void)
     g_free(addr.u.fd.str);
 }
 
+#ifdef __linux__
+static gchar *abstract_sock_name;
+
+static gpointer unix_server_thread_func(gpointer user_data)
+{
+    SocketAddress addr;
+    Error *err = NULL;
+    int fd = -1;
+    int connfd = -1;
+    struct sockaddr_un un;
+    socklen_t len = sizeof(un);
+
+    addr.type = SOCKET_ADDRESS_TYPE_UNIX;
+    addr.u.q_unix.path = abstract_sock_name;
+    addr.u.q_unix.tight = user_data != NULL;
+    addr.u.q_unix.abstract = true;
+
+    fd = socket_listen(&addr, 1, &err);
+    g_assert_cmpint(fd, >=, 0);
+    g_assert(fd_is_socket(fd));
+
+    connfd = accept(fd, (struct sockaddr *)&un, &len);
+    g_assert_cmpint(connfd, !=, -1);
+
+    close(fd);
+
+    return NULL;
+}
+
+static gpointer unix_client_thread_func(gpointer user_data)
+{
+    SocketAddress addr;
+    Error *err = NULL;
+    int fd = -1;
+
+    addr.type = SOCKET_ADDRESS_TYPE_UNIX;
+    addr.u.q_unix.path = abstract_sock_name;
+    addr.u.q_unix.tight = user_data != NULL;
+    addr.u.q_unix.abstract = true;
+
+    fd = socket_connect(&addr, &err);
+
+    g_assert_cmpint(fd, >=, 0);
+
+    close(fd);
+
+    return NULL;
+}
+
+static void test_socket_unix_abstract_good(void)
+{
+    GRand *r = g_rand_new();
+
+    abstract_sock_name = g_strdup_printf("unix-%d-%d", getpid(),
+                                         g_rand_int_range(r, 100, 1000));
+
+    /* non tight socklen serv and cli */
+    GThread *serv = g_thread_new("abstract_unix_server",
+                                 unix_server_thread_func,
+                                 NULL);
+
+    sleep(1);
+
+    GThread *cli = g_thread_new("abstract_unix_client",
+                                unix_client_thread_func,
+                                NULL);
+
+    g_thread_join(cli);
+    g_thread_join(serv);
+
+    /* tight socklen serv and cli */
+    serv = g_thread_new("abstract_unix_server",
+                        unix_server_thread_func,
+                        (gpointer)1);
+
+    sleep(1);
+
+    cli = g_thread_new("abstract_unix_client",
+                       unix_client_thread_func,
+                       (gpointer)1);
+
+    g_thread_join(cli);
+    g_thread_join(serv);
+
+    g_free(abstract_sock_name);
+}
+#endif
 
 int main(int argc, char **argv)
 {
@@ -265,6 +352,11 @@ int main(int argc, char **argv)
                         test_socket_fd_pass_num_nocli);
     }
 
+#ifdef __linux__
+    g_test_add_func("/util/socket/unix-abstract/good",
+                    test_socket_unix_abstract_good);
+#endif
+
 end:
     return g_test_run();
 }

util/qemu-sockets.c

@@ -863,6 +863,7 @@ static int unix_listen_saddr(UnixSocketAddress *saddr,
     char *pathbuf = NULL;
     const char *path;
     size_t pathlen;
+    size_t addrlen;
 
     sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
     if (sock < 0) {
@@ -879,9 +880,11 @@ static int unix_listen_saddr(UnixSocketAddress *saddr,
     }
 
     pathlen = strlen(path);
-    if (pathlen > sizeof(un.sun_path)) {
+    if (pathlen > sizeof(un.sun_path) ||
+        (saddr->abstract && pathlen > (sizeof(un.sun_path) - 1))) {
         error_setg(errp, "UNIX socket path '%s' is too long", path);
         error_append_hint(errp, "Path must be less than %zu bytes\n",
+                          saddr->abstract ? sizeof(un.sun_path) - 1 :
                           sizeof(un.sun_path));
         goto err;
     }
@@ -903,7 +906,7 @@ static int unix_listen_saddr(UnixSocketAddress *saddr,
         close(fd);
     }
 
-    if (unlink(path) < 0 && errno != ENOENT) {
+    if (!saddr->abstract && unlink(path) < 0 && errno != ENOENT) {
         error_setg_errno(errp, errno,
                          "Failed to unlink socket %s", path);
         goto err;
@@ -911,9 +914,19 @@ static int unix_listen_saddr(UnixSocketAddress *saddr,
 
     memset(&un, 0, sizeof(un));
     un.sun_family = AF_UNIX;
-    memcpy(un.sun_path, path, pathlen);
+    addrlen = sizeof(un);
 
-    if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
+    if (saddr->abstract) {
+        un.sun_path[0] = '\0';
+        memcpy(&un.sun_path[1], path, pathlen);
+        if (saddr->tight) {
+            addrlen = offsetof(struct sockaddr_un, sun_path) + 1 + pathlen;
+        }
+    } else {
+        memcpy(un.sun_path, path, pathlen);
+    }
+
+    if (bind(sock, (struct sockaddr *) &un, addrlen) < 0) {
         error_setg_errno(errp, errno, "Failed to bind socket to %s", path);
         goto err;
     }
@@ -936,6 +949,7 @@ static int unix_connect_saddr(UnixSocketAddress *saddr, Error **errp)
     struct sockaddr_un un;
     int sock, rc;
     size_t pathlen;
+    size_t addrlen;
 
     if (saddr->path == NULL) {
         error_setg(errp, "unix connect: no path specified");
@@ -949,21 +963,32 @@ static int unix_connect_saddr(UnixSocketAddress *saddr, Error **errp)
     }
 
     pathlen = strlen(saddr->path);
-    if (pathlen > sizeof(un.sun_path)) {
+    if (pathlen > sizeof(un.sun_path) ||
+        (saddr->abstract && pathlen > (sizeof(un.sun_path) - 1))) {
         error_setg(errp, "UNIX socket path '%s' is too long", saddr->path);
         error_append_hint(errp, "Path must be less than %zu bytes\n",
+                          saddr->abstract ? sizeof(un.sun_path) - 1 :
                           sizeof(un.sun_path));
         goto err;
     }
 
     memset(&un, 0, sizeof(un));
     un.sun_family = AF_UNIX;
-    memcpy(un.sun_path, saddr->path, pathlen);
+    addrlen = sizeof(un);
 
+    if (saddr->abstract) {
+        un.sun_path[0] = '\0';
+        memcpy(&un.sun_path[1], saddr->path, pathlen);
+        if (saddr->tight) {
+            addrlen = offsetof(struct sockaddr_un, sun_path) + 1 + pathlen;
+        }
+    } else {
+        memcpy(un.sun_path, saddr->path, pathlen);
+    }
     /* connect to peer */
     do {
         rc = 0;
-        if (connect(sock, (struct sockaddr *) &un, sizeof(un)) < 0) {
+        if (connect(sock, (struct sockaddr *) &un, addrlen) < 0) {
             rc = -errno;
         }
     } while (rc == -EINTR);