console: add ringbuffer

src/lxc/conf.c

@@ -80,6 +80,7 @@
 #include "namespace.h"
 #include "network.h"
 #include "parse.h"
+#include "ringbuf.h"
 #include "storage.h"
 #include "storage/aufs.h"
 #include "storage/overlay.h"
@@ -2428,6 +2429,7 @@ struct lxc_conf *lxc_conf_init(void)
 	new->autodev = 1;
 	new->console.log_path = NULL;
 	new->console.log_fd = -1;
+	new->console.log_size = 0;
 	new->console.path = NULL;
 	new->console.peer = -1;
 	new->console.peerpty.busy = -1;
@@ -2436,6 +2438,7 @@ struct lxc_conf *lxc_conf_init(void)
 	new->console.master = -1;
 	new->console.slave = -1;
 	new->console.name[0] = '\0';
+	memset(&new->console.ringbuf, 0, sizeof(struct lxc_ringbuf));
 	new->maincmd_fd = -1;
 	new->nbd_idx = -1;
 	new->rootfs.mount = strdup(default_rootfs_mount);
@@ -3079,6 +3082,64 @@ static bool verify_start_hooks(struct lxc_conf *conf)
 	return true;
 }
 
+/**
+ * Note that this function needs to run before the mainloop starts. Since we
+ * register a handler for the console's masterfd when we create the mainloop
+ * the console handler needs to see an allocated ringbuffer.
+ */
+static int lxc_setup_console_ringbuf(struct lxc_console *console)
+{
+	int ret;
+	struct lxc_ringbuf *buf = &console->ringbuf;
+	uint64_t size = console->log_size;
+
+	/* no ringbuffer previously allocated and no ringbuffer requested */
+	if (!buf->addr && size <= 0)
+		return 0;
+
+	/* ringbuffer allocated but no new ringbuffer requested */
+	if (buf->addr && size <= 0) {
+		lxc_ringbuf_release(buf);
+		buf->addr = NULL;
+		buf->r_off = 0;
+		buf->w_off = 0;
+		buf->size = 0;
+		TRACE("Deallocated console ringbuffer");
+		return 0;
+	}
+
+	if (size <= 0)
+		return 0;
+
+	/* check wether the requested size for the ringbuffer has changed */
+	if (buf->addr && buf->size != size) {
+		TRACE("Console ringbuffer size changed from %" PRIu64
+		      " to %" PRIu64 " bytes. Deallocating console ringbuffer",
+		      buf->size, size);
+		lxc_ringbuf_release(buf);
+	}
+
+	ret = lxc_ringbuf_create(buf, size);
+	if (ret < 0) {
+		ERROR("Failed to setup %" PRIu64 " byte console ringbuffer", size);
+		return -1;
+	}
+
+	TRACE("Allocated %" PRIu64 " byte console ringbuffer", size);
+	return 0;
+}
+
+int lxc_setup_parent(struct lxc_handler *handler)
+{
+	int ret;
+
+	ret = lxc_setup_console_ringbuf(&handler->conf->console);
+	if (ret < 0)
+		return -1;
+
+	return 0;
+}
+
 int lxc_setup_child(struct lxc_handler *handler)
 {
 	int ret;
@@ -3459,6 +3520,8 @@ void lxc_conf_free(struct lxc_conf *conf)
 		current_config = NULL;
 	free(conf->console.log_path);
 	free(conf->console.path);
+	if (conf->console.log_size > 0 && conf->console.ringbuf.addr)
+		lxc_ringbuf_release(&conf->console.ringbuf);
 	free(conf->rootfs.mount);
 	free(conf->rootfs.bdev_type);
 	free(conf->rootfs.options);

src/lxc/conf.h

@@ -36,6 +36,7 @@
 #include <stdbool.h>
 
 #include "list.h"
+#include "ringbuf.h"
 #include "start.h" /* for lxc_handler */
 
