From aa3aef4cf5f4dd98f9133df085e825ff5da7dcbd Mon Sep 17 00:00:00 2001 From: Patrick Ohly Date: Fri, 27 Oct 2017 15:23:35 +0200 Subject: [PATCH] chardev: connect socket to a spawned command The command is started in a shell (sh -c) with stdin connect to QEMU via a Unix domain stream socket. QEMU then exchanges data via its own end of the socket, just like it normally does. "-chardev socket" supports some ways of connecting via protocols like telnet, but that is only a subset of the functionality supported by tools socat. To use socat instead, for example to connect via a socks proxy, use: -chardev 'socket,id=socat,cmd=exec socat FD:0 SOCKS4A:socks-proxy.localdomain:example.com:9999,,socksuser=nobody' \ -device usb-serial,chardev=socat Beware that commas in the command must be escaped as double commas. Or interactively in the console: (qemu) chardev-add socket,id=cat,cmd=cat (qemu) device_add usb-serial,chardev=cat ^ac # cat >/dev/ttyUSB0 hello hello Another usage is starting swtpm from inside QEMU. swtpm will automatically shut down once it looses the connection to the parent QEMU, so there is no risk of lingering processes: -chardev 'socket,id=chrtpm0,cmd=exec swtpm socket --terminate --ctrl type=unixio,,clientfd=0 --tpmstate dir=... --log file=swtpm.log' \ -tpmdev emulator,id=tpm0,chardev=chrtpm0 \ -device tpm-tis,tpmdev=tpm0 The patch was discussed upstream, but QEMU developers believe that the code calling QEMU should be responsible for managing additional processes. In OE-core, that would imply enhancing runqemu and oeqa. This patch is a simpler solution. Because it is not going upstream, the patch was written so that it is as simple as possible. Upstream-Status: Inappropriate [embedded specific] Signed-off-by: Patrick Ohly --- chardev/char-socket.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++--- chardev/char.c | 3 ++ qapi-schema.json | 5 +++ 3 files changed, 90 insertions(+), 4 deletions(-) diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 1ae730a4..c366a02a 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -854,6 +854,66 @@ static gboolean socket_reconnect_timeout(gpointer opaque) return false; } +static void chardev_open_socket_cmd(Chardev *chr, + const char *cmd, + Error **errp) +{ + int fds[2] = { -1, -1 }; + QIOChannelSocket *sioc = NULL; + pid_t pid = -1; + const char *argv[] = { "/bin/sh", "-c", cmd, NULL }; + + /* + * We need a Unix domain socket for commands like swtpm and a single + * connection, therefore we cannot use qio_channel_command_new_spawn() + * without patching it first. Duplicating the functionality is easier. + */ + if (socketpair(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0, fds)) { + error_setg_errno(errp, errno, "Error creating socketpair(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC)"); + goto error; + } + + pid = qemu_fork(errp); + if (pid < 0) { + goto error; + } + + if (!pid) { + /* child */ + dup2(fds[1], STDIN_FILENO); + execv(argv[0], (char * const *)argv); + _exit(1); + } + + /* + * Hand over our end of the socket pair to the qio channel. + * + * We don't reap the child because it is expected to keep + * running. We also don't support the "reconnect" option for the + * same reason. + */ + sioc = qio_channel_socket_new_fd(fds[0], errp); + if (!sioc) { + goto error; + } + fds[0] = -1; + + g_free(chr->filename); + chr->filename = g_strdup_printf("cmd:%s", cmd); + tcp_chr_new_client(chr, sioc); + + error: + if (fds[0] >= 0) { + close(fds[0]); + } + if (fds[1] >= 0) { + close(fds[1]); + } + if (sioc) { + object_unref(OBJECT(sioc)); + } +} + static void qmp_chardev_open_socket(Chardev *chr, ChardevBackend *backend, bool *be_opened, @@ -861,6 +921,7 @@ static void qmp_chardev_open_socket(Chardev *chr, { SocketChardev *s = SOCKET_CHARDEV(chr); ChardevSocket *sock = backend->u.socket.data; + const char *cmd = sock->cmd; bool do_nodelay = sock->has_nodelay ? sock->nodelay : false; bool is_listen = sock->has_server ? sock->server : true; bool is_telnet = sock->has_telnet ? sock->telnet : false; @@ -928,7 +989,12 @@ static void qmp_chardev_open_socket(Chardev *chr, s->reconnect_time = reconnect; } - if (s->reconnect_time) { + if (cmd) { + chardev_open_socket_cmd(chr, cmd, errp); + + /* everything ready (or failed permanently) before we return */ + *be_opened = true; + } else if (s->reconnect_time) { sioc = qio_channel_socket_new(); tcp_chr_set_client_ioc_name(chr, sioc); qio_channel_socket_connect_async(sioc, s->addr, @@ -987,11 +1053,22 @@ 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 *tls_creds = qemu_opt_get(opts, "tls-creds"); + const char *cmd = qemu_opt_get(opts, "cmd"); SocketAddressLegacy *addr; ChardevSocket *sock; backend->type = CHARDEV_BACKEND_KIND_SOCKET; - if (!path) { + if (cmd) { + /* + * Here we have to ensure that no options are set which are incompatible with + * spawning a command, otherwise unmodified code that doesn't know about + * command spawning (like socket_reconnect_timeout()) might get called. + */ + if (path || is_listen || is_telnet || is_tn3270 || reconnect || host || port || tls_creds) { + error_setg(errp, "chardev: socket: cmd does not support any additional options"); + return; + } + } else if (!path) { if (!host) { error_setg(errp, "chardev: socket: no host given"); return; @@ -1023,13 +1100,14 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend, sock->has_reconnect = true; sock->reconnect = reconnect; sock->tls_creds = g_strdup(tls_creds); + sock->cmd = g_strdup(cmd); addr = g_new0(SocketAddressLegacy, 1); - if (path) { + if (path || cmd) { UnixSocketAddress *q_unix; 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->path = cmd ? g_strdup_printf("cmd:%s", cmd) : g_strdup(path); } else { addr->type = SOCKET_ADDRESS_LEGACY_KIND_INET; addr->u.inet.data = g_new(InetSocketAddress, 1); diff --git a/chardev/char.c b/chardev/char.c index 5d283b90..ccb329d4 100644 --- a/chardev/char.c +++ b/chardev/char.c @@ -782,6 +782,9 @@ QemuOptsList qemu_chardev_opts = { .name = "path", .type = QEMU_OPT_STRING, },{ + .name = "cmd", + .type = QEMU_OPT_STRING, + },{ .name = "host", .type = QEMU_OPT_STRING, },{ diff --git a/qapi-schema.json b/qapi-schema.json index 78a00bc8..790b026d 100644 --- a/qapi-schema.json +++ b/qapi-schema.json @@ -5004,6 +5004,10 @@ # # @addr: socket address to listen on (server=true) # or connect to (server=false) +# @cmd: command to run via "sh -c" with stdin as one end of +# a AF_UNIX SOCK_DSTREAM socket pair. The other end +# is used by the chardev. Either an addr or a cmd can +# be specified, but not both. # @tls-creds: the ID of the TLS credentials object (since 2.6) # @server: create server socket (default: true) # @wait: wait for incoming connection on server @@ -5021,6 +5025,7 @@ # Since: 1.4 ## { 'struct': 'ChardevSocket', 'data': { 'addr' : 'SocketAddressLegacy', + '*cmd' : 'str', '*tls-creds' : 'str', '*server' : 'bool', '*wait' : 'bool', -- 2.11.0