Commit 1723d6b1 authored by Daniel P. Berrangé's avatar Daniel P. Berrangé
Browse files

sockets: allow SocketAddress 'fd' to reference numeric file descriptors 



The SocketAddress 'fd' kind accepts the name of a file descriptor passed
to the monitor with the 'getfd' command. This makes it impossible to use
the 'fd' kind in cases where a monitor is not available. This can apply in
handling command line argv at startup, or simply if internal code wants to
use SocketAddress and pass a numeric FD it has acquired from elsewhere.

Fortunately the 'getfd' command mandated that the FD names must not start
with a leading digit. We can thus safely extend semantics of the
SocketAddress 'fd' kind, to allow a purely numeric name to reference an
file descriptor that QEMU already has open. There will be restrictions on
when each kind can be used.

In codepaths where we are handling a monitor command (ie cur_mon != NULL),
we will only support use of named file descriptors as before. Use of FD
numbers is still not permitted for monitor commands.

In codepaths where we are not handling a monitor command (ie cur_mon ==
NULL), we will not support named file descriptors. Instead we can reference
FD numers explicitly. This allows the app spawning QEMU to intentionally
"leak" a pre-opened socket to QEMU and reference that in a SocketAddress
definition, or for code inside QEMU to pass pre-opened FDs around.

Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: default avatarDaniel P. Berrange <berrange@redhat.com>
parent 30bdb3c5

qapi/sockets.json

+7 −0
Original line number Diff line number Diff line
@@ -123,6 +123,13 @@ 
#

# @unix:  Unix domain socket

#

# @vsock: VMCI address

#

# @fd: decimal is for file descriptor number, otherwise a file descriptor name.

#      Named file descriptors are permitted in monitor commands, in combination

#      with the 'getfd' command. Decimal file descriptors are permitted at

#      startup or other contexts where no monitor context is active.

#

# Since: 2.9

##

{ 'enum': 'SocketAddressType',

tests/test-util-sockets.c

+106 −6
Original line number Diff line number Diff line
@@ -73,7 +73,7 @@ Monitor *cur_mon; 
void monitor_init(Chardev *chr, int flags) {}





static void test_socket_fd_pass_good(void)

static void test_socket_fd_pass_name_good(void)

{

    SocketAddress addr;

    int fd;
@@ -104,7 +104,7 @@ static void test_socket_fd_pass_good(void) 
    cur_mon = NULL;

}



static void test_socket_fd_pass_bad(void)

static void test_socket_fd_pass_name_bad(void)

{

    SocketAddress addr;

    Error *err = NULL;
@@ -134,6 +134,98 @@ static void test_socket_fd_pass_bad(void) 
    cur_mon = NULL;

}



static void test_socket_fd_pass_name_nomon(void)

{

    SocketAddress addr;

    Error *err = NULL;

    int fd;



    g_assert(cur_mon == NULL);



    addr.type = SOCKET_ADDRESS_TYPE_FD;

    addr.u.fd.str = g_strdup("myfd");



    fd = socket_connect(&addr, &err);

    g_assert_cmpint(fd, ==, -1);

    error_free_or_abort(&err);



    fd = socket_listen(&addr, &err);

    g_assert_cmpint(fd, ==, -1);

    error_free_or_abort(&err);



    g_free(addr.u.fd.str);

}





static void test_socket_fd_pass_num_good(void)

{

    SocketAddress addr;

    int fd, sfd;



    g_assert(cur_mon == NULL);

    sfd = qemu_socket(AF_INET, SOCK_STREAM, 0);

    g_assert_cmpint(sfd, >, STDERR_FILENO);



    addr.type = SOCKET_ADDRESS_TYPE_FD;

    addr.u.fd.str = g_strdup_printf("%d", sfd);



    fd = socket_connect(&addr, &error_abort);

    g_assert_cmpint(fd, ==, sfd);



    fd = socket_listen(&addr, &error_abort);

    g_assert_cmpint(fd, ==, sfd);



    g_free(addr.u.fd.str);

    close(sfd);

}



static void test_socket_fd_pass_num_bad(void)

{

    SocketAddress addr;

    Error *err = NULL;

    int fd, sfd;



    g_assert(cur_mon == NULL);

    sfd = dup(STDOUT_FILENO);



    addr.type = SOCKET_ADDRESS_TYPE_FD;

    addr.u.fd.str = g_strdup_printf("%d", sfd);



    fd = socket_connect(&addr, &err);

    g_assert_cmpint(fd, ==, -1);

    error_free_or_abort(&err);



    fd = socket_listen(&addr, &err);

    g_assert_cmpint(fd, ==, -1);

    error_free_or_abort(&err);



    g_free(addr.u.fd.str);

    close(sfd);

}



static void test_socket_fd_pass_num_nocli(void)

{

    SocketAddress addr;

    Error *err = NULL;

    int fd;



    cur_mon = g_malloc(1); /* Fake a monitor */



    addr.type = SOCKET_ADDRESS_TYPE_FD;

    addr.u.fd.str = g_strdup_printf("%d", STDOUT_FILENO);



    fd = socket_connect(&addr, &err);

    g_assert_cmpint(fd, ==, -1);

    error_free_or_abort(&err);



    fd = socket_listen(&addr, &err);

    g_assert_cmpint(fd, ==, -1);

    error_free_or_abort(&err);



    g_free(addr.u.fd.str);

}





int main(int argc, char **argv)

{

    bool has_ipv4, has_ipv6;
@@ -156,10 +248,18 @@ int main(int argc, char **argv) 
                        test_fd_is_socket_bad);

        g_test_add_func("/util/socket/is-socket/good",

                        test_fd_is_socket_good);

        g_test_add_func("/socket/fd-pass/good",

                        test_socket_fd_pass_good);

        g_test_add_func("/socket/fd-pass/bad",

                        test_socket_fd_pass_bad);

        g_test_add_func("/socket/fd-pass/name/good",

                        test_socket_fd_pass_name_good);

        g_test_add_func("/socket/fd-pass/name/bad",

                        test_socket_fd_pass_name_bad);

        g_test_add_func("/socket/fd-pass/name/nomon",

                        test_socket_fd_pass_name_nomon);

        g_test_add_func("/socket/fd-pass/num/good",

                        test_socket_fd_pass_num_good);

        g_test_add_func("/socket/fd-pass/num/bad",

                        test_socket_fd_pass_num_bad);

        g_test_add_func("/socket/fd-pass/num/nocli",

                        test_socket_fd_pass_num_nocli);

    }



    return g_test_run();

util/qemu-sockets.c

+13 −3
Original line number Diff line number Diff line
@@ -1044,10 +1044,20 @@ fail: 


static int socket_get_fd(const char *fdstr, Error **errp)

{

    int fd = monitor_get_fd(cur_mon, fdstr, errp);

    int fd;

    if (cur_mon) {

        fd = monitor_get_fd(cur_mon, fdstr, errp);

        if (fd < 0) {

            return -1;

        }

    } else {

        if (qemu_strtoi(fdstr, NULL, 10, &fd) < 0) {

            error_setg_errno(errp, errno,

                             "Unable to parse FD number %s",

                             fdstr);

            return -1;

        }

    }

    if (!fd_is_socket(fd)) {

        error_setg(errp, "File descriptor '%s' is not a socket", fdstr);

        close(fd);