 #if HAVE_SCMP_FILTER_CTX
@@ -153,6 +154,7 @@ struct lxc_console {
 	struct termios *tios;
 	struct lxc_tty_state *tty_state;
 	uint64_t log_size;
+	struct lxc_ringbuf ringbuf;
 };
 
 /*
@@ -378,6 +380,7 @@ extern void lxc_clear_includes(struct lxc_conf *conf);
 extern int do_rootfs_setup(struct lxc_conf *conf, const char *name,
 			   const char *lxcpath);
 extern int lxc_setup_child(struct lxc_handler *handler);
+extern int lxc_setup_parent(struct lxc_handler *handler);
 extern int setup_resource_limits(struct lxc_list *limits, pid_t pid);
 extern int find_unmapped_nsid(struct lxc_conf *conf, enum idtype idtype);
 extern int mapped_hostid(unsigned id, struct lxc_conf *conf,

src/lxc/console.c

@@ -51,6 +51,8 @@
 #include <../include/openpty.h>
 #endif
 
+#define LXC_CONSOLE_BUFFER_SIZE 1024
+
 lxc_log_define(console, lxc);
 
 static struct lxc_list lxc_ttys;
@@ -167,12 +169,12 @@ static int lxc_console_cb_con(int fd, uint32_t events, void *data,
 			      struct lxc_epoll_descr *descr)
 {
 	struct lxc_console *console = (struct lxc_console *)data;
-	char buf[1024];
-	int r, w;
+	char buf[LXC_CONSOLE_BUFFER_SIZE];
+	int r, w, w_log, w_rbuf;
 
 	w = r = lxc_read_nointr(fd, buf, sizeof(buf));
 	if (r <= 0) {
-		INFO("console client on fd %d has exited", fd);
+		INFO("Console client on fd %d has exited", fd);
 		lxc_mainloop_del_handler(descr, fd);
 		if (fd == console->peer) {
 			if (console->tty_state) {
@@ -190,16 +192,30 @@ static int lxc_console_cb_con(int fd, uint32_t events, void *data,
 	if (fd == console->peer)
 		w = lxc_write_nointr(console->master, buf, r);
 
+	w_rbuf = w_log = 0;
 	if (fd == console->master) {
-		if (console->log_fd >= 0)
-			w = lxc_write_nointr(console->log_fd, buf, r);
-
+		/* write to peer first */
 		if (console->peer >= 0)
 			w = lxc_write_nointr(console->peer, buf, r);
+
+		/* write to console ringbuffer */
+		if (console->log_size > 0)
+			w_rbuf = lxc_ringbuf_write(&console->ringbuf, buf, r);
+
+		/* write to console log */
+		if (console->log_fd >= 0)
+			w_log = lxc_write_nointr(console->log_fd, buf, r);
 	}
 
 	if (w != r)
-		WARN("console short write r:%d w:%d", r, w);
+		WARN("Console short write r:%d != w:%d", r, w);
+
+	if (w_rbuf < 0)
+		TRACE("%s - Failed to write %d bytes to console ringbuffer",
+		      strerror(-w_rbuf), r);
+
+	if (w_log < 0)
+		TRACE("Failed to write %d bytes to console log", r);
 
 	return 0;
 }
@@ -632,7 +648,7 @@ int lxc_console_cb_tty_master(int fd, uint32_t events, void *cbdata,
 		struct lxc_epoll_descr *descr)
 {
 	struct lxc_tty_state *ts = cbdata;
-	char buf[1024];
+	char buf[LXC_CONSOLE_BUFFER_SIZE];
 	int r, w;
 
 	if (fd != ts->masterfd)

src/lxc/start.c

@@ -1254,6 +1254,11 @@ static int lxc_spawn(struct lxc_handler *handler)
 		 */
 		flags &= ~CLONE_NEWNET;
 	}
+
+	ret = lxc_setup_parent(handler);
+	if (ret < 0)
+		goto out_delete_net;
+
 	handler->pid = lxc_clone(do_start, handler, flags);
 	if (handler->pid < 0) {
 		SYSERROR("Failed to clone a new set of namespaces.");