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

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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: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2017-12-22 11:04:30 +00:00 • committed by Daniel P. Berrangé
parent 30bdb3c56d
commit 1723d6b1cf
3 changed files with 126 additions and 9 deletions
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112
tests/test-util-sockets.c
View file

@ -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();