From 85e2456983e8c284d304b8fcd7e9af8d37820cff Mon Sep 17 00:00:00 2001 From: Patrick Ohly Date: Fri, 27 Oct 2017 15:23:35 +0200 Subject: [PATCH 1/1] 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,cmd=exec socat FD:0 SOCKS4A:socks-proxy.localdomain:example.com:9999,,socksuser=nobody' Beware that commas in the command must be escaped as double commas. 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 Signed-off-by: Patrick Ohly %% original patch: chardev-connect-socket-to-a-spawned-command.patch --- chardev/char-socket.c | 88 ++++++++++++++++++++++++++++++++++++++++++++------- chardev/char.c | 3 ++ qapi-schema.json | 5 +++ 3 files changed, 84 insertions(+), 12 deletions(-) diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 1ae730a4..42a67f88 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -854,6 +854,58 @@ 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 }; + + 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. + * TODO: We don't reap the child at the moment. + */ + 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, @@ -861,12 +913,13 @@ static void qmp_chardev_open_socket(Chardev *chr, { SocketChardev *s = SOCKET_CHARDEV(chr); ChardevSocket *sock = backend->u.socket.data; - 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; - bool is_tn3270 = sock->has_tn3270 ? sock->tn3270 : false; - bool is_waitconnect = sock->has_wait ? sock->wait : false; - int64_t reconnect = sock->has_reconnect ? sock->reconnect : 0; + const char *cmd = sock->cmd; + bool do_nodelay = cmd ? false : sock->has_nodelay ? sock->nodelay : false; + bool is_listen = cmd ? false : sock->has_server ? sock->server : true; + bool is_telnet = cmd ? false : sock->has_telnet ? sock->telnet : false; + bool is_tn3270 = cmd ? false : sock->has_tn3270 ? sock->tn3270 : false; + bool is_waitconnect = cmd ? false : sock->has_wait ? sock->wait : false; + int64_t reconnect = cmd ? 0 : sock->has_reconnect ? sock->reconnect : 0; QIOChannelSocket *sioc = NULL; SocketAddress *addr; @@ -911,11 +964,11 @@ static void qmp_chardev_open_socket(Chardev *chr, qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_RECONNECTABLE); /* TODO SOCKET_ADDRESS_FD where fd has AF_UNIX */ - if (addr->type == SOCKET_ADDRESS_TYPE_UNIX) { + if (cmd || addr->type == SOCKET_ADDRESS_TYPE_UNIX) { qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_FD_PASS); } - /* be isn't opened until we get a connection */ + /* be isn't opened until we get a connection or fork a command */ *be_opened = false; update_disconnected_filename(s); @@ -928,7 +981,12 @@ 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 +1045,16 @@ 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 && path) { + error_setg(errp, "chardev: socket: cmd and path are mutually exclusive"); + return; + } + if (!path && !cmd) { if (!host) { error_setg(errp, "chardev: socket: no host given"); return; @@ -1023,13 +1086,14 @@ 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