kvm tools: Switch to using UNIX sockets instead of signals
This patch changes the IPC method to use UNIX sockets instead of
signals.
This allows for more flexibility in moving data between processes, for example
it would allow avoid printing output in the terminal of the guest.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/kvm-ipc.c b/kvm-ipc.c
new file mode 100644
index 0000000..f05e926
--- /dev/null
+++ b/kvm-ipc.c
@@ -0,0 +1,147 @@
+#include "kvm/kvm-ipc.h"
+#include "kvm/rwsem.h"
+#include "kvm/read-write.h"
+#include "kvm/util.h"
+
+#include <sys/epoll.h>
+#include <sys/un.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#define KVM_IPC_MAX_MSGS 16
+
+static void (*msgs[KVM_IPC_MAX_MSGS])(int fd, u32 type, u32 len, u8 *msg);
+static DECLARE_RWSEM(msgs_rwlock);
+static int epoll_fd, server_fd;
+
+int kvm_ipc__register_handler(u32 type, void (*cb)(int fd, u32 type, u32 len, u8 *msg))
+{
+ if (type >= KVM_IPC_MAX_MSGS)
+ return -ENOSPC;
+
+ down_write(&msgs_rwlock);
+ msgs[type] = cb;
+ up_write(&msgs_rwlock);
+
+ return 0;
+}
+
+int kvm_ipc__handle(int fd, struct kvm_ipc_msg *msg)
+{
+ void (*cb)(int fd, u32 type, u32 len, u8 *msg);
+
+ if (msg->type >= KVM_IPC_MAX_MSGS)
+ return -ENOSPC;
+
+ down_read(&msgs_rwlock);
+ cb = msgs[msg->type];
+ up_read(&msgs_rwlock);
+
+ if (cb == NULL) {
+ pr_warning("No device handles type %u\n", msg->type);
+ return -ENODEV;
+ }
+
+ cb(fd, msg->type, msg->len, msg->data);
+
+ return 0;
+}
+
+static int kvm_ipc__new_conn(int fd)
+{
+ int client;
+ struct epoll_event ev;
+
+ client = accept(fd, NULL, NULL);
+ if (client < 0)
+ return -1;
+
+ ev.events = EPOLLIN | EPOLLRDHUP;
+ ev.data.fd = client;
+ if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client, &ev) < 0) {
+ close(client);
+ return -1;
+ }
+
+ return client;
+}
+
+static void kvm_ipc__close_conn(int fd)
+{
+ epoll_ctl(epoll_fd, EPOLL_CTL_DEL, fd, NULL);
+ close(fd);
+}
+
+static void kvm_ipc__new_data(int fd)
+{
+ struct kvm_ipc_msg *msg;
+ u32 n;
+
+ msg = malloc(sizeof(*msg));
+ if (msg == NULL)
+ goto done;
+
+ n = read(fd, msg, sizeof(*msg));
+ if (n != sizeof(*msg))
+ goto done;
+
+ msg = realloc(msg, sizeof(*msg) + msg->len);
+ if (msg == NULL)
+ goto done;
+
+ n = read_in_full(fd, msg->data, msg->len);
+ if (n != msg->len)
+ goto done;
+
+ kvm_ipc__handle(fd, msg);
+
+done:
+ free(msg);
+}
+
+static void *kvm_ipc__thread(void *param)
+{
+ struct epoll_event event;
+
+ for (;;) {
+ int nfds;
+
+ nfds = epoll_wait(epoll_fd, &event, 1, -1);
+ if (nfds > 0) {
+ int fd = event.data.fd;
+
+ if (fd == server_fd) {
+ int client;
+
+ client = kvm_ipc__new_conn(fd);
+ kvm_ipc__new_data(client);
+ } else if (event.events && (EPOLLERR | EPOLLRDHUP | EPOLLHUP)) {
+ kvm_ipc__close_conn(fd);
+ } else {
+ kvm_ipc__new_data(fd);
+ }
+ }
+ }
+
+ return NULL;
+}
+
+int kvm_ipc__start(int sock)
+{
+ pthread_t thread;
+ struct epoll_event ev;
+
+ server_fd = sock;
+
+ epoll_fd = epoll_create(KVM_IPC_MAX_MSGS);
+
+ ev.events = EPOLLIN | EPOLLOUT | EPOLLPRI;
+ ev.data.fd = sock;
+ if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, sock, &ev) < 0)
+ die("Failed starting IPC thread");
+
+ if (pthread_create(&thread, NULL, kvm_ipc__thread, NULL) != 0)
+ die("Failed starting IPC thread");
+
+ return 0;
+}
